Phenolic Spar Bushings

[Bobdog]

OK Gang, I have a 1946 Taylorcraft advertisement that states that the phenolic bushings in the spars are "pressed and glued in". None of the bushings in my old spars were glued , they were a light press fit, and a couple of weeks ago I helped a friend remove the wings from his '45 Champ, and the bushings in those sprars weren't glued either. So, if they are supposed to be glued, what kind of glue? I would think resorcinol was used at the factory. Also, shouldn't the bushings have a couple of thousands for clearance so the glue doesn't get pushed out during installation?

Thanks,

PS My friend with the Champ bought a NEW set of wings from the factory, with METAL SPARS. REALLY NICE!!!!

[Guest]

Re: Phenolic Spar Bushings

OK Gang, I have a 1946 Taylorcraft advertisement that states that the phenolic bushings in the spars are "pressed and glued in". None of the bushings in my old spars were glued , they were a light press fit, and a couple of weeks ago I helped a friend remove the wings from his '45 Champ, and the bushings in those sprars weren't glued either. So, if they are supposed to be glued, what kind of glue? I would think resorcinol was used at the factory. Also, shouldn't the bushings have a couple of thousands for clearance so the glue doesn't get pushed out during installation?

Thanks,

PS My friend with the Champ bought a NEW set of wings from the factory, with METAL SPARS. REALLY NICE!!!!

I used plastic resin glue when I put them in. Resorcinol glue is red and the resin is clear or white-ish. The old bushing had white residue so I figured is was plastic resin.

Coat the hole and the bushing, mine pressed in with hand tools in the dining room.

My experience with spars and bushing has been that the only time a bushing is loose is when it's in a damaged spar so I would inpspect it very carefully.

Hope this helps, Dave.

[VictorBravo]

Re: Phenolic Spar Bushings

See my previous posts about spars. I just went through the process of drilling and gluing the bushings in my spar roots.

Bottom line is that IMHO the bushings should be glued in. It makes them a lot stronger.

Epoxy is the strongest.

I made the bushings .007 smaller than the hole, so I did not push out the epoxy. It also allowed the holes and bolts to self-align while the glue was drying, so there are no built-in stresses.

If you cannot find all my previous posts about the spar issues, bushings etc, then I can e-mail it to you.

Bill

[crispy critter]

Re: Phenolic Spar Bushings

I used Weldwood epoxy on Crispy Critter.

[Bobdog]

Re: Phenolic Spar Bushings

Thanks to everyone that posted a reply, I'm sure that either type of glue will be satisfactory. When you think about it, just drilling larger holes in the spars for bushings and not gluing them in would greatly weaken the spar. Any time you remove materal you weaken the structure. But you actually strengthen the spar by bonding the bushings to the wood, because the bushing materal is much stronger, and much less likely to "split" than the wood in the spars.

[Forrest Barber]

Re: Phenolic Spar Bushings

This guessing how to do things is a wee bit out of hand. The Harer ( old Gilberti STC) describes the bushing installation completely, drill hole; insert bushing, interference fit and that is it! the bushing allows for more purchase of the bolt ( better than using a 5/8th bolt) to prevent "tear out". from the STC G-108 drawing:

Bushing - Tcraft #2570-4 NEMA Grade "C" Fiber. 3/4in long +.000/-.015 dia. is .688 +/- .005 ....... hole is .250 +/- .005 "drill hole in spar .688 +/- .005."

Then from the 2570 drawing Spar Assembly front:
shows the gussets, plates, and bushings used on the F-19. ( this is a Feb., 1969 drawing. it says use High grade spar varnish or Lionoil; 2 coats.

Then from the upgraded drawing # B-A87 Wing Spar lay out:

bushing- coat with Lionoil before installing. Birch Plywood 1/16 gussets, glue one side with aircraft glue ( TCFT 102) under pressure 100-150 psi nailed with #19 steel cement coated nails.

These spar drawings will be copied for anyone needing them and I will probably sell both as a set. 2570 & B-A87 ( note B12-A80 & B-A87 are interchangable) drawings will be priced after I copy a few. Probably around $20 - 25.00 for set plus mailing e-mail me at [email protected] if interested.

[jgerard]

Re: Phenolic Spar Bushings

I'll take a set Forrest.

Jason
N43643

[Forrest Barber]

Re: Phenolic Spar Bushings

woof that was quick I just re posted with a slight correction. e-mail me at the posted e-mail address too and I will file them for a few days then copy....thanks

[Forrest Barber]

Re: Phenolic Spar Bushings

Now before someone gets their shorts in a knot. I just got back to Bob Harer and he agrees that the interference fit is correct, BUT there is nothing wrong with using the glue method to fill up any gaps , then the bushings are there to stay .... out in the field this may be necessary... off to lunch here in dreary Ohio , just saw a snow plow going north.....

[VictorBravo]

Re: Phenolic Spar Bushings

A recent post in this thread mentions drawing 2570, and it's relation to the Gilberti / Harer STC.

As for guessing on how to do things, I couldn't agree more. We should not be kept guessing, particularly when the technical information (and the people who know the real story behind it) are still around.

I believe there may be one or two people still waiting for a credible explanation of Drawing 2569 dated 1947 and it's applicability to the Gilberti / Harer STC.

[Forrest Barber]

Re: Phenolic Spar Bushings

#2569 had to be done for the F-19; after 1968 , what is the title of it? Who drew it and who approved it?

back in 1947 they used a different drawing number system. ( to my knowledge). All Gilberti/Harer drawings are numbered with a G in front. The old Taylorcraft number system was unique , I have the full explanation here somewhere AND the drawing lists. I will try to look.

[flyguy]

Re: Phenolic Spar Bushings

Can you really produce a hole in wood that is +/- .005. How would you measure it with out compressing the fibers that much?

[gmackay]

Re: Phenolic Spar Bushings

bushing- coat with Lionoil before installing. Birch Plywood 1/16 gussets, glue one side with aircraft glue ( TCFT 102) under pressure 100-150 psi nailed with #19 steel cement coated nails.

It's good to see details coming out. But I'm always slow to catch on... so what is lionoil? And is this saying to only glue one side (doubler) at a time?

Don't mean to be a pain. I'm just hoping to do this this week and would like to do it right.

[VictorBravo]

Re: Phenolic Spar Bushings

Don Eide was kind enough to send me the drawing. It appears that it is a 1970 drawing of a plywood piece called part number 2569, and the 1970 drawing supersedes drawing 2569 which was done on 10-29-1947. The 1970 drawing was drawn by C. B. and checked by KVK on 10-16-70. I don't have the 1947 drawing that was superseded by this one.

There are other notations, such as " E. O. 2569-B Incorp." which was initialed by KLE.

ASSUMING that there is an original 1947 version of this drawing that showed a similar part, and ASSUMING that several people who measured their spars for me in recent months are telling the truth (including a 1951 85HP 1500 pound gross Model 19 without these pieces), then it can be argued that some Taylorcrafts had this part on the spar and some didn't. Nobody knows why.

The Gilberti/Harer STC instructs the mechanic to weld the plates across the strut fittings 1 and 1/16" apart (a distance that assumes all airplanes did have these part 2569 pieces installed). Since airplanes built before 1947 probably did not have these parts, and even some Model 19's in 1951 didn't have them, Gilberti likely made an error one place or another.

If these extra pieces were really necessary for strength, then the STC mentions nothing about it, and even tells the mechanic to not make any changes. If the 2569 pieces are just shims, and not installed on most Taylorcrafts, then welding the strut fitting 1 and 1/16" apart creates a very loose fit on a 1" wide spar, and thus completely eliminates the rigidity of the triangular truss formed by the fuselage upright, spar, and strut.

Adding those 2569 pieces to an existing Taylorcraft built without them would cause all sorts of other problems, like making all the compression struts not fit right, having to re-adjust all the drag wires, changing all the bolt lengths through that fitting, etc. etc. None of that is anywhere on the STC.

The STC drawing G-108 or G-110 shows the outline of the 2569 pieces on the front of the spar, but does not say anything about them, and does not mention any of the other issues with the compression struts, etc. There is no parts callout for it, or mention of drawing 2569 in the STC. The STC even says NOT to change anything out there.

So (unless you HAPPEN to have a rare T-craft built with these extra plywood pieces installed), if you follow the STC to the letter, you wind up with a very loose strut fitting that can rattle back and forth on the spar, and a loose upper strut that can rattle back and forth in the fitting.

Bill Berle

[Forrest Barber]

Re: Phenolic Spar Bushings

I have not found a 2569 drawing on any approved drawing list for 1947. That numbering system does not make any sense.
The 1947 airplanes were quite a mixed breed, I will have to root around in the back drawers for an answer. Krisna Kathori was the engineer for Mrs. Feris and was even born in 1947. I do know that you do not have to make any changes to the spar just do what the STC says..... I may have a copy of the STC drawings in the back too! I will take a look after copying the spar drawings that I have....
Lionoil is just that not glue , it is used as a sealant, lubricant, inside tubes, on tight bushings etc.... the +/- .005 is more of a feel than a measurement, the bushings have to be tight not loose. I am sure the +/- was a call out to satisfy the CAA or FAA later on.
Kind of like the 37 & 29/64th " +/- 1/8th" that I still get a giggle out of on a Tcraft drawing.