What is under your 22 fuel tanks? (And how's it worked out.)

[Sunbeam]

Hi folks,

I'm installing the new Moeller fuel tanks I got to replace my originals, and I'm interested to know what (if anything) was placed under your fuel tanks and how it has worked out.

The original fuel tanks in my boat were not installed very well, so I already know I'm not duplicating that set up. They were installed directly on the fiberglass sole - in my era boat that's also the hull - and then Starboard™ cleats were butted up against them and screwed into the hull core (ouch), with partial height Starboard cover panels attached to them. Straps were used as hold downs attached to footman loops screwed into the core on the sole. No expansion room was allowed for (Moeller recommends ~3%) and so the tank expansion had bowed the tank cover pieces and partially pulled the cleats out of the sole.

I've already got the old holes dug out and filled, so they are gone, and the new installation partially worked out and done (cleats and straps), but still have to figure out exactly what/how I'm going to put under the tanks. I heard from the builder (last summer) that they use rubber strips, and I decided I would do something like that, but I'm wondering if they will tend to move around if not glued down and/or just exactly how they have worked out. I bought a couple of sheets of rubber to cut into three or four wide strips... thinking I may use dots of 3M4000 caulk just to "encourage" them to not wiggle around under the tanks.

I considered using Dri-Dek, and did cut a leftover piece to try it, but it was kind of "slippery" so I think I'm going back to the rubber. Also it held the tanks up a bit further than necessary as compared to the cleat height. I also figure the more-compressible rubber will help slightly to support the tanks, which are specified to be completely supported (they are flat on the bottom but the hull is slightly curved).

I'll write up the installation once it's completed, but for now I'm just slightly undecided about the "under the tank" material so figured I'd see what others had and how it has worked out (or not).

Thanks,
Sunbeam

 

[thataway]

Generally the fuel tanks on the C Dorys have lasted a good long time sitting on the floors, as long as they don't shift and abrade. The screwed in cleats were a bad idea--and a glassed in cleat which confirms to the bottom side radius of the fuel tank works very well. The 3% is to be sure that the tanks are not constrained more than that for expansion. But in the C Dory there is a strap which will allow for this much expansion. As for padding-neoprene is suggested. You don't really need to put the tanks off the bottom as you do with aluminum tanks (where you never use "rubber".

 

[Sunbeam]

Thanks for the reply.

Generally the fuel tanks on the C Dorys have lasted a good long time sitting on the floors, as long as they don't shift and abrade.

That's one thing I was trying to avoid - sliding/slipping and abrasion. Since the poly tanks need room for expansion, it's a bit less "easy" to use cleats that way.

The screwed in cleats were a bad idea--

Completely agree there! First they were screwed straight into the core, and second there was no room left for expansion (as Moeller specifies there must be) and so the tanks "levered" the screws out leaving exposed core (even though my boat was stored indoors, that was the one place I had to pull out a bit of wet core).

... a glassed in cleat which confirms to the bottom side radius of the fuel tank works very well.

I don't quite follow you here. Could you elaborate? I've actually already placed the main (forward) cleats, but I'd still like to understand what you are describing.

What I did was use fiberglass angle and epoxy it to the sole (thickened epoxy filled the gap between the rounded sole and the flat angle). (The bottom of the tanks is flat as molded, although apparently it can take the "bending" of bulging out to conform to the sole; the rubber I'm putting in should help smooth it all out and also hopefully keep the tanks from wanting to slide.) The same angle is lined up such that it can anchor the bottom edge of the hard/decorative panels to cover the tanks.

The 3% is to be sure that the tanks are not constrained more than that for expansion. But in the C Dory there is a strap which will allow for this much expansion.

I understand that, and agree on the strap. But... the cleats. What I'm doing is placing the cleats about 3% "past" where they need to be which is what Moeller calls for (this amounts to about 1/2" gap on a 22-sized tank) and then shimming the tanks-to-cleat gap with 1/8" rubber strips (this is separate from the rubber under the tanks). C-Dory had the cleats tight to the tanks, which did not work. I'm thinking I can remove rubber as necessary when the tanks swell (supposedly the swelling mostly stops after the tanks finish absorbing fuel and "bagging out").

(I think I did order neoprene rubber; in any case it is a medium durometer that seemed like a good material for around fuel - I got it from McMaster-Carr - I could look it up if anyone is curious.)

You don't really need to put the tanks off the bottom as you do with aluminum tanks (where you never use "rubber".

Understood on not using rubber on metal tanks. Since these are poly I figured it would not hurt, and figure it may sort of "help" with a few things:

1) It makes the tanks less likely to want to slide.

2) There can be some drainage in the gaps.

3) Any slight lumps in the fiberglass sole will not cause point pressure on the tanks.

4) I think it will help slightly to "make up" for the tanks being flat on the bottom but the sole being rounded. This may not be necessary but it makes me feel better, and Moeller does indicate they should be supported on the bottom.

When I've been involved in installing aluminum or stainless tanks I've glued (3M 5200) Starboard™ runner strips to the bottom of the tanks (kept them out of the water and seemed to do better than "loose" supports at preventing corrosion) -- but these poly tanks are a whole 'nother beast! Sort of a tug-of-war between not wanting them to shift or abrade, yet needing to leave 3% room for expansion. I know I probably worry about the details more than some; but on the other hand the original installation failed, so I want to do better than that.

Sunbeam

PS: I am also using straps to hold the tanks down. Difference from the original being that mine will run from near the top of the tanks at the transom to the bottom of the tanks forward by the sole, and the footman loop is glued on (to the transom). The originals had the footman loop screwed into the sole core at the bottom of the boat/tanks at the transom, and then tied into the top of the cover panels (kind of a weird leverage was thus applied to the theoretically decorative panels).

PPS: Triton gave me some rubber stripping and said they use it under the tanks, but I wasn't sure exactly how they placed it or how it worked out in the long run (did it shift around? work well? Etc.) I ordered sheet goods to put under the tank as there was not enough of the stripping, but same concept.

 

[mgarr682]

I'm installing the new Moeller fuel tanks I got to replace my originals, and I'm interested to know what (if anything) was placed under your fuel tanks and how it has worked out.

The current mounting (Fall of 2012) is pretty simple:



The tank sits on three black rubbery strips with a piece of starboard screwed to the hull on the inboard and forward sides to keep it from sliding around. No straps or anything that I can find to keep them from bouncing up and down.

The starboard is held in with three screws in each piece and a line of caulk. Of course, the caulk sticks to the fiberglass deck just fine but doesn't even begin to stick to the starboard.

How that set up will work over the long run I can't say.

 

[Wandering Sagebrush]

I changed my tanks attachment a bit, shortly after we bought the boat. The starboard fascia boards warped, and allowed the tanks to become malformed. I got the new style fascia boards (on warranty), and installed them. They cover the tank from bottom to top, and secure against the splash well bulkhead.

Keep your starboard for other projects, it's expensive.

 

[Sunbeam]

Mike,

I would keep an eye on those cleats (and/or change them). Not sure if your tanks are Moeller brand, but if they are a similar material they will probably behave similarly. Moeller recommends 3% expansion room on all sides. My original tanks (another brand but also plastic) were mounted similarly to yours (minus the rubber strips) and when they expanded they pushed the cleats/screws right out of the hull. Now, there may be one difference. On my tanks there was a Starboard cover panel that was also attached to the cleat, and when the tank hit that it had extra leverage on the cleats (although it touched the cleats too). I'll see if I can post a photo and add it to the thread.

Also, the tanks are supposed to be supported all along their bottom side. Not sure if the gaps between the strips are large enough to cause a problem - it may be a non-issue (but it does answer my question about how they used the strips and why I seemed to not have enough - so thank you for that). I'm using rubber too but in my case it's mostly rubber with small gaps, vs. mostly gap.

Wandering Sagebrush: I'm not using Starboard for this at all. My original cover panels were thin starboard, but they were only 7/8 height as the original tanks extended forward of the splashwell. I now have some of the gelcoated fiberglass full cover panels and the new tanks tuck back under the splashwell, allowing them to be used (now routing the new fuel hoses is another story :amgry and one that does not yet have a happy ending!).

Thanks for the input!

Sunbeam

 

[Sunbeam]

Here are a couple of photos of the original tank installation on my 22. This is the starboard side tank, but the port side ws the same. You can see a few things:

1) These 25-gallon tanks extended forward of the splashwell, thus allowed only partial height covers (vs. having the tops tuck up under the splashwell lip).

2) The specified room for expansion did not appear to have been allowed for, so when the tanks expanded they levered the cleats out of the sole (they were Starboard™ and screwed into the sole/core). This is one of only two places I have so far found damp core on my boat (subsequently removed). The other was the lower transom drain. This boat was stored indoors and only had 50 hours on it, so it had minimal exposure to water.

3) The tank hold-down straps ran from the top of the cover boards down to the sole at the transom behind the tanks. Seemed odd to hold something down to a free-floating decorative cover top. I'm changing that around so the new straps go from the sole (actually the angle-cleat) at the forward bottom edge to the transom near the top of the tank. So no leverage on the cover panels.



Same photo, zoomed in:

 

[thataway]

I can see the bad design in your boat Sunbeam. My current 22 has the cleats glassed in place--and there is some small amount of room so that the tanks do not seem to damage the cleats. The 1993 boat I owned still has the original plastic tanks to my knowledge. Things change with time--but not always for the better.

Agree that plastic tanks should be supported on the bottom,but I have 50 to 60 gallon holding tanks which are not completely supported on RV's (I don't think that is a good idea)

The tanks don't have baffles, and probably should have.

The edge of the poly tanks are slightly rounded--I suggested that the glassed in cleats follow that contour.

mgarr682 If the builder has set those screws of the Starboard into epoxy, then it may be OK--but there are still potential issues with the expansion of the poly material of the tank. If not set into epoxy--there is almost guarantee that you will have core water intrusion problems at some point. A glassed in set of cleats for and athwartships is a far better way to do it. Unfortunately the factory does not aways get it right.

As for the strips under the tank--probably OK--but you will end up trapping some materials under there. I don't know how one glues starboard with 5200. Tanks are often supported on fiberglass batons or PVC lumber with 5200. However, the adherence of 5200 to Starboard is not adequate to hold tanks in place.

 

[Grazer]

A note on the weldmount studs...
I fastened my starboard strips to the hull with weldmount studs after fixing the holes that previously held the starboard strips securing the fuel tanks. After only 2 outings I noticed one of these strips have come loose. They were only held on with 2 wm studs and smaller than I should have used. My plan now is to glass in some angled fiberglass brackets to hold the tanks in place. The three other strips held down with wm studs continue to hold, so I am not sure what happened (perhaps the bonds were compromised as they were done after the other side using the same batch).

Grazer

 

[Sunbeam]

I can see the bad design in your boat Sunbeam.

I'm glad to see you saw that, since yours was done much better from the get-go. I visualized you thinking "Now why is Sunbeam tearing out a perfectly good hold-down system?!" It really was pretty bad. Those photos are from when I first looked at the boat and that was pretty much #1 on my list for removal/fixing. Even with the boat stored indoors, and with so little use, I had wet core (and rusty screws, as you can see) below the forward edge cleats. Luckily it was not too extensive so I was able to dig it all out from a reasonably sized hole. I hate to think about how it might have looked if the boat had been kept outside.

A note on the weldmount studs...
I fastened my starboard strips to the hull with weldmount studs after fixing the holes that previously held the starboard strips securing the fuel tanks. After only 2 outings I noticed one of these strips have come loose.

Just a couple of thoughts that may or may not apply. I had some issues with a few WM studs I used. They were not holding much of anything, so I know it wasn't a strain issue (bus bar, for example). I called WM and they advised that I could have got a batch of bad glue. The glue is temperature sensitive while in storage, and though they try to have their distributors keep it refrigerated.... maybe it slips sometimes. They sent me some new stuff and now before I start a "session" of gluing I do a quick test batch. If it's bad it stays more rubbery-like instead of hardening.

I also decided to prep a little more (even though they say very little prep is needed). I now solvent wash with Interlux 202 in places that might have had mold-release wax or wax added to air-inhibited gelcoat (most places on the C-Dory hit one of those two), then I sand slightly (both the boat and the stud or loop), then a last solvent wash with denatured alcohol. Takes longer to type than to do, and I haven't had any failures since the new routine. Hope it stays that way. They use these studs to glue quite heavy arrays of things like fuel filters and water filters onto big boats, so they should be holding.

My plan now is to glass in some angled fiberglass brackets to hold the tanks in place.

I originally considered WM studs to hold the fiberglass angles in place (that are going to function as cleats to hold my fuel tanks in place), but decided instead to just epoxy them to the sole. Not that WM isn't a good way, but just relating what I did since you are considering it. I used angle from McMaster-Carr and have the tank hold down strap anchored to it on the forward side, and then running through a WM footman loop on the transom.

 

[handmeawrench]

This isn't exactly an answer to your question...but here is my answer to the LITERAL question of "what is under your fuel tanks".

On this particular 1987 22' Angler...WET CORE.

http://s1107.photobucket.com/user/handmeawrench/media/Wet_Core.mp4.html

Glad you aren't me?

The fuel tanks were screwed directly to the hull, just like yours Sunbeam. Apparently water found its way into the core from those holes, and the rest is history.

 

[thataway]

ouch! I hope that was not too wide spread. I'll bet that there were some screws in the floor to help hold the tank in place. Good luck on the repair.

 

[Sunbeam]

I may not "be you" on my 22 (luckily there were just a couple of half-doller sized damp spots under the cleats), but I have been there in the past on numerous sailboats. Ugh! It's never fun, and especially when you have to "destroy" a larger area of a new-to-you boat :amgry I guess if there is a good side, it's that when its done you know the boat is better than new, and the pain fades relatively quickly (once you'e done; not during!).

To follow up on the thread (which I had forgotten to do), I put strips of rubber under the tanks, running athwartships. They are 4" wide (width runs fore-and-aft) by the width of the tanks. There are four or five strips, with something like a 1/2" to 3/4" gap between them. They are mostly held in place by the angles I used as cleats, but I also put a few dabs of 3M4000 caulk under them to keep them from wanting to move. I ordered the rubber from McMaster-Carr. It came in sheets which I cut to fit. I made strips instead of one solid sheet for a couple of reasons. One is that there are drainage channels, of sorts; and two is that it allowed me to "stretch" the sheets such that the tanks still get comprehensive support, but I didn't have to order a whole 'nother sheet just for a wee bit more to use.

I'll see if I can post photos of the whole tank setup and put them in my "Sunbeam ~ 22 Cruiser" thread.

handmeawrench: Keep us posted if you want to. We can commiserate, encourage, or just lend you an ear -- and then :thup when you have 'er done

 

[handmeawrench]

After speaking to both the factory in Ferndale and the local C-Dory dealer I think we'll be dropping her off for a re-coring of at least the part of the deck under the fuel tanks. Yes, my friend and I can re-core and lay down epoxy and glass. But this is a bit more than the home project we wanted.

The factory pretty much agreed with thataway's guess that the water isn't too wide-spread. End grain balsa doesn't wick water very much (thank goodness).

But I won't know for sure until next week. Fingers crossed!

 

[CDory23]

I found this thread as I'm having issues with my tanks bulging and need to redo the supports on my twin 24gallon tanks on my 2003 22 cruiser.

"Thataway" When you say glassed in cleats are you referring to tabbing it in? If so how many tabs do you think are necessary?

My plan was to remove tanks. undercut all screw holes into core. If water damage fill with Smiths CPES, and then a hardened epoxy.

When going to reinstall I was considering using the same Starboard pieces and fiberglass tabbing them in. Is there any other ideas/improvements to this project others recommend? I didn't see there being a problem with setting the tanks back onto the core but I"m not opposed to setting them onto something.

Thanks

 

[anchorout]

When I removed my gas tanks for inspection, I found 1" or 2" diameters of rot under the floor in about half of the screw holes. I cleaned all rot around the holes, filled each with epoxy, and embedded bolts, head down, into the epoxy. Acorn nuts dress up the top ends of the bolts. I don't see how water can possibly seep into the core now.

 

[thataway]

C Dory 23, Do you mean setting the tanks directly on core material? If so, no. You need to have fiberglass between the core, and the tank, to protect the core.

There were many ways that the "cleats" were put in place. Mine were wooden core strips over the fully fiberglassed bottom of the boat (with core encapsulated). I don't know exactly how these were done, but it appears to have at least two layers of mat, and probably one layer of cloth. That layup would be good--and I would totally encapsulate the strips. I would prefer wood over starboard, because of resin adherence to the wood/vs poor adherence to Starboard. But you don't really need adhesion, if properly bedded, and the Starboard is a good material.

Anchorout's solution with SS bolts need down into the core would also work well. Probably an easier way would be to just cut out all of the old wet/rotted core, replace any bad core, or if in small areas, fill with thickened resign. then dill new holes, undercut, and put in new epoxy plugs to screw into. Any of these ways will work and prevent further water intrusion.

I have not put any strips under my tanks to elevate them off the bottom of the floor.