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Question for flying RV-10 owners

T

Tom Martin

Well Known Member
I have seven hours on this new RV10, C-GLWM, it is owned by Wayne and Lana Millson, Port Hope, Ontario. For insurance reasons I am flying the 25 hour test period off for Wayne.
Before today's flight I plugged the bottom of the nose gear faring with foam. My theory is that high pressure air is entering this faring and going up into the cowling. I have sealed, with baffle seal material, around the nose gear faring and the lower cowling. There are no louvers and the cowling extends aft of the firewall three inches or so. We did not trim the cowling. Lots of time has been spent on sealing the upper plenum area and getting the inlets sealed and smooth. I speculate that the air that is entering the cowling from the nose gear faring is not only disrupting the cowling exit area but it is allowing high pressure air into the low pressure area of the lower cowling.
After plugging this faring with foam my oil temperatures dropped 10 degrees.
I would like some other flying RV10s to repeat this experiment and see if they notice any differences in engine temps. Simply jam some foam in the bottom, or top of the nose gear faring, thus sealing this large leak into the lower plenum.
 
I plan to do so and will let you know.

I think it would be a good idea to get the louvers in and get the bottom cowl cut back (forward) flush with the firewall. That would be a big help in getting air out. On my Rv9 I cut the bottom at angle forward which lowered the temps more again. The ten is fine flush with the firewall.
 
Good idea, Tom

I've been flying my -10 for two summers now and manage to keep oil temps down to 205 F during climbs in very hot weather, by running 145 MPH or thereabouts, with CHT's going to 405 on the hottest cylinder.

In cruise, oil goes to 195 and CHT to 380, so I haven't been too motivated to change anything but that big hole has made me look for an efficient seal that still allows movement of the hinged nosegear though.

Best,
 
Troy
These first few flights have been made in the hot muggy conditions of Southwestern Ontario and oil temps have been in the 200 range with CHTs in the mid 300s. Plugging this hole in the gear faring seemed to bring the oil temps down 10 degrees to the 190 range. I have yet to install all the wheel pants main gear farings etc. The extra speed gained from these additions should bring temps down even farther. The goal is to have adequate cooling and reduce the associated cooling drag that comes from using more cooling air then is required.
It will be interesting to see if others can see a change from this simple mod or is it just an anomaly with this aircraft.
 
I agree that you should probably get the louvers in and cut back the cowling. It might also be coincidental that as you are getting more hours on the engine the oil temps are naturally coming down. The max temps I see on a sustained climb to 10k' or higher are around 205 before they start dropping while still in the climb. I do have the Airwolf remote oil filter, and I think that it is good for a few degrees of cooling as well. The oil cooler is mounted ont he firewall as per the plans. Max CHT's are in the 360-380 range. This is ijn the hot Altanta summers with ground temps in the 90's on both a cold and a hot engine.
Pierre, it's interesting you have to climb at such a high airspeed. I never climb above 110 knots. I climb at full throttle and 2500 rpms all the way to cruise altitude.

Vic
 
Vic
This is a half time engine, no break in required! I am quite happy with the current temperatures and so see no need to add drag to the airplane with louvers and by cutting the cowling back. I just noted an interesting result from plugging the gear faring and wondered if others would try the experiment. Who knows by plugging that gear faring you might be able to get rid of the louvers :)
 
Thanks for the tip

As someone who is still struggling with temp control, I am going to be giving this one a try.

When you say there are no louvers on the cowl, are you talking about aftermarket units, or the stock ones that come in the kit----the ones that mount on the bottom, inside the cowl?
 
No louvers, and the cowling extends aft of the firewall by at least three inches. Although I do not have a lot of RV10 time I have about 1500 hours of rocket time using the same engine. Rocket cowlings are much tighter and I have learned that proper inlet shape, and sealing leaks, is the key to success. I know that if required I can do some interior ducting on this cowling and drop the temps even more. However if I do that then the drag goes up, speed comes down and I would have to reduce inlet and or outlet area. It takes a bit of work to tune these cooling systems but it can be done. My experiments, as verified by my SARL results, have yielded controlled cooling with reduced drag at power settings that the average RV10 will not see.
 
I'd leave the extension alone

Seems that I read several places about an extended lower cowl reducing turbulence at the exit.

Tom, your temps without fairings look very good and will only get better faired.

Vic, I just favor cruise climbs anyway and besides, I'm only climbing 15 or so MPH higher than you.

Best,
 
How much would cooling improve if we installed cover plates over the two 2" htr intakes and removed muffler wraps/ducting during the hotter months? It seems to me that alot of hot higher pressure air gets released at htr valves. I would think having the hot air dumped overboard closer to outlet would help but would require redesigning the heat valves. Just curious as I am working on spinner now.
 
I have totally removed my heat muff on my rocket and have flown with it that way March -December for the last five years. The difference with the 10 is that you can not remove the whole heat muff system from the pipe. I think you still need to pass air through the heat muff/muffler system or it might over heat. This is certainly a question I would like to ask Larry Vetterman. If, during the summer months, we could remove the heat muff cover and disconnect the two inch hoses this would improve the upper to lower cowling pressure differential and thus cooling.
As a point of interest I have removed the short hoses from the heat boxes and pointed the hoses down at the cowling exit area. This dropped the internal temperature of the cabin tunnel by 5 or 10 degrees. Thus I do not believe that the heat boxes themselves are the main culprit in the tunnel heat issue. We have the aftermarket stainless boxes that seal very well when they are closed. I believe the heat must then be caused by radiant heat and I am going to experiment with some firewall forward and external floor insulation.
 
Tom,
I am curious why the kit provided louvers were not installed?
BTW, WRT the tunnel heat issue, my plan is to run cool air directly into one of the heat valves and warm air into the other. I am going to totally remove the heat muff from one exhaust. Most say that two are not necessary. I plan to dump 50% of the cool air down the tunnel and let it exit out the back. The rest will be used to mix with the heat so I can hae either cool air or warm on the floor.
 
Let us know what you find out. I have cowl heat shield to install as i am sure it would be needed even more as the inner layer of ss on our mufflers would give off more radiant heat even with it 1/2" further away. I think with all of the air moving across our unwrapped mufflers hot spots should not exist.

I also have ss boxes and fiberfrax on inside of tunnel fwd/bottom sides.
 
What Louvers?

I have been flying my RV 10 for a year now with about 100 hrs. I did not install louvers and also extended the bottom of the cowl. I have flown in the heat of interior California and the hot and humid days of the mid west and do not have cooling issues. I am sure the louvers must work but there will be a drag penalty.
As far as heat to the occupants, there is quite a difference in cabin temps between the front and rear seats. At higher altitudes, even in the summer your passengers will be chilly without some heat.
I want to try plugging that nose wheel fairing and see if there is a change.
Wayne
F1 Rocket 500 hrs
 
oil temps

i put the louvers on fter the first few test flights because i was getting high oil temps of around 230+ after a climb when the engine was already hot prior to takeoff. This dropped temps 10 to 15 degrees. I then proceeded do do everything under the sun to get the temps down especially in the middle of our texas summers after hard and hot climbs including your foam thing (well i used sheet metal instead. I mean I tried everything i could do increase the pressure differential from top to bottom. I went with a stewart warner cooler which helped none too much. Final fix was to put the small stewart warner oil cooler in series with the stock one on the right side of the firewall. if you place it right you only need to make one hose by using the original. now in cruise my temps sit at 188 or so. I can climb out at 90 knots all the way to 10,000 feet with an already hot engine and see maybe 220 and as soon as I level off it rapidly drops. I have since sold the RV-10 but I am going to build another one and I am gonna use two coolers from the get go. Probobly two medium size ones.
 
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