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Butterflies make RV-10's a whole lot faster!!!

G

glenmthompson

Well Known Member
Currently flying Jim in his Butterfly painted 331JH to visit his family and to attend his 60'th high school renunion. We are waiting for the WX to get above 1000 BKN at LIT and I just had to log on and tell the world what this plane is doing right now.
First, I must say (DUH!), I have had no fear about spreading some of the less than perfect RV 10 facts, ie..hot tunnel, somewhat indequate elevator authority at fwd cg's and what appeared to be slower than advertised numbers...Well, God has smiled on 331JH and I flew it in total awe and amazement yesterday as we flew from southern Fl to LIT. The plane now has been painted, flaps and ailerons tweaks, "gills" added to side of cowling (read - tunnel MUCH, MUCH cooler since now TONS of hot air now leaves the sides instead of all out the bottom of the cowl).,installed a small rudder trim tab to have a perfectly centered ball. On this trip, elevator was perfectly level with stab at 160 mph IAS, read, a lot less drag I assume.
Now in my normal bullet statement style what I/we observed.
****GTOW right at 2500 lbs, did not calculate CG, but felt pretty far aft, but obviously from past flying not at aft limit.
**** The UNBELIEVABLE data I/we collected.:
****3500 ft, WOT,2450 RPM 27" MP, leaned best power( listen..... low comp. pistons, so do not have a fit)...Oh my God R U ready????
191 KTAS ! ! ! That is 219 MPH TAS!!!!
****8500 ft, WOT, 2350 RPM, LBP( leaned best power), 181 KTAS, or 208 MPH TAS! A good bit faster than what Vans says we should be getting, and we have only 260 HP!!!!
***** Efis 1 TAS was confirmed and verified accurate by flying into the wind (referenced by winds on E-1), then 180 turn to take TAS/GS average. (No more boxes for me) I had my 296 also, to confirm any difference in ground speeds...there was none BTW. I also noted that the winds on the E-1 were/appeared to be dead nuts accurate based on TAS/GS calcs.
***** I had to reach under panel and pinch off tube running to stby A/S ind. due to the fact it bleeds down slightly, allowing some pressure in pitot line to lower the CAS in the E-1......Yet another discussion I guess for the Inst. forum.

Now, Jim just advised me we now have VFR weather and we are leaving to take more data and have more fun. OH, BTW, we Flew from West Palm area to Little Rock in 5.7 hrs, burned 81 gallons, and abused the heck out of our facial smiling muscles!!!!!
My quick opinion of all this is first it takes quite a while to accelerate to these speeds on autopilot in smooth air, and additionally, we lost 4 KIAS knots instantly when it got bumpy. This extra patience along with the more broken in engine, aft CG and paint and tweaking is my first guess why we are SOOOOOO MUCH faster now. Of course, other than devine intervention...
I am hurridly writing this to get it on the web so if there are any on the fence buyers who are not pleased by mine and other slow RV 10 reports, they can temper their 10 purchases with this info.
All I can say is.......I am amazed and am so sincerely sorry for EVER doubting Vans. I for one am eating a small portion of crow and sincerely apologize for ever doubting this unbelievable plane and company.
Also, Craig at Catto tells me that Noel Simmons is getting HUGE speeds out of his Catto 3 blade fire breathing Lycosorous, I hear even faster than these speeds..(Ok, I also hear 310 HP, but hey, who's counting?)....Where are those posts?
More to come......
Glen
 
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good to see high TAS for RV10

Glen
thanks for the post and more to the point the reassurance about the speed numbers...now you need to go to work to get the insurance premium down then you'll be my hero....
FWIW i got my first quote for the RV10 with 130K hull value is $2,800/yr ..premium for a comparable certified plane (ie. same hull value, retractable, same pilot) is half of that...there goes the economic advantage of an experimental
Son RV10 airframe completed
 
glenmthompson said:
The plane now has been painted, flaps and ailerons tweaks, "gills" added to side of cowling Glen
Click to expand...

Flap and aileron tweeks??????

You have always said the airplane was rigged perfectly, and that it was just plain slooooow. :D

Glad to hear you are getting better than advertised speeds.
 
Butterfly Wings

PJSeipel said:
Got any pictures??
Click to expand...

RV-10_Butterfly_01.jpg
 
Almost tweaked!!!

rvbuilder2002 said:
Flap and aileron tweeks??????

You have always said the airplane was rigged perfectly, and that it was just plain slooooow. :D

Glad to hear you are getting better than advertised speeds.
Click to expand...
.
.
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In reference to one of my first posts regarding my whining about the speeds, was a note that the plane had a slight roll to the left, very slight....ball slightly, ever so slightly touching the left lubber line, and the ailerons were about 1/4" below the wing tips. I had a small discussion also with someone concerning how his plane sped up once his ailerons were rigged correctly. Hmm, who knows, maybe the slight reflexing of the flaps to match the lower ailerons was a big difference? I cannot help but think too the pretty good aft CG we had mad a difference. When I was testing the plane, I loaded the CG to the aft limit, but did not do any REAL speed checks at the aft limit, just speed checks with an "after" CG.
The final numbers to fly from West Palm beach to 8K2 (Harper Kansas with a tour over Anthony Kansas, and a 180 turn to check TAS, are as follows.... 9.3 hrs total flying time, 113 gallons of liquid gold, 2 quarts of oil, alot of sore facial muscles, and an easy 201 MPH TAS the whole way! (Autopilot contributed significantly IMHO to the higher TAS, providing an overall more stable platform.)
 
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Glen, in the interest of saving a lot of folks the trouble of looking up your original numbers, what was the perf of the plane before the paint, & rigging changes?

Thanks, Mike
 
Oki doki..

Mike S said:
Glen, in the interest of saving a lot of folks the trouble of looking up your original numbers, what was the perf of the plane before the paint, & rigging changes?

Thanks, Mike
Click to expand...
Max I could get before all the above mentioned changes was 194.8 MPH TAS at any altitude or power setting or RPM. I am still freaking amazed, and am looking for an anomoly we all have missed. I still feel absolutely terrible about spreading (very loudly I might add) less than advertised speed news about this unbelievable plane!!!!
The new numbers were proven in 2 legs, with seperate GPS's and flying legs into and out of a headwind, twice. Wow, this crow tastes pretty good actually!
Glen
 
glenmthompson said:
"gills" added to side of cowling (read - tunnel MUCH, MUCH cooler since now TONS of hot air now leaves the sides instead of all out the bottom of the cowl Glen
Click to expand...

Glen,

Is there a thread on the "gills" you have added?
This may be the modification that greatly reduced your drag.

Chuck Stuhrenberg
http://rvparachutes.com
 
Gills...

Jim ordered (his idea, I cannot claim this one, I just blended them in during painting) a set of the "gills" that are sold to be installed also on the bottom of the 10 cowl, and we added them on the sides of the cowl too, next to the heat muffs. Very similar on what is found on the Cardinal's ( I think) cowling. Cessna's gills are chevron shape though, not the slotted Van's style.
When taxiing, there is a very hot stream of air passing the side of the fuselage that can be felt if your hand is stuck out and fwd of the door opening. Can you imagine how much heat goes out that gill at 180 knots?
Drag reduction to a significant order of magnitude we have observed here??? HHHHMMMMM..What say my fellow engineers of the aeronautical type?
This might be a justification maybe...Of my comments in my RV6 speed reduction thread for the huge drag reductions/speed increases one can see with lowering cooling drag? Maybe????
PS,.... bottom line, we are now getting the 201 mph at 75% Van's advertises, and 8 MPH F A S T E R than the B***s to the wall advertised speed of 210! Just how loud can one say WOW!!!! Basically this whole situation is very S.H..
Glen
 
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glenmthompson said:
Drag reduction to a significant order of magnitude we have observed here??? HHHHMMMMM..What say my fellow engineers of the aeronautical type?
This might be a justification maybe...Of my comments in my RV6 speed reduction thread for the huge drag reductions/speed increases one can see with lowering cooling drag? Maybe???? Glen
Click to expand...

It likely added drag not reduced it (though it is probably a small enough amount that it would be difficult to measure).

Having an airflow spill out into the airstream disturbs the flow on the skin surface causing a turbulent flow which will produce more drag down stream of this point.

Speed is gained when you reduce drag in the path that the engine cooling air flow takes. This air can be considered the same as air that is flowing around the airplane on the outside.
Causing more air to flow through the cowl without doing anything to make it flow more freely (with less drag) will likely slow you down (though probably very slightly in this case).

This is one of the reasons some airplanes have cowl flaps. To get enough air through the cowl for engine cooling when flying slow at high power such as when climbing (needing lots of cooling) but then reduce the amount of flow at high speed to reduce the cooling drag (and avoid over cooling the engine).

Airplanes like the RV-10 (actually all RV models) are a compromise in cowl design. Avoiding the complexity (and associated maint., etc.) of cowl flaps, the cowl inlet and outlet sizes are designed to cool well in most conditions but still have the minimume flow possible for the best drag situation. I think the principle of the louvers is that at lower speeds the air can more easily exit into the airstream flowing past the openings. At higher airspeeds it is more difficult for the air to merge into the airstream which sort of automaticaly reduces the amount of air flow through the cowl. An automatic cowl flap in a way, though not as low in drag as actually closing up the size of the opening as a cowl flap does.
 
P51 Style Push?

Your enthusiasm is addicting. Stop it! I can't afford it yet. :D

Maybe the hot air escaping provides MORE thrust, similar to a jet engine, and also similar to the belly cooler on a P51?

Than again, maybe not. But it sounds good doesn't it?
 
Whiskey Charlie said:
Does Vans sell them or where can I get them?

Do you have any pics of the cowl locations where you installed them?

Thanks,

Chuck
Click to expand...

Here's the best photo we have of the cowl vents added. N331JH is still in a hanger in Harper, KS and I'm down here 'neath the sun and the stars. Will have to wait until my Dad returns and get a better photo and post it FYI.

Would the paint job make it faster? Maybe it could be the butterfly effect, huh?

Brent
RV-10_Cowl_Vents.jpg
 
Thanks for the pic.

Looks like the side vents are creating less drag on the bottom by letting some
air through the sides instead of the bottom.
I bet there's alot of bottom drag created with all the air trying to exit
the bottom and going around the exhaust pipes.
Remember how much drag round pipe shapes make (like gear legs).

Chuck Stuhrenberg
http://rvparachutes.com
 
Drag reduction

Scott posted

"Having an airflow spill out into the airstream disturbs the flow on the skin surface causing a turbulent flow which will produce more drag down stream of this point."

This IMHO is not always correct, I remember expirements where air was purposly injected into the airstreem just aft of the wing high point in an effort to reduce drag-----worked. I think it was something the Air force did.

This is actually incroporated into some modern high perf gliders also.

The key here is WHERE the airflow is introduced, and how much.

Mike
 
Note..

This is a good pic to show the cool LED nav lights I built for Jim as well....., Painted inside the lens red/green for an even cooler effect in the dark.
As far as the mention of the gills, I think too and have previously mentioned that the drag around mufflers, engine mounts, large sharp angles on exit....Are HUGE drag areas. Is this significant on this plane? Hmmmm, please lets maybe see others install "Headberg Gills' and do some comparing! BTW these gills, as I prev. said, are a Van's part, the gills are installed on the bottom of all 10's cowls in a pair, one on each side on the flat bottom near cooling air exit. I have seen similar, longer & skinnier ones on some 8's. When I get Jim back to Fl. this week from Kansas, I'll see if we can dig up the part number.
All I know is that we are getting faster speeds than Vans at power settings above 75%, and that REALLY intrigues me, lemme tell ya. Remember boys and girls, the faster ya go, the more significant the results from drag reductions.....HHHMMMM
Glen
 
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Hey Chuck...

Whiskey Charlie said:
Glen,

Is there a thread on the "gills" you have added?
This may be the modification that greatly reduced your drag.

Chuck Stuhrenberg
http://rvparachutes.com[/QUOTE
IMH(experienced)O, these gills could very well be the solution to AT LEAST the tunnel heat problem, ( But lemme ask something here,... is a built in stove really a problem anyway? I mean, I love my eggs, and, did get to experience 2 engine failures when I boiled my fuel along with my eggs during testing) without significant changes to the tunnel area, ie. sub floor installed there to protect fuel pump, lines, legs, etc. What say 10 builders about another thread to discuss this?
I am interested in hooking back uo Jims' cabin heat to at least one heat muff ( Jim got cold on his trip last week flying to Kansas), and blocking the other one we have vented to the tunnel for better cyl. cooling. Then I am curious to see if we can still fry eggs on the tunnel now that we have the gills installed.
Glen
Click to expand...
 
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Depending on the volume and speed of the air coming out the bottom of the cowl, allowing some out the sides could reduce the overall drag even though it increase the drag in that one particular area.
 
The following is Van's info on the "Gills"

Cooler Shutter
Part Number = EA OIL COOLER VENT
Price = $85.00 Each
 
nope...

Nope, those are not the gills we used...., but, might be a good idea, since you can shut them to a degree if you wanna control the amount of air leaving there...As I have said several times, these gills we used, are the ones supplied by Van's for the 10 cowling bottom. It will have a 10 part number. I will post the part number as soon as Jim gets back. I am sure there are others out there for sale, and even IMHO, those louvers you find on hot rod hoods are similar in style, albiet diffrent shapes and made out of heavier steel. Also, go to the airport and look on some Cessana cowls, even THEY think they are at least good for something!
Glen
 
Anyone check with Van's

Hi all, I am just curious if anyone has discussed this with the Van's engineering team. They understand the issues, and I'm sure they would like to have a 'cooler tunnel' solution. IMHO, letting more air escape from the sides relieves some of the forward air blockage area of the cowl. In either case, I am interested in the 'results' far more than the engineering. Looking at the picture, does breaking the airstream at the wing root actually help reduce the drag it creates as it cuts through the airstream? Again, let's ask the engineers.

I would appreciate those closer to the problem/solution running this past the Van's team then posting their thoughts - it might even be good discussion for an RVator article.

Cheers!

Pete James - Iowa Pete, Not Aussie Pete!
 
osxuser said:
Depending on the volume and speed of the air coming out the bottom of the cowl, allowing some out the sides could reduce the overall drag even though it increase the drag in that one particular area.
Click to expand...

Your right. It might, but it is only speculation and guessing without any real proof.
It has alread been mentioned that quite a few things were changed/adjusted between the time that the airplane flew at speeds well below the claimed performance, to now having speeds that exceed them.
The only way to know if the extra gill vents provide any speed benefit is to do detailed flight testing on an RV-10 before and then again after installation. Anything other than that is just engineering being performed with your thumb out and your tongue held just right ;)
 
Seems to me that a bit of duct tape over tha gills, and a quick flight might yield a bit of data----------------

Wish my -10 was in condition to make that flight.

Mike
 
Mike S said:
Seems to me that a bit of duct tape over tha gills, and a quick flight might yield a bit of data----------------

Wish my -10 was in condition to make that flight.

Mike
Click to expand...

Same thing that I was thinking Mike. Maybe Glenn could do the test?

Kent
 
F-10109

Whiskey Charlie said:
I checked with Van's.
They say the gills (vents) come with the RV10 finish kit.
Click to expand...
The part number is F-10109 as depicted on page 47-12 of the plans. $4.60 each.

F-10109 LOUVER $4.60
 
Even fater than Vans says. Wow, holy wow!!!!

Well, I am not going to come out and say anything except, man ohhh man, this plane has humbled me. The previously mentioned Vans speed of 201 mph @ 75% is, ..well, what appears to be now actually less than what we are getting! In other words, N331JH, to my complete and total amazement, is F*A*S*T*E*R, let me repeat myself faster than what Vans says!!!!!! All I will say officially for the record, is that my TAS calcs showed several mph higher than 201 during our trip back from Kansas. By my Garmin 296, we flew from 8K2 to KMEI, 626 miles (all numbers mentioned will be in statute except where noted) in 3.5 hrs, take off to landing, including ATC vectoring, climb, and approach, T/O to LDG. Now, simple math says 178.8 mph right? Did I also mention the EFIS 1 showed left quartering headwinds @ 30 knots on the average, and we flew @ 9500'. Do the ol' simple order of magnitude math and you will see by the guessing method that we pretty much had to be over 201 mph TAS to get that number. Further justifying my higher than 201 TAS calcs during cruise.
The next leg was from KMEI to FD38, in 3.4 hrs, total distance of 653 for.....192.1 mph. Now, this leg showed an average left quartering headwind of ooohh like 12 knots. the lowest groundspeed we saw this leg was 193 mph, and the highest was 202, aaannnnddddd folks, the EFIS 1 showed ALWAYS a headwind (hence my nickname Headwind Glen ! ), much to my chagrin and confusion. Other aircraft also concured with the winds we we experiencing @ 9500'.
I finally got the E-1 fuel flow dialed in REALLY accurate, and the FF and tank fill, showed 13.5 GPH @ cruise.
How loud can one say WOW?
Glen
 
Gills...

Per a recent request...Please note...
****The gills leave the fuselage warm to the touch 18" fwd of the door leading edge, and fwd as far as I can reach from the pilot seat with my lanky *** arms. The warmth measures, centered, 4.5 inches above the top of the wing spar.
****IMHO I cannot help but doubt that the gills are affecting the "wing fairing effect" much if any, due to the 4.5 inches above spar flow of hot air.
**** The cowling aft of the gills is showing the typical "raised grain" effect due to higher heat in the area aft of the gills, further demonstrating the HUGE amount of heat leaving the gills at cruise. This cruise was at 9,500', 160 mph IAS and OAT of 65 deg F.
**** It is my observation and humble opinion, that when we take the fresh air from the unused heat muffs from out of the tunnel, we just find we have cured the tunnel heat problem. Standby for further testing when I get a free day to even breath and check my theory.
What say Vans in relation to this tunnel theory? ( PS, they ARE aware it is hot, and are quietly addressing the problem.).
Glen
 
Lo Presti Design

Look at this month's AOPA. In their regular article regarding their give away airplane, and then in a separate longer article, there is a good discussion about the effect of air exiting the low pressure side of the cowl.
 
For those of you who get Bob Collins's newsletter, theere is a story there about how an aft C/G effects speed--------------about the same as what was reported in the start of this thread.

Seeing as the C/G change was only one of the changes to the plane, it makes me wonder what-----if any-------effect the gills, and the re-rigging of the flaps and alierons had.

Anyway, glad to hear that Glen is enjoying the plane, and that it is making Vans numbers.

Mike
 
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