poly tank

[scoflaw]

Seeing poly tanks are about half the price of aluminum and moeller makes a ton of them anyone have any luck dropping 1 in on a 1982 20' ccp?

[Capt. Bob]

The only restriction I see is the tank dimensions themselves.
Maybe fill and pickup locations but you could work around those.

73 gal.?

Just need to measure and search.

Good luck.

[scoflaw]

What foam product do most use?

[Capt. Bob]

Here's Wing's tank on his old 200XF (same hull as yours).



Here's something close.
http://www.moellermarine.com/sites/moellermarine/files/FT7205.pdf

Yes it's longer but I believe you have the room (I may be wrong) in your coffin. Seems to meet the height requirement (the real sticking point).

Sticky question on the foam. Some like some don't. Again, since the tank is poly, it may not really have an adverse affect on its surface. If it's just used for mounting (duh) I'd use the lowest weight I could get for costs savings.

Starting spot anyway.

Good luck.

[scoflaw]

Not understanding the lowest weight comment. Are we talking spray foam from Home Depot?

[Blue Agave]

What foam product do most use?

Do not foam in the poly tank or an aluminum tank for that matter.  Much better to secure the tank with straps and leave the surrounding areas open to air.  With a poly tank, once you add fuel the tank expands, if foamed in the poly tank may crack.

Capt. Bob's comment regarding weight refers to 2lb or 4lb foam.

[gran398]

Agree with Nando, no foam or minimal foam. We used a little foam in each corner to set (chock) the tank. Placed gallon ziploc freezer bags in the corners, then shot the foam in the bags. Then a few longitudinals across the top to chock. We used hollow 2X2 fiberglass girders with rubber between.  You could also used untreated wood, aluminum, etc.

[scoflaw]

Where does one buy this foam and what is it called?

[CLM65]

As Nando pointed out, poly tanks will expand when fuel is added.  Most manufacturers state that 2%-3% is normal.  This may not seem like a lot, but if you consider a 24" wide by 72" long tank (which will put you in the ballpark of a 72 gallon tank), it will expand about a half inch in width and about 1.5" in length.  If you constrain the tank by surrounding or blocking it with foam, you are asking for trouble (as in a ruptured tank).  The lighter density foam (i.e., 2 lbs/cubic ft) will compress more easily than higher densities (i.e., 4 or 8), but I wouldn't rely on that when it comes to mounting a poly tank.

And don't limit yourself to just Moeller.  Another manufacturer is Inca.  There are others as well.  I have a 72 gallon Inca for my project boat.  But I will say that Moeller is much easier to find literature on (drawings, instructions, etc.).

[Capt. Bob]

Again I agree.

Here's the type foam I was referencing. You see it can get costly.
http://www.uscomposites.com/foam.html

I forgot about the expansion factor of poly tanks. Still, you want it secure and not sliding around.

We have seen a poly that had suffered chafing from the tie down strap.
http://classicaquasport.com/smf/index.php?topic=12511.msg126230#msg126230

So they're not trouble free but properly mounted, they don't suffer from corrosion like the aluminum.

Good luck.

[scoflaw]

Moeller tech says no foam, neoprene for surrounding material
OK I get it.
Thanks for the input

[Capt. Bob]

I'm reading your post to mean "use neoprene" rather than foam for mounting, correct?

[scoflaw]

Correct, neoprene will contract enough to allow for the poly tanks 3% expansion

[scoflaw]

Had the coffin cover off today to take a look.
My tank, which appears original, is 48 x 24 x 19. approx.
 I have plenty of length to make  Wings tank work. Was Wings tank a custom ?
Moeller doesn't seem to have what I'm looking for

[Capt. Bob]

My tank, which appears original, is 48 x 24 x 19. approx.

Hmmm, something's missing.

To calculate the size in gallons, take the area (in inches) x .00433

Wing's tank shape is a trapezoid. (two sides parallel, top and bottom in his case) so...
(24" + 20" / 2) x 11" (the height of the tank) That gives you the area of one section of the tank. In Wing's case, he has 72 sections (length) which equals 17,424 cubic inches x 0.00433 = 75+ gals. 

I have plenty of length to make  Wings tank work. Was Wings tank a custom ?

Wing had it built I believe, to its original dimensions. Factory lists the stock tank at 73 gals. Wing's dims equate to a 75gal. so it's the same quantity (mine was 100 gal from the factory specs but was stamped 105 gal on the tank itself) so your tank should be the same as Wing's (from the factory).

If your tank is only 48" long but is shaped like Wing's, your gallons would be much less.
 (24" + 19" / 2) x 11" (assuming same height as Wing's) x the length (48") X 0.00433 = 49 gals

Can you see a sticker on the tank from the manufacturer?