Classic AquaSport

Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter => Fuel tanks and anything about fuel systems => Topic started by: scoflaw on March 18, 2015, 08:36:13 AM

Title: poly tank
Post by: scoflaw on March 18, 2015, 08:36:13 AM
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?
Title: Re: poly tank
Post by: Capt. Bob on March 18, 2015, 08:45:52 AM
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.
Title: Re: poly tank
Post by: scoflaw on March 18, 2015, 08:52:58 AM
What foam product do most use?
Title: Re: poly tank
Post by: Capt. Bob on March 18, 2015, 08:59:11 AM
Here's Wing's tank on his old 200XF (same hull as yours).

(http://i80.photobucket.com/albums/j196/wingtime/Aquasport/200xffueltank.jpg) (http://s80.photobucket.com/user/wingtime/media/Aquasport/200xffueltank.jpg.html)

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.
Title: Re: poly tank
Post by: scoflaw on March 18, 2015, 09:13:02 AM
Not understanding the lowest weight comment. Are we talking spray foam from Home Depot?
Title: Re: poly tank
Post by: Blue Agave on March 18, 2015, 10:05:55 AM
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.
Title: Re: poly tank
Post by: gran398 on March 18, 2015, 10:44:19 AM
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.
Title: Re: poly tank
Post by: scoflaw on March 18, 2015, 10:59:30 AM
Where does one buy this foam and what is it called?
Title: Re: poly tank
Post by: CLM65 on March 18, 2015, 11:30:54 AM
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.).
Title: Re: poly tank
Post by: Capt. Bob on March 18, 2015, 05:36:27 PM
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.
Title: Re: poly tank
Post by: scoflaw on March 18, 2015, 06:29:58 PM
Moeller tech says no foam, neoprene for surrounding material
OK I get it.
Thanks for the input
Title: Re: poly tank
Post by: Capt. Bob on March 18, 2015, 08:17:56 PM
I'm reading your post to mean "use neoprene" rather than foam for mounting, correct?
Title: Re: poly tank
Post by: scoflaw on March 19, 2015, 10:27:08 AM
Correct, neoprene will contract enough to allow for the poly tanks 3% expansion
Title: Re: poly tank
Post by: scoflaw on March 23, 2015, 12:35:18 PM
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
Title: Re: poly tank
Post by: Capt. Bob on March 23, 2015, 01:30:19 PM
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?



Title: Re: poly tank
Post by: scoflaw on March 23, 2015, 01:43:12 PM
The tank and foam look old enough, but who knows. Trying to get a working # on Inca.
Title: Re: poly tank
Post by: Capt. Bob on March 23, 2015, 02:13:56 PM
You can contact Inca at (615) 350-7290.

Here is a start (notice phone# on sticker)but it may be too wide at the top????

http://greatlakesskipper.com/inca-f07203d-poly-72-gallon-68x27x11-boat-fuel-diesel-gas-tank

I left a voice mail with Inca's Customer Service requesting dimensions.

Let's see what happens.
Title: Re: poly tank
Post by: scoflaw on March 23, 2015, 02:58:22 PM
Yup too wide, coffin box is 27" at top and 13" down it's 21" wide,
Fill tube and vent would be nice at opposite end of pickup, like what I have.
Now I know why people have aluminum tanks made.
Title: Re: poly tank
Post by: RickK on March 23, 2015, 03:02:38 PM
You can contact Inca at (615) 350-7290.

...Let's see what happens.
I called them when I bought my tank from a surplus place 2 years ago.  Still waiting for a return call. :(
I think they only answer the big boyz when they call (Major accounts).
Title: Re: poly tank
Post by: scoflaw on March 23, 2015, 03:18:17 PM
Heard that earlier, that they only deal with boat manufactures and only with tanks with OEM specs

I have gas coming out of the drain plug but see no gas leaking from the top of tank or from the aft bulkhead, must be a drain hole at bottom of coffin?

Title: Re: poly tank
Post by: Capt. Bob on March 23, 2015, 03:35:13 PM
I have gas coming out of the drain plug but see no gas leaking from the top of tank or from the aft bulkhead, must be a drain hole at bottom of coffin?


I'd bet your tank is corroded under one (or both) straps (if they exist) under the bottom of the tank. Even if you do not have a strap(s), the tank has moisture trapped underneath and that is where your leak(s) reside.

The idea of the coffin was to allow below deck tank storage without the need for bilge ventilation. The tank was placed in the coffin and should a leak occur, it would be contained within.

We have seen coffins with drain holes. Factory installed or by owners, who knows.

I do know that when my tank ruptured in my CCP, gas did enter the bilge and came through the hull drain plug. The coffin had cracked and allowed fuel to drain into the bilge. I would guess yours is suffering from a cracked coffin or that a drain hole is there.
(http://i76.photobucket.com/albums/j7/GoneFission/CIMG0041.jpg) (http://s76.photobucket.com/user/GoneFission/media/CIMG0041.jpg.html)

How long is your existing tank? Would you have enough clearance to install the Inca tank I linked to?

Good luck.
Title: Re: poly tank
Post by: scoflaw on March 23, 2015, 03:45:39 PM
About 48", and have a couple of feet of unused area aft.  Math says I have 56 gal. now which sounds correct. I don't make long trips, so what I have is plenty.  Bottom line is I'm flexible on length
Title: Re: poly tank
Post by: Capt. Bob on March 23, 2015, 03:57:07 PM
Here's something a tad smaller:

http://greatlakesskipper.com/blue-wave-inca-fxv6020sbw-crosslink-60-gallon-72-x-23-x-10-inch-boat-fuel-gas-tank

Different shape:

http://greatlakesskipper.com/blue-wave-inca-fxv6020sbw-crosslink-60-gallon-72-x-23-x-10-inch-boat-fuel-gas-tank
Title: Re: poly tank
Post by: scoflaw on March 23, 2015, 04:50:48 PM
Who makes a reasonably priced aluminum tank in SW Florida or Boston area.
Hope to get the last 2 weeks of my vacation out of this one.
Title: Re: poly tank
Post by: Capt. Bob on March 23, 2015, 05:27:04 PM
RDS is up in my neck of the woods. They have made many Aqua tanks over the years and had the specs on my 91.

I had them build it exactly the same surface size but half as long. Went from a 105 to a 55 gal.

No shipping in my case but the tank was still about $10 a gal. for aluminum.
Title: Re: poly tank
Post by: scoflaw on March 23, 2015, 06:06:49 PM
They got a box stock 1 on their site that looks perfect.  I'll call tomorrow for a price

Thanks for the tip
Title: Re: poly tank
Post by: scoflaw on March 27, 2015, 10:10:23 AM
I gave up on the poly tank, too expensive and a poor fit.

Contacted RDS, and Alloy Metal Works, price is good, but both of these places have lost the drawings.

If anyone has info on this, 20' CCP would be helpful. Not going to tear into this until next year
Title: Re: poly tank
Post by: GoneFission on March 27, 2015, 10:25:49 AM
With a little notice, Phil at Alloy Metal Works will build you a tank and ship it the same week you order it.  So you could just wait until you have the tank out, measure it, call Phil on Monday and have your tank maybe on Friday.   :08:
Title: Re: poly tank
Post by: Capt. Bob on March 27, 2015, 10:43:12 AM
While you're deciding, let's add to the confusion.
Note: These two threads intertwine.

http://classicaquasport.com/smf/index.php?topic=11872.0

http://classicaquasport.com/smf/index.php?topic=11944.msg119946#msg119946

Two things:

You should (according to the above info) have the "72" gal. tank from the factory. The dimensions of Wing's tank should fit your coffin but....

As GF states, actually getting your tank out and physically measuring is your best bet.

Good luck.

Title: Re: poly tank
Post by: scoflaw on March 27, 2015, 11:23:23 AM
Says he's booked up for at least a couple weeks plus ship time. Also shipping to Mass. would be cheaper than to SW Fla.
Title: Re: poly tank
Post by: scoflaw on March 27, 2015, 01:12:16 PM
Def. got a 50 and it looks original. Front of the coffin begins under the cc. Looks to have original fill and vent hose, which would  be a big job to replace and makes fitting replacement important

Any pics of an older 20' with the smaller gas tank?
Title: Re: poly tank
Post by: Capt. Bob on March 27, 2015, 02:02:07 PM
Look at the 2nd link I posted above, the 11th post down (author "Fighting Irish 45").

79 200 CCP. 50 gal.

Layout look like yours?

Title: Re: poly tank
Post by: scoflaw on March 27, 2015, 03:42:51 PM
Nope, fill neck and vent are further forward , and pickup and sending unit further aft, and my tank doesn't extend that far aft.
Title: Re: poly tank
Post by: Capt. Bob on March 27, 2015, 04:04:34 PM
Can you post a pic, something I can work with?

Thanks. :thumright:
Title: Re: poly tank
Post by: scoflaw on March 27, 2015, 04:18:38 PM
Boats together and running, headed north next weekend, hope to burn more fuel next week before I leave
I will be ripping it up when I return next Jan.

I would recognize the configuration if I saw it. Should of taken pics when I patched up the floor, a couple of months back
Title: Re: poly tank
Post by: Capt. Bob on March 27, 2015, 04:54:38 PM
I'll keep lookin'

Enjoy. :13:
Title: Re: poly tank
Post by: scoflaw on March 27, 2015, 04:57:46 PM
Thanks CB, sent you an email of the only pic I could find

Title: Re: poly tank
Post by: Capt. Bob on March 27, 2015, 05:35:00 PM
Thanks CB, sent you an email of the only pic I could find

Great shot of the towel :mrgreen:

I'll dig some more. :det1:

It sure looks like it's been lying in there for a long time. :ScrChin:

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