Any ideas for a good filler?

[Guest]

Hi all,

I am assembling a wing and installing bolts and fittings.

I have the drawings for the parts and a clearance can exist between the i.d. of the bushings in the wing and the bolt that goes through it. (its not a t-craft wing )

So that means that some bolts fit tight and some loose.

I have one or two bolts that do fit loose.

I recall that in the past I have made such bolts fit tighter by smearing it with epoxy or varnish...

Epoxy seems to aggressive as the bolt may not come back out unless perhaps I coat it with a release compound.

My reason for posting is this; does anyone have any any experience or suggestions about what compounds or process may be good the fill in that clearance, provide a tight fit and allow the bolt to be removed later?

Thanks, Dave.

[skip]

Re: Any ideas for a good filler?

Hi all,

I am assembling a wing and installing bolts and fittings.

I have the drawings for the parts and a clearance can exist between the i.d. of the bushings in the wing and the bolt that goes through it. (its not a t-craft wing )

So that means that some bolts fit tight and some loose.

I have one or two bolts that do fit loose.

I recall that in the past I have made such bolts fit tighter by smearing it with epoxy or varnish...

Epoxy seems to aggressive as the bolt may not come back out unless perhaps I coat it with a release compound.

My reason for posting is this; does anyone have any any experience or suggestions about what compounds or process may be good the fill in that clearance, provide a tight fit and allow the bolt to be removed later?

Thanks, Dave.

Dave,

I use epoxy and milled fibre. One reason is that I found some numbers for crush strength of West Systems epoxy and milled fibre. I like numbers.

Even where new holes are properly drilled in new spruce, good sealing of the holes is a nice touch. Some folks say to varnish the holes and then ream, but that defeats the purpose. The reaming will remove the varnish right back to the wood. I like to both seal the wood in the hole and at the same time ensure a perfect fit for the bolts. So here is the approach that I have used on my AcroSport-II wing. This procedure is not in AC 43-13 that I can find, but the literature is full of recommendations to seal bolt holes.

After the varnish is on the outside of the wing coat all the bolts, washers, and the associated fittings (picture for example, a spar root fitting) with a good carnuba floor wax. Don't use a car wax. The floor wax is a better carnuba usually. If you are really paranoid about the epoxy sticking, you can then hit it all with a silicon waterproofing spray.

Mix a good epoxy with enough milled fibre to make a peant-butter-like paste. Use a small stick, screwdriver, or that antique diamond-encrusted hat pin that your wife treasures so much to rub a good coat of the milled fibre paste into the bolt holes. Place the fitting in place and insert the bolts. Wipe any excess epoxy that gets pushed out the hole and add washers and nuts. Tight torque is not needed. Let dry overnight. The next day. loosen the nuts, give the bolts a quarter turn to tell yourself that you didn't really glue your wing together permanently, and remove all the bolts and fittings.

You now have a set of perfectly aligned sealed bolt holes that have any slop removed. The procedure is basically identical to how hunters and target shooters have been glass-bedding rifles for decades.

I did find some numbers that give West System with milled fibre having a 19000 PSI crush strength. For comparison, the Linen Phenolic bushings in our Taylorcraft wings have a crush strength of 15000 PSI.

For what its worth, One guy's experience, etc.

[N96337]

Re: Any ideas for a good filler?

Same thoughts here Dave. Especially the West System. That's the only epoxy I use. They have some great fillers too.
John

[Robert Lees]

Re: Any ideas for a good filler?

Use close-tolerance bolts?

[Hank Jarrett]

Re: Any ideas for a good filler?

Makes a big difference if this is a primary load path or not (safety, not legality). You can do a lot with fillers in non-load path joints. It also matters if this is a certified plane or not. YOU take the risk on a home built, but you could be in trouble with the ""Feds" if you use an UN-approved method on a certified plane. You could make her UN-airworthy "legally" even if it is a safe fix. Check with whoever is going to sign her off (legality has to be considered, even if it is not necessarily a safety issue).

Hank

[Guest]

Re: Any ideas for a good filler?

Thanks everyone, I appreciated all the comments and suggestions.

According to the drawings a clearance for the bolt is allowed according to the tolerances given.

I just prefer a zero clearance fit.

Good suggestion about legality Hank, I have to ponder that one.

Dave

[Guest]

Re: Any ideas for a good filler?

Hmmm, 3/8" close tolerance bolts are hard to find.

Anyone have a favorite or good source for them?

Thanks, Dave

[3Dreaming]

Re: Any ideas for a good filler?

I will also note that the diameter of AN bolt will vary some. It might be a simple as trying a different bolt for that spot.

[tcraft759]

Re: Any ideas for a good filler?

Dave..... www.skygeek.com has stock of the AN176- close tolerance 3/8-24 bolts in varying lengths.

Helen

[Guest]

Re: Any ideas for a good filler?

thanks all!

I really appreciate it.

I am going with the close tolerance scheme.

Hank has a very good point and that changed my direction.

Thanks again, Dave.

[otrcman]

Re: Any ideas for a good filler?

PM sent.

Dick

[Guest]

Re: Any ideas for a good filler?

hi Dick,

I never got a PM, not ignoring you.

Dave

[Hank Jarrett]

Re: Any ideas for a good filler?

I have been told I have a good point, but I try to comb my hair to hide it. ;-)
Hank

thanks all!

I really appreciate it.

I am going with the close tolerance scheme.

Hank has a very good point and that changed my direction.

Thanks again, Dave.