Proseal round 2 - 6 hours

One of the potential issues when back riveting the prosealed rivets is to be left with a protruding head in instances where the proseal is too thick around the rivet head. In my efforts to guard against this, i have chose to set the rivet head into the hole with a dolop of proseal, but after it is set, I give a bit of a swirl motion around the rivet head with my finger to ensure that there is no 'doughnut' of sealant around the rivet. The idea is that it is nice and flush when I put the back rivet tape (electrical tape) over the rivets.



I have used 3M green tape to protect the areas that I want to keep clean. It is important to do this work before you mix up the proseal. Ask me how I know.

I applied proseal to the skin to ensure all aluminum is covered. Then I back butter the stiffners. Ready to back rivet. Once done, then I made sure that i had a good fillet seal all the way round. Then I removed the tape and gave the skin a good cleaning with polywipes. I chose to keep the skin clean after riveting with a good wipe after, but I avoided cleaning up around the rivets themselves in efforts to make sure I had a good seal. I put proseal into a large veterinary feeding syringe and gave each rivet head a dolop of sealant.



Two tank skins...done. Ready for more!

Proseal round 1 - 6 hours

Well the dreaded day starts. The very first attempt to work with proseal. Glad to get this going...Im a little past half way on the shelf life of the proseal. It's only good for 9 months after the date of purchase and I bought it back in January.

I needed to clean the skin, so I gave it all a good rub down with MEK. Next I used a acid cleaner/etcher called Clean-Brite 218 (mixed at about 15% strength) From www.chembrite.ca

Since the chem-brite is a powerful acid, it etches the aluminum and takes the mirror finish away and leaves the aluminum a bit cloudy in appearance. But it is instantly noticeable that the aluminum is clean and etched. It's also apparent that it has also cleaned the dimple holes as its run through the rivet holes.

Everything gets a wipe down again with a clean cloth, and then another once over with MEK.

Well I will say this. Mixing proseal up is a breeze. Just weigh the parts out (10:1) according to my components. and mix. I have jumbo craft popsicle sticks that I bought at Michaels craft store. Worked like a charm. Applying the proseal is a bit tricky with popsicle sticks.

I tackled the fuel filler cap first. I was sure to figure out my rivet call outs before starting proseal. I also grabbed to vent clips and put them in a visible location so I would not forget them.

(really hard to proseal and take pictures at the same time) so sorry....few pictures.

I used a toothpick to place proseal in the rivet holes. I then placed tape over the rivets and flipped the skin over. I backbuttered the skin and flange and installed the assembly. I then back riveted the fuel flange. made sure the vent clip was in the right place.

Once I was done, I painted a layer over top of the flange with proseal. I then bent the vent clip into position and touched up with proseal.

I cleaned up the proseal around the rivets with polywipes (available from Aircraft spruce). The wipes are fairly dry and to a great job of removing proseal. The fact that the wipes are dry is good since it mitigates the worry of compromising  the proseal under the rivet head the way a wet MEK soaked rag may do.

Since I had a small amount of proseal left, I completed the right tank access anti-hangup bracket.


Ready for more....I decided to jump into the tank access rings. I used the same method as the fuel flange. Back buttered both pieces.

but then...this is where things get a bit ugly. I had posted a questions on Vans Airforce about how much of the NAS nutplates that I needed to encapsulate with proseal (as the manual states that I can leave the standard nutplates non-prosealed. The consensus was to seal them up. So I back buttered the top of the stiffener ring, cleaned out the screw hole, placed the NAS nutplate on and tried to rivet. Riveting these things is really tough. I cant really backrivet due to the tight clearance of the rivet to the nutplate body. So I elected to use the squeezer. Again....clearance is really tough and there is potential to not get a good seat on the rivet with the dies. I managed to screw up a few rivets and had to drill a few out. Not fun with proseal already on. Lots of cleaning and inspecting.

Once all was done and I was happy. I then set to work at sealing up the NAS nutplates.

I spent a good deal of time cleaning up the messy proseal to a point where i was happy with the end result. Not pretty but it's sealed well!!!

Even more tank prep - 7 hours

A big day at it finally!! I finished up preping the odds and ends with the nylon wheel.
I finished the tank access stiffeners and the outboard rib stiffeners.




One important item that I wanted to take care of was ensuring that all of the tank nose ribs where cleaned up had proper rib flange faceting as noted in the Van's manual. Darin, another local builder had warned me how important this was to have a clean and smooth leading edge. So I was very diligent to not be cavalier with this step.
I used files (flat and round) to take down the sharp edges and them smoothed them with scotchbrite on the 3M wheel.  

I then deburred all the holes in the ribs. This is not an easy process. Accessibility to the flange rivet holes is fine, but getting to the inside is another story. The leading edge ribs are not fun as the tight fit/clecos have a tenancy to make more pronounced burrs that don't come off easily. I ended up using a combination of a light deburr and a once over with  scotchbrite on the dremel to ensure no burrs.
Finally I was ready to dimple the ribs with the tank dies.


Then it was the same process on the stiffeners. Clean, deburr, nylon wheel, dimple.

More final tank prep - 2.5 hours

Once I was happy with the matting surface of the skin with a few second passes over here and there it was time to dimple with the tank dies.
 
I made quick work of the tanks skins. Next was to start the prep work on the ribs. I traced out the necessary areas on the ribs and miscellaneous pieces and went to work with the nylon brush and the cordless drill.
 

Final tank prep - 3.5 hours

Its funny when you say that you are ready to proseal but really there is still much to do. There is lots of holes to debur. This gets to be a long process. I managed to do the left skin and after have very sore fingers!

I need to go over each area where proseal makes contact with a nylon wheel brush. I used the air drill but soon found that the compressor just couldn't keep up and was running quite hot and the air was getting moist (the air dryer couldn't keep up). So I ditched the pneumatic drill in favor of the electric drill.

Takes a bit of getting used to to ensure good coverage and straight lines but I was successful in the end. The first pass is made, and then a second pass is done to form a criss-cross pattern. The key is to try to keep your lines/passes straight, while applying just enough pressure to score the aluminum but not dig too deep. Its easy to maintain the right pressure, but a little more tricky to hold it straight.
Going slow helps a lot. 


I managed to prep the skins of both tanks.

Right tank skin prep - 2 hours

Still battling a lack of desire to build (now that spring is here and there is so much outside work to do), I managed to get a couple of hours of work in on the right tank skin. First order of business is to de-vinyl the outside tank. Then, I deburred. Once I was happy with all of that. I wiped down everything with MEK.

Its getting late and I'm yawning.

Finishing new anti-hangup bracket - 1 hour

Managing to find a little bit of desire to build today, I managed to cleco up the other fuel tank and fabricate the new anti-hangup bracket. Much easier this go around as I already have the paper template drawn out and the 1/2" wide material.