Pre-made FRP board PART II

Ceasar Choppy · Post by **Ceasar Choppy** » Mon Apr 16, 2007 3:47 pm

So I'm replacing my fuel tank on my P-39. The old one was a cylindrical beast made out of steel and set in a 3/4" plywood "box" frame, tabbed into the hull. Once the tank was out, the tabbing was surprisingly easy to remove because the wood was rotten and the tabbing was barely wet-out to begin with. A scraper and a small hammer was all it took to remove.

I have a new plastic tank and am now ready to construct the floors and stringers to support it. It is 30 gals. diesel (like the old one) except built to use the space better and allow me some extra room for a battery bank.

I'm looking to use the McMaster pre-fab'd square "pipe," which is 1/4" thick on all sides and 3" x 3" as floors and then use either more of this stuff for stringers on top of the floors, or use Biax with coosa board core.

It's getting a little too complicated for my taste, but it boils down to using the pre-fabed glass to save myself a lot of laminating over forms. I plan on laminating over most of it where I'll be tabbing of course. It will support roughly 250 lbs. rockin and rolling under the cockpit.

Without seeing any pictures, does anyone have an opinion on my plan? I can post some diagrams and pics once I get all this stuff to my web site.

cc

Post by **Tim** » Mon Apr 16, 2007 5:21 pm

Without really knowing the specifics, offhand I'd say the concept sounds fine. The prefab FRP is certainly a lot stronger than what you took out of there.

Remember that the plastic tank will require more support directly beneath, since it isn't as self-supporting as the heavy steel.

Post by **Tim** » Mon Apr 16, 2007 5:22 pm

Oh, and allow me to be the first to make the generic--yet heartfelt--call for PHOTOS!

Hirilondë · Post by **Hirilondë** » Mon Apr 16, 2007 5:48 pm

Hmmm, no pictures? I shouldn't even be replying till they are up!

Off-hand it sounds more than strong enough. Depending on how well you can tab some of the framing to the hull you could probably bolt the FRP to it and maybe even some of the framing to itself.

Ceasar Choppy · Post by **Ceasar Choppy** » Mon Apr 16, 2007 6:28 pm

Ok OK... Let me try and get something up. I gotta digitize the drawings.

OK, here is the full description: http://www.pearson39.org/fueltank.html

Here is just a pic of what I'm talking about. Visualize the curves of the hull. :)

Thanks!

Post by **Tim** » Tue Apr 17, 2007 6:09 am

It sure looks like that will be strong. I don't see any problems with the concept.

Ceasar Choppy · Post by **Ceasar Choppy** » Tue Apr 17, 2007 8:49 am

Thanks for taking a look. I think the hardest part will be the tabbing as Dave suggested. Also, I still need to nail down adding support in the front of the tank.

Post by **Tim** » Tue Apr 17, 2007 9:37 am

How's your working access back there? If you have decent room to move, I don't think you'll have much trouble tabbing that all in securely. But it can be miserable underneath cockpits!

Good luck.

Ceasar Choppy · Post by **Ceasar Choppy** » Tue Apr 17, 2007 10:04 am

It is actually not that bad. It is actually gi-nor.. (nevermind, you hate that word!).

I've been in and out of there so many times, I've got my boat-yoga down pretty well. The other nice thing is that since most of the old tabbing came right up, I won't have to do a lot of grinding to prep for the new.
Getting good pics of the area is hard because there is no good spot to get a full view.

My main concern was avoiding sharp corners. I was originally going to do this with two "U" shaped "floors" using cheap foam and lots of fiberglassing over them... but that plan had a lot more corners! The other problem is that the tank actually sits quite high in the front (still at the waterline), but it would have taken a lot of glasswork to support it properly I thought. The hull down there is wide and steep as it is where that big skeg is attached. In fact I can see where the foam for the skeg was poured in. See the pics here: http://www.pearson39.org/fueltank.html

I'm so ready to get this done and get back in the water!

Ceasar Choppy · Post by **Ceasar Choppy** » Tue Apr 17, 2007 1:04 pm

I've added more pics at the link above in case anyone is interested...

Ceasar Choppy · Post by **Ceasar Choppy** » Mon Apr 30, 2007 10:38 am

So here is how I've done so far in case anyone is interested.

The web page I have for this is a mess, but here's a couple pictures:

Figment · Post by **Figment** » Mon Apr 30, 2007 4:04 pm

Can you give some details on the construction of that tank?

Ceasar Choppy · Post by **Ceasar Choppy** » Mon Apr 30, 2007 4:49 pm

Sure.

It is 30 gal polyPROPYLENE 3/8" thick which was nitrogen welded and fabricated by Triple M Plastics up in Kennebunk, ME.

I couldn't find anything comparable for a crosslinked Polyethylene rotomolded tank which I would probably prefer, but Triple M has done tanks for me before, are reputable, and I've been very happy with them.

Here's the diagram I did for them:

Ceasar Choppy · Post by **Ceasar Choppy** » Mon Apr 30, 2007 4:56 pm

Oh, and in case you are wondering, the fuel line and return connections are tapped into the inspection plate cover.

Ceasar Choppy · Post by **Ceasar Choppy** » Fri May 11, 2007 1:32 pm

So, I'm getting closer on this project and am excited that I've recovered enough space to store my batteries in all one bank just forward of the fuel tank. See the link to my site above with updated pictures.

One of the problems I faced was access to the rear of the engine (or front-- it is turned around because of a v-drive). I needed to get in a 30 gal. tank, batteries and a waterlift all in the space underneath the cockpit of my P-39. IT IS A LARGE AREA... but not as large as you might think once everything gets put in.

Anyway, by using the prefabed 2" square FRB tube (0.25" thick) as stringers, and taking Hirolande's suggestion of using bolts to attach this stuff, I will be able to unbolt the cornered pieces once the batteries are removed to allow for any access I will need to the engine.

stone · Post by **stone** » Wed May 23, 2007 10:46 pm

Well that is certainly alot more excotic than mine.Looks good so far. I just used 2X6" Cypress glued with epoxy to the hull and then glassed in with Vinylester and two layers of 24 oz. Biax. I then just primed and painted with an oil based paint. For the top I just used 1/2" ply with two layers of Biax on top and one on the bottom(Vinylester). I used a piece of foam to make a template for the stringers.

Ceasar Choppy · Post by **Ceasar Choppy** » Thu May 24, 2007 6:19 am

Looks good stone!

If you had seen both the amount, and state, of the wood I pulled out of that area you would know why I was avoiding wood. The one picture doesn't show the 3 garbage bags of rotten stringy wood I pulled out.

Off today to make the final fit of the fuel tank and hopefully install the batteries.