Tip: Proseal / Sealant usage

Thought I'd share this in case anyone is wondering how much proseal gets used.

I think the plans said a quart of sealant should be enough to do both tanks? HAH! I'll be scraping the can dry to get enough to finish the access plate. Here's my usage as I sealed everything. I did this tank the old wet sloppy way - so I tried to make enough sealant to do each job without a lot of leftover.

I used:

3 oz for the center rib, outboard tooling hole, fuel sender
4 oz for each pair of interrior ribs x2
4 oz at least for each end rib (I laid in another 2 oz ea for more fillet)
8 to 10 oz for the baffle, I did 7 oz I think and had to make another oz to dip rivets in.
That leaves me with about 2 oz I'm guessing to close the access panel.

You'd have to be very stingy and careful to seal a tank with 16 oz of sealant, and I'm hoping I don't have to crack it open if the leak test fails.

Bruce,

I've done multiple tanks and typically use about 1/2 to 2/3 of a quart can to do both tanks combined. And that is WAY more than they use on the factory built tanks.

If you're seriously over the amount I use, you might want to check with some other builders. More isn't necessarily better... you'll have less fuel capacity and that stuff is plenty heavy!

An acid brush with the bristles clipped to about 1/4" length is your best friend for spreading the black stuff. Your second best friend is a baggie with a corner clipped off to squirt the stuff on like an icing bag. The only hard part is putting the stuff into the bag.

Try those tips and see if things don't get markedly easier.

BTW, keep the stuff in the fridge and it will last a long time. I have a can from 2003 that is still useful, though I don't use it on fuel tanks. Nonetheless, that rubbery stuff has many other uses once you make friends with it.

vfrazier said:

The only hard part is putting the stuff into the bag.

Click to expand...

Don't put the sealant in the bag, put the bag over the sealant. I usually put my hand in the bag, load up sealant on the outside, then invert the bag.

thanks

Thanks Vince,

Maybe the next time around I'll feel more confident in going lighter on the stuff. I'm happy that both tanks leak checked ok (with air). I do have some pretty heavy fillets on the end ribs and around the service panels, but I scraped most of it away from the interior ribs - so I won't actually be flying less a quart of fuel on either tank. Most of the batches ended up on paper towels and leftover in the plastic bags like you mentioned.

I do have a question - is there a potential problem with "mixing" sealant on a part - two different stages of cure. In other words I start putting the baffle on and run out of sealant as I'm setting rivets - will it mess things up if I mix more sealant and continue the job - the first batch having been mixed an hour or so before?

vfrazier said:

Bruce, I've done multiple tanks and typically use about 1/2 to 2/3 of a quart can to do both tanks combined. And that is WAY more than they use on the factory built tanks. If you're seriously over the amount I use, you might want to check with some other builders.

Click to expand...

On the other hand, you might want to obtain a copy of a widely accepted aerospace standard like SAE AIR4069A or B, which is very specific about the required sealant thickness over fasteners and along seams.

The original document is hard to obtain with paying a fee, but there are excerpts on the web, for example:

http://cdn1.bergdahl.com/wp-content/uploads/2014/04/Sealant_Contours.pdf

A 'mil" is 0.001", so 250 mils is 1/4" thick, 100 mils is 1/10", etc. Although a minimal sealant approach is pretty and certainly weighs less, aerospace pros found reason to agree on these dimensions.

Thanks Dan.

Use plenty and remove excess

My friend had some tanks professionally built and the insides are pristine.. now hes repairing tanks that leak like a sieve.

Cm

I think we are mixing terms here. The quart kit is 32oz (fluid) but mixing is done by weight. I have the tanks on my 14A done except for the rear baffles and I have used a full quart (32 fluid oz) but that equates to much more then 32oz by weight as the sealant is heavy.