Brodak Warbird dihedral, engine question

[Ken Deboy]

I read on another forum that the Brodak P-40 is easier to trim if you add dihedral to the wing. I'm building an A6M Zero, and I'm wondering if the same is true for this bird. If so, how much to add? Would it be enough to make the top flat with all the taper on the bottom? If I build it with dihedral would it be better to build the wing according to the plans then cut in half and add the dihedral, or better to cut tapered leveling bars and build it in one piece with the dihedral?
Would an LA 25 be enough power (flying field is ~4500' elevation)? My other choice would be a Stunt 35 modified with a Hemi head. Modern 40-46's seem like a bit much for a plane this size, but I'm not sure if the 25's are quite enough.

Thanks,
Ken

[Bill Little]

Hi Ken,

I bilt th prototype Brodak Zero from Mike Garmon's pencil drawings.  I powered it with a well used OS 35S.  The plane was one of my better flying planes off the board!

I saw no reason to put dihedral in the Zero.

Bill <><

[Sam Laughery]

Pat Johnson has done some designs for Brodak and believes that dihedral is the way to go with the warbirds..  I'll send you his email address and you can ask him directly.

Sam

[brucefinley]

Hi Ken,

I bilt th prototype Brodak Zero from Mike Garmon's pencil drawings.  I powered it with a well used OS 35S.  The plane was one of my better flying planes off the board!

I saw no reason to put dihedral in the Zero.

Bill <><

Bill said it, I believe it and that settles it!  Trust Bill!

[Mike Clark]

Hi Guys,
Just like Bill I also built a Zero but mine came from a Brodak Kit. LA40 for power and she flew right off the board and flew the pattern with ease. No dihedral needed.

I have seen and flown the Brodak P40. It is a totally different airplane from the Zero size, wing and cord wise. It sounds as if some one is attempting to upgrade to a profile stand off scall airplane.

LA25? The Brodak Zero has a sharp leading edge and if yanked into a manuver will stall and generally just act up. The LA40 will be a good choice, it will pull the Airplane through most circumstances.

Enjoy your zero it is a good flyer.

Mike Clark

[Sam Laughery]

The Lagg was designed by John Miller and does not have dihedral.

[Bill Little]

Pat Johnson has done some designs for Brodak and believes that dihedral is the way to go with the warbirds..  I'll send you his email address and you can ask him directly.

Sam

Hi Sam,
Pat is a gerat designer, that's for sure!  And I totally agree that the P-40 does need dihedral or some other kind of fix like moving the wing "up" in the fuselage.

But, the Zero has no apparent vertical CG issues like the P-40.  Old Mr. Garmon nailed the first Warbirds pretty good.  And, like I said, the Zero never showed a need for any change.  The necessity of dihedral is for vertical CG purposes in those cases for our stunt planes.  If the wing is mounted in a very low configuration with an abundace of fuselage above it (P-40) then adjustments are pretty necessary, but I have still seen a former Jr. World Champion fly a very close to (if not winning) flight at Brodak's Fly In with an out of the box P-40 ARF. (Derek Barry)

Not meaning to argue with Pat, I respect him a whole bunch, I just believe it is a design vis a vis design situation.

Bill <><

[Bill Little]

BTW:  The Warbirds that Mike Garmon designed used a stock, but slightly shortened '57 Green Box Nobler wing.   Mike told me that he dropped the #1 ribs (IIRC) to shorten the span to 48" with tips. 
I have built a new wing for my Zero.  It lost it's outboard panel due to a line clip being flipped over and it released at the bottom of an inside loop.  Minimal damage to the rest of the aircraft!

Bill <><

[Dennis Moritz]

We have a number of P40s running in our club, both kits and ARFs. Excellent flying planes. Our top 20 flyer jokes about flying one in the NATS. He will fly it at Brodak in profile. That plane was trimmed out by bending the outboard tab down (the extension of flap mounted in a fixed position on the wing). This compensates for the low wing mount that creates a vertical cg imbalance. For this plane, with the wing mounted somewhat low in relationship to the stab, dihedral would be another approach. If figured correctly it could provide a better dynamic solution, since the vertical cg would be close to the exit point of the lines. In other words the cg imbalance itself would be handled as opposed to using an aerodynamic patch.
In any case, the P40 has proven to be an excellent controllable stunt plane, even when trimmed out using familiar tweaks. It turns tight enough to bight its tail. A riot to see that. While being smooth and responsive in the pattern. The Zero looks like it may differ in airfoil, moments and wing mounting position.

[Bill Little]

We have a number of P40s running in our club, both kits and ARFs. Excellent flying planes. Our top 20 flyer jokes about flying one in the NATS. He will fly it at Brodak in profile. That plane was trimmed out by bending the outboard tab down (the extension of flap mounted in a fixed position on the wing). This compensates for the low wing mount that creates a vertical cg imbalance. For this plane, with the wing mounted somewhat low in relationship to the stab, dihedral would be another approach. If figured correctly it could provide a better dynamic solution, since the vertical cg would be close to the exit point of the lines. In other words the cg imbalance itself would be handled as opposed to using an aerodynamic patch.
In any case, the P40 has proven to be an excellent controllable stunt plane, even when trimmed out using familiar tweaks. It turns tight enough to bight its tail. A riot to see that. While being smooth and responsive in the pattern. The Zero looks like it may differ in airfoil, moments and wing mounting position.

Hi Dennis,

Yes the Zero is pretty much a totally different design and IIRC, the last of Mike Garmon's designs. 
The P-51B, FW-190, Me-109, Sea Hurricane, and Zero were Mike Garmon's designs AFAIK.  Those used a Nobeler airfoil and different numbers than Pat used on the P-40.  Plus, the P-40 was modified for production, dropping the dihedral that Pat had used initially.

I have flown most all of them in various conditions.  All have been good fliers, with the P-40 needing the work that is mentioned to allow for the vertical CG.

Bill <><