Help Needed with stringer mods to fit Underfloor fuel tank

2nd Barry

I would prefer the straight shot to the gunwhale. Just don't hole the stringer top!

 

Hey guys thanks for the reply I can't get a photo of under the tank for a couple days. But as soon as I get home I will take some more detailed photos of the repair areas. Originally I wanted to put the filler in the gunwale but I was not sure about how to get the filler hose to the side of boat without going through the stringer . Hey fallguy is what your saying about not putting a hole on top of stringer mean I can put a hole in the side of stringer then a hole in floor and go up to gunwale after all the repairs and strengthening has been made?

 

There are reasonable ways to hole the stringer. For the fuel line at 1.5"; you make a round hole below the top of the stringer that is the same dimension as a piece of pvc that will go into the stringer. Then use a very good glue, not epoxy to seal the pvc and route the fill thru it. Then another hole same way for the vent tube a bit away from the other one. The glass stringer is very hard on the fuel lines. If you don't chafe guard; it will fail. But never cut the top glass of the stringer, stay below it.

I'm not there to determine the best course, but you want the fill and vent near each other so you can monitor for overfill and the fill higher and the vent overboard, not inboard ever and a swan neck for the vent and like Barry says, avoid low spots for the vent.

If you want to reduce the hole size; you could also chafe guard with a cut piece of hose or a multiple wraps of rubber innertube or some other means. The bottom of the fuel lines is most at risk..and you must mitigate and prevent the lines from moving over sharps..

If you hate going thru the stringer, then the long path aft is okay, but be careful you are not heading downhill with the vent. If you need to split the vent and the fill, at least put the fill where you can watch the sender gauge and vent to avoid major overfill spills.

 

I also 100% agree and is why I put this forward in the my last post. There is already a hole in the inside stringer and he might be wanting to reinforce this anyway due to the removal of the cross frame at this point. He could go at 90 degrees
to the fill/vent on the tank but a smooth sweep up through the square hole should not impact fill or vent On a few of our boats where it was necessary to have a slightly longer filler run, ( we built our tanks)
we would use 2 inch hose, (normally) the top flange would have the word Diesel cast into the fitting, and the 2 inch allowed for venting during the filling process much better than the 1 1/2 inch.
We would just grind off the word Diesel. At one point we did find a very few 2 inch fittings marked Gas.

Re the vent hose, again as we could choose the tank fitting ID, we would use 5/8 inch as we could find 5/8 inch hull fittings to accept this hose.

 

Perfect guys thanks for the reply, I will go with your advice and run it to the gunwale makes a lot more sense to go there then all the way to the back. thanks for the advice on the chafing I will def implement those strategies. The fuel breather on this tank is 5/8 Barry, the gunwale on this boat is about 600mm higher then the fill on tank. You guys advice has been amazing and has defiantly made this job im doing safer and way better then what i was originally just going to throw together much appreciated! In terms of the filler would it be better to use a filler cap that has the breather and filler Cap as one or have a seperate breather just a bit lower then the fill Cap? I will get photos in next few days of under the tank to get more advice on the fix strengthening when i get a chance.

 

Up to you on whether to use all in one. All based on spaces available.

i'd not use the existing hole because a smaller round hole is less obtrusive...that massive crater you made needs glasswork

round holes are structurally stronger if you must go thru the stringer

 

Hey mate I managed to get some photos today I also went to a fibreglass shop to see what I could buy here and looks like I can buy 1708 and the West systems epoxy unless you suggest something else I have attached some photos of under the tank appreciate the help to make sure I do this repair properly

 

So, I can give you what I would do later today. Gotta run for now.

To get started, you'll need to shave off any high spots around the cuts and then repair the cutaway with filler. The vee areas you should fill in a couple of lifts to make sure it doesn't overheat.

You don't need to do the entire section with glass, but if you don't, you'll create a hump, so it might be best.

So, also give us measurements of it.

You will need 1708, epoxy, and cabosil, aka fumed silica.

 

Hey mate I have taken some measurements hopefully this is what you needed

 

In the picture, it seems that one stiffener is removed, and another is slotted... Be carefull. In addition to structural issues, the tank has to be properly fixed, and the compartiment should not only be watertight, but also gaz tight from the interior.

 

Crickeys, you blew threw another transverse I see now..

That is frustrating, because it means the stringers are a bit more compromised.

Repair that section first. Lay a timber up into the top edge; it may require some fancy rips. Bond it in and use screws to hold it. Make sure the top edge has a radius. On the bottom, put a timber in about 6" wide. Make them just a bit longer than the cutout. They are stay in place formers. Then cut three
Pieces of fiberglass the width of not the hole, but the original stringer plus the height to the top edge and then make each one about 2", 3", and 4" longer than the height of the cutout; the excess will lay on the bottom of the opening. Make fillets with epoxy and fumed silica where all sharp edges are on the former/old stringer web interface. Start there, ask questions if you need to

For ordering, calculate all the glass needs. So measure this repair and then add another four pieces the width of the entire section plus the height of the sides times 4. It cannot be measured short. If I was doing the work, I'd use a 50" wide piece and go up the sides.

present back here the pieces planned dimensions and we can give you an epoxy estimate and make sure you planned correectly

you'll only need maybe about a gallon or two of silica by volume

 

Thanks for the reply and solid info I will give yous an update on progress cheers!!

 

hey fallguy, the large hole i have put in aft transverse was because my tank was 20mm longer and needed to go into that transverse what would be my best option to be able to repair that hole but in 20mm to compensate for the tank im thinking i could glue wood to create a form and then glass it in do you have a better idea? I could also remove the floor to behind the transverse and beefen up the other side of transverse

thanks

 

No. Form with wood and then taper grind the glass so the new stuff lays down nice, and put 3, min or 4 layers down. Taking up the floor is not needed.

 

i will give it a go cheers mate