Fuel tank clearance

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rbecker08
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Fuel tank clearance

Post by rbecker08 »

Today hoping to start building out the frame for the casting deck. Dropped the fuel tank in there and not sure if I should raise the deck or good as is. I am not sure what is attached to the fuel tank or how flexible that hose will be but need to allow .5 inches for tank expansion. What do you all think raise the deck or build on. Deck level will be the bottom of the wood above.

The tank is sitting on 3/4 ply (real deck will be 3/8) and really need .3" for expansion so there is some fudge factor built in here
20221215_075743.jpg
20221215_075733.jpg

TomW1
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Re: Fuel tank clearance

Post by TomW1 »

You are on the very edge of being able to bend a 2" fuel hose with what you have now. I also do not see a fuel outlet on the back of the tank, maybe I'm missing it, but normally it is center back from the fill fitting. It also looks like you have the tank in the bow, if so, I would turn it so that the fuel gage was towards the rear and fill was forwards.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

fallguy1000
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Re: Fuel tank clearance

Post by fallguy1000 »

All the fittings require access panels or an access to the whole tank.

I think Tom is being awfully kind; that hose is going to be pretty hard to bend under a deck as shown, but if you use a flush deck plate; those sit above the deck.

Why is the tank up so high?

Sucks that the tank inlet isn't 90 deg.
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rbecker08
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Re: Fuel tank clearance

Post by rbecker08 »

TomW1 wrote: Thu Dec 15, 2022 10:20 am You are on the very edge of being able to bend a 2" fuel hose with what you have now. I also do not see a fuel outlet on the back of the tank, maybe I'm missing it, but normally it is center back from the fill fitting. It also looks like you have the tank in the bow, if so, I would turn it so that the fuel gage was towards the rear and fill was forwards.

Tom
So here it is rotated, and in the orientation I can fit it between the stringers and drop it down. This will impact where I plan on batteries going. So probably will keep it as it was unless there is a functional issue with it. I think the easy solution is just to add a 3/4 inch cap to each frame and raise the deck. Any objections?
20221215_105841.jpg
Thanks for the catch on access, I'll plan on an above deck access panel. This will give a water intrusion point but will have it drain to a compartment that is empty and separate from the bettery.

fallguy1000
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Re: Fuel tank clearance

Post by fallguy1000 »

The battery and fuel tank cannot share a compartment. Needs a bulkhead to separate. fyi
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rbecker08
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Re: Fuel tank clearance

Post by rbecker08 »

fallguy1000 wrote: Thu Dec 15, 2022 12:54 pm The battery and fuel tank cannot share a compartment. Needs a bulkhead to separate. fyi
Yup you cleared that up on my last post :)....will be venting the battery compartment too.

rbecker08
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Re: Fuel tank clearance

Post by rbecker08 »

So here is the final result.

Deck raised to give close to 3" clearance
20221216_074714.jpg
Tank will be orientated this way to make room for a additional bulkhead and battery compartment
20221216_074736.jpg
End result will be fuel line down the right gunnel and electric down the left gunnel to a small side console.
20221216_074725.jpg

fishgitr
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Re: Fuel tank clearance

Post by fishgitr »

Why not put the battery in the next compartment? Fuel fill is going to be a pain to install, but not to mention battery and fuel together.

fallguy1000
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Re: Fuel tank clearance

Post by fallguy1000 »

Realize not the question, but dynamic weights are best closer to the lcg, because they can change the trim too much between tank full and tank low..

The battery weight is static, so better forward. Of course, start battery forward is another issue entirely for voltage drops.

I believe this is the hmd19 which may have some careful trim issues to deal with iirc.

But generally, tank further back (here) is better because the fuel will have less impact on trim.
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TomW1
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Re: Fuel tank clearance

Post by TomW1 »

Dan he is building the FS17LS, you can follow his build down in Builder Power Boats. Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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