I have about 20 hours on the 180 HP RV-9 floatplane and have an issue with high cylinder temps. Rear cyls go to 440 on climb out. Fronts are fine. Have experimented with dams but no change. Changed to -41 carb which helped a bit, but not enough. Baffling is very good and it was always fine on wheels, but with slower speeds in all configurations on floats temps are a bit too high. OATs in Anchorage are generally cool, 70 or so. anyone have any ideas? Am thinking of louvers on each side of bottom cowl, maybe opening bottom a little more. I now have to level off and reduce the power to get temps down 75% level cruise and rears go to 415. Help.
Van's Air Force
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RV-9 floatplane high cylinder temps
- Thread starter questair
- Start date
Louvers will probably work, but before you do check out Tim Olsen's suggestions;
http://www.myrv10.com/N104CD/maintenance/20061022/index.html
even beads of RTV between cylinder heads can help
make sure your baffling is making a good seal, get a flashlight in under the cowling if you can, rub your hand around
http://www.myrv10.com/N104CD/maintenance/20061022/index.html
even beads of RTV between cylinder heads can help
make sure your baffling is making a good seal, get a flashlight in under the cowling if you can, rub your hand around
RV-9 floatplane
here is a picture: http://www.flickr.com/photos/bob_butcher/5989426778
The baffling is very tight. Have put a washer between rear baffling and rear cyl. have experimented with dams. No help. the -041 carb kit helped quite a bit but not enough. Since I did not have the issue on wheels in a hotter climate (Prescott, AZ), I believe the problem is simply the plane does not go as fast through the air on floats as on wheels. Avery has louvers that could be put on each side of the bottom tunnel that might help. has anyone had experience with them. I am even considering a small 3/4" lip on the exit end of the lower cowl. Perhaps a removable one. Plane does around 145 - 150 mph IAS on floats at 75% down low. It has a BA 72 " CS propeller. I put it on Baumman 2100 straight floats. It gets on the step right now and takes off remarkably quick. Empty weight is 1235#.
here is a picture: http://www.flickr.com/photos/bob_butcher/5989426778
The baffling is very tight. Have put a washer between rear baffling and rear cyl. have experimented with dams. No help. the -041 carb kit helped quite a bit but not enough. Since I did not have the issue on wheels in a hotter climate (Prescott, AZ), I believe the problem is simply the plane does not go as fast through the air on floats as on wheels. Avery has louvers that could be put on each side of the bottom tunnel that might help. has anyone had experience with them. I am even considering a small 3/4" lip on the exit end of the lower cowl. Perhaps a removable one. Plane does around 145 - 150 mph IAS on floats at 75% down low. It has a BA 72 " CS propeller. I put it on Baumman 2100 straight floats. It gets on the step right now and takes off remarkably quick. Empty weight is 1235#.
LifeofReiley
Well Known Member
snoop9erdog
Well Known Member
Increased Exit
One suggestion is to increase the exhaust exit to gain an overall upper and lower plenum pressure differential. You may need to do some experimentation with aluminum tape to change the exit sizing/area to find a good temp average. We did this with the Adam A500 Carbon Composite Push Pull aircraft in Denver and this was a major factor to lowering cylinder and cowling temperature.
Correction...to avoid the confusion, I meant a change to the lower plenum exit area rather than a change to the actual exhaust piping area.
One suggestion is to increase the exhaust exit to gain an overall upper and lower plenum pressure differential. You may need to do some experimentation with aluminum tape to change the exit sizing/area to find a good temp average. We did this with the Adam A500 Carbon Composite Push Pull aircraft in Denver and this was a major factor to lowering cylinder and cowling temperature.
Correction...to avoid the confusion, I meant a change to the lower plenum exit area rather than a change to the actual exhaust piping area.
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Tight plenum over cylinders maybe? Some ideas discussed here http://www.vansairforce.com/community/showthread.php?t=81785&highlight=plenum+pictures
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Would you think that putting louvers on the bottom on each side of the tunnel would be effectively the same as opening up the opening on the bottom in the middle? I have even though of putting a NACA duct on the top of the cowling to get more air into the cyls with the thought that it is not a problem getting the air out at the speeds i travel, but getting enough in.
Is that picture taken in Moose Pass? I flew the Super Cub on floats there.
The picture, taken last June, is in the take-off channel at Lake Hood.
N941WR
Legacy Member
I would try the lip. You can either bolt it through the cowling or add some stiffners and platenuts. It won't take much.
150 MPH sea plane is outstanding!
I note your first post says "Rear cyls go to 440 on climb out." You use a different climb speed with floats, compared to climb speed on wheels in the hotter climate?
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The plane will not see the same speeds in climb out as on wheels. On wheels I would climb at 140 MPH or sometimes higher.On floats it is around 110 to 120 at around the same power settings. Rate of climb is less. Lots of drag with those floats and attach fittings.
Sorry for the ignorance, but what are PM's. I have done quite a few things and still would like to know if anyone has experience with opening the lower cowl opening or installing louvers. My baffling is very good, am using cooler spark plugs, have good fuel flows, good oil temps and still have higher cyl temps than i would like. In cruise at 60% with 70f oat the rear cyls run right at 400 and the front at 360. I have to manage climb out to keep temps in the 425 range, but could see 435+ in a climb at full power. thanks everyone for your help.
fl-mike
Well Known Member
I put louvers on my 6A and it helped.
I still have to watch things when heavy, hot, high power, high AoA. You probably have three of those anyway.
My unsubstantiated opinion is that at high AoA the cowl exit airflow is impeded. But, my problem mostly went away, so I just fly. I saw no noticeable impact on speed.
I still have to watch things when heavy, hot, high power, high AoA. You probably have three of those anyway.
My unsubstantiated opinion is that at high AoA the cowl exit airflow is impeded. But, my problem mostly went away, so I just fly. I saw no noticeable impact on speed.
jmbrwn
Well Known Member
Private Messages....look at the top right corner of the page and you'll see number of Unread Messages and Total Messages. Click on blue "Private Messages" to view.
Karl:
I sent you a PM giving you my phone number and saying that I was going to the Airmen's show in Anchorage this weekend. I put a large cowl flap on my RV and it made a huge difference in temps in steep climbs. When you get to altitude you close it and eliminate the drag. Maybe we can meet at the show and I can explain in detail.
Tim
I sent you a PM giving you my phone number and saying that I was going to the Airmen's show in Anchorage this weekend. I put a large cowl flap on my RV and it made a huge difference in temps in steep climbs. When you get to altitude you close it and eliminate the drag. Maybe we can meet at the show and I can explain in detail.
Tim
While on wheels you had to climb at 140 mph to control the temperatures of those same two cylinders? Is that normal?
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snoop9erdog
Well Known Member
"Would you think that putting louvers on the bottom on each side of the tunnel would be effectively the same as opening up the opening on the bottom in the middle? I have even though of putting a NACA duct on the top of the cowling to get more air into the cyls with the thought that it is not a problem getting the air out at the speeds i travel, but getting enough in"
Yes, the louvers shoould accomplish the same effect. That may be the only way to increase area to create a higher delta P without tearing up the bottom of the cowling. It sounds like a previous poster had success. let us know how turns out.
Yes, the louvers shoould accomplish the same effect. That may be the only way to increase area to create a higher delta P without tearing up the bottom of the cowling. It sounds like a previous poster had success. let us know how turns out.
How much did it help? Thanks
frankh
Well Known Member
No one has mentioned a simple fix that can make a significant improvement.
Take the top cowl off and with a flashlight look very carefully down between the fins between the valves...Often the gaps between the fins are blocked with casting flashing..I have seen excess flashing almost blocking (in some cases completely blocking) the airflow path on 50% of the engines I've looked at. Even a single gap completely bocked will have a significant impact.
I had to use a drill to poke a hole in the blockage and then file it open.
My CHT's dropped 20 degrees on my #4 cyl when I did this.
Frank
Take the top cowl off and with a flashlight look very carefully down between the fins between the valves...Often the gaps between the fins are blocked with casting flashing..I have seen excess flashing almost blocking (in some cases completely blocking) the airflow path on 50% of the engines I've looked at. Even a single gap completely bocked will have a significant impact.
I had to use a drill to poke a hole in the blockage and then file it open.
My CHT's dropped 20 degrees on my #4 cyl when I did this.
Frank
Thanks Frank. I had done exactly what you suggested last summer and found no blockage. The temps were just fine on wheels when i cruised and climbed so much faster, so i have been assuming that it is just a matter of getting more air over and through the cyls. So far from what i have read and researched, that will require either opening up the bottom cowl, putting louvers on the bottom, perhaps building a plenum, putting a lip on the bottom cowl, or even considering using a NACA duct on the top cowl to get more air in. I will start using the least invasive measure and see how that works before going to the next measure. I will put on a temp lip first. I suspect that opening the bottom a bit combined with the louvers will be a big help. I will let you know. By the way, i asked someone at Van's last summer and got no help whatsoever. When they heard i had 180 HP and was on floats, that was about the end of the conversation in terms of getting any help. The guy could not suppress his curiosity however and did ask some questions about the floats. Thanks everyone for the comments. Karl
At the fundamental level, there are two ways to increase cooling.
(1) Increase the quantity of cooling mass passing through the system, i.e. flow more air. The classic example is a larger cowl exit, adding louvers, or increasing climb speed.
(2) Increase the transfer of heat to the cooling mass, i.e. raise the delta between inlet and outlet air temperature. Classic examples would be better baffling and sealing, or fin details like Frank relates above, or other changes.
If your installation does not match the temperature norm for RV9's with stock cowls (standard mass flows), then you probably have a heat transfer problem. Given the 140 mph climb speed for good cooling and two, not four, hot cylinders, I think you need heat transfer work.
(1) Increase the quantity of cooling mass passing through the system, i.e. flow more air. The classic example is a larger cowl exit, adding louvers, or increasing climb speed.
(2) Increase the transfer of heat to the cooling mass, i.e. raise the delta between inlet and outlet air temperature. Classic examples would be better baffling and sealing, or fin details like Frank relates above, or other changes.
If your installation does not match the temperature norm for RV9's with stock cowls (standard mass flows), then you probably have a heat transfer problem. Given the 140 mph climb speed for good cooling and two, not four, hot cylinders, I think you need heat transfer work.
MauiLvrs
Well Known Member
Opening the exit is easier ... cost less ... (been there ... done that ... works like a champ on the A)
And most likely works better (at least on the bottom on each side of the tunnel).
Go look where Archers and Bonanzas have their louvers (on/around the bottom corner)...
Getting more air in ... means ... need away to get it out...
Starting with bigger exit ... may not need to get more in...
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MauiLvrs
Well Known Member
Before opening the cowl exit 5/8 inch: who knows how high they would go. Well above 470
. Cruise 380-410.After opening the cowl exit 5/8 inch: 450 max and usually 430 climb. Cruise around 368-380
With opened cowl and drilling jet from #42 to #40 380-410 climb. Cruise 330-350.
smokyray
Well Known Member
Cool it...
Karl,
Many years ago I met Canadian Bush Pilot Eustace Bowhay at OSH and closely examined his RV-6F, the first ever RV on floats. His 0-360 cowling was stock but he did have a "20 degree forward slice" on the lower lip which was common for the 0-360 then. I have it on my current "X" Factor and my 0-320 CHT's actually run almost too cool. The "slice" opens the cowl approximately 5% and was noticeable. Later, I think he added a cockpit adjustable cowl flap.
FYI...
Smokey
http://www.vansaircraft.com/public/amphib.htm
Karl,
Many years ago I met Canadian Bush Pilot Eustace Bowhay at OSH and closely examined his RV-6F, the first ever RV on floats. His 0-360 cowling was stock but he did have a "20 degree forward slice" on the lower lip which was common for the 0-360 then. I have it on my current "X" Factor and my 0-320 CHT's actually run almost too cool. The "slice" opens the cowl approximately 5% and was noticeable. Later, I think he added a cockpit adjustable cowl flap.
FYI...
Smokey
http://www.vansaircraft.com/public/amphib.htm
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Doug
Well Known Member
Ok, I'll admit I'm lost with this description. What I am picturing is the bottom lip of the cowling air outlet drooped down about 20 degrees from say 2" forward of the firewall. Correct? Photo?
I would like to reduce the CHTs on my '6 and have followed the various threads on the subject. I am forming the opinion that the 6/7 lower cowling does not do a good job of turning the exit air through the 90 degree bend and accelerating it through the exit. I think the 20 degree droop is more critical than the increase in area and achieves a similar result to louvers by ejecting the air before it makes the turn.
In time I will build some deflectors but my problems are not at all critical like questair's.
smokyray
Well Known Member
Make the cut
Doug,
Here is a photo of my RVX lower cowling which hopefully helps with the description.
V/R
Smokey
The "X" Factor lower cowling
Doug,
Here is a photo of my RVX lower cowling which hopefully helps with the description.
V/R
Smokey
The "X" Factor lower cowling
I really appreciate all the suggestions. Thanks for taking the time to offer your help. I am forming the opinion that putting louvers on the bottom on each side of the tunnel would do somewhat the same as opening up the bottom of the cowl either with the slice or just cutting the opening the 5/8" or more as also suggested. I have already put in the -41 carb kit and am getting the proper fuel flows. When i get back to Anchorage in a week or so, i will make the decision. i am leaning towards the louvers because I can install them in such a manner that when not needed ( on wheels for example) i can slide in a plate to cover them. I just hope that it is not because i am getting insufficient air into the cowl at the lower speeds that is causing the overheating. i would not want to put a NACA duct on the cowling unless absolutely. We shall see.
southtarnation
Well Known Member
So am I right to state that this is the only the 2nd ever RV- on floats of any kind? I would love to hear more about your -9F. If you find the time maybe you could add it to the "Virtual Hanger" section? Id like to learn more about if you chose the -9 for the purpose of floats or if it was an after thought. Some pictures and info on how you made your attach points and some of your thought processes throughout the conversion.
Tip of my VAF hat to you Sir!
Tip of my VAF hat to you Sir!
There are presently two RV's that i know of on floats. the third, a 6 was removed from floats long ago. The 7 is on a set of Clamar Amphibs. I converted my 9A to a 9 so the front motor mount could be used for the front float attachments. I never thought about floats initially in flying the 9A. However i saw Trey Johnson's 7 on floats and thought that the 9's wing and larger tail surfaces would make for a better float plane than the 7. After converting to the 9, i flew it to my summer home, Anchorage, and the process began with me purchasing a set of 2100 Baumman straight floats. I had fittings fabricated and used the only set of rear float fittings left after Trey put is 7 on floats. They had to be adapted, because they attached to the rear wing spar bolt which we enlarged to 3/8's. The flap hangar( not found on the 7) interfered with the float strut attachment that connected with the fuselage attachment so we used a heavy wing strut fork screwed into the float strut which while plenty strong was smaller in diameter than a conventional float strut fitting. By being able to screw in in and out it facilitated the development of the proper throat angle. There was quite a bit of test flying to get the throat opening and float location under the fuselage correct. The first test flight was real exciting and close to a bad result. But we got it right and it flies very well with no bad flight or water handling issues. Empty weight is slightly over 1200# and i use 1900 as my gross. Floats are oversize and while they present some additional drag are quite light and the plane gets on the step right now and off the water in less than 10 seconds at gross, less at lighter weights or into a wind which we often have in Anchorage. That airfoil on the 9 is so much better than the other RV series for the low flying speeds that are important to short field performance. The low DA we have in Anchorage certainly helps as well. I wanted a go fast float plane that would use little fuel and get off of the short lakes that i have been using over the years. I no longer feel a need to take more than one person at a time flying. It is certainly less stressful being responsible for only one and especially if it is a spouse. Loading is an issue as everything has to be loaded from the wing top. rain will get you and the inside of the plane wet when loading and getting in and out. we do not have many docks we use, so docking which could be an issue for a low wing is not a problem. I no longer pull up to a river bank, but didn't do much of that anyway. It is easy to step off the front of the float with the step I installed on the front float step. Fueling is much easier as now i don't have to climb up to the top of the wing to fuel it. flying into short lakes takes some getting used to at first because the wing obscures your vision of exactly how close to the water you are. but I have figured that out. same for glassy water landings. but you really can't see how high you are anyway so i just set up a constant descent and feel my way on. Overall this has been mostly a success and once i figure out how to get the CHT's down a bit will be even better. Hey 150 MPH on floats makes up for some other shortcomings. sorry, but I just cannot figure a way to post photos. Karl
fl-mike
Well Known Member
Sorry for the delay.
Two louver plates, bottom of the cowl, one each side of the tunnel.
I saw an CHT improvement of about 18F.
6A, 180hp, FP, carb, half EI (Plasma II)
Fix worked
I installed 10 louvers on each side of the tunnel under the cowl and opened up the tunnel by 2". Max temp I saw afterward was 430 in a sustained high power best angle climb starting at 385 degrees. In cruise at 75% highest cyl was 385 and lowest 360. Very acceptable temps. The fix reduced temps by at least 25 degrees, maybe even more since I may not have allowed temps to to go higher than 450 when flying before the fix. IAS @ 5,000msl at 75% is 147mph on floats. TAS is around 157. Pretty cool! Thanks to all for their suggestions. Karl
I installed 10 louvers on each side of the tunnel under the cowl and opened up the tunnel by 2". Max temp I saw afterward was 430 in a sustained high power best angle climb starting at 385 degrees. In cruise at 75% highest cyl was 385 and lowest 360. Very acceptable temps. The fix reduced temps by at least 25 degrees, maybe even more since I may not have allowed temps to to go higher than 450 when flying before the fix. IAS @ 5,000msl at 75% is 147mph on floats. TAS is around 157. Pretty cool! Thanks to all for their suggestions. Karl
Sunriver Ken
Well Known Member
Louvers Worked for Me
I installed the Avery louvers in my 9A and they seemed to drop CHTs about 20F. That said, I still need to climb out at around 120KIAS to keep the CHTs down. I also reduce to around 2,500 RPM within two minutes of takeoff. I am running an O-360 that has been balanced, ported and polished and have a C/S Simitar prop. Louvers are an easy mod. I can send project pictures if that would help.
I installed the Avery louvers in my 9A and they seemed to drop CHTs about 20F. That said, I still need to climb out at around 120KIAS to keep the CHTs down. I also reduce to around 2,500 RPM within two minutes of takeoff. I am running an O-360 that has been balanced, ported and polished and have a C/S Simitar prop. Louvers are an easy mod. I can send project pictures if that would help.
This is an update on my RV9 floatplane. After putting the louvers and cutting back on the tunnel a couple inches, temps were acceptable. The take off was quite short and landings acceptable. I just changed from my hartzel blended airfoil 72" prop to a MT 210 constant speed( 83") prop. That resulted in taking 15 # off the nose. The results are almost unbelievable. The plane now handles much better and the landing and takeoffs are much better with the weight off the nose. It will get on the step right now and takeoffs into a 8 mph wind with me (230#) and full fuel take around 6 seconds at sea level. That contrasts with around 10 to 12 seconds with the blended airfoil. cruise speed at 23 sq is 138 mph and 150 at 25 sq all at 500MSL. Just wish I had a baggage door to assist in loading it.
rv10 on floats
karl,
Would be very much interested in your thoughts on how an RV10 would handle/perform with floats?
ajay
karl,
Would be very much interested in your thoughts on how an RV10 would handle/perform with floats?
ajay
