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Charlie · 16-12-2007, 21:28

Here is a drawing of the access port I plan to cut in my diesel tanks.

http://www.cruisersforum.com/forums/...1&d=1197869235
It is based upon the Seabuilt model
Seabuilt - Access Plate Systems
and a picture of Catamounts job.
SSCA Discussion Board :: View topic - Diesel fuel tank access ports
I plan to use 1/4" x 1" Aluminium for the frame inside the tank. My thought would be to either drill and tap 1/4" Alum bolts thru the frame or to push the bolts thru the frame into some 5200. Any idea if the latter would be sufficient?

I was also thinkg that a few dabs of 5200 would help hold the frames to the inside of the tanks. I don't see how the frame is held other than by the gasket in the seabuilt system. Any ideas on how to secure the interior frames w/o hurting the integrity of the gasket on the top of the tank.

delmarrey · 16-12-2007, 21:52

I would not use 5200 in a fuel tank. Peratex carries sealers for that purpose.

As for the bolts you could drill and tap the lower plate & loctite to hold them from rotating or falling out.

And a 1/4" plate on the inside would be sufficient to just hold the bolts as long as you don't use nylock nuts.

And alum. bolts are almost nonexistent, use SS. There should not be any sea water to cause electrolysis....................._/)

BYW a rectangle hole, you would not need to fold it like the Seabuilt. It'll go in caticorner or what ever that word is.

seafox · 17-12-2007, 01:20

Does diesel disolve sikaflex or silkaflex?

**GordMay** · 17-12-2007, 02:15

Diesel fuel softens and damages polyurethane adhesive sealants, such as Sikaflex 296 and 3M 5200.

Polysulfide (Thiokol) sealants, such as 3M “101" or Boatlife “Life Calk”, are most often used in conjunction with diesel & gasoline fuel systems.
I don’t think (may be wrong) that Sika makes a polysulfide product.

Do not use polysulfide to bed plastics such as ABS (Acrylonitrile Butadiene Styrene) or PVC (Poly Vinyl Chloride), acrylic (Plexiglas) or polycarbonate (Lexan).
It is compatible with Epoxy, Nylon, and Delrin.

Charlie · 17-12-2007, 07:36

Del:
Thanks for the heads up on 5200. I was wondering if it would be the right thing to use in a diesel tank. I was also wondering about Aluminum bolts SS would be much easier to acquire but wasn't sure about the electolysis. Not sure what you mean by "And a 1/4" plate on the inside would be sufficient to just hold the bolts as long as you don't use nylock nuts." The inside frame would be 1/4" thick by 1" wide. Do you mean 1/4" on the outside plate?

GM:
Thanks for the tip on different adhesives. It always amazes me how much you know about how many different things!

gonesail · 17-12-2007, 08:33

for all your troubles .. why don't you just install a seabuilt port and be done with it?

Charlie · 17-12-2007, 09:04

Quote:

Originally Posted by gonesail

for all your troubles .. why don't you just install a seabuilt port and be done with it?

1) The price $138 x 4

2) I like building things.

3) I'm against rampant (sp?) consumerisim.

delmarrey · 17-12-2007, 12:56

Quote:

Originally Posted by Charlie

Del: Not sure what you mean by "And a 1/4" plate on the inside would be sufficient to just hold the bolts as long as you don't use nylock nuts." The inside frame would be 1/4" thick by 1" wide. Do you mean 1/4" on the outside plate?

Probably a misread, but 1/4" thick by 1" wide is fine IMO. I thought you meant 1" thick, that would be over kill.

As for 1/4" plate, it will be fine as long as the spacing of the bolts are close enough to avoid dimpling the plate while trying to get a seal. Your drawing didn't specify spacing. The thinner the plate the closer the holes. Personally, with 1/4" plate I would make the holes no more then 2-1/2" apart using a 1/4" rubber gasket.

In your drawing I see your cut-out is much smaller then the inside flange, or is that 4 separate flanges???? If it's one piece, the cut-out should be to the inside dimension of the flange so you can get it inside.

And the gasket, I assume you are going to use a Buna-N/Nitrile rubber seal, which is diesel resistant. You could use one of the sealers mentioned above to hold the inside plate in place, while a gasket on the outside should be all it needs.

Enjoy................_/)

Charlie · 17-12-2007, 14:29

Quote:

Originally Posted by delmarrey

Probably a misread, but 1/4" thick by 1" wide is fine IMO. I thought you meant 1" thick, that would be over kill.

As for 1/4" plate, it will be fine as long as the spacing of the bolts are close enough to avoid dimpling the plate while trying to get a seal. Your drawing didn't specify spacing. The thinner the plate the closer the holes. Personally, with 1/4" plate I would make the holes no more then 2-1/2" apart using a 1/4" rubber gasket.

In your drawing I see your cut-out is much smaller then the inside flange, or is that 4 separate flanges???? If it's one piece, the cut-out should be to the inside dimension of the flange so you can get it inside.

And the gasket, I assume you are going to use a Buna-N/Nitrile rubber seal, which is diesel resistant. You could use one of the sealers mentioned above to hold the inside plate in place, while a gasket on the outside should be all it needs.

Enjoy................_/)

Thanks Del:

I was planning on using 4 different pieces to make up the interior frame. The holes will be amaximum of 1.5" apart. I was wondering what type of gasket to use and you answered it. Thanks again.

never monday · 17-12-2007, 15:15

Charlie,
Are your tanks Aluminum or glass?

Charlie · 18-12-2007, 08:39

Quote:

Originally Posted by never monday

Charlie,
Are your tanks Aluminum or glass?

Hi Pat,

Tanks are aluminum. I have no idea how thick though.

**David M** · 18-12-2007, 13:09

I used aviation grade Permatex to seal up my aluminum fuel tanks. This is what the commercial airlines use to seal up their jet fuel (essentially kerosene, which is one grade above diesel fuel) tanks. It was not expensive just because it was aviation grade.

I used stainless steel bolts with rubber that is meant for diesel...I forgot the name of the rubber. You only have to worry about corrosion if the stainless steel to aluminum has water or moisture contact...so I covered the outside nuts, locknuts and washers, and put Permatex over the inside bolts (still wet) before tightening down with the Permatex just to be sure. I made the holes in the rubber gasket about a 1/32 smaller than the bolt holes and brushed on plenty of Permatex on both sides of the gasket. I waited a few days for the Permatex to cure before filling the tank..although the Permatex never it really gets hard.

Tip: cutting the gasket material 1/32 smaller than the diameter of the bolt helps make a better seal AND it also grips the bolts so they don't slide back into the tank when you place the access port over the opening. Holding the bolts so they don't turn is easy if you double nut the bolts while you are turning the nut that tightens things down.

The bottom lines is that it did not leak, there has been no corrosion and it has been 5 years now. More importantly, there has been no corrosion from when the boat was made (tanks integral with the hull) from over 25 years ago. Therefore, this method of sealing an aluminum diesel tank works. It does for my boat at least.