Fiberglass Fuel Tank

It's been said by other Nor'sea owners the hardest job is replacement of the fuel tank. If you saw my last post about the removal of the old tank, you may agree.

The reason I cut out the fuel tank instead of all in one piece like other owners have done, is because there's a portion of the cabin floor running above the tank. This made replacement a little tricky. Do I install a smaller one-piece tank that doesn't go under the cabin floor (and giving me a larger bilge)? Do I get two tanks made that fill the same space? What about making a tank in the keel using the whole space? Now there's an idea...

I went back and forth with these questions on how I was going to reinstall a fuel tank. At one point, I was thinking of a smaller tank that didn't go under the cabin floor, but many say extra fuel is always a good thing if you're out cruising (motoring). I also thought two smaller tanks could work by dropping one in and sliding it forward, then the second dropped behind it, using the same space. That idea didn't work well either because the bottom of the keel narrows as it goes toward the back. Well, I'm wrong there, it COULD work, just means the bottom would have been narrower and fuel capacity could have been reduced a few gallons.

One of my random ideas popped up. How about fiberglass? A material that doesn't corrode, could be made in place in the keel and maximize the space for fuel capacity. I researched this idea (at the same time I was looking into the tank ideas above) for the better part of a year. In my research, I discovered how not all resins are created equal. Some are better at resistance to chemicals than others. Apparently, many fuel tanks are made of fiberglass. Just one issue that has come up over the years is the use of ethanol in gasoline that can eat through the resin of a fiberglass tank, turning it into a HUGE mess. I just happen to be using diesel. ;-)

I know of only ONE other Nor'sea 27 owner who went with a fiberglass tank in his replacement (photos). His process was a little different than what I decided to go with. The main thing was the type of resin used. He used an epoxy type resin, and I decided to go with a vinylester resin. I found information that vinylester was commonly used for situations involving some chemicals and fuels.

Working with vinylester has been an interesting experience. While West System epoxies have pumps that come out to a measured ratio, vinylester uses MEKP as a catalyst at a very small percentage of 1.25%. In order to achieve this ratio, I used a digital scale that was sold for measuring out food with different scales. I used grams as the unit of measure. So, West System epoxy many boaters are familiar with is about a 3.5:1 ratio. The vinylester I used was more like 80:1 and that's where the digital scale came in use. Most of the resin batches I mixed up were around 400 grams of resin to 5 grams of catalyst.

The lay up of this tank is alternating layers of 1.5oz chopped mat and 18oz woven roving. I have been asked before why I don't use biaxial cloth that is roving and mat stitched together. I didn't need each lay up to have both mat and roving at the same time. Having separate layers have allowed a full wetting of each layer with resin. Most of the fiberglass was placed into the keel, piece by piece. The forward part of the tank and the baffle were initially laid on a mirror coated with PVA as a mold release. 5 layers (3 roving, 2 mat) brought the flat pieces to 1/8" thick. Strong enough for making a cutout and tabbing it in place in the keel. By the way, the flat pieces were not installed until the sides had 5 layers as well. By this time, the tank was taking shape and gaining strength as additional layers are added.

When I started researching this project, I reached out for advice by someone who makes fiberglass tanks. On his suggestion, I was to lay out this tank with a total of 11 layers, starting and stopping with woven roving, bringing it to 3/8" thick all around. While I did add more layers to the front of the tank, and a few more to the baffle, I was considering the sides could stay 1/8" thick. The reason is that the sides wouldn't be as flexible with outward pressure from fuel since it's up against the hull. With that in mind, I'm thinking I could be closer to finishing than I had thought. But still, a little extra layers on the sides that overlap the front, back, and baffle couldn't hurt for strength.

The last two flat panels I made were for the top of the tank. The idea was to cut these into shape, place at the top of the tank to get tabbed into place. Then, I could do some sanding around the top edges so the additional lay ups could reach out onto the hull for added strength and bonding.

Then, there leaves the inside of the tank. Would there be a coating?

Yes.

Along with the suggestions I received before, I was also told that the tank could be coated with several layers of Interlux 2000E barrier coat, then a fuel tank liner. Both of which would seal the inside of the tank providing additional layers of protection of the fiberglass. Then, to finish it off, an inspection access port on each side of the baffle. This will give me a way to look into the tank from time to time to check its condition. It'll also give me a good way to mount fittings to be used for the engine, pickup, return, vent, and possibly a fuel guage.

lay up of flat panel on a mirror

tape holding first layer didn't work out too well. Should have used smaller pieces

Front of tank

trying to keep the glass in place while I wet it out

had to redo part of the bottom

Was getting a little hot, resin set to quickly

PVA peeled off the fiberglass and mirror

template for the baffle

dry fit of baffle

one of the two flat panels to be used for the top

trimming the extra fiberglass

trimmed down

At about this point of the project, I got a bit side tracked with getting the mast ready for some work. While I was going to do myself, decided to hire it out so it could be done quicker and better. Then around hurricane Mathew, a tree hit the boat so another distraction to take care of.

Here, I was checking the space available in the keel to make sure there was enough clearance for placing the inspection ports. At this point, I only had one, to check the size, but would have another one for each side of the baffle.

The first top piece for the aft section in place and able to start seeing how it'll look when it gets closed up. This was cut to shape around Oct 2016.

Jumping forward to the end of December 2016, I was able to get back to work on the tank project, mainly due to the side projects/distractions mentioned earlier.

I made the forward part of the tanks top and had to make a template. A little more difficulty due to additional shapes to deal with but overall, it turned out well. First attempt to cut that piece, it ended up being too wide and had to cut another 1/4" off one side for it to fit. At this point, there's still some fine tuning to take care of, but it's just about ready to start glassing into place to close it up and add additional layers.

visualizing hardware placement

Here, I finally got around to putting in fiberglass tape, just thin strips, around the edges just to hold the top in place. Couldn't do it all at once so it took a few visits. The flat panels had a little twist in them, so I used some seizing wire to life one corner, or something else to push another down. Not exactly even all around, but I think it's close enough for what I'm doing.

seizing wire wrapped around the wrench to help old things in place

Once all the edges were all in place to seal the top, It allowed me to work on the full layers to build up and strengthen the top.

Templating for additional layers of glass

vacuuming never ends

Roving ready

Chopped mat ready

Woven roving ready

dry fit of first piece

additional 6 layers laid down at once time

Trim needed around the edges

trimmed the front edge, that's 5/16" thick

And this is where I'm at as of 28 Apr 2017. The top is set, edges are mostly trimmed and just a little more work to do.

 
With the way the top is put on, there's now a lip around the edges of around one inch. I had thought of cutting the front edge down more, but now thinking to keep it, just in case any oil or anything else from the engine leaks, it's contained and keeps from going into the bilge, and then pumped out into the water. Probably not a bad idea.

Someone on the Nor'sea owners group asked me about fittings. So this is my reply:

Having a tank made entirely out of fiberglass and vinylester resin, it'll last forever. 

A bit more info on finishing this out, there's some spots around the edges I still need to clean up, and small gaps between the latest layups and the hull to be filled in with thickened resin.

I intend to paint the engine compartment white. Before I started this project, I contacted someone who stated they built fiberglass tanks for other people's boats. It was suggested that I paint the inside of the tank as well, with a barrier coat, like Interlux 2000E, then the last coat being a fuel tank liner. While I read vinylester can withstand direct contact with diesel fuel, the paint and tank liner is just added projection to fill in any pores of the resin/glass layup.
 
For connections, (left this part out of the video to keep it from being too long) I have one (still need a second) inspection port, by Seabuilt with the intention to mount any fittings (pickup tube, return, vent) on the removable plate. I also have a separate bulkhead fitting, for 1.5"ID hose, I planed to use for the fill port. 

Right now, I think I need to find a welder who can attach the fittings on the access plates. I just need to also confirm the sizes of fittings I need too.
 
Once I do the painting and installation of inspection/fill ports, Then it's a matter of getting the engine back in the boat and associated hardware (shaft, muffler, new cockpit drain seacocks, exhaust hose. With that, I guess there's a glimmer of light at the end of the tunnel. or is that the train coming to run me over? We'll see soon enough I guess.

Thanks for sticking with me through this long post. As I was finishing up this post, my wife was looking over my shoulder asking about all the work I've been doing. Looking back, I removed the old tank in March 2016 and for the most part, have been working on this fiberglass tank since then.

Certainly not for the faint of heart.

This is a lot of info, so I may have missed explaining something. So, post below any comments, questions, criticisms.