Oh Boy...This Smell Ain't Good

[TownsendsFJR1300]

it's a hard foam and it's meant to be glassed over, resin does not melt it.

I just meant he could use pieces of this material as spacers AFTER he gets the tank secured in. To make sure it doses not shift around.

I made stringers from it and glassed them in, very stiff and strong and will never rot like wood.

Interesting!

Well, if it's strong enough to be a stringer, epoxying pieces to it (the bigger the better-more surface area), would be the way to go...

[Jason2tpa]

I would think think the stringers have to have wood in the middle...

How would you make a stringer of foam, then Fiberglas over it, just doesn't make sense..

Foam filled fiberglass. The pictures below will help you visualize. First pic the foam has been extracted from the fiber construct. 2nd pic shows the fiber construct filled with foam, ready for deck installation. These pics are not of my hull, they are of the same model/year hull ('76). Fuel coffin is the forward compartment, bilge aft.

This innovative stringer construction is one of the primary reasons AQ hull's last as long as they do. All other hull manufactures in the late 60's & 70's used wood and/or fiber stringer systems. How many 1970s Ranger hulls do you see around these days?



[IMG][/IMG]

[pstephens46]

I believe that precision foam board is called a few different names by manufacturers. If it is what I think, they build modern transoms with it. Drill holes and mount big motors. With washers, it doesn't compress.
Brutally strong. So no wood needed..... I don't build boats. Wish I knew how. Like those guys that live around Rodbolt and build those killer 70 ft Carolina boats. They also told the stuff doesn't absorb water. So no freezing damage...of course some of you have no worries about that!

[panasonic]

Precision Board Plus HDU - Coastal Enterprises

[Jason2tpa]

Ok Jason, here's how my aluminum tank is securred:

Four tabs on each upper end of the tank. The two (looks like 1/4, 20 screws) going thru a small spacer block, then into the stringer.. There is NO foam anywhere to be seen. And obviously, air can get to everywhere(except the bottom I gather).

Above the tank is the deck, I'm photographing thru the ONE access hole. The camera is literally sitting atop the sender unit..


The screws showing from the top secure the two separate seats..

Possibly a dumb question, but oh well here goes. The 4 tabs that would be welded to AL tank...do these tabs need also be AL or could they also be SS? Same applies to the screws. Not sure if SS has an "alergic" reaction to AL. Is there a metallurgist on forum

[pstephens46]

The "harder" metal wins. I would use thick AL if available. If touching tank.
Sometimes you have no choice. Fasteners, etc. bolts screws

[TownsendsFJR1300]

Possibly a dumb question, but oh well here goes. The 4 tabs that would be welded to AL tank...do these tabs need also be AL or could they also be SS? Same applies to the screws. Not sure if SS has an "alergic" reaction to AL. Is there a metallurgist on forum

Don't need a metallurgist for this one.....

You can't weld aluminum to SS so those tabs have to be aluminum..

I'm sure the screws are SS with flat SS washers spreading some of the load.
If they weren't, they'd be rusty after 19 years on the head.

Mixing the two there isn't an issue. If you want to make/put a plastic washer between the aluminum and SS bolt you can.

The screws would simply be slipping thru the tabs and "threaded" into the wood/anchor/what ever you use as a spacer...

Mine doesn't appear to have anything.. You likely won't be touching that tank for another 20 years...

[DennisG01]

You're correct, that is a concern. Your suggestion talked about securing tank by using a "few lengths of 1-1/2" PVC angle "iron" secured to the stringers". Scott's suggestion is similar, in that you're using the stringers as an anchor. My concerns about using the stringers as an anchor is detailed in my reply to Scott.

That's what I was trying to get at, sorry for confusion.

Oh, OK. I see what you're saying, now.

OK, here's a way you could go if you're unsure how thick the coffin sides are and whether or not they will support being screwed into. But, one thing to note..... the primary strength of stringers comes from the vertical section of the fiberglass. Even with a wood cored stringer, the fiberglass is the main component, not the wood....... Have the tank built slightly narrower (maybe an inch to an inch and a half) than the coffin sides. This will allow you to build out the wall of the "stringer" with another 1/2" of fiberglass in the area that will receive the tab screws. This will now be PLENTY strong in this area. And because the tank is still narrower than the built-up areas, it can still easily drop in, or out. If there ends up being a gap between the tab and the built-up area, that's easily remedied with a couple washers (or even a nut) as "spacers".

The foam board referenced, while solid stuff, should not be placed against the tank (unless it's epoxied FULLY to the tank). If it is, we're basically back to the same issues we can have with the pourable/expandable foam... trapping moisture against the tank. Ideally, we want AIR SPACE around the tank (including the bottom) to help it last as long as possible.

The tabs should be made out of aluminum, but the hardware will be SS. It should be just fine. If you want to take an extra precaution, you can use a nylon washer between the screw head and the aluminum tab. EDIT: Looks like Scott typed his response faster than me!

[TownsendsFJR1300]

The tabs should be made out of aluminum, but the hardware will be SS. It should be just fine. If you want to take an extra precaution, you can use a nylon washer between the screw head and the aluminum tab. EDIT: Looks like Scott typed his response faster than me!

With just my two pointy fingers yet!

[panasonic]

Possibly a dumb question, but oh well here goes. The 4 tabs that would be welded to AL tank...do these tabs need also be AL or could they also be SS? Same applies to the screws. Not sure if SS has an "alergic" reaction to AL. Is there a metallurgist on forum

It's a catch 22 situation
The aluminum tabs on the tank need to bolted/screwed to boat. What to use? Stainless bolts or screws. But these are dissimilar metals and galvanic corrosion will occur, with the aluminum on the losing end. OK use regular zinc plated bolts, not so dissimilar but the old zinc plated bolt will rust away in quick order on a boat. So back to stainless.

So like Scott said you can isolate one from the other with a plastic washer and it should be fine. I use sealant on the washer under the head or nut to prevent direct contact between the stainless and aluminum.

See chart.

[DennisG01]

With just my two pointy fingers yet!

EDIT: I tried to just respond with just the smilie face thingy, but the forum said I had to use at least 10 characters. So I edited by adding these two statements... which is now much longer than 10 characters...

[99yam40]

anyone ever wonder how they make connections between aluminum and copper for buss bar electrical connections?
The SS to aluminum statement made me think of this.

they use explosions to force the 2 metals together, and then press the parts back flat and machine them down to the final size and shape
aluminum and copper do not get along well together, but the explosion makes them bond together well and the copper surface on one side makes a better bolted connection that holds up well

[Jason2tpa]

You know, if it wasn't for my good conscience I'd be 100% with using the complete pascoe method (5200/4200 bonding pvc strips to coffin bed). It's simple and the least amount of tank prep time. I'll have this boat for maybe 5 more years, 7 at most. I'll sell it off and buy a bigger boat.

My point is, I won't be the owner of this boat when it needs another fuel tank. Bonding the pvc strips to the coffin bed with 5200/4200...extracting the tank will be an absolute nightmare. It would have to be lifted straight up to break the bond, and along with it would come the coffin or pieces of it. It won't be my problem....but then my conscience kicks in

[DennisG01]

You know, if it wasn't for my good conscience I'd be 100% with using the complete pascoe method (5200/4200 bonding pvc strips to coffin bed).

Are you saying that Pascoe says to bond the PVC strips to the coffin bed? If so, that wouldn't affect pulling the tank later as the PVC is only bonded to the bed, not the tank. It also would allow moisture to possibly collect between the strip and the tank.

Or, are you saying that Pascoe says to bond the PVC strips to BOTH the bed and the tank? If so, that's wrong. As I wrote above, the PVC strips HAVE TO BE BONDED to the tank ONLY. But they need to be bonded completely (ideally with a faired edge) to avoid moisture staying in contact with the tank for extended periods of time.

I'm not sure if you're reading Pascoe incorrectly or if he is actually wrong, but... do as I mentioned - bond the PVC strips to the tank bottom.

[Jason2tpa]

Are you saying that Pascoe says to bond the PVC strips to the coffin bed? If so, that wouldn't affect pulling the tank later as the PVC is only bonded to the bed, not the tank. It also would allow moisture to possibly collect between the strip and the tank.

Or, are you saying that Pascoe says to bond the PVC strips to BOTH the bed and the tank? If so, that's wrong. As I wrote above, the PVC strips HAVE TO BE BONDED to the tank ONLY. But they need to be bonded completely (ideally with a faired edge) to avoid moisture staying in contact with the tank for extended periods of time.

I'm not sure if you're reading Pascoe incorrectly or if he is actually wrong, but... do as I mentioned - bond the PVC strips to the tank bottom.

How to Install an Aluminum Fuel Tank : Boats, Yachts - Maintenance Repair and Troubleshooting

There is actually a term used to describe the method you're speaking of...bonding only the pvc to tank...it's called the modified pascoe method. The standard pascoe method bonds both pvc to tank and pvc to coffin bed with 5200.