86 22' Classic - Tank Replacement

[BADABINGJR]

OK Fellas,

After reading your posts and some liquid courage I am ready to undertake a deck lift and a tank replacemement.....2 questions;

where to find a new tank made from PVC?

what kind of foam to use and where to get it?

thanks.

[MOP]

Nate filled his poly tank with water before it was foamed to hold the shape, he may chime in with where to get the tank and other tips.

Phil

[BADABINGJR]

do you recommend getting a tank made of another material?

[Tom Davis]

Have an Aluminum tank made and do not foam in place. Fit tank to stringers and then make glassed in pads (rectangular blocks) to support the tank. after glass work and gel coating of the area adhere 3/8 or 1/2 inch thick rubber to the tops of the pads. Then using stainless strapping material covered with bike innertube, strape the tank firmly in place to the rubber padded blocks.

Two advantages to doing it this way are; 1) easy tank removal and access if needed. 2) better drainage of water around the tank and down the keel of the boat out the stern drain.

I have pictures of this process from Steve Marr's X-18 if you are interested.

Just my .02

Tom Davis
Winni Bandits

[BADABINGJR]

thanks for the input but i have no experience working with fiberglass and that sounds a little too ambitious for DIY project for me.....

[gcarter]

There is nothing wrong with foaming in aluminum tanks when the tank is properly coated.
No coating is the reason there was ever any problem with foamed in aluminum tanks.
Proper coating is the answer to safely foaming in aluminum tanks.
If an aluminum tank is properly coated, it will probably NEVER fail from exterior corrosion.
Foaming in a tank is the safest, and strongest method of mounting a new aluminum tank.
Also, it is quite easy to foam in an aluminum tank.

This may sound redundant, but it is true.:)

[MOP]

Foam!You Speakith of that evil stuff that will only let a tank last 20-30 years!! Yet adds structural rigidity to the boat and holds the tank firmly in place where it takes two men and a boy to break it loose from the hull!

[Cuda]

I had the tank replaced in the 22 last year with an aluminum tank from RDS. The original tank was foamed in place, and didn't have any leaks when we got it out. I just figured after 25 years, it was do to be replaced. They foamed in the new one too, and added four extra tabs. Here's the thread about it.

http://www.donzi.net/forums/showthread.php?t=45332&page=2&highlight=tank

[Bob]

Foam or No Foam. Windshield or grab rail. Merc or Volvo. Here we go!:boggled:

[Cuda]

Foam or No Foam. Windshield or grab rail. Merc or Volvo. Here we go!:boggled:
I could care less if someone foams or not. I'm just relaying how I had it done. It was their choice on how to do it. They know a lot more than I do about it. They don't tell me how to lay tile, and I won't tell them how to install a tank.

[Donzigo]

They don't tell me how to lay tile, and I won't tell them how to install a tank.

CUDA, you're killing me.............on the floor laughing.

You da man.

So, Joe, does anybody try to tell you how to get along with Debbie?

OOPS, hijacking the thread. I did "no foam" - I hate the stuff - I did 2 tabs on each corner and through bolted everything right through the stringers...........I also put 1/2 neoprene strips on the bottom every 8 inches (140 gallon tank).........and I don't think that tank is going anywhere soon. The "no-foam" makes it so I can wash underneath the tank with a hose and keep the salt away. Another thing I did was to use two coats of primer and one coat of epoxy white paint. It shold last until I am swimming with the fishes out at Marker 19, 40 years from now. BTW, Nate did use plastic and the installation is pristine. So, choose your flavour and go for it. Both ways will work fine.

[Mr X]

http://smilies.vidahost.com/cwm/cwm/lurk.gif

[BUIZILLA]

how is plastic going to get along with the new ethanol party mix??

[gcarter]

How much fun this is....:) :yes: :yes:
There's no doubt a tank can be mounted a number of perfectly satisfory ways.
The problem in my mind is a stock design tank isn't a straight VEE on the bottom of it. It is very shallow at the bow end of the tank w/ a much deeper and steeper Vee than at the stern end of the tank where it is much deeper and with something closer to 24* deadrise. In between the two ends, the two bottom halves (port and starboard) are constantly warping and changing. There is no simple way to mathmatically calculate the location of a given point of the bottom ( X,Y, & Z axis) so that it and 20 or 30 other similar points can be adequately supported so that there is not greater stress placed on one support point than at the rest of them.
A 22C fuel tank is over 5' long and holds 50 (?) gallons or about 360# of gasoline plus the 100# or so of the tank.
If one support is higher or thicker than the rest and is near a welded seam (the tank consists of 8 pieces of .125 aluminum sheet welded together with eight of those seams on the bottom) this is where joint fatigue is going to occur.
Stated another way, if you had 20 or 30 supports under the tank, due to the shape of the tank and the inconsistantsies of the inside hull glass layup, the tank will only be sitting on 3 or 4 points. Add in the weight of the gas, during the typical operating envelope (in the air a good bit of the time and reintry generating fairly high G loads), there will be considerable stress placed on the tank at those few locations and there is a good possability of metal fatigue at those points.
Now compare this process to foaming in the tank where the entire tank bottom is supported uniformly, and in my mind anyway, this is a no brainer.

[Ed Donnelly]

George: Like someone once said, "Great minds think alike" ( could have been Mop)

I tend to agree with the foam:wink: :wink: .......Ed

[Carl C]

After some liquid courage Well you got the most important part down. Oh oh, here we go. I would think plastic would be most durable; the ethanol problems have been with the 'glass tanks. Foam or not? Pass that popcorn. :wink:

[LKSD]

We epoxy coat the aluminum tanks & then foam them back in & make sure everything is bilge coated as well.. :) You want it mounted solid & you want to keep the elemants off of it as well as possible.. & Yes taking out some foamed in stuff is a real MF'er to get out.. ;) Jamie / Lakeside


.

[BigGrizzly]

Each has it good points. here is a link since everyone think boats should be survey then look at this http://marinesurvey.com/. In a salt water situation salt will get under anything. the real problem is trapped moisture. personally I like the foam but not for the reasons stated. When I put the tank in the Corsican I have not decided which way to go yet. The final decision will be my gut feeling on that day.

[gcarter]

Each has it good points. here is a link since everyone think boats should be survey then look at this http://marinesurvey.com/. In a salt water situation salt will get under anything. the real problem is trapped moisture. personally I like the foam but not for the reasons stated. When I put the tank in the Corsican I have not decided which way to go yet. The final decision will be my gut feeling on that day.
Good morning Randy;:)
I bet I have read Mr Pasco's article 15 or 20 times. I agree w/ everything he states. However if you build a flat deck between the stringers, (and that's what he's saying to do) You give up half or more of your tank capacity.
Or, you attempt to do what was stated by Mr Davis and Mr. Aaron and you run into the problem that I was describing previously, i.e., insuficient support which may result in stress cracks.
So the one solution that may solve all of these problems is proper coating of the tank, i.e., eliminate the possibility of corrosion.
Several here have done this, and I believe with good results. Morgans Cloud likes to thouroughly clean the tank and coat it w/ Gluvit, a very flexable epoxy. Jamie likes epoxy also. I, at the suggestion of Mop, used an epoxy primer w/ a lot of zinc chromate, and thouroughly coated the tank w/ coal tar epoxy. Coal tar epoxy was specifically designed for coating steel pilings in salt water, where it does a very good job. I used this product on my Minx w/good results, I also sold some to a couple of other members. Also I'm preparing to coat and foam in a new RDS tank into a 18' barrelback, probably next week.

[BigGrizzly]

Just for the record Mr. Pasco didn't mean all tanks should be flat. just that the mating surfaces should mate. like I said both have their good points and I haven't decided yet. BTW you were going to send me your tank installation on your minks so I would not have to piece all the threads together. There are so many opinions out there on this subject it is confusing. The other part is there isn't enough data out there to support any of them. Does anyone know anyone who has put an aluminum tank in there boat 38 years ago and still has the boat to reference, except for our 1966 16. we did the tank in 1969. I won't tell you why the tank went bad so early. lets just say it was a bad winterize experience.

[Cuda]

I haven't inspected the construction, the coatings, or the installation of every tank put in a Donzi, but I can state that an aluminum tank, foamed in, with no coating lasted 25 years in my case, with no leaks.

Your mileage may vary.

[gcarter]

I just ran out to my shop and took some pictures of the new tank for Baron Kamp's boat ('60's 18C Barrel Back).
The first three show the warp in the tank bottom, while the fourth shows the very indefinate shape of the hull bottom in the area of the tank. In fact, you can see where the old tank bulkhead was located and the new tank bulk is epoxied into place but hasn't been 'glassed in yet.
I think these pics demonstrate that properly supporting the tank w/something other than foam, while may be possible, would be difficult.

[realbold]

No foam for me. My new tank is coated with epoxy primer and epoxy bottom paint. I do admit getting the bunks right for a belly tank was a challenge. The bunks will be covered with 1/4" neoprene and Tank will be bedded to that with Woolsey Dolphinite bedding compound. Before painting I welded angle to the top for and aft of the tank and it will be bolted to the bulkheads, will need to make shims. Being a machinist that wont be a problem. I am making a full size hatch for access. Here's a pic of the glassed in bunks. They're made of PVC foam.
http://i40.photobucket.com/albums/e243/realbold/barehull004.jpg

[Cuda]

No foam for me. My new tank is coated with epoxy primer and epoxy bottom paint. I do admit getting the bunks right for a belly tank was a challenge. The bunks will be covered with 1/4" neoprene and Tank will be bedded to that with Woolsey Dolphinite bedding compound. Before painting I welded angle to the top for and aft of the tank and it will be bolted to the bulkheads, will need to make shims. Being a machinist that wont be a problem. I am making a full size hatch for access. Here's a pic of the glassed in bunks. They're made of PVC foam.
http://i40.photobucket.com/albums/e243/realbold/barehull004.jpg
I could be wrong here, but won't the neoprene deteriorate when exposed to gasoline?

Here's what I found on that matter.

Neoprene
Neoprene has moderate resistance to oils and gasoline. It features good flame resistance, weathers well, and has very good resistance to abrasion, flex cracking, alkalis, and acids. However, expect poor resistance to aromatic and oxygenated solvents and limited flexibility at low temperatures. Neoprene is generally considered an excellent all-purpose material with a solid balance of properties and few limitations

[gcarter]

No foam for me. My new tank is coated with epoxy primer and epoxy bottom paint. I do admit getting the bunks right for a belly tank was a challenge. The bunks will be covered with 1/4" neoprene and Tank will be bedded to that with Woolsey Dolphinite bedding compound. Before painting I welded angle to the top for and aft of the tank and it will be bolted to the bulkheads, will need to make shims. Being a machinist that wont be a problem. I am making a full size hatch for access. Here's a pic of the glassed in bunks. They're made of PVC foam.
http://i40.photobucket.com/albums/e243/realbold/barehull004.jpg
That's an admirable undertaking. I'm sure you will be pleased with the outcome. It looks like it should work very well.
However, since the tanks are coated in both cases with materials that would work in most any environment,.......will your method, as good as it is, last, say ten years longer than $50.00 worth of foam???????????

[realbold]

I guess I just dont like idea of the compartment being sealed off with pipes running underneath, so if any water does get in there it cant drain. This way any drainage runs under the tank and the compartment can be vented. Also be a lot easier to remove the tank if I ever have to.
As for the neoprene deteriorating from gasoline, I guess if it ever gets gas on it its from a leaky tank that has to be removed anyway.

[MOP]

Like Randy says there are several ways to mount a tank, do what makes you comfortable follow proven mounting designs make sure it is good and secure. Cribbing with good tie down straps will work for most all applications, I went with foam as I feel it has more then proven it does the job in our rough and tumble boats. Anyone how is not satisfied with 20-30 year life span may choose another route. As most know I have been in the working and now a broker, I see many boat with well "aired" tanks having to change them out. A tank will fall prey to corrosion sooner or later from within or without, I feel with the added alky content in the gas they will be going sooner from the inside then outside. The question was raised about poly, I do not know the difference between corn alky and rubbing alky but rubbing alky has come in plastic bottles as long as I can remember. We need a chemist!!!

Phil

[BigGrizzly]

Alky will have little or no effect on the poly tanks. The problem people had was they though the poly wasn't as strong as steel or aluminum. Neither of which is true except in extreme cold climates where plastic can fracture from impact. Also remember there are a million different types of poly. I am assuming the right one is used for the tank. thickness is also an issue. I would use a poly tank if it were available and that could be foamed in easily and give support to the tank as well.

[realbold]

I would have bought a poly tank if I could've found one the right size.

[BigGrizzly]

Realbold, I like your thinking and your tank installation procedures along with your water evacuation though for mine are the same. No matter what you do you will have water intrusion. Getting it out is the problem.

[Rootsy]

how is plastic going to get along with the new ethanol party mix??


HDPE is impervious to alcohol.

[zelatore]

My tank experience is no match for others on the board, but I'm a fan of poly for smaller tanks like these as well.

One example: on our 28 Albin fishing boats we used to use aluminum tanks. Twice we had to replace tanks under warranty due to leaks from poor welds (OK, probably more a supplier issue than an aluminum issue). Later they switched to poly and we haven't had a problem since. Granted, this is a diesel application instead of gas so the alky isn't a concern. But never having to worry about corrosion is a big piece of mind point.

[gcarter]

I have no problem with poly tanks. I think they're wonderful.
However I've not been able to find any tapered deep Vee poly tanks. So....using any stock poly tanks would mean losing tank capacity.

[Conquistador_del_mar]

I have had to replace fuel tanks in many sport boats over the years since I used to do this professionally. If you need a drainage valley under the fuel tank, you can fiberglass a sub-floor across the bottom of the V bottom using a ¼” fiberglass plate from bulkhead to bulkhead. This does not need to be very far off the bottom – just enough to allow water to pass under it and it will provide the needed strength with the fuel tank overhead. You will want the entire fuel tank area to be a waterproof compartment when replacing the tank. When you have the tank built, leave at least 1” all the way around it for clearance. If you use an aluminum tank, be sure to seal it with a water barrier coating. Place some short narrow strips of a closed cell foam using an adhesive to the bottom and sides of the compartment. These are simply to help keep the tank suspended in the right position when you pour a urethane two part closed cell marine foam into the compartment. The two part marine foams activate very quickly depending on the temperature. I found the best way to foam in the tank is to first get the fuel tank compartment area level so that the foam liquid mixture will not go to the lowest point. Calculate how much to mix so that it will at least start coming up the sides of the tank when it starts to expand. The foam I used came in gallon kits. One gallon of part A mixed with one gallon of part B will expand to about 10 cubic feet (many times more than you will use, but you can calculate according to these expansion rates). Now mix and quickly pour your mixture in the middle of the compartment area from front to back and quickly set in your tank. You will need to hold it down as it expands or it will float up the tank. The foam will expand and harden in a very short period of time depending on the temperature. Now you can come back and pour more foam mixture to the top of the tank sides. Any foam that expands higher than what you want can easily be trimmed off after it hardens with a good knife. You will now want to fiberglass a few pieces over the top of the tank between the stringers using more of the closed cell foam pieces for a cushion. This will help to keep the top of the tank from flexing too much when the fuel is sloshing around. If you have an access plate hole in your floor (highly recommended) for access to the fuel sending unit, be sure to seal that plate with silicone and apply grease or silicone to the o-ring seal for a better seal. Now your fuel tank will be totally surrounded by a very strong support cushion for hitting those waves. I hope this helps. Bill

[sweet 16 1966]

I used closed cell on my tank 3 years ago and just recently pulled it out- Epoxy sealed the top and it was water tight. All was dry as a bone. Took some doing to get it back out though. HAD TO USE THE SAW and a long prybar.

[sweet 16 1966]

I can't get motivated to complete mine at this time but have not forgot about you Griz. Don't have much time but willing to help!

[BigGrizzly]

Russ we do have to get together with or with our your boat. working on mine isn't a priority at this moment. I am finally getting to clean up the Garage. Give me a call and come over you know how to get there. I will be going to lake George next week for a week or so.