Tunnels Tips

I wanted to pass on a suggestion for those looking to keep their RV 10 TUNNEL cool. Take your Black & Decker Wet vac and hook the hose to the blower/discharge air. Then place the hose over one of the heat vents on the firewall simulating hot air blowing into the cabin. Close the vents and see if air is still entering the cabin with the vents shut and the wet vac blowing air into the vent on the firewall side. What we discovered was alot of air was entering the OPPOSITE vent when both were closed. The air was coming in under the hinge on the vent door. When I placed a small aluminum divider between the air vents on the firewall the air ceased leaking into the cabin tunnel. After playing with a few DEFLECTOR designs, I used the inside mounting bolt on the vent box to hold a deflector in place and then also put an 1/8 inch deflector inside the vent box so air could not sneak under the front of the vent door. This should solve the problem with HOT air entering the Tunnel with the vents CLOSED. There still may be a Radiant heat problem but insulation on the firewall and tunnel floor and silicone between the firewall and vent box helps for Radiant heat. I have pics if anyone is interested.

Dean
40449

Tunnel Fix

We are certainly interested in your Tunnel Fix. Can you post the photos here? If not send them to [email protected].

Our louvers on the bottom of the tunnel had no effect on removing heat. Tunnel is still very hot to the touch.

N331JH

Sorry, I must loudly announce...

I truly am getting the reputation as one who repeats himself, but please for the umpteenth time. THE VAST MAJORITY, IF NOT ALL THE HEAT IS COMING INTO THE TUNNEL VIA CONVECTED, AND/OR RADIATED HEAT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! OK?????????????
The first flight in N331JH is the only flight that had the heat muffs hooked up for cabin heat. I repeat, I repeat, I repeat......This plane has ONLY THE FRESH AIR FROM THE CABIN HEAT S U P P L Y ducts installed. As in blowing HUGE amounts of cool air, directly from the plenum into the tunnel. Is anybody listening? CABIN HEAT IS N O T THE ISSUE. Period, end of discussion, please do not distract from an obvious design flaw. I will most enthisiastically entertain objective commentary on this subject, especially anybody who has over 100 hrs in an RV-10 and been working on hot tunnels for months...like myself.
Glen

glenmthompson, You are absolutely correct. You can remove both heat scat tubes entirely and tape over the heat duct valves with stainless tape and fly the aircraft only to get burned literally! I also have stuffed the aircraft I worked on with insulation with only minor success. This is a design flaw that Vans has only provided a bandaid fix for and should be giving utmost attention to before serious consequences occur.

Brules U R my HERO!

brules said:

glenmthompson, You are absolutely correct. You can remove both heat scat tubes entirely and tape over the heat duct valves with stainless tape and fly the aircraft only to get burned literally! I also have stuffed the aircraft I worked on with insulation with only minor success. This is a design flaw that Vans has only provided a bandaid fix for and should be giving utmost attention to before serious consequences occur.

Click to expand...

Thanks dude! I thought I was the only one out there who realized there is a significant problem in this area! I also spoke with a fellow RV'r who said a certain 10 driver had a 100% engine failure (to an off field landing), and hhhmmm, guess what? They later could not find ANY engine or fuel problem!! Well, of course except for the fact the boiling fuel in the tunnel can cause this, up to vapor lock/engine failure and has to me on several occasions (albiet mine was just a minor, short, heart pounding event).
Maybe my incessent whining about this will lead to a permanent/professional/safe/easy/cheap solution...As in..hhhmmm..Maybe continuing the false floor under the tunnel too? HHmm, where have I heard that before? lol...hahaha
Glen

I understand that the RV10 has the dual muffler setup, and I also understand that they (The muffler/heat exchanger combo) run hotter...providing great heat when you want it.

What about only disconnecting the scat from the firewall flapper valve, and exhausting that air into the cowl exit?

I just wonder if, with both scat tubes disconnected, there is no air flowing through the heat exchanger part of the mufflers, allowing them to radiate more heat. If this is at all happening, I just thought that running the scat from the baffles, through the heat shroud, and then out the cowl exit would remove heat from these, and into the airstream...reducing the radiated heat.

This might be a dumb question, but what is all of this heat doing to the strength and fatigue life of the aluminum?

PJ
RV-10 #40032

Cold air?

Why not just put some cold air into the tunnel? Bring a 1 or 2" scat from the baffle down to the firewall and direct it into the tunnel. Thus you have a continous flow of cooling air inside the tunnel. The cold air will just run out the back along with the elevator push tube... and then out the tailcone.

This could be tried temporarily by using one of the heat shuttles by removing the heat to the shuttle and then instead, route cold air to the shuttle from the baffle inlet. Then go inside the tunnel and remove the same shuttle's hose in there thus dumping the cold air into the tunnel. All easily reversed if you are not happy. If it works, rehook up the heat shuttle and then punch a 1 or 2" hole through the firewall into the tunnel and duct cold air to it permanently.

cl

chickenlips, I believe some have already tried this approach by reading earlier posts, and have also installed cutouts below to evacuate the tunnel air with limited or no success. Is the tailcone providing suction and a route for the bleed air you suggest a way to escape, or is the tailcone air under pressure? This is going to require testing, and my question is... did Vans know about this from the start and hurry this aircraft to market? I keep getting the impression that as far as they are concerned this is a trivial matter and it's really not! Has anybody heard if a design change is pending on future 10 kits?

Chickenlips, one item I forgot to mention, before people start cutting 2 inch holes in their firewalls for a scat blast tube as suggested. If there should be a fire this hole is now a direct route for the heat and flame to breach the firewall and enter the cabin with no means of closing the hole.

Cool air for tunnel

Add a NACA duct (or 2) like the one for the eyeball vents at the panel. Put it (or them) down low on the side of the fuse. run scat to the tunnel at the floor level, behind the rudder pedals.

No holes in firewall to worry about.

AND, seal the aileron linkage cutouts with something like a shifter boot.

False floor, insulation.

My $.02

Mike

MikeS, The false floor concept has been mentioned several times and has possibilities. If/when someone has a 10 flying with that configuration can we get some data? Perhaps fly with a thermometer before the install and after for comparrison so we know how much good it does ? And then add the blast cool air and measure that ? Building the floor in during construction would be easier than a retrofit later!

Well, if you are willing to wait, I will do basicly that----------only trouble is I am still at the start of my -10, hope to jump into it full time soon, but I have a house get sold first.

Mike

AAARRGGHH!.....deep breath... aaahhhhhh

Chickenlips said:

Why not just put some cold air into the tunnel? Bring a 1 or 2" scat from the baffle down to the firewall and direct it into the tunnel. Thus you have a continous flow of cooling air inside the tunnel. The cold air will just run out the back along with the elevator push tube... and then out the tailcone.

This could be tried temporarily by using one of the heat shuttles by removing the heat to the shuttle and then instead, route cold air to the shuttle from the baffle inlet. Then go inside the tunnel and remove the same shuttle's hose in there thus dumping the cold air into the tunnel. All easily reversed if you are not happy. If it works, rehook up the heat shuttle and then punch a 1 or 2" hole through the firewall into the tunnel and duct cold air to it permanently.

cl

Click to expand...

Hey Chicken lips...If ya read mine and other posts, the amount of air it takes to cool the tunnel to even remotely acceptable levels, is absolutely imense! As in, BOTH cabin heat supply ducts (read fresh air, no heat muffs connected) entering the tunnel with the cabin heat valves wired wide open! And, as myself and others have mentioned, this is merely a bandaide, not a solution. Remember, for the umteenth time please. The heat is radiating/conducting through the firewall and bottom skin, and "cooking" the tunnel. NOT FROM THE CABIN HEAT VALVES!!! OR THE EXHAUST GASSES! I and others have proven this!
The solution HAS TO BE from the prevention of heat entering the tunnel. IMH(but experienced)O, by a false floor on the bottom, and insulating the firewall from the FRONT side. This false bottom installed after flying the plane, would be a rather huge chore. My advise to all again...*****************************Continue the false floor through the tunnel and mount all gas lines/pumps/flow transducers, etc., up away from bottom, and maybe divert some cabin vent air for safety and hot days.
Glen***************
(PS TO Vans and others. Let me be put on record, that Vans suggestion via SB, is a total failure in their attempt to keep the tunnel cool, unless of course you never fly on a day above, say, 40 deg F.*******************

doing it...

so as i build my forward fuse section, i'm trying to head off the hot tunnel at the pass, and i had a few questions for anyone, or Glen specifically. if i continue the false floor into the tunnel, how far back do you think it needs to go? as i see it, you could probably only go to the butt position of the front seat occupants until it ran into some linkages - is this correct? how about room for the fuel pumps etc? if i make the floor the same height as where you put your feet, will i run out of room for the pump? from pics of the area, it doesn't look to be a problem, but i don't have the hardware in hand as of yet, so i want to be sure... also, Glen - here's a question... in your experience, does it get hot where you put your feet? it seems like if it doesn't, then the false floor and insulation is going to be a "for sure" fix. right?

cj

Here ya go..

conlimon said:

so as i build my forward fuse section, i'm trying to head off the hot tunnel at the pass, and i had a few questions for anyone, or Glen specifically. if i continue the false floor into the tunnel, how far back do you think it needs to go? as i see it, you could probably only go to the butt position of the front seat occupants until it ran into some linkages - is this correct? how about room for the fuel pumps etc? if i make the floor the same height as where you put your feet, will i run out of room for the pump? from pics of the area, it doesn't look to be a problem, but i don't have the hardware in hand as of yet, so i want to be sure... also, Glen - here's a question... in your experience, does it get hot where you put your feet? it seems like if it doesn't, then the false floor and insulation is going to be a "for sure" fix. right?

cj

Click to expand...

Ok limonsito....
1.) If U comtinue the floor across the bottom, there will be plenty of room for a B-767 size fuel pump,FF, etc. IMHO, if it were MY plane, I would actually make the floor higher, say 3 or 4 inches higher then the front seats floor, to allow MORE insulation. Maybe urethane foam? Like minimal expanding for example? PLENTY of room for even higher "floor" level if desired.
**
2.) As far as how far back, well, that is a problem. You obviously need to stop at the fwd part of the carry through box. Aft of that there is NO ROOM below the elev. push rod....This brings up another issue. The passenger tunnel area. Today after Brent and Jim insulated the WHOLE firewall with a double sided, pretty cool mylar heat barrier, the whole tunnel fwd and aft of the spar was still SCALDING HOT all the way back to the flap torque tube covers. As in the whole tunnel area in the pax compartment.BTW...I COULD PUT MY BARE FEET ON THE FIREWALL LADIES AND GENTLEMEN!
**
3. There is no room below the elev push tube to insulate the floor in the pax tunnel area.
**
4. The floor as I have said quite a few times, is VERY cool to the touch in the cockpit area. So...IMHO, yep, an insulated floor is the only way to go. The thicker, more insulated floor the better. VERY minimal weight increase.
**
5. ONE CAVEOT guys and gals..Remember your feet are above free air, outside the aft part of the "chin", not heated by the engine exhaust or cooling air, so this is why it is obviously pretty cool, and why I recommend a REALLY thickly insulated area inside the tunnel.
Hope this helps. I for one have given up, but will ALWAYS~entertain questions and objective PM comments.
Glen

Another thought

Here's something I'm planning on doing soon. I'm aware of at least one other non-flying -10 builder who also did this. Basically it involves insulating the firewall on the forward / engine side. I've ordered and received a new shiny new 4' x 4' piece of .020 stainless, I also got some Fiberfrax from ACS, which is a heat barrier material I used on a Long-EZ firewall. (I'm also investigating a material called ZETEX that the Lancair guys use for the same purpose). I'll then attach the new/"Faux" firewall to the insulating material creating an insulating 'sandwich'. I figure this should be good for eliminating/reducing most of the heat that radiates from within the cowl. It will add about 3 lbs at a fwd cg that I'll counter with a composite prop. (I've also ordered ceramic coated exhausts).

Deems

Awsome!

Deems Davis said:

Here's something I'm planning on doing soon. I'm aware of at least one other non-flying -10 builder who also did this. Basically it involves insulating the firewall on the forward / engine side. I've ordered and received a new shiny new 4' x 4' piece of .020 stainless, I also got some Fiberfrax from ACS, which is a heat barrier material I used on a Long-EZ firewall. (I'm also investigating a material called ZETEX that the Lancair guys use for the same purpose). I'll then attach the new/"Faux" firewall to the insulating material creating an insulating 'sandwich'. I figure this should be good for eliminating/reducing most of the heat that radiates from within the cowl. It will add about 3 lbs at a fwd cg that I'll counter with a composite prop. (I've also ordered ceramic coated exhausts).

Deems

Click to expand...

Hey Deems..AWSOME idea dude! Yes, this is heavier, but probably a whole lot better idea, since with your idea, it will (hopefully) keep the heat out of the inside of the plane, unlike my double floor idea. I love the way you think!
It will also look better IMHO, cuz it will be stainless instead of paint catching all those nasty exhaust fumes, and vaporized oil.
Glen
PS, see my next blog for a revelation.

Finally, a "sort of" revelation today!!!!!!!!!!!!

This morning, Jim had me install 2, 4"x12" "gills", just like the ones we put on the cowling side. These were installed in the bottom of the cowl, on each side of the "chin". The aft edge of the gills, is 4 inches fwd of the firewall(Maybe yuz guys could bug Brent for some fotos).
When I opened up the square hole, the vetterman muffler was actually touching the cowl. So, it appears that the heat from the mufflers (read HUGE heat genetaror of rather large size), would/should exit rather rapidly there.
Well, guess what??? To sum up, this made a HUGE difference! When I flew Jim yesterday, before the new gills, we both burned or hands messing around with where the heat was coming from. The more fwd toward the firewall one went, the hotter the tunnel got, as well as the lower one puts their hand. Back seat was untouchable. At that point, to sum up to date, we had the following:
*****One 2" scat duct from plenum blowing into front of tunnel per Vans (worthless) SB.
***** Both cabin heats were disconnected.
*****The other 2" cabin heat fresh air was taped off.
***** Entire firewall on front side is insulated with mylar heat shield.
*****Aft firewall side insulated with same.
*****Bottom fus. skin insulated with same, inside tunnel only.
*****Under pax tunnel area, gills installed to let air vent out.
************With all the above, one can literally fry egges on the tunnel. If the second 2" fresh air scat is hooked up, blowing into tunnel, it is BARELY acceptable temp wise, and at cruise, barely warm, at say 8000'.

**************Now fast fwd to today. Two additional gills installed, the tunnel is as follows on this 85 deg Fl. day:
@@@@@Beginning @ firewall, sides of tunnel are now room temp. Top slightly warm
@@@@@Move aft say 16", sides are barely warm, top, I guess 115 deg F, and side near floor almost cool.
@@@@@ When one moves aft to about the fuel selector, it starts to get warm, but not too bad as to scare pax.
@@@@@ Pax area, tunnel is same freaking scalding hot.
@@@@@Felt floor (bare bottom skin) under pilot seat, about 2 " laterally of tunnel sides. Floor was scalding hot just like most RV floors are aft of cowl exhaust.
############Jim wants to try straight pipes now, with an elbow that move sexhaust laterally, hence ridding the heat sink of the muffler/cabin heat assy. and blowing exhaust sideway, instead of down, like tried previously. We will also he says, cover up the gill under pzx tunnel area, since seems to do no good, and also lets in exhaust gasses in the pattern.
%%%%%%%%% Don't shoot me, I am just the very vocal messenger, BUT, this pretty much solidifies my theories/observations that the heat is radiated/convected into the tunnel from engine heatand/or exhaust gasses/muffler heat.
Glen

So,

again, if you left the scat connection intact from baffles to muffler shroud, and from muffler shroud ran scat tube to exit of cowl, it would seem that it would extract the heat from the mufflers and out the cowl, hence keeping the mufflers cool.

Of course the mufflers bake and radiate when they are simply surrounded by a shroud which gets no cooling....

An thoughts on trying this out?

My theory

I believe that this heat problem is also a by-product of the cowl design. In talking to Will James he believes that the cowl inlets are too large and that as a result, a lot of the air that comes in through the inlets ALSO exits the same place, i.e back out the front of the cowl!!!! that implies that there is a lot of turblent airflow within the cowl which give the air a lot longer time to heat-up. Apparently the 'louvers' that Van's has on the bottom of the cowl were an attempt to equalize the pressure and provide a more efficient airflow. I'm not sure this is being achieved. Will sees 7-10 mph gains from his cowl and plenum on the RV installations, that also implies that there's a bunch of drag associated with the cowl. I believe/hope that the addition of a plenum which directs the cooling air more efficiently, along with the reduced cowl inlet size, coupled with ceramic coated exhausts, coupled with a 'faux' firewall, should make a dent in this situation. ..... I'll know for sure sometime next year.

Deems

Deems Davis- Yes, Yes, Yes! I have thought that the air entering the cowl was either restricted from exiting and superheating the engine compartment or turbulating within. In either case it's getting too hot in the engine compartment! Cowl flaps, a larger exit tunnel or inlet air changes are all ideas that should be investigated.

Almost a good idea....

As far as the keeping the heat muffs cool, seems to me a great idea that fails in application. If you have the heat muffs blowing the fresh air throuigh the shrouds, well, the heat still has to exit the "chin" out the back of the bottom of the cowling, hence "cooking" the fuselage bottom and firewall.
Please note to all....Seems we have finally cured the fwd tunnel heat problem with the extra cowl bottom gills, BUT,,, MY FRIENDS<<<<<<<<<
The aft tunnel in the pax area is still scalding hot, top to bottom, hence, therefor, in conclusion, etc. the hot air that makes it way back is STILL a problem. but, I love the way we are thinking.
(Note to self, please stop dreaming about how to finally and formally fix the tunnel problem, haha)
Glen

Bingo Mr. Brules!

brules said:

Deems Davis- Yes, Yes, Yes! I have thought that the air entering the cowl was either restricted from exiting and superheating the engine compartment or turbulating within. In either case it's getting too hot in the engine compartment! Cowl flaps, a larger exit tunnel or inlet air changes are all ideas that should be investigated.

Click to expand...

I agree...

Hot Tunnels?

I have not seen anything about tunnel heat for quite some time. I would like to know if -10s flying with the Sam James cowl have any hot tunnel issues. How about those with the firewall insulated on the front side?

Summer is coming and so is tunnel heat!

dmaib said:

I have not seen anything about tunnel heat for quite some time. I would like to know if -10s flying with the Sam James cowl have any hot tunnel issues. How about those with the firewall insulated on the front side?

Click to expand...

Winter rolled around!


But it will reappear this weekend when temperatures across the US are warming up! I've heard Gore is attributing global warming to tunnel heat.