T

tyvaf01

Member
according VAN`s instructions the spanwise holes in the T-701 skin should machine contersinked,to make it easier to slide the baffle into position.Did anybody try if dimpling those holes also works?I don`t like machine countersinking thin material like the tank skins are.
 
Baffle

I countersunk per the instruction but would not do it again. I had a difficult time maintaining alignment between the skin and baffle during install. Naturally this install occurs while working with pro seal so it isn't like you have lots of time to sort out alignment. With a dimpled baffle the holes would become self aligning.

The dimples in the skin probably present a challenge when inserting the baffle but I think others have done it successfully.
 
I had read previous posts of people having trouble after countersinking, but frankly that was the least of my troubles at that moment in time. Sure it slid slightly off position, but it was easy to correct. The baffle can't drop into the tank since the aft end of the ribs prevents it. Just hold each end of the baffle and lower it into position. Based on what I had read previously I was expecting a lot worse. I really don't see the big deal.

The one comment I would make is to make sure your countersinks are deep enough. I think mine could have been slightly deeper.
 
Van's engineering has approved the CSK depth, shear and tension loads for the assembly with the 426-3 rivet, so why would you use the 1097?
 
I dimpled in this location and had zero problems putting it together. I agree that it helps with the alignment also.
I have seen tanks which were machine countersunk that had tilted rivets due to slight misalignment of the two skins.
 
The one caution I saw was that on the most inboard 10 or so rivets on the top side of the skin, if dimpled, the shop heads could contact the top spar bar. If you look, it is tight and I agreed that these could hit the bar, so I countersunk them all.

If I were doing it again...I would probably have countersunk these only and dimpled the rest.
 
I did mine pretty much to plans and instructions, and it worked out great. Considering how the baffle seals by its radius pushing a fillet ahead on installation, sealant in the baffle holes probably isn't necessary, but I countersunk the holes a few thousandths deeper than flush so I could install them with sealant anyway.

When everything was ready, I just laid down the 3/16" diameter beads on the skin just forward of the baffle attach holes, and, per instructions, applied a thin layer of sealant around each rib hole before dropping the baffle in place (baffle flanges dry). I'd read other build logs talking about misalignments, so I just took a few minutes to maneuver the baffle to eyeball the hole alignmnets, checked the fit of the rivets in each of the four corners, then clecoed away. The final result was some the best looking rivets on the build so far.

I'm a bit of a fan of "belt and suspenders" approaches, so I encapsulated the shop heads and painted on a thin fillet across the aft edge of the baffle flanges and skins.NO LEAKS! I built an HRII tank this way, and I'm about half way through the second of my -7 tanks and plan on doing it the same way.

Pictures and details.
 
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