TOPIC: new stringers and custom fiberglass fuel tank

To start of i haven,t sold my Commando U2 yet a couple offer but didn,t take it.Anyway let get back to my Dorsett as you can see i got the new stringers all glass in and reinforce the bottom with extra 3oz of matt.I try to find a fuel tank in the local marine store here that i need but no one carry one so i decide to make 1 that i want.Check around to shop for material and found afew extra scrap of carboard paper,malinine and what ever you want to call that wood is on the side.Afew cut later i hotglue everything together and i have a mold.tape it all up with blue masking tape and gelcoat my mold.I glass it all and make a bafful and flange to glass my top lid on after i pull the tank from the mold.I dry fit it between the stringer just to make sure it fit and took it out again sand the inside of the fuel then i coat it.not done yet but will post pic of under floor before i cover it up.

Will you have the fill and vent in the splashwell?

Are you sure you want to use a fiberglass fuel tank, give all of the problems between ethanol and fiberglass?

We use to made fishing boat about 20 yrs ago and we made fiberglass fuel tank for them those boat are still around until today.so what I see is that if you do it right it should last.

Commander, do what you want but I would not use fiberglass for a fuel tank in this age. 20 years ago or even earlier in the 70's gasahol was starting to come into use and the effects showed up later with carb internals plugging, engine failure, fuel line failure because of the alcohol eating away at the rubber content. Here is a partial article you might want to read and also a link to the whole study.

"A few years ago there began to be reports of fiberglass tanks failing. Over the last few years the trickle became, if not a flood, a running stream. The Boat Owners Association of the US (BOATUS) commissioned a laboratory to do testing of fiberglass tanks and found out the alcohol can dissolve the resins in the laminate. As we now know, fiberglass is not impermeable, as had been thought back in the 60's and 70's. When boats began blistering in the 1980’s, the Coast Guard and others began studies to find out what was going on. To make a long story short, fiberglass reinforced plastic or FRP, is actually a semi-permeable membrane and liquids will penetrate the resins. This is what led to blistering. Alcohol will penetrate FRP as well and dissolve uncatalyzed resins. That is, resins that were not mixed well with the catalyst and never set up. If alcohol dissolves these then eventually the damaged will be extensive enough that the laminate will fail. This does not happen overnight. It takes years, and it takes long exposures to alcohol. Boats typically sit for long periods of time with full fuel tanks, allowing the components of the fuel to do the damage. This has not been seen on automobiles or trucks because fuel simply does not sit in the tank and system for very long. However, the research shows that the potential exists for tanks to be damaged in a short time span, 6 months to a year, depending on the laminate, the resins used and how well the FRP laminate was made. But almost all of the tanks that have been reported as leaking have been built in the 1980’s or earlier. "


Cal

newboatbuilders.com/docs/Ethanol.pdf

Dam, i didn,t know that until now.i hope that layer of expoxy help,s it somehow.if i get 2-3 yrs out of it then that is good enough.i just have to kept in mind that the fuel tank have to come out and don,t built anything on top of that area.thanks i pass this on.

Is Ethanol Free gas available in your area Commander? Luckily, there are still some gas stations between my house and my home lake that still offer that option. I've started using it exclusively, since I did have some problems with the newer "alcohol resistant" rubber products! I was using StarTron fuel treatment, and will continue to do so. But I don't believe there's any "magic exlixer" to fully offset the damage that stuff can do completely?

Is there a chance you could put a bladder in it? Airplanes used bladders for fuel.

A number of us on the West Coast have been forced to pull the fiberglass fuel tanks out of out boats. The resin slowly gets washed away and hundreds of tiny fibers get into the filter, carb jets - it is a major problem. I'm inclined to try "SLIME" on the Skagit tank I have. That stuff is designed for rusted/leaking tanks, and the company says that it works on fiberglass tanks as well. It is some type of special resin that gasoline will not touch. I have a friend that races motorcycles and swears by it - says he has been using the goop since the 80s and never had it fail yet. You would need a ton of it to completely coat a boat tank though - not sure on the price. I personally feel that plastic tanks are now the best way to go - I have seen too many aluminum tanks crack at the welds and weep gasoline into the bilge.

Bruce, what is "slime"? I have an older 18 gallon steel tank that has rusted inside but not leaking. Would it work on that. Is there a product link somewhere.
Cal

Cal,

"Slime" is just a generic nickname for tank coating. A lot of companies make the stuff. It is a special type of liquid polymer that you pour into a leaking / rusty tank to coat and seal it from the inside. You clean out the tank as best as possible, then it gets treated with a pre-coat wash (probably metal etch if some sort) then when that is dry, you dump in the slime. The tank is turned end-for-end, over and over to slosh the crap around enough to coat every surface and seal it. You then let it dry / cure, and put the tank back in service. I've never done this - but I have watched my friend use it on aluminum and steel motorcycle tanks. Is not a hard job - but you must follow all the mfg. steps carefully to have it turn out right. You can find the stuff all over the web.

Bruce

Maybe looking in classic car part suppliers would help. Be kinda hard to slosh a built in tank around. I didn't think of that. Frustration is just another part of living we have to deal with from time to time.

Don't want to hijack this thread anymore...but.... Here is the tank. Was removed when I started the rebuild. Looked at some of the sites for the liner stuff and I think that's what I will do. Thanks for the info.
Cal

Cal, POR 15 makes the stuff as part of their line.

Bob

i've used por 15 on the bed of my dump truck. theres nothing tougher! 3-4" river rock being dropped in the dump by an 4yd. loader doen't even chip it. ron

Regarding fiberglass tanks:

I was advised at the start that even though my boat had the original fiberglass tanks that I should not try to use them with my new Mercury outboard for the reasons stated herein elsewhere.

I was however given a great suggestion. Why not remove the gunnel tanks and have the backside cut out with a new aluminum custom fabricated tank put in the Shell of the old fiberglass tank. Then the modified tank could be put in the place where they originally came from and if properly done nobody would be the wiser.

I took them to the local aluminum boats fabricator and he really liked the idea, and quoted me a very reasonable price for the job. The downside is that I will lose some capacity, which I believe is a small price to pay for such an elegant solution.

Here is a picture of the boat parked at the fabricator, with the vintage trailer I got with the boat.

How's your tank coming Commander? I've been keeping up with a Scimitar (Gary's) project Ole Red is doing, with a Fiberglass gas tank (due to the size). He mentions using a sealer inside, details are in the thread;
www.olered.com/GaryPage2.html