First Strake Closed

[Dave Clifford]

Attatched is a photo of the musketeers work today. The fuel lever sending unit was bent to fit and temporarily installed in the hardpoint, without breaking I might add, thanks to the diligence of Dust and some new tools he purchased, surfaces were prepared, floxed, and the top laid in place. I wasn't there to supervise, however I have no doubts we have a "no leak" installation!

[mplafleur]

D***! I wanted to see that before it got closed. Been busy lately, but you got 3 more to do. I'll try to get out a couple of more times before the year is over.

[dust]

We planned on a detail set of pictures and had the camera all ready, but cliffords wife decided that she needed the camera for my nephew's college graduation. So that is the only picture of tank 1, but tank 2,3,4 will be documented better.

 

We made a few minor mods.

 

2" flat flanges on all external bulkheads, 2 plies bid laid up on bench and microwed and nailed to bulkheads and after hardening, sanded and taped in place internally.

 

extra 1 oz fine weave bid on all internal surfaces

 

45 degree 1" flange from two layers of 1 oz bid in leading edge bulkhead

 

What we hope to accomplish is a leakproof tank, yea like most want a leaky tank

 

1 oz fine weave glass should, i mean we hope should stop pinholes

 

flanges on all external surfaces change the mating area from 3/8 inch to 2 inches.

 

we floxed the internal part of the flange and thick microed the external part of the flange

 

So there, in a year we should know, he he he

 

enjoy the build

 

Mike

[Dan Tomlinson]

I've seen the work, and read the book,

but WHY does the leak test need to wait until the outer skin is installed?

 

Certainly it is the internal glass and epoxy that shouldn't leak - not the combination of internal and external.

 

The external will give additional structural flex strength to the strake, and protect the inner glass somewhat, but a very low pressure and low vacuum test now would make finding, repairing and confidence in the tank easier, no?

[dust]

i agree, probably will do it this plane day

 

enjoy the build

 

dust

[Wayne Hicks]

Why not pressurize the tanks for leak checks before glassing the outer skins?

 

I think I have an answer for you. The strength in foam core sandwich construction comes from having BOTH sides glassed. Ever notice how flexible the foam is when only one side is glassed? Ever notice how stiff it becomes once the other side is glassed?

 

Now take into account that the strake surfaces have only 1 ply of glass on the interior surfaces. Now consider that there is alot of unsupported area to each strake surface. 0.5 psi doesn't sound like alot of force, but there could be trouble when applied over a significantly large surface area.

 

Consider too if there's a leak? Even though the foam we use is considered "closed cell", there can be migratory paths. So how do you detect the leak? If you find the air leak, how can you tell if the source is directly under it?

 

Grant it, I'm not poo-pooing this idea. But I will tell you that until the outsides are glassed, the strake surfaces are very flexible. Just be careful. A good way to do leak checking would be to inject a small amount of freon (which by the way you're not supposed to legally do) and use a sniffer to find the leaks. I'd also recommend helium, but helium passes through most everything!

 

...Wayne Hicks