Borer rudder centering STCJim

Who has any info about this? Without an additional vertical fin, my Tcraft is not stable in yaw. This device might help the problem if I had info and better yet, pictures. Any help would be appreciated.

Jim

TcraftF21 said:

Who has any info about this? Without an additional vertical fin, my Tcraft is not stable in yaw. This device might help the problem if I had info and better yet, pictures. Any help would be appreciated.

Jim

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I think the problem is you don't have enough vertical area. Can't you do the same thing as the centering spring just by holding it centered with your feet?

Glenn

I hold the rudder centered with my feet now. I make long flights to Arctic Quebec and Labrador in the summer and at the end of these, my legs get sore holding it straight. A couple of hours here and there are no problem but 8 hours in a day are.

Jim

try Ron Sullivan, Aircraft Innovations LLC, Anchorage Alaska. rsullivan@alaska.com 907-345-4630 not sure if he has it, or if that contact info is still good

can you add a fin below fuselage? and angle it

The STC (as I recall from 1997-2001) calls out installation of tailwheel springs and cables from the outer end of the float wire to rudder horn extension bar to a forward location on the fuselage, or convenient lift handles if present. The springs can go forward in the assembly, or rear and attach to the outer horn extension near or where the float rudder cables attach on either end. Cabling is fabricated to provide little or no extension to the springs as required...typical Scott tailwheel springs...two general sizes and tensions are available I believe (or common hardware springs). A turnbuckle on each cable would allow for later tension adjustment. The forward attachment can be something as simple as thumbscrew hose clamps installed over the lower longerons about 18-24" in front of the rear bar (cabling goes to holes drilled in the thumbscrew), or common adel or similar clamps. If fastened to lift handles figure out a convenient method.

The springs add linear tension to the rudder and help center it similar to tailwheel springs in flight. You could also try lowering your water rudders as on some floats that added area can add some longitudinal stability.

Edit: I have an original belly fin for a Taylorcraft in my shed. If you want I could take pics and get dimensions. It attaches to the rear tail spring clamp on the fuselage and a pair of ears extended below the belly forward. I assume the forward ears are welded to a cross tube. My Taylorcraft has them but the fin isn't required on 85 Taylorcrafts so must have come from earlier when it had a 65.

Experiment.

Gary

TcraftF21 said:

Who has any info about this? Without an additional vertical fin, my Tcraft is not stable in yaw. This device might help the problem if I had info and better yet, pictures. Any help would be appreciated.

Jim

Click to expand...

TcraftF21 said:

I hold the rudder centered with my feet now. I make long flights to Arctic Quebec and Labrador in the summer and at the end of these, my legs get sore holding it straight. A couple of hours here and there are no problem but 8 hours in a day are.

Jim

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You can weld the rudder solid in the correct position and the plane will still yaw and you will still tire yourself out by the end of the day. Your plane needs more vertical tail area. You can install the Taylorcraft ventral fin which is already approved. You can copy the original Aeronca stabilizer fins or the later Citabria fins. You could cheat and move the leading edge of the fin forward increasing the area. You may find that a set of Champ fins mounted only on the top side of the stabilizers will be sufficient or perhaps a set both top and bottom.

No matter how you do the deed, you need a bigger tail. The springs are only useful for BSing the FAA into certifying the installation. They do not solve the problem.

My PA-12 had squared off rudder and elevators plus a forward extension to the vertical stabilizer. Even with the centering springs it would wander about on ED0 2000's a little with certain loads. Not bad but noticeable versus the previous PA-18A with the same floats and rigging.

Taylorcraft built two general tails in their production history. Pre-WW2 they had a shorter vertical stabilizer but a longer chord rudder. Mine is like that. Post war they had a taller stabilizer but shorter chord rudder. Never measured the difference in area. Pre-war used three hinge points for all.....post two. So they're not directly interchangeable by size or attachment method.

The factory didn't certify post war models on floats (TCDS 1A9) so any installations were either Field Approved or STC'd. Who knows what extensive flight testing was done during the approval process?

Gary

Good catch Gary, I have been thinking BC-12D which is TCDS A-696 which is post war.

TcraftF21, We're assuming that yours is a F-21. What floats do you have and what does the STC say which would address this issue?

Whichever model the answer is still more tail.

I think F21 has Baumann's 1500a amphibs made out of rare unobtanium: http://www.supercub.org/forum/showthread.php?39978-Baumann-Floats&highlight=TcraftF21

I can certainly photo and measure my Taylorcraft ventral fin if required. Not for sale as it's worth more than my plane :roll:

Per TCDS A-696 the ventral fin wasn't required with C-85 equipped models, or with 1320's for all if the rear CG was limited probably per your earlier note on aft CG causing instability.

The stabilizer and rudder changed with the intro of the BC12-D in 1945 as noted in the TCDS.

Gary

My F21 had Baumann 1500 that were STC’d for the plane with no fin. I now have Baumann 1500 amphib that we’re a project to get approved but good prevailed over evil(faa)and I got it done.

Jim

If the Baumanns have more side area or volume forward than the 1320s there likely would need to be a larger tail. I suspect this to be the case.

The STC in this case would still need to have met CAR 3 stability requirements.

Jim, is it worse with the amphibious than it was with the straight floats? As I recall the 1500As are the same basic dimensions as the 1500s, just has the wheel wells. I agree with others, sounds like either a ventral fun or fins on the horizontal stabs would solve the issue.


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If a plane just marginally passes with straight floats, then those floats are replaced with another set which is identical except for a protruding nose wheel, that nose wheel could be just enough to upset the stability. Sometimes it doesn't take much to make a difference. You have made me suspicious that this discussion should now go off the air.

I wonder if larger water rudders would help? Baumanns are pretty big but maybe make them larger in the right dimension?

As I noted the fin attaches forward to two welded ears on the belly and the tail spring clamp at the bottom of the vert stabilizer. Wouldn't be hard to duplicate.

Gary

BC12D-4-85 said:

I wonder if larger water rudders would help? Baumanns are pretty big but maybe make them larger in the right dimension?
Gary

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Water rudders are located in a dirty air area behind the floats so they would need to be very large which could open up a can of worms with the water handling. Extra fin area on the stabilizers or under the aft fuselage would be best.

Switching to amphib made no difference to the yaw, speed, performance, etc. They are the same as the straight floats, just with wheels added plus the retract mechanism. I know that more vertical would help but that is not worth the effort. The yaw is not that big a problem. I was just curious about the rudder centering because it seemed like a quick method to try. Everything on the plane is legal and certified. TrickAir skis, the floats, battery box, skylight, etc. so putting a vertical skew on would be another 337. I have enough of them now. Thanks for all the responses.

Jim