Permanent fuel tank questions

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Rogerogrant
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Permanent fuel tank questions

Post by Rogerogrant »

Hey y'all!

I could spend some time with my good friend Google researching the answers to these questions, but I thought I'd take the easy route and tap the brain trust here instead. :D

I'm spending an irresponsible amount of time mentally designing and physically drawing out the MG20 as a center console, and need some learnin' about permanent below-deck fuel tanks, and specifically their installation. I know the basics that are outlined in the plans - basically to electrically isolate the tank and ground everything - but I'm wondering what the best practice is in terms of accessibility. Should I plan inspection ports for any part of the system? Just how "permanent" should I make the installation (i.e. is it prudent to design things in such a way that the piece of sole over the tank can be removed)?

Any and all knowledge that y'all care to share is most appreciated - thanks!!!

fallguy1000
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Re: Permanent fuel tank questions

Post by fallguy1000 »

I really hate not having access to the senders. If the sender fails or is junk like the one in my Lund it is so annoying. The one in the Lund reads full full full empty and it is really low on empty.

If you can at least open a removeable panel for the senders; it will allow you to repair or change them if they fail or you hate their behavior.

My floors will need cutting out to take out the tanks. In hindsight, I could have removeable paneled over the entire tank I suppose...

You can use butyl tape or duct seal to close the margins. Duct seal even takes paint.
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BB Sig
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Re: Permanent fuel tank questions

Post by BB Sig »

Isn't the sole considered in part of the stiffness of the hull? I like the idea of easy to replace senders but that's another point for water to find a hole.

I wonder if the 3" rule would apply to the sole...

Rogerogrant
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Re: Permanent fuel tank questions

Post by Rogerogrant »

I doubt it. Obviously the fewer holes the better, but the beam strength of the entire sole - the compressive strength between port and starboard - has to be tremendous, even with hatches and stuff cut into it. If the tank is oriented across the beam then hiding an access hatch under a gunwale would work. I guess in the case of a belly tank it would have to be smack in the middle of the sole, but as you say, Barry, that seems like an invitation to get h2o in there.
:doh:

fallguy1000
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Re: Permanent fuel tank questions

Post by fallguy1000 »

Rogerogrant wrote: Mon Aug 24, 2020 9:50 pm I doubt it. Obviously the fewer holes the better, but the beam strength of the entire sole - the compressive strength between port and starboard - has to be tremendous, even with hatches and stuff cut into it. If the tank is oriented across the beam then hiding an access hatch under a gunwale would work. I guess in the case of a belly tank it would have to be smack in the middle of the sole, but as you say, Barry, that seems like an invitation to get h2o in there.
:doh:
Nah.

You just seal it well with say 4200. My caps are like 5/8" deep, so the lid size and the length of the seal (5/8") are a factor, but 1/2" plywood with glass is about the same thickness. The base flange must be plenty good and all around.
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TomW1
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Re: Permanent fuel tank questions

Post by TomW1 »

Yep just build an inspection hatch over the tank. You will need to check the hoses for wear, maybe replace the sender, etc. Treat it as a locker, seal it well, water proof it with foam and and SS screws or however you want, provide water drainage just in case. The fuel hose should be checked yearly anyway as part of your safety check for wear.

Tom
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Re: Permanent fuel tank questions

Post by BB Sig »

BB Sig wrote: Mon Aug 24, 2020 8:58 pm Isn't the sole considered in part of the stiffness of the hull? I like the idea of easy to replace senders but that's another point for water to find a hole.

I wonder if the 3" rule would apply to the sole...
Rogerogrant wrote: Mon Aug 24, 2020 11:43 am Just how "permanent" should I make the installation (i.e. is it prudent to design things in such a way that the piece of sole over the tank can be removed)?
This is what I was referring to. A large part of the sole removable... One of the 6" Inspection plates isn't going to matter.

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Re: Permanent fuel tank questions

Post by TomW1 »

BB Sig wrote: Thu Aug 27, 2020 7:32 pm
BB Sig wrote: Mon Aug 24, 2020 8:58 pm Isn't the sole considered in part of the stiffness of the hull? I like the idea of easy to replace senders but that's another point for water to find a hole.

I wonder if the 3" rule would apply to the sole...
Rogerogrant wrote: Mon Aug 24, 2020 11:43 am Just how "permanent" should I make the installation (i.e. is it prudent to design things in such a way that the piece of sole over the tank can be removed)?
This is what I was referring to. A large part of the sole removable... One of the 6" Inspection plates isn't going to matter.
See my response. Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

Rogerogrant
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Re: Permanent fuel tank questions

Post by Rogerogrant »

Copy that, thanks guys!!

Based on various websites and youtube videos it looks like it’s not recommended to foam them into place nowadays, but powder coating the tank seems like a good idea...

I know we want to keep fuel and electrical stuff separate, but at some point they have to converge to go through the motor’s rigging tube. Any advice on how to configure that, and where to put the squeeze bulb that’s out of the way but not in the bilge?

TomW1
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Re: Permanent fuel tank questions

Post by TomW1 »

Put the squeeze bulb in the area with the motor. You will probably need to pump it it a couple of times every time unless your going out every day? As far as keeping them separate at the stern just run them as far apart as possible until the last possible moment and send them out two different holes if possible. Good luck you will figure it out.

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

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