Semco Sealant Gun

Here's my new (used) Semco sealant gun. It's a Model 250-B. The Model 250-A is the same except it has a handle and trigger instead of the flat paddle trigger like in the photo below. I tried both and much prefer the paddle trigger. I can get into much tighter places like the fuel tank when sealing the ribs when using the paddle trigger. The tubes also come in several sizes. I've used both the 2.5" and the 6" and prefer the smaller for inside the tank work. I didn't see any use for the 12" unless you're building a 747. It uses pneumatic pressure to push out the sealant in a very controlled manner with the ability to stop the flow instantly. It was much easier to encapsulate the rivet shop heads with it instead of scooping and dabbing with a popsicle stick. I also wet sealed every rivet by putting a tiny dab in each countersunk hole before putting the rivet in and the Semco gun made it fast and clean as it doesn't continue to flow when you let up on the paddle or trigger. You do have to fill the plastic tube (goes inside the metal housing) with your sealant but that wasn't too hard. I told Paula that this would make a great cake or cookie decorating tool...just use icing instead of proseal! Edit: I tried icing a cake with it and it worked fine but the nozzle was too plain to make fancy designs like the dedicated decorating tips.

I purchased several on ebay for such a good deal that I gave some as gifts. If you're shopping for used, make sure you get the factory air line as the fittings look hard to source. I got extra plastic tubes and nozzles from Brown Tool. I ordered 6 or 8 different nozzles and the only two I like are the straight 4" and 2.5" with a 1/8 opening.

For cleanup, I unscrew the plastic nozzle and set it aside. I also pull the plunger out. Then I put a piece of scrap "handle" in the tube and use it to pull the old proseal out after it dries. I don't squeeze any leftover out as it makes it easier to remove almost all the dried proseal including from the nozzle. Leaving it overnight is just the right amount of time as it's rubber like but not too hard. Makes cleanup a breeze.

I've also used the Semco for applying RTV to seal the baffles. I got a caulk gun size container of red high temp RTV from NAPA for just a little more than a retail tube. It was easy to squirt it into the plastic Semco tube and it was much easier to apply in tight spaces. I left the RTV in the tube and it stays fresh and can be used again after pulling a small plug of dry RTV out of the tip.