Another thread about tank skin dimpling vs. countersink

Hi all!

The manual is asking me to countersink the baffle to tank skin holes, which is 0.032" thick material, the reason stated in the manual is to allow the baffle in easier. If "getting the baffle in easier" is the only reason to countersink the skin, then I rather dimple it as it is not taking metal off, and less chance to screw something up. I read a few other post on the subject, and it's giving me an impression that it's okay to deviate from the manual and dimple the tank to baffle holes. Just want to see if you have any thoughts on the subject before I punch that dies thru the holes.

Also, is tank dies a "must"? I bought the RV tool kit from Avery and I don't think it comes with it. Can I get away with any other methods?

Many thanks!
Hank

Hi,
i followed the instruction and machine countersunk the skin. The problem in dimpling it is that the baffle will not slide straight in place. You'll still be able to put the baffle in place if you dimple the skin, but sliding it straight down will allow to form a even fillet of sealant along the baffle/skin contact line reducing the risk of leaks. A leak on the baffle joint will need to cut big holes in the baffle to seal it. Probably dimpling will work too, but I don't see any reason to deviate from instruction in this case. Machine countersink work well even if the skin is thinner than .040.

In my opinion tank dies aren't a must. I used them but the difference is so small I don't think it'll be noticeable if you use standard dimpling dies.

I dimpled the skin and baffle and it worked perfectly..

The dimple v countersink is your choice. I had no problem putting the baffle in for final riveting. Its the proseal that is important. I put a bead of proseal on the tank skin right at the level of the rivet holes and I also used a popsicle stick to butter up the baffle flange with a thin layer of proseal. Then I sort of slightly angled in the first flange of the baffle and once that was in place I slightly spread open the opposite side of the tank skin while pushing down the tank baffle. It went straight in and on both sides after clecoing, the sealant was squeezed down forming the ''bead'' which you could see from the end rib opening. Tank passed the leak test. I also used the tank dimple dies and liked the fit of the rivets with proseal under the heads. Its a very slightly deeper dimple and it worked well. My first tank was done years ago with normal dimples and frankly I don't see any difference. When I ended up with a slightly high rivet, I hit it again and it flattened out better. For me, the occasional high rivet was due to me not setting it enough, not because the dimple was too shallow. Hope that helps. There is nothing wrong with countersinking the skin. That is after all what is called for in the plans. Both ways work.

Dimpling works fine.

I prefer dimpling. It is a little more difficult to install the baffle, but you are hopefully only going to do it once. I dimpled mine and haven't had a leak in over 17 years, so far.

I dimpled mine, had no real issues getting the baffles in. My tanks hold pressure, but not flying yet.

Dimpling

I dimpled the skin of the first tank by accident (just got on a roll with the c-frame), but it came out so well I decided to do both tanks the same way. Only issue is that you'll need a close quarters dimple die to dimple the baffle since the holes are very close to the bends.

I'd do it the same way if I did it over again.

Yeah, I just realized the holes on the baffle is too close to the edge for the regular dimple die.

Thanks guys! Will post feedback on how it turns out. Thanks!
Hank

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Hank,

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Richard

I just got through putting in both baffles with the skins dimpled and had no problems, however they have not been leak tested yet.