# Fiberglass fuel tanks longevity



## Chris Morejohn (May 12, 2014)

I received this photo yesterday in an email asking about some of my other builds that the person was looking at buying.
This is a picture of Whipray Hull #1 that I built in 3 weeks for Flip to use with Lefty for a Walker Cay Chronicles show that they were to do together in two weeks time.
The hull is from the new mold and the deck is just Core pieces all glassed together.Everything was Gelcoat rolled over finish.
Very rough basic finish. It killed me to show it at shows till we got hull #2 done with all the molds I had not yet finished building.
Because there were no aluminum tower or fuel tank welders about in St. Augustine back then I just glassed in my standard fiberglass fuel tank in the bow using the hull sides as part of the fuel tank with a wax barrier to separate the two for Coast Guard regs.
This skiffs has an interesting history. The stern was pulled right out of it once rounding the southern end of Great Abaco when it was being towed behind a big freight boat with a 40 Merc on the stern in big seas. A sea washed over her and out went the stern and the engine.
Seeing her in this picture brought back memories for me along with the fact that that’s a 22 year old fiberglass fuel tank in her.


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## Tigweld (Oct 26, 2017)

Something to be proud


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## Fritz (Jan 17, 2017)

Chris I’ve read a good bit about your glass tanks and I would not be against trying one if the very specific directions were all in one place and included a detailed ‘bill of materials.’ By that, I mean I want you to tell me exactly what resin to buy, etc...

When the answer is ‘you need to do the research on resins...’ the risk for me making a mistake that blows the project up rises rapidly and I start thinking a plastic or metal solution might be better.

I think you have proven a properly built tank is durable, at least if you can avoid Ethanol, which I can. And it would be a huge space saver plus shift the CG of the boat forward. I could be convinced to really like the idea, maybe even love it.


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## RogueTribe (Apr 14, 2019)

I am interest as well and Fritz questions are the same that I would have. What resin, what cloth, how many layers, how much wax, how far forward and how many gallons should it be. Does the hull need more reinforcement under to avoid cracking when hitting a sharp wave while running? 

Interested to hear more...


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## Chris Morejohn (May 12, 2014)

Fritz said:


> Chris I’ve read a good bit about your glass tanks and I would not be against trying one if the very specific directions were all in one place and included a detailed ‘bill of materials.’ By that, I mean I want you to tell me exactly what resin to buy, etc...
> 
> When the answer is ‘you need to do the research on resins...’ the risk for me making a mistake that blows the project up rises rapidly and I start thinking a plastic or metal solution might be better.
> 
> I think you have proven a properly built tank is durable, at least if you can avoid Ethanol, which I can. And it would be a huge space saver plus shift the CG of the boat forward. I could be convinced to really like the idea, maybe even love it.


It’s already shown in the plans but I will show and explain here this weekend. Too busy till then. It’s real easy and a no brainer.


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## Cut Runner (Jan 25, 2017)

From my previous research on this topic, the tanks at actual gas stations are fiberglass and vinylester is the resin used. Everything I've gathered is that there cannot be 1 microscopic bare fiber showing on the inside of the tank or it will wick the fuel into the laminate then game over. Where people trip up the most is putting the lid on the tank. Building a tank incorporated into the hull is very risky (maybe not so much on a small skiff. But much certainly on larger boats) and why the coast guard isnt a fan of it.


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## Stevie (Jun 27, 2017)

Yellowfins - 31 & up used to have glassed in tanks


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## el9surf (Dec 23, 2008)

Had a glassed tank on a 2007 Maverick hpx and it was a nightmare in under a year. Aside from the tank having to be replaced the entire fuel system including everything in the motor had to be replaced. They may work but if you get it wrong the cost just to get the motor back to running correct is very expensive. What's wrong with aluminum or plastic?

In my experience e10 and fiberglass/ resin don't get along. I don't run anything but pure gas now. At the time when this happened to me back around 2008 all you could find at the gas stations was e10.


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## lemaymiami (Feb 9, 2007)

Fiberglass fuel tanks have a very bad reputation - because so many of them eventually failed when ethanol came along (this is about boats of every size from big sportfishermen on down...). Bertram is just the first boat builder that comes to mind having lots of older boats that needed tanks replaced entirely (and on a big boat you'll be in the serious boatyard type removal and replacement using heavy duty cutting tools just to gain access to the tanks - a major repair item).

I'm sure there are careful builders that can do a great job with a fiberglass tank and get a good lifespan with it for small craft... but for me - I'd never take the chance under any circumstances. My current rig is an old Maverick skiff (1988 model) that still has the original aluminum tank... I may have to replace it one of these days but at present it's still solid and tight. Doubt that would have been the case with a fiberglass tank.... By the way I've never run anything other than ethanol laced fuel - from day one....


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## State fish rob (Jan 25, 2017)

I wonder what the real world cost of ethanol is. About the same time frame, I started rebuild carbs on lawn stuff regularly. 
I like my alcohol neat , not mixed w gas 
Ruined tons of fuel systems. 
Ethanol causes few problems if it doesn’t sit. 21 day shelf life on fuel w ethanol these days ,before it breaks down. Best to drain tanks if equipment sitting ( like my chain saw )


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## Pole Position (Apr 3, 2016)

Let me be the dumbass to go ahead and ask....what benefit does a fiberglass tank offer, especially on a presumably small tank ( 10g?? ) for a skiff? A 5 lb weight savings?


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## mtoddsolomon (Mar 25, 2015)

I think because you can build it yourself. It's one more thing on the boat that you can make when making a skiff.


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## State fish rob (Jan 25, 2017)

More to make use of odd shapes I would think ...?


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## el9surf (Dec 23, 2008)

Just to clarify my issue wasn't an issue of ethanol going bad. I was told that the ethanol was breaking down the inside of the tank, basically dissolving the hardened resin back into a sticky glue that was getting sucked into the fuel lines and motor. The insides of the engine looked like they had dried sticky coca cola all over. I haven't run ethanol gas in any of my small engines since. While the idea of a fiberglass tank sounds good if you plan on using regular e10 from the pump you may want to reconsider.


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## lemaymiami (Feb 9, 2007)

I was told years and years ago that ethanol was being added to many fuels and this was long before they were required to notify customers... The guy, a long time Omc master mechanic also told me that modern fuels (this was more than 30 years ago..) weren’t very stable and would begin to break down chemically much too soon.

Just one more reason to be careful with fuel tanks and never repeat never use cheap or unknown fuel lines or other fuel system components...


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## Cut Runner (Jan 25, 2017)

Bertrams, yellowfins, it was a disaster.
I'm not against fiberglass tanks at all, I would prefer to be able to build my own but I would have to see success first


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## Chris Morejohn (May 12, 2014)

Guess I put my foot in my mouth again. 
Well for those of you out there that don’t have to use Ethanol gasoline here’s how I have built over 30 fiberglass fuel tanks over 30 years ago that are still in perfect shape.
Most of my life has been spent in SW Florida,Bahamas, Caribbean and Atlantic waters using fuel from all kinds of out the way places. So,I myself have personally not been near Ethanol gas. All the tanks I have built were for Florida based clients and commercial working craft in the 3rd world.
2 years ago I talked at length with the Coast Guard building inspector about my past method of building and he said it all sounded fine to him. 
The key to my method is to NEVER use any other type of fiberglass material other than 1-1/2 oz. chopped strand Matt. You MUST do a neat job through out the lay up. 
Epoxy resins work just as well as good polyester resins like vynelester. I always used a brand of resin called Dion at the time. I have used just regular shop polyester resin too.
The deal is to wet the matt out well and hard roll out ALL air bubbles. Using chopped strand Matt the fiberglass strands are all less than 1-1/2” long so the chance of wicking fuel is almost impossible if being neat and rolling out properly all the corners.
Just contact your particular resin company and ask them about its ability with gasoline.
Here is my build sequence.
-Pour from a known bucket size the amount of gallons of gas you want to carry into the area where the tank is to go. Use water, say a five gallon bucket you have checked to make sure where the 5 gallon waterline is.
- once you have your amount in the boat...say 25 gals then take a sharpie pen and trace along the top edge of the waterline all around the hull sides and the bulkhead.
- bail out the water and then dry out the hull. Next use a car wax, mold wax etc and wipe on 3 layers from where all the fuel will be to the sharpie line. Do not buff out just get a good wax barrier coat on. This is your layer and separation of tank from the hull and interior parts. Coast Guard rules say you can’t have the tanks sides as part of the hull. Hence the wax barrier to separate the new tank from the old hull.
- after waxing lay in and glass in the 4 layers of Matt as shown with all over laps being nice and neatly 
hard rolled out so ABSOLUTELY NO AIR IS SEEN. This is easy in polyester and a bit more effort is needed with epoxy resin as it’s not as viscous. It’s not a big area so not hard to do all at one go.
Make sure the matt layers extend at least 3-4” above the un waxed hull and bulkhead. This is your fuel tanks attachment flange- point.
- now you have a nicely glassed in tank shape that takes up no extra space. It should look nice and smooth and not too resin rich but not to dry looking. 
- layup your tank top-lid in 4 layers on a flat panel of waxed Formica or what ever is smooth. When cured cut it to shape to fit on top as neatly as possible. A cardboard pattern is easiest to make and transfer to the fiberglass sheet.
- after the wax is ground off the lids sheet then drill out and install the fill and vent through hulls. Use bronze ones. The fuel pickup can be a store bought plastic one or what has lasted the best is copper tubing glassed into the lid. You can also lay up a section of the lid in thick Matt and then drill and tap into this. Using Teflon tape to seal the threads. Make sure all the fittings are at least 4” away from the lids side so you have room to glass the tanks lid in place.
- last thing is to glass the lid all the way around as shown.
If installing the fuel tank in the bow of any of my designs you could add a baffle to support the lid better or you could core the middle part of the lid. When opening your hatch it will now look like you have a nice floor in your skiff. You need to make the lid at least 1” higher than your fuel fill line to get the best at filling your tank.
You could slope the tanks lid a bit too if wanting water to drain aft.
When it’s all done you can pressure test the tank for leaks. 

President Bush #1&2 and all family members have fished out of skiffs I built using the above method for the past 32 years. Skiff is still in the same family and still being used.
It’s easy, it works, but just stay away from ethanol gas.


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## lemaymiami (Feb 9, 2007)

Chris, you didn't say anything wrong - I'm certain you've built more than a few great fiberglass fuel tanks that are still in service. I only spoke up because the terrible trouble manufacturers got into with fiberglass fuel tanks was a lot of years ago - so many may never have heard about it...

Can't say I can think of any commercial builders whose fiberglass tanks are anything I'd want - but they're doing production work - and rarely have anyone with high end skills on their production lines... and if you do have a tank that goes bad - it's rarely a quick and easy fix from what I've heard myself...

Please keep the info coming I'm sure there are quite a few hear who really want to hear about how things should be done - me included...


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## Chris Morejohn (May 12, 2014)

lemaymiami said:


> Chris, you didn't say anything wrong - I'm certain you've built more than a few great fiberglass fuel tanks that are still in service. I only spoke up because the terrible trouble manufacturers got into with fiberglass fuel tanks was a lot of years ago - so many may never have heard about it...
> 
> Can't say I can think of any commercial builders whose fiberglass tanks are anything I'd want - but they're doing production work - and rarely have anyone with high end skills on their production lines... and if you do have a tank that goes bad - it's rarely a quick and easy fix from what I've heard myself...
> 
> Please keep the info coming I'm sure there are quite a few hear who really want to hear about how things should be done - me included...


Ha, I just felt I started stirring up the past. 
I am in no way promoting fiberglass fuel tanks for production builds. It’s a job that, well you have to be a good worker with. Do a good job every time.
In the Bahamas I built all my fuel tanks in the Spanish Wells 19’3” skiffs like I described above. About 160 skiffs were built this way. Now and then I would here about a fuel leak but never have I heard about the tank going bad, and trust me I would hear about it even though I only built the first 10 skiffs. My home is there. These tanks were built 25-29 years ago.
Now for myself I will always build in glass if the client wants it. This winter I will video the procedure when I build the Beryllium skiff. 
They are very easy to get rid of too. Just cut the lid out with a fien tool, and viola you are back to putting in an aluminum tank. 
Takes about 4 hours to complete a glass tank. Way less cost. Perfect for all my designs.
I have always made a profit when selling my one-off builds. So will everyone else.


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