Purpose of material under fuel tank in aluminum boat?

[nea]

I am restoring a 1985 Sea Nymph Fish And Ski 195. I have removed the fuel tank. It is a polyethylene 24 gal tank made by Kracor. The tank sits on a riveted in alum cradle about 2 inches above the inside if the hull. Under the tank and lining the cradle is a thin liner that has the consistency of brown kraft paper with reinforcement string throughout. It resembles the brown reinforced shipping tape used on packages. Of course it is disintegrating and in very poor shape. I pulled up about 8 inches and decided to stop until I determined its purpose. It is too thin to provide any cushioning. My thought is leaning toward some kind of anti- static membrane. Any thoughts on its purpose???

 

[alldodge]

Purpose is to absorbe vibration so it doesn't damage the tank over time. USCG current requirements uses a rubber type material

 

[nea]

Purpose is to absorbe vibration so it doesn't damage the tank over time. USCG current requirements uses a rubber type material

This seems to be paper and would offer no cushioning whatsoever. I looked at the Coast Guard regs on fuel tanks and found many regs but nothing about your mention. Can you forward that CG info you referred to.
Thank You

 

[alldodge]

This seems to be paper and would offer no cushioning whatsoever. I looked at the Coast Guard regs on fuel tanks and found many regs but nothing about your mention. Can you forward that CG info you referred to.
Thank You

Don't think you actually looked
Start reading at page 61 (and note paper is "no longer" ok, years ago it was)

https://www.uscgboating.org/assets/1/AssetManager/ABYC.1002.01.pdf

 

[nea]

Don't think you actually looked
Start reading at page 61 (and note paper is "no longer" ok, years ago it was)

https://www.uscgboating.org/assets/1/AssetManager/ABYC.1002.01.pdf

As I had mentioned before this is a poly tank mfg by Kracor. I see many regs regarding mounting non ferrous metal tanks (aluminum) with a concern toward corrosion and abrasion but nothing for cushioning a poly fuel tank.

 

[04fxdwgi25]

I would suspect that installing an "insulation" layer between a poly tank and and it's mounted substrate would be prudent. The minute vibrations between the tank and the substrate would induce rubbing / wear on the poly and potentially cause a leak in the tank.

Don't know why someone would balk at putting a layer of rubber or thick plastic sheet between them. In the automotive industry, the straps that hold the poly fuel tanks to the chassis have a rubber / plastic band or sheet between the straps, the chassis components and the tank for this very reason.

 

[Scott Danforth]

originally paper was allowed to be used as an abrasion guard. however kraft paper is effectively 2000 grit sand paper and it wore thru the tanks

Follow the new regs on using rubber. I have used epdm sheets from mcmaster carr and in one instance, conveyor belt material from the local co-op

 

[nea]

I would suspect that installing an "insulation" layer between a poly tank and and it's mounted substrate would be prudent. The minute vibrations between the tank and the substrate would induce rubbing / wear on the poly and potentially cause a leak in the tank.

Don't know why someone would balk at putting a layer of rubber or thick plastic sheet between them. In the automotive industry, the straps that hold the poly fuel tanks to the chassis have a rubber / plastic band or sheet between the straps, the chassis components and the tank for this very reason.

I am not balking at putting a cushion under the tank!. Just trying to find out the purpose of the paper because it is obviously not for cushioning. I have had some responses from knowledgeable charter captains on the Great Lakes that it is VCI paper which is used to prevent electrolysis and corrosion. That makes the most sense of all. Looking at the description of reinforced, poly lined VCI, I believe that makes the most sense. In my case with a aluminum shelf supporting a poly tank, it would protect the alum shelf. In fact the shelf is bright and shiny as if it were new. I have had other responses of paper looking media being under aluminum tanks on Sea Nymph boats.

 

[JustJason]

Purpose is to absorbe vibration so it doesn't damage the tank over time. USCG current requirements uses a rubber type material

Can you elaborate as to what you mean? ABYC H-24 is the authority on fuel tank installation. H-24 doesn't use the word vibration......

Fuel tanks are not only allowed to vibrate, but they are also allowed to move. They just can not move by more than 1/4 of 1 inch.

 

[JustJason]

I am not balking at putting a cushion under the tank!. Just trying to find out the purpose of the paper because it is obviously not for cushioning. I have had some responses from knowledgeable charter captains on the Great Lakes that it is VCI paper which is used to prevent electrolysis and corrosion. That makes the most sense of all. Looking at the description of reinforced, poly lined VCI, I believe that makes the most sense. In my case with a aluminum shelf supporting a poly tank, it would protect the alum shelf. In fact the shelf is bright and shiny as if it were new. I have had other responses of paper looking media being under aluminum tanks on Sea Nymph boats.

ABYC H-24 states the entire fuel tank must be supported. IE the fuel tank should not be "floating". For example, if a fuel tank had brackets mounted to it, and the brackets were screwed into stringers, and the bottom of the tank wasn't touching the bottom of the boat (or anything else) that would be a non-compliant installation.

I'm not there to see this "paper" you are seeing, but whatever material is being used to support the fuel tank should not absorb water to prevent/mitigate corrosion of metallic fuel tanks.

 

[alldodge]

Can you elaborate as to what you mean? ABYC H-24 is the authority on fuel tank installation. H-24 doesn't use the word vibration......

Fuel tanks are not only allowed to vibrate, but they are also allowed to move. They just can not move by more than 1/4 of 1 inch.

ABYC H-24 IMO as a non-legal type, the USCG Regs are. See post 4 link for Reg requirements. ABYC come from the Federal Regs

Page 59 states " Each fuel tank must not move at the mounting surface more than one-fourth inch in any direction."

Tanks shall also not help support any deck or stringer

My guess is you might be looking at tanks which are strapped in sitting on decks

 

[JustJason]

ABYC H-24 IMO as a non-legal type, the USCG Regs are. See post 4 link for Reg requirements. ABYC come from the Federal Regs

Page 59 states " Each fuel tank must not move at the mounting surface more than one-fourth inch in any direction."

Tanks shall also not help support any deck or stringer

My guess is you might be looking at tanks which are strapped in sitting on decks

Couple of things....

1. What you posted is out of date.

2. ABYC very much holds up in court.

3. ABYC does not come from USCG requirements.

Here is the current version of 33CFR 183.550 - https://www.ecfr.gov/current/title-...ect-group-ECFR64ce65eed2ac921/section-183.550

Where is the word vibration written or infered?

 

[alldodge]

CFR code of Federal Regulations - USCG enforces them so saying CG Regs is my bad, I should have said for you Title 33 I'm guessing. Title 33 is what gives the USCG (part of Homeland Security) authority of enforcing maritime laws and Regs. Many of the Regs often use terms to make it easier for the public to understand.

Specifically, Title 33 CFG Chapter 1, which includes Subchapters A thru S.
Subchapter S (Boating Safety) contains sub parts 1 thru 199, which is where 183 comes in at

Wording I used above while a little old it still has same words 183.550 (b)

Your trying to pic a fight for some reason. Vibration is my term based on seeing terms like abrasion

 

[JustJason]

CFR code of Federal Regulations - USCG enforces them so saying CG Regs is my bad, I should have said for you Title 33 I'm guessing. Title 33 is what gives the USCG (part of Homeland Security) authority of enforcing maritime laws and Regs. Many of the Regs often use terms to make it easier for the public to understand.

Specifically, Title 33 CFG Chapter 1, which includes Subchapters A thru S.
Subchapter S (Boating Safety) contains sub parts 1 thru 199, which is where 183 comes in at

Wording I used above while a little old it still has same words 183.550 (b)

Your trying to pic a fight for some reason. Vibration is my term based on seeing terms like abrasion

I'm not "trying to pick a fight". I am simply correcting misinformation. You said the paper is there to absorb vibration. That is not true.

 

[alldodge]

I'm not "trying to pick a fight". I am simply correcting misinformation. You said the paper is there to absorb vibration. That is not true.

ok ya got me, you win

 

[nea]

ABYC H-24 states the entire fuel tank must be supported. IE the fuel tank should not be "floating". For example, if a fuel tank had brackets mounted to it, and the brackets were screwed into stringers, and the bottom of the tank wasn't touching the bottom of the boat (or anything else) that would be a non-compliant installation.

I'm not there to see this "paper" you are seeing, but whatever material is being used to support the fuel tank should not absorb water to prevent/mitigate corrosion of metallic fuel tanks.

Once again, NOT A METALLIC FUEL TANK !!

 

[JustJason]

Once again, NOT A METALLIC FUEL TANK !!

H-24 does not differentiate tank types in terms of supporting the tank. Tanks of all types must be fully supported.

You should dig all that crap out to see if poultice corrosion is forming on the inside of the hull.

Also, no need to shout. You are getting free help from a master tech.

 

[alldodge]

Once again, NOT A METALLIC FUEL TANK !!

Let it go its not worth it

 

[Scott Danforth]

Once again, NOT A METALLIC FUEL TANK !!

Does not matter. Applies to all fuel tanks

 

[alldodge]

Does not matter. Applies to all fuel tanks

Watch it, master tech is watching
yes I was being bad aging