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RV-3 with balanced elevator ?

L

Larry DeCamp

Well Known Member
Who is the guy from New Mexico at OSH 2011 that had a -3 with custom balanced elevators ( not RV4)? It was yellow , had storage in the cheek cowell and Paul Dye was at the group discussion. I don't have any desire to burn the fuel to exceed VNE, but it could be an asset trading G's for speed exiting a loop ?
 
Larry DeCamp said:
Who is the guy from New Mexico at OSH 2011 that had a -3 with custom balanced elevators ( not RV4)? It was yellow , had storage in the cheek cowell and Paul Dye was at the group discussion. I don't have any desire to burn the fuel to exceed VNE, but it could be an asset trading G's for speed exiting a loop ?
Click to expand...

You may be referring to this thread. If someone doesn't come up with the name I can get the N number from other photos.
 
David Paule said:
When I clicked on the owner's name, the description of the aircraft said it was a "fixed wing multi engine." Still looking for number two in the photos.

Dave
Click to expand...

Yes, the information says multi engine and also says turbo-prop but it is the right guy.
 
Is this the right guy ?

I got a nice response from Vyking regarding his elevator. He even has a superb document with pics detailing how he did it. My elevator is done so I will incorporate the balance as "repeat offender".
 
Counterbalanced Elevators

I had breakfast this morning with John Harmon - I asked him about the tail feathers of Rocket 1's - RV3 w/counterbalanced elevators.

To his knowledge only 4 built (one got built twice! - maybe that makes 5)

HFS
 
RV 3 Balanced Elevators

Any chance you could send a copy my way

Chris
RV8 627CS Second Chance
Tech counselor 1424
RV3B Empennage under construction.
 
The write-up describes elevator ribs build by riveting flanges to a web. You could build them the old-fashioned way, by making a hardwood form block and forming the flanges around it.

You'll need to also make a backing form, which is another piece the same shape but with plain edges. The form block needs undercut edges to allow for spring-back. 11 degrees is good. Don't forget to radius the form block's edges too.

Clamp the material in position between the two blocks and tap with a soft-ended mallet. The flanges will come out wavy and the rib will have a bend. Flute the flanges and it'll straighten out and be pretty.

You can do this with 2024-T3, amazingly enough.

Dave
 
Any Elevator Flutter Cases Reported?

Right now I'm at the point on the elevator where I'd need to build the balance weights, if I were going to install them. I'd figured out a pretty slick way of doing it using a welded steel fitting that rivets to the tip rib and the spar web and extends forward to hold the weight, and if I were going to build these, well, today's the day to order the materials.

And then I got to thinking that there are well over 200 of these planes without elevator balance weights and a handful with, and there isn't any difference in the reported cases of elevator flutter: there aren't any that I know of for either situation. So why add six or seven pounds, since it doesn't appear necessary?

Has anyone heard of elevator flutter in the RV-3?

Thanks,
Dave
 
David Paule said:
Right now I'm at the point on the elevator where I'd need to build the balance weights, if I were going to install them. I'd figured out a pretty slick way of doing it using a welded steel fitting that rivets to the tip rib and the spar web and extends forward to hold the weight, and if I were going to build these, well, today's the day to order the materials.

And then I got to thinking that there are well over 200 of these planes without elevator balance weights and a handful with, and there isn't any difference in the reported cases of elevator flutter: there aren't any that I know of for either situation. So why add six or seven pounds, since it doesn't appear necessary?

Has anyone heard of elevator flutter in the RV-3?

Thanks,
Dave
Click to expand...

Good question Dave - and I dont know the answer. I think that I can tell you that I had a discussion with Van about the flutter testing on the RV-3, and it was not extensive (it was the early days of homebuilding), so I am VERY cautious about going much above Vne. The problem with balancing the elevators to make it more flutter resistant is that without a very extensive test program (in which you take a risk of flutter), you really don't know if you have gained anything. It is probably (not a precise term) not going to do any harm to add it (except, as you say, to add weight, and that weight is WAY aft...), but that's just a guess.

It truly is easy to exceed redline in Tsam with the IO-320....we can do that in level flight at 1,000'. So it is something to think about - but we moved the CG significantly by adding a lightweight tailwheel (which weighs slightly less than a pound lighter than stock). Several pounds at the elevator may make a huge difference, and not for the better.

Paul
 
RV3 elevator flutter testing

I tested all my control surfaces to 210mph IAS at 5000' (what's that in TAS? Well ... it's faster, so I was above redline). Typical profile: get it going fast downhill, ease up and get the velocity vector aimed upwards, then excite the stick/rudder, just like Van says in the manual. Work up from 160mph or so in 5mph increments. Wear a parachute. Practice egress beforehand (test pilot stuff).

No problems at all.

I saw a high-performance acro ship on the ramp recently - I think it was a two seat Extra 300 - elevators drooping down. Asked the owner about elevator mass-balancing? "Nope, none", he replied.

If it ain't broke, don't fix it!

- Steven
700+ RV3 hours
(two more last weekend!)
 
No Elevator Mass Balances

Decided not to add the mass balances. An offline conversation with Paul reinforced that decision.

The main reasons were -
1. The success of the fleet that doesn't have them,

2. The impact on the center of gravity,

3. And the fact that elevator mass balances have a positive effect on one mode of flutter, but a negative effect on others - and unless I did the analysis from scratch and flight tested with instrumentation, I'd never know how successful the project was. It could have adversely affected flutter.

Better to build per the plans.

Dave
 
LH ELevator Balance Weight, FYI

As I said, I'm not going to do this. However, with the LH elevator and trim tab mounted on the stabilizer, I had an opportunity to see how much weight would be needed.

Assuming that you could hang it 7 3/8" forward of the hinge line, you'll need something like 2.25 pounds for just this side.

Conditions - the trim cable, paint and tip were not installed. The trim tab, hinge pin and blue film were included.

Dave
 
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