Wing Spar Insert trouble

[jiott]

Help! I just got started and am already in trouble. I was puting the SS7 wing spar I-beam inserts into the wing spar tubes. 3 of them went in just fine with no trouble. On the 4th one it went in a little tighter but not too bad. I could push it by hand until it got in about 1" inside the end of the spar tube. I then probably did a foolish thing and tapped it in a little farther with a stick and mallet-not too hard but hard enough that now it is stuck and won't go in any farther and I can't seem to tap it out from the other end. I am afraid to beat on it too much. I have tried the clamp method shown in the manual to egg shape the tube but it does not seem to help. It has probably galled itself (soft aluminum on soft aluminum) and semi-welded itself together.

What should I do now?

Jim

[HighWing]

Jim,

I think what I would try is a bit of Relton A-9. It is an aluminum cutting fluid based on mineral oil with some secret stuff - and it smells good. It has an affinity for aluminum and will wick into the gap and prevent further galling and may even wick into the galled area. If this doesn't work, My guess is it might take a new spar and insert.

Since it is oil based, I suspect you would then want to remove the insert, and clean up both parts to remove the oil residue if you have plans on an anti corrosion coating.

I use a lathe and milling machine on aluminum from time to time and the cutters will pick up a spur if cutting dry. You may have seen these things on drill bits. Trying to scrape them off is a chore, but a drop of the A-9 and it wicks between the cutter and the aluminum spur and clean again.

Lowell

[Dave S]

Jim,

Don't know if you got your spar problem resolved or not yet.

I would approach this with a whole lot of caution - it is impossible to see what has happened with the galling/sticking once the parts are assembled.

The instructions with the kit make it pretty clear that scratches, etc are not good - they become the start of stress risers that can result in a crack later.

I had one spar/insert which started sticking - never hammered on it but diddling with it didn't make it go any easier - if you end up having to put force on it - it will gall worse if pushed further. My curiosity got the better of me - once I got my new spar & insert for a replacement - I cut the sticky spar apart - no little scratch - found a real nasty balled up & galled damage zone - pretty well confirming that it is not a good idea to trust one's hide to a spar that doesn't slip together easily.

My suspicion is one little speck of dirt can start galling when slipping in the inserts - once started - grows badly as the parts are pushed together with more force - Cleaning and swabbing the spar tubes as well as being very careful with the insert with regard to starting with a smooth clean surface is essential.

Aside from the one that went bad for me and got replaced - I ended up with all spars slipping together easily with no resistance or catches. If I did another one and a spar insert stuck - I'd replace it in a heartbeat - or quicker.

It is going to happen when building an airplane that there will be a few things a person ends up having to re-do - Never consider these incidents to be issues of failure - the failure would be not to re-do what needs to be redone.

Sincerely,

Dave S

[jiott]

You're reply is interesting and is exactly what I finally decided to do. Using oil and a good sharp bang on a dowel from the opposite end, I was able to get the stuck insert out of the spar. Inspection of the inside of the spar showed several long but very light scratches. I worked on them for a while with Scotchbrite on a dowel but could not get rid of them to my satisfaction. John McBean said anything more than .005" deep is scrap. I think they may have ended up less than .005" but I could not be sure, so I decided as you did to replace it and start over. I made a quick trip to the Idaho factory and picked up new spar. They suggested using baby oil to help insert the insert, which worked like a charm (I wish the manual had mentioned this-it might have saved me some trouble and money). Anyway, I now have 4 good spars and insert all riveted in and am back on track. But best of all my mind is at ease and I can move ahead with confidence.

Jim

[Sabre]

Those that did not get the QB wing, did you remove the aluminum chips from inside the spars after done riveting? If so, what is the best method? I used baby oil when installing the inserts and there is still a slight residue that the chips are clinging to. Was thinking potentially a shop vac. Thanks

[jiott]

I used a wood stick to knock off as many burrs and chips as possible. Then pulled an oily rag thru several times to drag the chips out. Then sloshed denatured alcohol thru to clean out the baby oil. Then sloshed the inside with epoxy primer for corrosion protection.

[jtpitkin06]

If it happens to anyone else, try this...

Warm the spar with a heat gun. No torch allowed here. The heat gun can't get the spar tube hot enough to do any damage but the aluminum tube should expand to let you get the i-beam out.

Heat also works well for inserting the I-beams. If you get the beam in almost all the way and it hangs up just use the heat gun. The I-beam will not get hot on the inside of the spar tube.

And, yes, always use some type of lubricant.