Voodoo Update!!!!!!

[boomtown]

Re: Voodoo Update!!!!!!

Rare Bear has a similar mod. When first installing the 3350 they went from 6 degrees nose down and compromised at 3 degrees.

[Desertdawg]

Re: Voodoo Update!!!!!!

Theoretically it keeps all components of the thrust in-line with the way the airplane moves through the air, but it also affects handling and stability so it has to be approached very precisely. Think of it this way, if the engine is tilted propellor-end down relative to the airframe, a small component of the prop's thrust is now wanting to push the nose down, and the tail has to be trimmed to push the nose back up and the wing has to generate a little more lift to offset the tail and engine pushing down. That trim on the tail and extra lift demanded of the wing translates to some drag. Same way the other way around- engine is tilted to pull the nose up a bit, the tail has to be trimmed to push the tail up as well (push the nose down). That all actually sounds good because it unloads the wing, but now the handling may get squirrely when you transition from straight-and-level to a G-loaded turn, depending on the fore-aft weight distribution and how it has to be trimmed for straight-and-level.

Thats a very good explanation - great to have people on this site that translate into terms common folk can understand.

AAFO rocks.

Many thanks.

[Gibbs]

Re: Voodoo Update!!!!!!

Strega has a wing incidence change that no other p-51 has.

Kerch has wanted to do the zero deg engine thrust line mod for a long time on a racer. I don't believe any merlin p-51 has ever had this.

Don't forget, Kerch was behind much of what made Strega go fast and helped make Dago even faster. He's familiar with all of this. Modifications come in stages. Voodoo took a long time to get refined. 2009 was just race it as it is, 2010, wing reprofile and system refinement, 2011, engine work, 2013, get it flying again,etc...

Michael

What does "wing reprofile" mean? Completely new wing build with other airfoil (ribs and skin) than stock NACA 45-100?
If so, that would be a really major undertaking; or means this "only" bondo and paint for slippery surface?

thx
Gibbs

[thunderstangfan]

Re: Voodoo Update!!!!!!

they don't "bondo" a wing so the paint comes out shiny... the profiling trues up the airfoil so that it gets as much laminar flow as possible. laminar flow is tripped pretty easy and the original mustang wings are pretty rough.

[Mluvara]

Re: Voodoo Update!!!!!!

What does "wing reprofile" mean? Completely new wing build with other airfoil (ribs and skin) than stock NACA 45-100?
If so, that would be a really major undertaking; or means this "only" bondo and paint for slippery surface?

thx
Gibbs

The wing came off the aircraft after the 2009 races for some internal repairs and a go through. In the process, it was profiled to a desired airfoil and painted.

Michael

[John]

Re: Voodoo Update!!!!!!

Wow! ...this is what really makes Reno so interesting...the technical aspects and modifications! Considering the amount of power a race Merlin can deliver it makes sense to get all the thrust going in the proper direction. I like the way they lowered the back of the engine instead of raising the front; thus keeping the thrust position essentially the same. Good to hear they have done extensive testing of the new handling qualities. Hope it handles Ok on the course in the turns. Thanks for the excellent update team Voodoo!

...Didn't the P-51A basically have a zero thrustline engine?

...wonder if those guys can see thru those radical sunglasses?!!

[Fence Sence]

Re: Voodoo Update!!!!!!

The wing came off the aircraft after the 2009 races for some internal repairs and a go through. In the process, it was profiled to a desired airfoil and painted.

Michael

Any info you can give out on the "desired" airfoil? Why was it desired? Obviously speed but, I'm hoping for a few more technical tid bits on the details of that particular foil shape and who and why and all the little things geeks like us pop wood over.

[Mluvara]

Re: Voodoo Update!!!!!!

Any info you can give out on the "desired" airfoil? Why was it desired? Obviously speed but, I'm hoping for a few more technical tid bits on the details of that particular foil shape and who and why and all the little things geeks like us pop wood over.

The wing was profiled to the stock NACA design by North American using templates. Basically, clean up the wing and make it an ideal (or close to ideal) surface.

Michael

[Fence Sence]

Re: Voodoo Update!!!!!!

Ah, so no actual "re-profiling" then? Just back to the original but, done right. It is a thing of beauty that wing on Voodoo.

[Gibbs]

Re: Voodoo Update!!!!!!

The wing was profiled to the stock NACA design by North American using templates. Basically, clean up the wing and make it an ideal (or close to ideal) surface.

Michael

What do you think about bionic surface "shark skin film" like some F1 racers have (at least Cassutt III M from Swiss Air Racing Team) - is this not working with alu skin plated Unlimited airframes?

The Austrian producers are talking about a speed increase from 3 to 5 percent...

Gibbs

[Idaho_cowpony]

Re: Voodoo Update!!!!!!

I've been curious about this myself..

[Mluvara]

Re: Voodoo Update!!!!!!

What do you think about bionic surface "shark skin film" like some F1 racers have (at least Cassutt III M from Swiss Air Racing Team) - is this not working with alu skin plated Unlimited airframes?

The Austrian producers are talking about a speed increase from 3 to 5 percent...

Gibbs

I'm not an aero guy, but here are my thoughts and understanding of the subject:

It's one thing to get the airfoil to the right shape so that there are no discontinuities or issues with the overall shape. It's another whole discussion about surface smoothness,etc.

The formula 1's are operating in a different reynolds number range than the unlimiteds and I've heard there are good results with various types of surface texture (like shark skin film). It appears to be beneficial in their speed range.

Michael

[Gibbs]

Re: Voodoo Update!!!!!!

Michael, thank you very much for this explanation from an expert's view - I love this forum!

@all:
I think, this is no secret squirrel stuff: does anybody know, if PM also have zero deg thrust line and/or wing incidence? Maybe Thom or Wild Bill will answer us...

Gibbs

[Thom Richard]

Re: Voodoo Update!!!!!!

I think, this is no secret squirrel stuff: does anybody know, if PM also have zero deg thrust line and/or wing incidence? Maybe Thom or Wild Bill will answer us...

Gibbs

PM has two degrees. However, the thrust line is lower so the jury is out on what the correct angle should be for racing. Wind tunnel testing would be the only answer. We've talked about doing this mod. But comparing Voodoo and PM is not an appropriate course of action. They are aerodynamically quite different.