Adding an inspection cover to my plastic tank... tips please

[Jayrock]

I have a 1996 Wellcraft 218CCF. The fuel tank is not accessible except for a small cover under the console. The Fuel level sender, fuel vent and fuel feed all come out of this small hole. What is odd is that this is at the front of the tank. I Pulled the integral bait tank/seat combo, and underneath I can see the tank. This is the back part of the tank. What I want to do is add a cover, plate, something. I need to be able to clean this tank out. The ethanol is wreaking havoc, dissolving all the stuff in the tank. I have already replaced all the fuel system components. Last on the list is this cover. This tank is a kind of plastic, hard to say what kind for sure. I was planning on using a piece of 1/4" aluminum, probably 6-8" square. This is a Gas tank, not a diesel tank. My question to you guys is, " are there any good ways to do this safely?" Cutting the deck out and pulling the entire tank IS NOT AN OPTION. I work on a fishing boat for a living, and I am very capable. Fiberglass work, shipfitting, working with four part epoxy paints, and welding are a common things for me. I need the input of some experienced people on this one. Thanks again all. Jason

 

[Jayrock]

Re: Adding an inspection cover to my plastic tank... tips please

ttt

 

[sasto]

Re: Adding an inspection cover to my plastic tank... tips please

Hi Jason,

Can you supply photos, if so I'm pretty sure you will get an answer.

Can you add a pickup tube with a barb fitting in the aft part of your tank that will reach the bottom of your tank? Perhaps run a hose from the tank to an acceptable place where you can pump from when needed.

 

[Jayrock]

Re: Adding an inspection cover to my plastic tank... tips please

I do not need another pick up tube. I need an inspection cover. They are common on diesel tanks. The only thing I need to really know is what type of sealant to use. I know neoprene sealant works good on gasoline applications. I have friends in the aviation industry, they are looking into getting me a Semkit. PRC makes a sealant called PROSEAL. They use it in wet-wing fuel tanks. Great stuff according to a buddy-o-mine. I have this under control. I was just looking for someone who had experience doing this exact task. Thanks guys, Jason

 

[sasto]

Re: Adding an inspection cover to my plastic tank... tips please

The only reason I recommended a pick up tube is because I use them on diesel tanks to inspect the fuel. I pump a little out into a glass container and that's my inspection. I found it difficult to truely inspect the tank without pulling some fuel out from the bottom, as the engine pickup generally dosen't go to the bottom.

If your way works for you then all the better. Good Luck!

 

[crewscontrol]

Re: Adding an inspection cover to my plastic tank... tips please

If you are determined to do this, I suggest making a gasket out of VITON material. VITON willl stand up to most liquids, chemicals, and petroleum products. What I cannot suggest is how you can screw / bolt / attach your inspection cover to the gas tank. As I am sure you know, even a VERY LITTLE leakage can make a VERY BIG problem (bang).

 

[Jayrock]

Re: Adding an inspection cover to my plastic tank... tips please

I am aware that the aluminum would allow for condensation, but not enough to worry about. I usually keep my tank topped off for that exact reason. Secondly, I had thought about the High density poly, But I will look into the nylon 12, and that Viton. I have hand tools that I will use. I know better than to use any electrical apparatus around flammable vapors of any kind. I have an old 20 gal fuel tank in the back yard. I am going to do a test run, making a cover then sealing it with different types of goo. I will fill with fuel then let it sit for a while, see how it goes. I am going to make the backing plate for the cover in 2 pieces, so I can get it in the hole. This is why I wanted to use aluminum. Plastic threads cant handle to much torque before they strip. My test run should answer a few questions before I decide on the best way to do this. Thanks again guys, Jason

 

[Silvertip]

Re: Adding an inspection cover to my plastic tank... tips please

One word of caution (well -- a sentence or two). While cutting a hole in the tank is not an issue, fastening the cover to it is a problem. The fuel sender very likely has metal nuts embedded into the tank as is the female fitting into which the dip tube (pickup) screws into. When you create a new hole you will not have anything to fasten too other than the plastic shell of the tank. That cover also needs to be on almost a perfectly flat or just slightly curved area of the tank. If you could fashion a two piece aluminum plate shaped like the letter "C" and adhere them inside the tank that would give the screws something to grip. You would obviously drill and tap those before inserting them in the tank. Screwing into the tank with plain screws is not going to cut it from a safety standpoint as the tank material simply is not thick enough.

 

[Bob's Garage]

Re: Adding an inspection cover to my plastic tank... tips please

How about using "blind nuts". Just google it and find the type that suit's your needs.These are also called "rivet nuts" or "threaded inserts", not the "t" nuts used in woodworking.

 

[jeeperman]

Re: Adding an inspection cover to my plastic tank... tips please

If you now have the tank clean, it would be a whole lot cheaper and less work to use a high quality filtering funnel when filling the tank instead.

 

[Jayrock]

Re: Adding an inspection cover to my plastic tank... tips please

One word of caution (well -- a sentence or two). While cutting a hole in the tank is not an issue, fastening the cover to it is a problem. The fuel sender very likely has metal nuts embedded into the tank as is the female fitting into which the dip tube (pickup) screws into. When you create a new hole you will not have anything to fasten too other than the plastic shell of the tank. That cover also needs to be on almost a perfectly flat or just slightly curved area of the tank. If you could fashion a two piece aluminum plate shaped like the letter "C" and adhere them inside the tank that would give the screws something to grip. You would obviously drill and tap those before inserting them in the tank. Screwing into the tank with plain screws is not going to cut it from a safety standpoint as the tank material simply is not thick enough.

From my previous post: "I am going to make the backing plate for the cover in 2 pieces, so I can get it in the hole. This is why I wanted to use aluminum. Plastic threads cant handle to much torque before they strip." But I will make them in 2 pieces like this: [ ] Instead of Round () I will tap them, Then use the backing plate as the template for the actual screw holes. When I actually do This I will post a follow up, with pics. Jason