88M: Aileron spar question

[mhorowit]

I’m trying to determine what my options are with respect to my aileron spar. The two pictures show what I believe is a bond failure starting from somewhere underneath each plywood doubler. 43.13, para 1-44 says “cracked spars may be repaired by bonding plates of spruce or plywood of sufficient thickness… . both sides of spar. As shown in Figure 1-10”. Figure 1-10 shows the spar sandwiched between two plates. The illustration also contains the phrase “No fittings within these limits” and is referring to the length of the reinforcing plate. I’m glumly interpreting that as meaning the use of doublers in this case won’t fly (no pun intended). I don’t immediately see a work-around in this chapter.
Am I going to have to build a new spar or does anyone know of a way to repair it? - Mike

[Robert Lees]

Re: 88M: Aileron spar question

Mike: there seems to be some question about the future airworthiness of these aileron spars. I'd suggest that repair is more difficult than full replacement for these small spars.

I've seen the selection of photos: I rest firmly in the "if there is any doubt, there is no doubt" camp, and I would suggest you bite the bullet & overhaul these ailerons to replace the spars (or get replacement ailerons).

The cost is only that of the timber (I paid about $60 five years ago for all the necessary timber for both ailerons from Aircraft Spruce).

A few hours grift is necessary, I'll confess. I don't think you will find the technical challenge too hard, bearing in mind your previous very successful overhauling and learning skills.

Hope this helps...

Rob

[mhorowit]

Re: 88M: Aileron spar question

Well, here's an example of another door opening!
Fortunately I have access to a nice wood shop and a friendly instructor.

To get an idea of what might be involved, I went back to your restoration pics (thanks (at least for the fourth time)for putting them at our disposal)to see if you might have worked on a spar. sure enuf.

I see the husky template you built to insure the mounting holes would be correct with respect to each other, but I can't tell how you insured the template was placed correctly on the spar. Can you address same? Why not simply lay the old spar over the new one and drill away?

Also, wasn't there a thread a long ago about cutting your own blanks out of an old wing spar? maybe it was more economical to buy one wing spar than two aileron spars??? - Mike

[Robert Lees]

Re: 88M: Aileron spar question

Mike:

When I looked at making new aileron spars, I thought of two issues: firstly that of getting the hole spacing right in each of the three "clusters" of attachment holes, and secondly: of getting the position of each "cluster" correct along the length of the spar.

For the former problem, I measured the hole distances in the centre cluster, and from these I made a drilling jig with the necessary five holes that go through the centre attach point of the spar. (Of course the inboard and outboard aileron attachment points are the same, but they only use two of the holes, but the observent restorer will note that the ply doublers have all five holes (very sensible...why use two types of doubler when one will do?)

The second issue is where to position these three "clusters" of holes along the spar length. I not only used my original (damaged) spars, but also used the D model drawings available through Ron Greene as a dimensional reference. Ron offers a copy service for the CD's, and a very large & generous proportion goes towards the Taylorcraft Foundation. In particular, these drawings detail the chamfers of the spar edges.

Mike: I do need to document the dimensions of my jig; I will endeavour to do so soonest. It's lost in my "jig pile"...[20 minutes later of looking, and can I find it? Doh!]

Just be aware: the description of how I made my new aileron spars might include some non-FAA practices, but I don't care, since I'm on the G-reg!

[still looking where that darn jig is.........]

[Doc]

Re: 88M: Aileron spar question

Howdy: My aileron spars on N43306 looked better than yours, but when I removed the AN hardware there was considerable corrosion on the shafts of the through bolts with corresponding rot noted in the bolt holes. Based on this I decided to replace all spars (and hardware). I used both aileron spars and the left wing spars as templates for new wood spar fabrication - I purchased spar stock through Aircraft Spruce. Ask for a dealer discount. Doc

[crispy critter]

Re: 88M: Aileron spar question

Well, here's an example of another door opening!
Fortunately I have access to a nice wood shop and a friendly instructor.

To get an idea of what might be involved, I went back to your restoration pics (thanks (at least for the fourth time)for putting them at our disposal)to see if you might have worked on a spar. sure enuf.

I see the husky template you built to insure the mounting holes would be correct with respect to each other, but I can't tell how you insured the template was placed correctly on the spar. Can you address same? Why not simply lay the old spar over the new one and drill away?

Also, wasn't there a thread a long ago about cutting your own blanks out of an old wing spar? maybe it was more economical to buy one wing spar than two aileron spars??? - Mike

Mike,
To answer part of your question...yes ,you can simply use the old spar for a pattern. Just be careful and make sure you clamp everything secure so not to slip out of line but at the same time don't clamp tightly enough to damage the new wood. If you do rebuild(replace) your spars "MAKE SURE" you use a good quality drill press that is level,straight,and true with spars supported level. It's not hard to do,just take a little time. I should have a few servicable spars but I will need to inspect them very close before I promiss anything.

[mhorowit]

Re: 88M: Aileron spar question

The Taylorcraft Bulletin came in yesterday.
Very timely as it had Bob's article on rebuilding an aileron spar.
One question: why did the reienforcement plate have to be planed to the correct angle? why could it not have been stood on edge and bandsawed? - Mike