What if I drilled a hole just a bit off?

[mhorowit]

I was very clever in using my old spar as a template to locate and drill holes in my new spar. Then I glued the reinforcement plate in place and that forced glue into my new holes so I couldn't use the holes in the spar to act as pilot holes for continuing the holes into the reinforcement plate. Well, after some gently picking I removed sufficient glue to align the bit and do what I wanted. One hole however is off by 1/16". I'm thinking I can simply plug the hole with a 3/16" dowel (glued in place) and redrill the hole. Anyone see a problem with that approach? - MikeH

[N95334]

Re: What if I drilled a hole just a bit off?

What about drilling out the hole to 1/4 size, spar and fitting? Is there enough edge clearance?
Alternatively, drill the wood spar with a larger hole( 1/2 inch) and insert an alum 1/2 inch dia bushing with epoxy and have the 3/16 hole off center that aligns with the spar fitting. This was done on my Volksplane per plans in the bulkheads attachments to the wing struts and wing spars.

[Guest]

Re: What if I drilled a hole just a bit off?

Mike- glue the reinforce plates in place then drill the holes.

When you clamp the template spar on top of the blank put pieces of plywood same thickness as reinforce plates between the spares at clamp points to maintain true parallel axis.

Which bole hole are you talking about? Aileron belcrank?

[mhorowit]

Re: What if I drilled a hole just a bit off?

What about drilling out the hole to 1/4 size, spar and fitting? Is there enough edge clearance?
Alternatively, drill the wood spar with a larger hole( 1/2 inch) and insert an alum 1/2 inch dia bushing with epoxy and have the 3/16 hole off center that aligns with the spar fitting. This was done on my Volksplane per plans in the bulkheads attachments to the wing struts and wing spars.

Don't think there is room to enlarge the hole in the existing bracket and I wouldn't wanna weaken it.

The bushing is an option.

Is there any downside to my approach? - MikeH

[Guest]

Re: What if I drilled a hole just a bit off?

Don't think there is room to enlarge the hole in the existing bracket and I wouldn't wanna weaken it.

The bushing is an option.

Is there any downside to my approach? - MikeH

It doesn't sound like an approved process- there's a downside -what does ac43.13 say ? I don't recall.

[mhorowit]

Re: What if I drilled a hole just a bit off?

Mike- glue the reinforce plates in place then drill the holes.

When you clamp the template spar on top of the blank put pieces of plywood same thickness as reinforce plates between the spares at clamp points to maintain true parallel axis.

Which bole hole are you talking about? Aileron belcrank?

DAve - in the same picture where I ask about the gap, the hole I'm concerned about is the lower of the two holding the vertical piece on the far left; it could very well be the anchor point for for the hardware to which the bellcrank rod connects - MIke

[alwaysoar]

Re: What if I drilled a hole just a bit off?

Just off the cuff, it would seem to me that if you used a spruce dowel and installed it with the grain in the same direction, used appropriate glue, you would be ok. Is this the aft spar you're talking about or the aileron spar? I don't remember. This however us just a guess. 43-13 does not refer to this but it says for elongated holes you need to splice a new section in.

[mhorowit]

Re: What if I drilled a hole just a bit off?

Just off the cuff, it would seem to me that if you used a spruce dowel and installed it with the grain in the same direction, used appropriate glue, you would be ok. Is this the aft spar you're talking about or the aileron spar? I don't remember. This however us just a guess. 43-13 does not refer to this but it says for elongated holes you need to splice a new section in.

It's the aileron spar. 43-13 seems to leave it up to my IA.
I think I can make an arguement for a dowel.
The dowels I have are cut with the grain. Isn't what you are suggesting (building a dowel across the grain) going to be much weaker; you'll only have the diameter of the dowel (3/16") worth of grain? - MikeH

[alwaysoar]

Re: What if I drilled a hole just a bit off?

What I am thinking is to use one of those plug cutters and to make your own dowel by cutting a plug out of your old spar. I don't know how deep those plug cutters go, however. They are used in wooden boats. A dowel from a hardware store would probably do just as well, though. I'll PM you here.

[astjp2]

Re: What if I drilled a hole just a bit off?

Well they BUSH the spar for the bolt holes with Phenolic if I remeber correctly and that is an approved process. Just drill it oversized a little and use a phenolic bushing and redrill to the correct size and use an approved glue....or even a press in fit. If you make it a little long, you can sand it flushl. Tim

[mhorowit]

Re: What if I drilled a hole just a bit off?

Well they BUSH the spar for the bolt holes with Phenolic if I remeber correctly and that is an approved process. Just drill it oversized a little and use a phenolic bushing and redrill to the correct size and use an approved glue....or even a press in fit. If you make it a little long, you can sand it flushl. Tim

Sometimes it makes sense.
In this case, I could insert a phenolic rod, glue it in place and then redrill. Using that logic, substitute a wooden dowel in place of the phenolic rod; unless there is some property of phenolic that beats wood. ???

Anyway, I'm taking the spar to my IA on Friday where I'll show him what I've plan; I'll take the opportunity to discuss the lacquer as an intermediate step (I'd like to avoid clean,prime; clean, prime and instead go clean, preserve, clean, preserve, prime), pick up my gear and see if he wants me to demo my stitching prior to covering (he's given me the OK to cover tailfeathers but how would he know my stiching is correct since the knot is hidden?)

[astjp2]

Re: What if I drilled a hole just a bit off?

All you have to do is pull the stitch and it will come loose if it is wrong, It happened to me before when I checked my stitches and I did a 2" spacing for everything, including the tail feathers....... At least I can sign off my own work. Tim

[mhorowit]

Re: What if I drilled a hole just a bit off?

All you have to do is pull the stitch and it will come loose if it is wrong, It happened to me before when I checked my stitches and I did a 2" spacing for everything, including the tail feathers....... At least I can sign off my own work. Tim

He wouldn't be able to get to the stitch with the finishing tape in place - MikeH

[mhorowit]

Answer: What if I drilled a hole just a bit off?

Talked with my A&P and he has no problem with me inserting a dowel and redrilling(;f - MIkeH