Van's Air Force
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Hot Tunnels
- Thread starter rv6ejguy
- Start date
rv6ejguy said:
So far, the simplest solution is to connect the scat-tubes that are suppose to connect to the exhaust muffs and connect them directly to the cabin heat door assembly on the fire wall. This eliminates the cabin heat control, but it does cool the tunnel down to the point you can lay your hand on the tunnel and not burn your skin during flight. Now that cooler weather has arrived, the tunnel is even cooler. Not sure what to do for cabin heat if we needed it.
I think one of the problems in our early flight testing was excessive heat in the tunnel creating a serious vapor lock with the fuel being super heated in the fuel lines inside the tunnel. We actually insulated in and around the fuel lines and that helped tremendously.
Vans is certainly aware of this and has indicated that they are working on a solution.
Hope this helps.
Hot tunnel
I thought I had poisted this already. My apologies. I THINK I have solved the hot tunnel problem in this manner. I took one of the fresh air tubes off of the back of the right rear baffles and added a "Y" to it. You can get them from A/C Spruce for $20. From the "Y" I went to the right hand heat muff, and then to the heat box on the firewall. I took the other tube off of the "Y" and pointed it right at both heater boxes. It seems to cool the tunnel down just fine, and the hot air from the rear seats is hot enough to heat the entire cabin. As a matter of fact, it's usually just cracked open just a little. These heat muffs put out way too much heat. I've tested it only as low as 20 degrees F.
The other heat muff is connected, but the hot air is dumped overboard. Vetterman tells me that we need airflow over the muffs.
For those who have easy access to the heat boxes, I would recommend installing an insulator (phenolic, silicone rubber, etc) between the heat box and the firewall. I'm sure that would help, as right now with them attached directly to the firewall, the whole firewall is getting hot because it is acting as a heatsink.
Vic
I thought I had poisted this already. My apologies. I THINK I have solved the hot tunnel problem in this manner. I took one of the fresh air tubes off of the back of the right rear baffles and added a "Y" to it. You can get them from A/C Spruce for $20. From the "Y" I went to the right hand heat muff, and then to the heat box on the firewall. I took the other tube off of the "Y" and pointed it right at both heater boxes. It seems to cool the tunnel down just fine, and the hot air from the rear seats is hot enough to heat the entire cabin. As a matter of fact, it's usually just cracked open just a little. These heat muffs put out way too much heat. I've tested it only as low as 20 degrees F.
The other heat muff is connected, but the hot air is dumped overboard. Vetterman tells me that we need airflow over the muffs.
For those who have easy access to the heat boxes, I would recommend installing an insulator (phenolic, silicone rubber, etc) between the heat box and the firewall. I'm sure that would help, as right now with them attached directly to the firewall, the whole firewall is getting hot because it is acting as a heatsink.
Vic
vic syracuse said:
Has anyone actually insulated the firewall with flame resistant material? Just wondering what should be used to glue the insulation to the firewall. Vic...sounds like you're on to something here. We have actually even thought about adding some cowl vents in the lower cowling, near the mufflers, to draw out some of the heat.
What say you?
Brent
glenmthompson
Well Known Member
mY OBVERSATIONS...
Take this as fact guys, the heat entering the tunnel is a result of radiant heat from the firewall and the exhausted cooling engine gases (NOT combustion exhaust gases).
Lets think about this a minute gentlemen.. now,... go fly your 6, 7, etc with bare feet. Put your bare feet on the floor at cruise on a warm day. They will not be there very long. Now, this tunnel is directly over this hot area, with no outlet for the radiated heat. Does this all make sense now?
Now....How you prevent this heat from entering the tunnel, ie. insulation (which alone had no measurable effect on 331JH), venting, etc...Is where this conversation needs to go.
I think I, along with Jim have spent more time on this than any other 10 owners/mechanics, so I hope we can save time from not heading down blind alleys ie. insulating heat boxes, etc...
Glen
Hey Vic, as I have said earlier, your idea of insulating the heat box, as it acts as a heat sink, is a very good idea, but fails in application. In 331JH, we hae completely disconnected BOTH heat exchangers, and have run BOTH fresh air inlets to the heat exchangers directly into the tunnel. This makes the tunnel IMHO ....JUST tolerable. Therefore, the idea of insulating the heat boxes as heat sinks is not the right direction, and IMHO is ill advised as phenolic will burn/coke rapidly in the event of a fire and burn throught the firewall in short order, and it will not affect anything as far as cooling any way.vic syracuse said:
Take this as fact guys, the heat entering the tunnel is a result of radiant heat from the firewall and the exhausted cooling engine gases (NOT combustion exhaust gases).
Lets think about this a minute gentlemen.. now,... go fly your 6, 7, etc with bare feet. Put your bare feet on the floor at cruise on a warm day. They will not be there very long. Now, this tunnel is directly over this hot area, with no outlet for the radiated heat. Does this all make sense now?
Now....How you prevent this heat from entering the tunnel, ie. insulation (which alone had no measurable effect on 331JH), venting, etc...Is where this conversation needs to go.
I think I, along with Jim have spent more time on this than any other 10 owners/mechanics, so I hope we can save time from not heading down blind alleys ie. insulating heat boxes, etc...
Glen
Glen, there certainly seems to be something different about yours, as mine works as described. We just went to Kansas City and back, about 10 hours of flying, at altitudes up to 11K' and below freezing temps to 60 degree temps. The tunnel is OK now. We get all of the heat we need with the valves cracked about 1/8 to 1/4. Again, I have only 1 heater hose hooked up to the rear ducts from the right rear heat muff, and am blowing fresh air from the "Y" directly at the heat valves on the firewall. I am taking the air off of the right rear baffle.
I'm sorry you are having such a hard time. There must be something different between the 2 airplanes. Don't hesitate to call me and we'll see if we can figure it out together.
Vic
I'm sorry you are having such a hard time. There must be something different between the 2 airplanes. Don't hesitate to call me and we'll see if we can figure it out together.
Vic
Hot Tunnel
Hello Vic,
Had to chime in here. 331JH is my Dad's -10. Glen and I helped build this wonderful flying machine. This -10 shouldn't be any different than yours...firewall forward was assembled per the plan. The next time you have the cowl off, send us some pictures.
We are considering adding a small hinged door in the bottom of the tunnel, aft of the front seats and controlling it with a push-pull cable...similar to a cowl flap. What do you think? We're still hoping Vans will come up with a solution.
Brent
vic syracuse said:
Hello Vic,
Had to chime in here. 331JH is my Dad's -10. Glen and I helped build this wonderful flying machine. This -10 shouldn't be any different than yours...firewall forward was assembled per the plan. The next time you have the cowl off, send us some pictures.
We are considering adding a small hinged door in the bottom of the tunnel, aft of the front seats and controlling it with a push-pull cable...similar to a cowl flap. What do you think? We're still hoping Vans will come up with a solution.
Brent
I'll try to get some pictures this week. Where do you live. Perhaps we could meet halfway?
Vic
Vic
What about meeting for lunch at Cedar Key? We like to go there.
Vic
Vic
vic syracuse said:
Hey, that would be a nice trip. We're looking for quick hops before our long trip back to Kansas this Spring. As soon as we get some paint on the outside, we'll coordinate a rendevous.
Thans for the offer Vic....would like to see your -10 and see how you did the interior.
Brent
just reading interesting threads and came across this one. Some time has elapsed and seems a fix for this problem hasn't been adressed. Trouble shooting this from the outside looking in from what I have read indicates that the feed air for the heater system is being taken from the pressure side of the engine cooling plenum. The air is being directed via scat tubes to heat shrouds on the mufflers or exhaust pipes, and then being sent to a firewall mounted valve assembly that I assume is metal because of previous post suggesting isolation barriers. The problem is the firewall is getting hot and tranfer of the heat is superheating a tunnel structure inside of the aircraft?
If the heater feed tubes were removed from the valve assemblies and vented overboard outside of the engine compartment, and the aircraft test flown would the tunnel be cool or remain hot? If still hot I would guess you have an issue with getting the air out of the hot side of the plenum. Using part of the cooling air to feed the heater muffs and dumping it out on the hot side dosen't help. Where is the oil cooler dumping it's hot air and is it robbing it's feed air from the same cool side of the plenum? What else is robbing cool air from the plenum side making it hot and dumping in the hot side, mag blast tubes, fuel pump cooling tube etc? It may be there is just too much hot air inside the lower cowl that cannot exscape rapidly. You may need cowl flaps like production aircraft utilize or clean up the exit area of the lower cowl. What is in the way, landing gear and exhaust pipes and breather tube restricting the area? One post indicated fuel vaporlocking? I think this is a serious problem that should be getting some serious attention. Good Luck!!!
If the heater feed tubes were removed from the valve assemblies and vented overboard outside of the engine compartment, and the aircraft test flown would the tunnel be cool or remain hot? If still hot I would guess you have an issue with getting the air out of the hot side of the plenum. Using part of the cooling air to feed the heater muffs and dumping it out on the hot side dosen't help. Where is the oil cooler dumping it's hot air and is it robbing it's feed air from the same cool side of the plenum? What else is robbing cool air from the plenum side making it hot and dumping in the hot side, mag blast tubes, fuel pump cooling tube etc? It may be there is just too much hot air inside the lower cowl that cannot exscape rapidly. You may need cowl flaps like production aircraft utilize or clean up the exit area of the lower cowl. What is in the way, landing gear and exhaust pipes and breather tube restricting the area? One post indicated fuel vaporlocking? I think this is a serious problem that should be getting some serious attention. Good Luck!!!
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glenmthompson
Well Known Member
Yep, vapor lock alright. And it was avgas, not mogas!
Yep, I had 3 engine failures in Jim's plane I tested for him, all were at or above 75% power, Elec. fuel pump off, hot day, and with "egg frying hot tunnel temps". Actually had 1'st degree burns on my leg one day. ( I now NEVER turn off the elec. fuel pump in this plane... Jim and I are working on "our" solution and hopefully will have the plane flying by tomorrow, and I will fly (TD #1 permitting) tomorrow to see if we have at least a partial solution.
I have said MANY times guys, now listen, this is not guessing, rather a statement of fact.......THE HEAT IS COMONG OFF OF NOT JUST THE FIREWALL, BUT GREATLY FROM THE BOTTOM SKIN TOO...... Our side cowl "'gills" have helped and we are slowly removing the cabin heat fresh air in stages to see what happens.
IMHO, I would like to see the cabin heat reinstalled as heat, and something like a 1" "pitot" style tube placed in the cabin vent NACA duct and have 2 of these vents blowing into the tunnel full time. One can also then "T" off of one line for an avionics cooling source if so desired.
In my experienced humble opinion, the ONLY way to eliminate this built in stove top, is to insulate the firewall and belly inside the tunnel with a false floor similar to what is under your feet in the 10. The 10 floor is room temp with this false floor. Would be a relatively easy/light fix. I also would "stand off" the fuel pump, FF transducer and all fuel lines to further them from any radiated floor heat. TIFWIT.
Glen
Yep, I had 3 engine failures in Jim's plane I tested for him, all were at or above 75% power, Elec. fuel pump off, hot day, and with "egg frying hot tunnel temps". Actually had 1'st degree burns on my leg one day. ( I now NEVER turn off the elec. fuel pump in this plane... Jim and I are working on "our" solution and hopefully will have the plane flying by tomorrow, and I will fly (TD #1 permitting) tomorrow to see if we have at least a partial solution.
I have said MANY times guys, now listen, this is not guessing, rather a statement of fact.......THE HEAT IS COMONG OFF OF NOT JUST THE FIREWALL, BUT GREATLY FROM THE BOTTOM SKIN TOO...... Our side cowl "'gills" have helped and we are slowly removing the cabin heat fresh air in stages to see what happens.
IMHO, I would like to see the cabin heat reinstalled as heat, and something like a 1" "pitot" style tube placed in the cabin vent NACA duct and have 2 of these vents blowing into the tunnel full time. One can also then "T" off of one line for an avionics cooling source if so desired.
In my experienced humble opinion, the ONLY way to eliminate this built in stove top, is to insulate the firewall and belly inside the tunnel with a false floor similar to what is under your feet in the 10. The 10 floor is room temp with this false floor. Would be a relatively easy/light fix. I also would "stand off" the fuel pump, FF transducer and all fuel lines to further them from any radiated floor heat. TIFWIT.
Glen
you are saying the inside tunnel of the aircraft gets hot enough to cause a first degree burn to the occupant? Didn"t Vans build the first RV-10 prototype and fly it for awhile before building ship number 2, and if so did they experience a hot tunnel? Was ship number 2 produced identical to ship number one or were refinements made to correct defficiences and does it have hot tunnel as well or was this corrected ? Might be good to find out !
glenmthompson
Well Known Member
Yep, I agree...
This hot tunnel thing is hard to believe until you see it fer yerself. My other observation that many have swept under the rug, is the total lack of elev. authority available to flare the 10 with a fwd CG and full flaps. IMHO, worse than at least, the 6 I test flew. hhhmmm, yet another thread???? (read, 727 drivers will have the perfect technique for landing this plane!)
Glen
This hot tunnel thing is hard to believe until you see it fer yerself. My other observation that many have swept under the rug, is the total lack of elev. authority available to flare the 10 with a fwd CG and full flaps. IMHO, worse than at least, the 6 I test flew. hhhmmm, yet another thread???? (read, 727 drivers will have the perfect technique for landing this plane!)
Glen
Inflight departure of the cabin doors is another item swept under the rug...seems the prototype rv-10 lost a door enroute to snf on its first debut there and was publicised as being just a latch problem..I'll say! And several others have lost doors as well..Guess we all are test pilots of sorts everytime we fly.
attackpilot
Active Member
Call Me Dumb, but...
Call me dumb, but what is the tunnel section that everyone is refering to. I am assuming it is near the bottom of the engine compartment near the firewall, is this correct?
As far as reducing the temperature around the exhaust section, has anyone thought about thermal barrier coatings? I would think that it would help some. Also, the heater box could be set off from the firewall with metal stand-offs. Sort of like someone else mentioned. Finally, it seems like Vetterman could angle the exhaust outlet down a few more degrees to give some more space between it and the fuselage.
Now for a far fetched idea I would like to throw out there. The way the
AH-64 Apache exhaust/transmission/engine is cooled by venturi effect. The primary exhaust nozzle lays inside a larger nozzle assembly. The hot gases from the ehaust nozzle creates a venturi effect and draws air in to the larger nozzle where it mixes with ambient air to cool it from around 700 C to less than 200 C. Granted turbine engines are essentially air pumps, so the volume of air that it pushes is way more than a piston engine, but I think this could be adapted to the RV-10 fairly easily. Any thoughts?
Joe Hutchison
RV-10 Tail Kit
Call me dumb, but what is the tunnel section that everyone is refering to. I am assuming it is near the bottom of the engine compartment near the firewall, is this correct?
As far as reducing the temperature around the exhaust section, has anyone thought about thermal barrier coatings? I would think that it would help some. Also, the heater box could be set off from the firewall with metal stand-offs. Sort of like someone else mentioned. Finally, it seems like Vetterman could angle the exhaust outlet down a few more degrees to give some more space between it and the fuselage.
Now for a far fetched idea I would like to throw out there. The way the
AH-64 Apache exhaust/transmission/engine is cooled by venturi effect. The primary exhaust nozzle lays inside a larger nozzle assembly. The hot gases from the ehaust nozzle creates a venturi effect and draws air in to the larger nozzle where it mixes with ambient air to cool it from around 700 C to less than 200 C. Granted turbine engines are essentially air pumps, so the volume of air that it pushes is way more than a piston engine, but I think this could be adapted to the RV-10 fairly easily. Any thoughts?
Joe Hutchison
RV-10 Tail Kit
thermal barrier coatings would help but would add weight and cost. this problem IMHO could be designed out of the aircraft without additional penalty. the airflow inside the lower cowling and across the belly skin just aft of the firewall should be investigated to see if the heat is not being allowed to escape from the engine compartment properly. some items i would look at are the slot opening for the nosegear travel. it could be pressurizing the area in question and maybe the louvers should become cowl flaps instead. the air outlet ramp is blocked with numerous items restricting that area and the heat blast from the cabin heat valve boxes certainly should be dealt with. as an example the cherokee six aircraft from pipers lineup has a tunnel that runs from the firewall to the tailcone and i don't remember that aircraft having this issue as it also was powered with a lyc 540.
Hot Tunnel Mods
We are in the process of trying to cool down the HOT TUNNEL issue in 331JH. We made a 4" x 10" cutout in the bottom of the tunnel, just aft of the front seats. We're designing a custom louver to cover the hole, similar to the gills on the bottom of the cowl. As soon as it's complete, we'll fly and see if this vents the hot air out of the tunnel.
Will get back here and report our experiment.....hence, that's why we call them Experimental Aircraft, huh?
Posting for Jim Headberg - RV-10 N331JH
Brent Headberg
West Palm Beach, FL
We are in the process of trying to cool down the HOT TUNNEL issue in 331JH. We made a 4" x 10" cutout in the bottom of the tunnel, just aft of the front seats. We're designing a custom louver to cover the hole, similar to the gills on the bottom of the cowl. As soon as it's complete, we'll fly and see if this vents the hot air out of the tunnel.
Will get back here and report our experiment.....hence, that's why we call them Experimental Aircraft, huh?
Posting for Jim Headberg - RV-10 N331JH
Brent Headberg
West Palm Beach, FL
Mike S
Senior Curmudgeon
more than exit needed???
brenthg-----have you already provided a fresh air source to the tunnel, or you just planning to suck out cabin air with the bottom vent??
I have been watching this thread with carecully, and find some interesting things going on.
The tunnel is hot------not the floorboards. The floorboards are double layered with an air gap between.
There have been cases or engine stoppage in flight, attributed to possable vapor lock---------the fuel lines, and pump, valve, and sometimes gascolator etc reside in the tunnel.
After lots of discussion with my RV mentor up the street, I have come to the following conclusion/plan for my -10.
1. false floor in tunnel, one or two inches up.
2. insulate the top side of the false floor.
3. duct fresh air in at the front of area under false floor.
4. exit gills as per above post on a/c bottom.
5. mount all fuel system componets above false floor.
6. if needed, heat shield mounted to exterior of a/c with standoffs for
cooling air, and exhaust deflection.
Mike
brenthg-----have you already provided a fresh air source to the tunnel, or you just planning to suck out cabin air with the bottom vent??
I have been watching this thread with carecully, and find some interesting things going on.
The tunnel is hot------not the floorboards. The floorboards are double layered with an air gap between.
There have been cases or engine stoppage in flight, attributed to possable vapor lock---------the fuel lines, and pump, valve, and sometimes gascolator etc reside in the tunnel.
After lots of discussion with my RV mentor up the street, I have come to the following conclusion/plan for my -10.
1. false floor in tunnel, one or two inches up.
2. insulate the top side of the false floor.
3. duct fresh air in at the front of area under false floor.
4. exit gills as per above post on a/c bottom.
5. mount all fuel system componets above false floor.
6. if needed, heat shield mounted to exterior of a/c with standoffs for
cooling air, and exhaust deflection.
Mike
glenmthompson
Well Known Member
!
Hi Mike, I am glad somebody is beginning to listen my recommendations and observations. If your 10 was mine..You and I would have identical tunnel sections. Maybe Vans will take heed!.
Here is our latest update. We changed the erl and filter and improved the fit of the carb inlet seal, lest we were pressurizing the lower cowl (# 5 was still running up to 460 on most takeoffs, but would cool well even at high cruise power settings. AN washers on aft shroud is my plan upon next cowl removal) Note, the #5 now hits 440, and cools quicker (90 deg day too!) after the following was done. see below....
We took the right cabin fresh air tube that was on the right side of the plenum, and blocked it off with high quality al. duct tape. Flew with Jim on 20 June...92 degs here in Wellington that day!
It appears we are almost at square one again ( but remember it WAS a really hot day Jim pointed out) as far as the tunnel is concerned. The top of the tunnel was very warm, just "cool" enought to hold your hand there without discomfort. As the hand is moved down the side toward the floor, one is unable to hold the hand on the side of the tunnel once you reach about 4" below the top of the tunnel. I believe at this point, the temp here is above 140 F, MUCH hotter as you go lower towards floor.
Please remember at this point, Jim has one cabin heat fresh air scat tube blowing into the tunnel for fresh air. Hence why he wants to try to let some air out through the proposed louvers on the bottom...Can you say more volume via louvers, equals more heat lost with the single proposed and VERY necessary scat tube? So maybe we can have cabin heat, with the other tube in the future?
****Also please note the following...The tunnel at the front near the firewall, is just as hot (using the ouch touch method with my hand) as the tunnel near the fwd spar. It is just barely cooler aft of the front seats next to the pax feet. Lending more proof to my theory the heat is radiating/convecting from exhaust/cooling air escaping from the cowl.
*****Gills, IMHO, the gills HAVE helped, since without the gills and just one scat tube entering the tunnel, in prev. testing, the top of the tunnel was scalding hot!!!! And on these previous flights, the temp was no where near 90 deg! So IMHO, the gills help,.... significantly? hhhmmmm, no, but noticably? YESSSSSSS!!!!!!!!!!!!!!
************TAS update 1500 feet, we had 29" and I held 2400RPM, (sorry, higher rpm, MAKES THIS PLANE SLOWER!!!!! FF was an enormous 24 +++ gph. We acheived 214 MPH TAS, STILL HIGHER THAN VANS PUBLISHED NUMBER. The CG was pretty far fwd as compared to the trip we took, prev. mentioned Can you say S*** Hot! ?
Come on guys/gals get off your *** and order this awsome plane!!!!
Glen
Hi Mike, I am glad somebody is beginning to listen my recommendations and observations. If your 10 was mine..You and I would have identical tunnel sections. Maybe Vans will take heed!.
Here is our latest update. We changed the erl and filter and improved the fit of the carb inlet seal, lest we were pressurizing the lower cowl (# 5 was still running up to 460 on most takeoffs, but would cool well even at high cruise power settings. AN washers on aft shroud is my plan upon next cowl removal) Note, the #5 now hits 440, and cools quicker (90 deg day too!) after the following was done. see below....
We took the right cabin fresh air tube that was on the right side of the plenum, and blocked it off with high quality al. duct tape. Flew with Jim on 20 June...92 degs here in Wellington that day!
It appears we are almost at square one again ( but remember it WAS a really hot day Jim pointed out) as far as the tunnel is concerned. The top of the tunnel was very warm, just "cool" enought to hold your hand there without discomfort. As the hand is moved down the side toward the floor, one is unable to hold the hand on the side of the tunnel once you reach about 4" below the top of the tunnel. I believe at this point, the temp here is above 140 F, MUCH hotter as you go lower towards floor.
Please remember at this point, Jim has one cabin heat fresh air scat tube blowing into the tunnel for fresh air. Hence why he wants to try to let some air out through the proposed louvers on the bottom...Can you say more volume via louvers, equals more heat lost with the single proposed and VERY necessary scat tube? So maybe we can have cabin heat, with the other tube in the future?
****Also please note the following...The tunnel at the front near the firewall, is just as hot (using the ouch touch method with my hand) as the tunnel near the fwd spar. It is just barely cooler aft of the front seats next to the pax feet. Lending more proof to my theory the heat is radiating/convecting from exhaust/cooling air escaping from the cowl.
*****Gills, IMHO, the gills HAVE helped, since without the gills and just one scat tube entering the tunnel, in prev. testing, the top of the tunnel was scalding hot!!!! And on these previous flights, the temp was no where near 90 deg! So IMHO, the gills help,.... significantly? hhhmmmm, no, but noticably? YESSSSSSS!!!!!!!!!!!!!!
************TAS update 1500 feet, we had 29" and I held 2400RPM, (sorry, higher rpm, MAKES THIS PLANE SLOWER!!!!! FF was an enormous 24 +++ gph. We acheived 214 MPH TAS, STILL HIGHER THAN VANS PUBLISHED NUMBER. The CG was pretty far fwd as compared to the trip we took, prev. mentioned Can you say S*** Hot! ?
Come on guys/gals get off your *** and order this awsome plane!!!!
Glen
w1curtis
Well Known Member
Service Letter for high Tunnel Temps
Van's has published a service letter on the tunnel temps and it pretty much echos what Mike S has stated above.
http://www.vansaircraft.com/pdf/tunnel_temp.pdf
Van's has published a service letter on the tunnel temps and it pretty much echos what Mike S has stated above.
http://www.vansaircraft.com/pdf/tunnel_temp.pdf
glenmthompson
Well Known Member
I give up...
Brent installed the 4x10 louvers today in the bottom of the tunnel, aft of the spar. It apppears all that has been done is to now make the aft tunnel as scalding as the front, by apparently drawing the blistering air to the back. Top of tunnel warm to touch, down sides 4 ", too hot to touch. Please note that the cabin heat blast tube has just been removed and blows mainly toward the top of the tunnel, straight aft, causing IMHO the top to stay tolerably cool, while the bottom of the tunnel remain VERY hot. All is hotter towards firewall.
Right now only 1 cabin heat blast tube blowing into tunnel as per Vans SB (We did this many months ago). Gills installed in sides of cowling. Louvers installed in floor aft of main spar in tunnel area under elev. push tube. Vans bandaid is not the solution ladies and gentlemen.
**
**Please re. my original idea of a false floor. Also note that with BOTH cabin heat fresh air tubes blowing into the tunnel, all is acceptably cool.
This is such a sweet flying example of how a 10 should fly,.... even faster now than Vans says it should be.
Gawd, this tunnel is annoying on this 89 deg fl. day.
*
* Signed....Discouraged and giving up until we pull the cowling again and try to further insulate the firewall on the engine side, per jim's suggestion.
Glen's further $.02 for current builders. Leave the tunnel accessable until somebody can figure out an ACCEPTABLE, NON BANDAID fix.
Some people are poo pooing this issue, but lemme tell ya, it is a P R O B L E M !!!
********
On a brighter side guys, We all L O V E this plane, I am just still whining about this tunnel heat issue.
***** I now pose a question to qualified metalurgists and/or engineers. Lets say the spar carry through on some planes, in the tunnel reaches, say oh 150-160 deg. F virtually on every flight. Very possibly higher at the very bottom of the spar where it touches the bottom skin What will this do to the temper/strength of the spar over the long run? Especially for those that ignore the heat in there and just insulate and carpet their tunnels?
Glen
Brent installed the 4x10 louvers today in the bottom of the tunnel, aft of the spar. It apppears all that has been done is to now make the aft tunnel as scalding as the front, by apparently drawing the blistering air to the back. Top of tunnel warm to touch, down sides 4 ", too hot to touch. Please note that the cabin heat blast tube has just been removed and blows mainly toward the top of the tunnel, straight aft, causing IMHO the top to stay tolerably cool, while the bottom of the tunnel remain VERY hot. All is hotter towards firewall.
Right now only 1 cabin heat blast tube blowing into tunnel as per Vans SB (We did this many months ago). Gills installed in sides of cowling. Louvers installed in floor aft of main spar in tunnel area under elev. push tube. Vans bandaid is not the solution ladies and gentlemen.
**
**Please re. my original idea of a false floor. Also note that with BOTH cabin heat fresh air tubes blowing into the tunnel, all is acceptably cool.
This is such a sweet flying example of how a 10 should fly,.... even faster now than Vans says it should be.
Gawd, this tunnel is annoying on this 89 deg fl. day.
*
* Signed....Discouraged and giving up until we pull the cowling again and try to further insulate the firewall on the engine side, per jim's suggestion.
Glen's further $.02 for current builders. Leave the tunnel accessable until somebody can figure out an ACCEPTABLE, NON BANDAID fix.
Some people are poo pooing this issue, but lemme tell ya, it is a P R O B L E M !!!
********
On a brighter side guys, We all L O V E this plane, I am just still whining about this tunnel heat issue.
***** I now pose a question to qualified metalurgists and/or engineers. Lets say the spar carry through on some planes, in the tunnel reaches, say oh 150-160 deg. F virtually on every flight. Very possibly higher at the very bottom of the spar where it touches the bottom skin What will this do to the temper/strength of the spar over the long run? Especially for those that ignore the heat in there and just insulate and carpet their tunnels?
Glen
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glenmthompson
Well Known Member
Little demonstartion...
I just thought of a little demonstration for those non believers out there. Next time you fly, take off your shoes and put your bare feet up against the firewall. Then, take your scalded toes and further burn them by placing them on the floor directly on top where the exhaust/cowling air blows across the bottom of the plane. Those who have insulated their floors, already know how blistering a hot it gets. An RV6 I test flew, literally melted the heals of my sandals, until we insulated significantly the floor.
Now, imagine all of this heat entering a "tunnel area". Hence "The" problem.
I don't create the problems, I just furiously point them out and search for acceptable answers.
Guys, when we get some of these things fixed, I predict the 10 wil be THE plane to have and even non experimental types, will just have to have one.
IMHO this is SOOOO much more plane than the Columbia, and it could be certified and built so much cheaper. But lets get the really annoying things fixed and fixed well!
Glen
I just thought of a little demonstration for those non believers out there. Next time you fly, take off your shoes and put your bare feet up against the firewall. Then, take your scalded toes and further burn them by placing them on the floor directly on top where the exhaust/cowling air blows across the bottom of the plane. Those who have insulated their floors, already know how blistering a hot it gets. An RV6 I test flew, literally melted the heals of my sandals, until we insulated significantly the floor.
Now, imagine all of this heat entering a "tunnel area". Hence "The" problem.
I don't create the problems, I just furiously point them out and search for acceptable answers.
Guys, when we get some of these things fixed, I predict the 10 wil be THE plane to have and even non experimental types, will just have to have one.
IMHO this is SOOOO much more plane than the Columbia, and it could be certified and built so much cheaper. But lets get the really annoying things fixed and fixed well!
Glen
attackpilot
Active Member
My Hot Tunnel Plan, Please Advise
Ok, now that I know that it is the actual tunnel that gets extremely hot in the RV-10, I would like to suggest my plan to deal with it and see what you guys/gals think:
1. Extend the exhaust by a few inches and have it point more down than the prototype. Yes, it may cost a knot or two, but it should help.
2. Have exhaust ceramic coated to contain the heat.
3. Have the cabin heat selector on standoffs or some other insulating material (any suggestions?).
3. Spray on a ceramic insulating paint on the cabin side of the firewall, bottom sub-floor, bottom of floor where your feet are, and both inside and outside of the tunnel (I plan on having carpet going up to the top of the tunnel)
4. Firesleeve all the fuel lines inside the cabin area to help reduce chance of vapor lock.
5. Install the extra louvers in the cowling.
6. If required, I think I will run a duct to the tunnel with an exit toward the back so that fresh air can flow through it.
I have also thought of somehow placing the cabin heat selector on the heat muff itself to help reduce the conductive heat problem, but that might be a big headache.
Yes it will add weight (maybe 10 lbs max) and make it a knot or two slower, but I think it will be worth it in the end.
I would appreciate any insight and further ideas.
Joe Hutchison
RV-10 Tail Kit
Ok, now that I know that it is the actual tunnel that gets extremely hot in the RV-10, I would like to suggest my plan to deal with it and see what you guys/gals think:
1. Extend the exhaust by a few inches and have it point more down than the prototype. Yes, it may cost a knot or two, but it should help.
2. Have exhaust ceramic coated to contain the heat.
3. Have the cabin heat selector on standoffs or some other insulating material (any suggestions?).
3. Spray on a ceramic insulating paint on the cabin side of the firewall, bottom sub-floor, bottom of floor where your feet are, and both inside and outside of the tunnel (I plan on having carpet going up to the top of the tunnel)
4. Firesleeve all the fuel lines inside the cabin area to help reduce chance of vapor lock.
5. Install the extra louvers in the cowling.
6. If required, I think I will run a duct to the tunnel with an exit toward the back so that fresh air can flow through it.
I have also thought of somehow placing the cabin heat selector on the heat muff itself to help reduce the conductive heat problem, but that might be a big headache.
Yes it will add weight (maybe 10 lbs max) and make it a knot or two slower, but I think it will be worth it in the end.
I would appreciate any insight and further ideas.
Joe Hutchison
RV-10 Tail Kit
glenmthompson
Well Known Member
Been there done that..
We have done all U mentioned, except ceramic coating, which IMHO is not worth the cost, since it will not help the heat significantly... Any more ideas?
Glen
We have done all U mentioned, except ceramic coating, which IMHO is not worth the cost, since it will not help the heat significantly... Any more ideas?
Glen
Ceramic coating
From my experience I think ceramic coating would be a worthwhile option. It reduces radiated temps by 40+%. Coating the firewall any panels in question. I have personally had a "coatings guy" use a blow torch to heat up a piece of stainless, cherry red hot on the uncoated side, then hand it to me to hold (by the coated side of course). It was very comfortable to hold. Pretty "cool" stuff.
From my experience I think ceramic coating would be a worthwhile option. It reduces radiated temps by 40+%. Coating the firewall any panels in question. I have personally had a "coatings guy" use a blow torch to heat up a piece of stainless, cherry red hot on the uncoated side, then hand it to me to hold (by the coated side of course). It was very comfortable to hold. Pretty "cool" stuff.
glenmthompson
Well Known Member
WOW!
Man Wade, sounds like awsome stuff. Any history on chipping, cracking, flexibility etc? Cost? Can it be applied to aluminum, ie, bottom skin aft of firewall, ie, on my 6 before install?
Glen
Man Wade, sounds like awsome stuff. Any history on chipping, cracking, flexibility etc? Cost? Can it be applied to aluminum, ie, bottom skin aft of firewall, ie, on my 6 before install?
Glen
Coatings
I am sorry I cannot answer that , but believe the coatings are baked after being sprayed, but am not sure as to what temp. I did not think to ask, because I was doing steel and stainless. I was planning on coating some stainless sheet to install on top of the aluminium. I would think it best to ask the local or nearest guy you might want to use.
I spent alot of time with the guy I am using, www.Cradin.com (Boerne,TX), since I wanted to be a face to face customer. He is an "old school" A&P, ex-Pratt&Whittney engineer, who brought jet engine coatings to engines and the like. He said that there are alot of different coatings so compare carefully. I have had my IO-360 pistons, intake tubes, and valve covers (heat dispersent) coated. And am going to have the 4 into 1 exhaust, and possibly the cylinders (heat dispersent) and oil pan coated (teflon inside, heat dispersent out). I also plan on installing a venturi pump tunnel for my lower cowl exit so am planning on having some stainless sheet pieces coated, which I will rivet in strategic locations in the tunnel to protect the aluminium.
I have started following you guys on the -10 section because my partner and I plan to build one we when finish our -8. Yeah, yeah, I know that sounds really ambitious!
I am sorry I cannot answer that , but believe the coatings are baked after being sprayed, but am not sure as to what temp. I did not think to ask, because I was doing steel and stainless. I was planning on coating some stainless sheet to install on top of the aluminium. I would think it best to ask the local or nearest guy you might want to use.
I spent alot of time with the guy I am using, www.Cradin.com (Boerne,TX), since I wanted to be a face to face customer. He is an "old school" A&P, ex-Pratt&Whittney engineer, who brought jet engine coatings to engines and the like. He said that there are alot of different coatings so compare carefully. I have had my IO-360 pistons, intake tubes, and valve covers (heat dispersent) coated. And am going to have the 4 into 1 exhaust, and possibly the cylinders (heat dispersent) and oil pan coated (teflon inside, heat dispersent out). I also plan on installing a venturi pump tunnel for my lower cowl exit so am planning on having some stainless sheet pieces coated, which I will rivet in strategic locations in the tunnel to protect the aluminium.
I have started following you guys on the -10 section because my partner and I plan to build one we when finish our -8. Yeah, yeah, I know that sounds really ambitious!
OOPS!
OOPS sorry.
I forgot to answer about cracking. The heated piece he handed me, he then quenched it under cold running water then gave it back and said "bend it". I carefully bent it 90deg and he said "no, really bend it" so I doubled it over one way and back over the next. No cracks! The coating is also TIG weldable, so if you should have an exhaust problem, you don't have to scrape or sand it off, just weld it like it was not there.
OOPS sorry.
I forgot to answer about cracking. The heated piece he handed me, he then quenched it under cold running water then gave it back and said "bend it". I carefully bent it 90deg and he said "no, really bend it" so I doubled it over one way and back over the next. No cracks! The coating is also TIG weldable, so if you should have an exhaust problem, you don't have to scrape or sand it off, just weld it like it was not there.
[email protected]
Well Known Member
The tunnel on my RV10 has always been a little warmer than I would like. Not so hot I could not put my hand on it, but quite hot to touch. I did insulate the bottom of the tunnel with 1" Soundex and used 1" square tube to space the fuel filter/pump up above it. Originally I did not insulate the firewall inside the tunnel because of the difficulty in doing so with the brake lines running up it. Recently I insulated the firewall (on the inside) with some 3/4" firewall insulation I had leftover as well as I could, but not completely, and installed a 90mm computer fan in the top of tunnel fairly far forward and a little to the left to avoid the 2" sceet tube for the back heater. Since it only draws .2 amps I wired it off my USB charging port with a .5 amp fuse. When I turned the battery switch on, I noted that most of the air exited the tunnel through the openings in the seat platform that the control sticks go through. The tunnel does not get warm at all now so this was quite helpful for me.
If the problem with heat is coming from radiant heat from the exhaust pipes it would be helpful to install them as far outboard as possible and angle them down, away from the airframe. This will also reduce the exhaust gas impulses impinging on the bottom skin. I have the Showplanes cowl and Vetterman exhaust which sends the exhaust pipes further outboard than stock systems which reduce radient heat on the tunnel bottom from the exhaust pipes. This setup is quite different from the stock cowl and exhaust so the fan may not be as good a solution for a stock system.
I also had trouble with the tunnel getting hot in cold weather if I used the rear heater. The problem is the sceet is really not insulated at all and there is a lot of heat transfer into the tunnel with the 5 foot section going to the back heater. I solved the problem with some 2” fire sleeve. I pulled it over the sceet to insulate it. There may be a cheaper way to do this but I know the fire sleeve will take the heat. I paid $300 for 6 feet at All Hoses in Las Vegas. That will provide enough to cover both aluminum T’s and both heater hoses.
I tested this afterwards with the rear heat full on and the front vents open so I would not burn my behind. The tunnel did not get warm at all.
If the problem with heat is coming from radiant heat from the exhaust pipes it would be helpful to install them as far outboard as possible and angle them down, away from the airframe. This will also reduce the exhaust gas impulses impinging on the bottom skin. I have the Showplanes cowl and Vetterman exhaust which sends the exhaust pipes further outboard than stock systems which reduce radient heat on the tunnel bottom from the exhaust pipes. This setup is quite different from the stock cowl and exhaust so the fan may not be as good a solution for a stock system.
I also had trouble with the tunnel getting hot in cold weather if I used the rear heater. The problem is the sceet is really not insulated at all and there is a lot of heat transfer into the tunnel with the 5 foot section going to the back heater. I solved the problem with some 2” fire sleeve. I pulled it over the sceet to insulate it. There may be a cheaper way to do this but I know the fire sleeve will take the heat. I paid $300 for 6 feet at All Hoses in Las Vegas. That will provide enough to cover both aluminum T’s and both heater hoses.
I tested this afterwards with the rear heat full on and the front vents open so I would not burn my behind. The tunnel did not get warm at all.
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