Bellcrank for original Sterling Yak 9

[Dick Pacini]

Last year I found a NIB original Sterling Yak9 here on this forum.  I bought it for my cousin's birthday because he built one back in the mid 60's.  He is a slow builder but I saw it a couple of days ago during a vacation visit to Florida.

He hasn't completed the wing yet because he can't find a bellcrank to fit.  It appears that the leadout spacing is 2 3/8".

Current nylon bellcranks are too thick.  Probably the only one that will fit is the old Veco or Perfect bellcranks.

Suggestions?

[Phil Spillman]

I suggest that you find an old Fox, Perfect or similar bell crank and cut it to length. Then bush the ends with brass tubing using 1/8Th" od ball point pen refills for the push rod hole and 3/32" for the lead out ears. Start the spread with a counter sink then peen them over with a ball peen hammer. Make sure that the id of all holes accommodate the various wires and rods before assembly. I've done many of these models this way and they have lasted for many years! My oldest P-51 has been in service since 1975! Still going strong! I use breaded leadout cables.

Phil Spillman

[Steve_Pollock]

Brodak shows both large and small Perfect bellcranks in stock for less than $3, but they are out of Fox bellcranks.

[builditright]

Last year I found a NIB original Sterling Yak9 here on this forum.  I bought it for my cousin's birthday because he built one back in the mid 60's.  He is a slow builder but I saw it a couple of days ago during a vacation visit to Florida.

He hasn't completed the wing yet because he can't find a bellcrank to fit.  It appears that the leadout spacing is 2 3/8".

Current nylon bellcranks are too thick.  Probably the only one that will fit is the old Veco or Perfect bellcranks.

Suggestions?

Dick, you should have mentioned it on Monday I could have given you one while you were here .

[RknRusty]

I built an NIB Sterling Yak-9 in the winter of 2013-14. Doc Holiday sent me a Sig 3" bellcrank with a hole drilled through the dot over the "i" in the Sig stamp. I had to elongate some holes in the rib and it works fine. This is a seriously fun plane to fly. I added a thick tripler to the inboard nose and a double thick center rib to withstand the Fox Stunt 35 vibration.
I did put flaps on mine, and I left out the spar.

EDIT: I also laminated two 1/4" sheets of balsa for the fuse. It was stronger, straighter and lighter than the Sterling fuselage, which had a poorly(to say the least) cutout for the wing root.

[Mike Keville]

I built several Sterling Yak-9s thru the years, each using the 3" Perfect bellcrank.  Easy solution: bore-out the holes in the inner wing ribs.  The leadouts then fit just fine.  No need to omit the spar, either.

[RknRusty]

Hi Mike
The reason I left the spar out is I'd had several Ringmaster, Yak and Mustang builders from our Philly friends tell me it does more damage ripping the ribs in case of a nose bonk. My wing was stiff and straight with the oak-like Sterling LE and wing balsa, and seemed to be fine for mine, but I have not tested that bonking thing. But you are in the majority in disagreeing with me on this point though.
Btw, yours is a beauty.
Rusty

[Howard Rush]

The reason I left the spar out is I'd had several Ringmaster, Yak and Mustang builders from our Philly friends tell me it does more damage ripping the ribs in case of a nose bonk.

We left it out in the old days for the same reason.  It doesn't do anything structurally.   

[Motorman]

We left it out in the old days for the same reason.  It doesn't do anything structurally.   

Same on Ringmaster?


MM

[Steve Helmick]

The central "spar" does help keep the ribs straight, but not much else. Not much bending strength or stiffness spanwise. Some good covering helps a lot more in bending, i.e., not film.   Steve  

PS: I've only built one Ringmaster, a RM Jr., and a Sterling Me-109 (or Bf-109, Mark), and no Yak. It looks, however, like a 3" SIG BC would fit fine if moved forward some. The BC location isn't at all critical, only the leadout locations. I'd narrow those down to 3/4" apart, 1" max, and locate them off the CG location and not off the plans LO locations. Use "Line II" or "Line III" calculators. That is, of course, assuming the plans show the recommended CG.

There is a problem with Rusty's leadouts on his SIG bellcrank. They need the cable to be protected with a piece of 1/16" OD brass tubing. Otherwise, either the cable will saw through the bellcrank or the bellcrank will saw through the leadouts. Either can happen, from what I've seen.

[Howard Rush]

Same on Ringmaster?

Yup.

[Mike Keville]

Often wondered about that:  why I even bothered with the spar on the Sterling kits, since the original PDQ Super Clown/Flying Clown designs didn't use--or need--them, and were plenty strong.

[Tony Drago]

I built several Sterling Yak-9s thru the years, each using the 3" Perfect bellcrank.  Easy solution: bore-out the holes in the inner wing ribs.  The leadouts then fit just fine.  No need to omit the spar, either.

Mike , Is that the combat wing you use to fly at Whittier Narrows.

[Mike Keville]

Mike , Is that the combat wing you use to fly at Whittier Narrows.

=====================================

Yep.  Barry Baxter design, the "Melamij"...built & covered in one quick afternoon.  The damage you see wasn't the result of a Combat match.  On a solo flight, the bellcrank pulled loose, and the thing took off, "free-flighting" across the circle until it planted itself.  Man, was I embarrassed!  

...and of course the Super Clown in that photo above was one of your CLC kits -- far & away a cut above the original PDQ kit.  Wish I still had it, but I left it in Kuwait when returning home in 1999.

[Tony Drago]

=====================================

Yep.  Barry Baxter design, the "Melamij"...built & covered in one quick afternoon.  The damage you see wasn't the result of a Combat match.  On a solo flight, the bellcrank pulled loose, and the thing took off, "free-flighting" across the circle until it planted itself.  Man, was I embarrassed!  

...and of course the Super Clown in that photo above was one of your CLC kits -- far & away a cut above the original PDQ kit.  Wish I still had it, but I left it in Kuwait when returning home in 1999.
 
 I thought so. I was there that day and watched its maiden solo flight attempt.