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  #11  
Old 04-13-2018, 03:34 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by RV10inOz View Post
Carl, that is way faster than Vans numbers, have you checked your TAS vs flying a GPS box to verify static error?

If the static is pretty close you have one slick machine!
David,

That screenshot in my post #9 above was taken in a 450 FPM descent. That's why it appears fast.

The screenshot below is in level flight cruise and shows 207 MPH TAS. My RV-8 appears to be about 3 to 4 MPH faster than Van's book speed (180 HP, Hartzell CS prop, Solo Weight, 75% @ 8000 ft = 204 MPH TAS). Most of that may be attributed to the Hartzell Blended Airfoil CS prop that's installed. Van's numbers were measured with the older Hartzell CS prop.

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RV-8, 290 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

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Last edited by RV8JD : 04-13-2018 at 03:58 PM.
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  #12  
Old 04-13-2018, 04:02 PM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by RV10inOz View Post
Carl, that is way faster than Vans numbers, have you checked your TAS vs flying a GPS box to verify static error?

If the static is pretty close you have one slick machine!
My checks show TAS readout is about right. There is no magic here. The cowl/plenum setup has less cooling air coming into the engine, so less drag. The plenum uses the cooling air about as effectively as possible. I do offer that there is a trade off. I find cooling is fine for how I fly. It would not be adequate if you want to do a 100kt climb to 10K’. I climb at 130kts to keep the engine cool.

Carl
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  #13  
Old 04-14-2018, 11:23 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
In the RV-10 I needed to add a 0.063” shim to get the elevators in perfect trail for normal loads.

Carl
Carl,

I am curious how you dealt with the fairing after this change. Did you initially fly without the fairing or did you re-work the fairing after adding the shim.

Also did you try to optimize the wing rigging or did you just use the pre-drilled pilot hole on the aft spar attach.

Larry
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  #14  
Old 04-14-2018, 11:46 AM
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Carl Froehlich Carl Froehlich is offline
 
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Originally Posted by lr172 View Post
Carl,

I am curious how you dealt with the fairing after this change. Did you initially fly without the fairing or did you re-work the fairing after adding the shim.

Also did you try to optimize the wing rigging or did you just use the pre-drilled pilot hole on the aft spar attach.

Larry
There was enough play in the RV-10 empennage fairing to not need to redo the fairing. I did replace the fairing on the 8A but as I was going to paint it was painless.

The RV-10 wings are installed per plans. I don’t recommend messing with the wing angle of attack.

Carl
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  #15  
Old 04-14-2018, 12:15 PM
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Weasel Weasel is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
You don’t mention the prop you are using. This makes a big impact.

The rigging topic itself is way too wide a subject to adequately respond. The first thing I recommend you do is get other experienced builder eyes on your plane and start looking for the obvious, then get the straight edges out and measure everything. As example, I was with a buddy visiting open hangar doors. An RV-4 owner mentioned that he was not sure his plane (flying for 15 years) was ever rigged right. The right flap hanging down a half inch from up jumped out at me, and from there all the other classic ailerons high/low mount problems. He gained 5 knots after a few simple corrections.

Wheel pant rigging is another “hard to get just right” issue.

One item that is less obvious is the HS angle of attack. In normal cruise, is the elevator trailing edge hanging down? If so, this tells you the HS is providing too much downward force. In the 8A a 0.040” shim under the HS forward spar made a hugh difference - so be careful. In the RV-10 I needed to add a 0.063” shim to get the elevators in perfect trail for normal loads. If you are thinking of adding a shim bigger than that, time to stop and look at what else is going on.

So - call your buddies to come on by. After you fix stuff your wingtip trailing edge may by out of wack. Don’t be afraid to glass over the wingtip holes and re-drill it.

One other point. This is not a “one and done” deal. It is an iterative process. Make it part of your 40 hour test program.

Carl
Consider by adjusting the horizontal stabilizer angle of incident in that direction, you are reducing the amount of available tail down force at low speeds in the flare with forward most CG loading. Each plane is unique and should be tested to determine change effects.
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  #16  
Old 04-14-2018, 01:20 PM
rocketman1988 rocketman1988 is offline
 
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Default Yeah

Stability and control are not the best areas to employ TLAR engineering...
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  #17  
Old 04-14-2018, 01:33 PM
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Carl Froehlich Carl Froehlich is offline
 
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Originally Posted by Weasel View Post
Consider by adjusting the horizontal stabilizer angle of incident in that direction, you are reducing the amount of available tail down force at low speeds in the flare with forward most CG loading. Each plane is unique and should be tested to determine change effects.
I could not agree more. Full envelope flight testing is frequired when doing such a rigging change. My results:
- RV-8A solo and no baggage (most forward CG condition). Before the shim, elevator trim tab on landing was mid range nose up postion. After the 0.040” shim, the elevator trim tab was right at full nose up travel (but stick Force was still neutral). Any loading other than most forward CG the trim tab was less than full nose up on landing.
- RV-10 solo and no baggage (most forward CG condition). Before the shim the elevators were slight trailing edge low in cruise. After shim the elevators were in the trail during cruise. The RV-10 nose up trim authority is huge and I really did not see much of a change in elevator trim setting before and after shim. The relative moment arm on the RV-10 is much less than the 8A so even though the shim was a little bigger, it had less effect. I do not recommend going bigger than 0.063” or so with an RV-10. I’ll also note that serveral data runs showed a zero to 2 knot gain in speed with the shim. Do not expect miracles unless your rigging is further out than mine to begin with.

So bottom line, changing the HS angle of attack would be down the list of things I check when working rigging. Most common rigging problems I’ve seen on RVs are:
- Flaps do not go up as far as they should
- Asymmetric flap and/or ailerons
- Flap and/or aileron twist
- Alieron hinge point to high or low on inboard and/or autboard mount
- Once flaps and aileron rigging is corrected the builder finds his wingtips are out of wack (another reason to defer mounting wingtips until after the other rigging is done).
- Wheel pants not mounted in trial (first thing I look at if the owner reports his ball is out one way or another). First test is see how much the ball is out flying with no wheel pants.

As I mentioned before, rigging is not trivial and is very much an iterative process.

Carl
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  #18  
Old 04-15-2018, 03:59 AM
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rmartingt rmartingt is offline
 
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Quote:
Originally Posted by Weasel View Post
Consider by adjusting the horizontal stabilizer angle of incident in that direction, you are reducing the amount of available tail down force at low speeds in the flare with forward most CG loading. Each plane is unique and should be tested to determine change effects.
This is key. You need to test the change.

However, adjusting stabilizer incidence by the amounts we're talking about to make the elevators faired in cruise will not suddenly make the airplane unstable (I've seen that argued before ). Remember, quite a number of airplanes adjust stabilizer incidence for trim, and some (like the RV-12) just use the stabilizer itself for all pitch control.
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  #19  
Old 04-15-2018, 05:04 AM
RV10Pilot RV10Pilot is offline
 
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Location: Medford, NJ USA
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Quote:
Originally Posted by Chippster1 View Post
There seems to be a paucity of aftermarket products to make an RV-10 go faster. Is it because it is already so perfectly designed?
Does anybody know of any mods worth looking at?
Yes there is a paucity of go fast mods for the 10 and in my mind that is because that is not where the RV-10 is lacking. It is not perfect, but it is not an area where you can get improvement with easy modifications. Doors, nose wheel, main fairing attachment, and INTERIOR are areas where improvements could be made and that is where most of the modifications are focused. The interior is the big area and that is because the RV-10's interior is designed in typical Van's fashion, light and spartan. But most builders of a 10 what a much more luxurious interior.
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  #20  
Old 04-15-2018, 08:25 AM
Chippster1 Chippster1 is offline
 
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Default Paucity

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Originally Posted by Veetail88 View Post
Totally OT, but paucity, had to look that up, good job.
Having grown up with paucity, it became a useful word for me
Didn’t mean to sound like an English teacher in an SAT prep course!
Glad you learned something though!
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