Gross Weight Increase Mods

[MBednarek]

I'm in the unfortunate situation that, due to butt cracks, I need to replace the spars on my 1946 65hp BC12D1. While I do not plan to upgrade to higher horsepower at this time, since the wings are presently disassembled, I'm looking into accomplishing the various gross weight structural beef-ups associated with Terry's STC (SA1-210). I have a couple of questions:

1) Wag-Aero (SAFE-AIR Repair) has PMA'd replacement main spars - does anyone know if these incorporate the larger bushings at the spar butt attachments?
2) I've mic'd my existing wing attachment fittings and, while the main spar butt fittings are already 0.95", not so for the either the strut attachment or aft wing spar butt fittings. Does the SA1-210 data package include fabrication drawings for these fittings or will one need to create a drawing based on earlier 65hp fittings (for owner-producted parts)?

Thank you for any feedback you can provide.

[3Dreaming]

I am pretty sure Wag-Aero sells spars both with and without the bushings, at least they used to. I saw both when I was at their location one time.

As far as installing the mods I spoke with Terry about installing the wing mods without installing the complete STC, which I think is a smart idea by the way, and he said he would issue an approval for that.

[Robert Lees]

I'm in agreement with 3Dreaming....it is certainly worth installing the STC spar and strut attachment upgrades (even if you do not fulfil the whole STC requirements yourself [engine-wise]). The time to do these structural STC upgrades is while the wings are apart, and there is a very small price/cost involved, in relation to all the other expenses, which you will see returned if you ever sell the aircraft onwards.

I can see no structural/engineering reason to NOT install the structural mods if you are in possession of Terry's STC, and retain an A-65 engine, but then I'm not a USA IA. ot a legal-eagle.

The STC drawings do show the correct and accurate dimensions for the fittings to which you refer.

Just make sure you and your IA ensure the paperwork record is in order!

[Scott]

I purchased the STC drawings for the wing upgrades only from Terry when I built my spars.

Basically fabrication of the plates for the strut fittings and welding in place, and turning the fwd spar root bushings from fiber bar stock purchased from Aircraft Spruce.

http://1.bp.blogspot.com/-L6k3-Vcv0Qo/U-Ennc1crxI/AAAAAAAAA0c/C1XXGyGzdoY/s1600/DSCN2066.JPG

http://2.bp.blogspot.com/-7ko62uvqaCw/U6hXN3Faj3I/AAAAAAAAAxc/Rz2UScezA3M/s1600/DSCN1603.JPG

Is concidered a major modification for certificated aircraft, and that part cost me more than the mod.
S

[MBednarek]

In regards the Wag-Aero main wing spares, they list both the BA87 (BC12 series) and the 2570 (F-19 series). Is the # 2570 spar the same spar as the #BA87 but with the enlarged bushing added?

[3Dreaming]

I believe that is the only difference, but you would need to confirm with them.

[bluerooster]

Recent investigation into the spars sold by Wag, They have no bushings installed. You must install your own bushings. As to the fabrication of the fittings, I would hazard to guess that one could use the old ones as a pattern, and fabricate new ones using .095 thick steel. But would probably be easier to order new ones for a BC12D-85, or the F-19

[3Dreaming]

Wag Aero used to have spars drilled for bushings, along with those that were not. I saw both there hanging on the wall when I was there for Rotax engine training. It might be worth calling and asking.

[bluerooster]

Yes worth a call. But in their most recent catalog, they note that no bushings installed.

[braol]

(Please excuse my ignorance...I am a new Taylorcraft owner and have no idea of how the wings/struts/fuselage interface...I am learning): Is the structural mod something that can be accomplished with the wing supported on stands without full removal/disassembly?

Out of curiosity, was there ever any thought to a smaller gross weight increase STC for a 65 hp equipped airplane (like 1260 or 1300lbs gross)? I know that the CG of the BC-12D is basically impossible to exceed...given the 2-seat arrangement and locations of the fuel tanks... I would assume the structural changes required for the 85hp conversion would translate into a potential higher gross weight for the 65 horse (although not the full 1380)...that's assuming that the 1200lb gross weight limit of the BC-12D came from a structural limitation and not due to 65 hp performance.

[Hank Jarrett]

Don't assume you can't get in an Aft CG condition! When I first got my 41 the W&B had errors in it (actually it was just copied from the TC and I wondered if there had ever BEEN an actual weight check!) Turned out that at minimum fuel the CG was on the Aft Limit. I sure did like the light control forces and crisp reaction to control input! Also sure glad I didn't do any stalls or spins before I actually weighed her! There was 20# of wires and other junk in he tail cone that got torn out which corrected the CG but she was quite a bit heavier than on the W&B. I would NEVER buy a plane again and not do a W&B to see if past ones were pencil whipped. Also says a lot about how safe a Taylorcraft is! She had been flown for years with a CG that was on the ragged edge of too tail heavy. One low fuel flight with extra junk in the baggage sling could have been really bad.
Doing a W&B is NOT hard! I have done dozens now for others.

Hank

[3Dreaming]

I have one that has extra layers of paint that is very aft CG. It is heavy, but it was faster than our '41.

[Hank Jarrett]

In theory aft CG will give a higher speed. The stab normally lifts DOWN in flight to provide stability in pitch. Moving the CG aft reduces the down lift of the stab and that reduces drag. Of course it also reduces stability and the ability to recover from a spin. That is what makes aft CG so dangerous. The planes controls will get lighter and maneuverability will increase as well as speed. Your plane will fly GREAT right up till it kills you. Aft CG is a REALLY bad idea!

Hank