Bait tank/ holding tank fabrication question

[searaytuna]

I am planning on building a bant tank & holding tank across the transom of my boat. THe overall width is 102". I am thinking to have 2 30~40 gallon soze tanks on each ends--port & starboard side of the transom and the mid section to have a live well/holding tank. All of this will be mounted on the swimstep as well as have u-brackets that will fasten it on the transom as well.

What would be the best material for this project? I am thinking waterproofed balsa laid with fiberglass on the exterior for uniform apperance as the hull. Any insights & directions would be greatly appreciated. Thanks in advance.

JW

[gonzo]

Are you refering to a sewage holding tank? If so, it needs to be up to Federal standards.

[searaytuna]

Originally Posted by gonzo

Are you refering to a sewage holding tank? If so, it needs to be up to Federal standards.

NO. a bait tank on either sides of the livewell--where I put my catch with some water running thru it from the overflow from the bait tank on either sides of it. Strictly for fishing.

[wdnboatbuilder]

One day I was watching Ship Shape TV and he took a laminating table ( a piece of plywood with formica over (counter top) and waxed it. then he took woven roven or some heavy weight glass layed out across the table coated it with epoxy. Allowed it to dry, peeled it up and rolled it into shape. At the time I was in the process of building my flats boat and was in need of some bait wells, I tried it with a medium weight cloth with mat on one side and it worked out well. In your case your looking for something a little larger than a bait well but don't see why it would not work for you. just remember that corner should be round and the water should circulate counter clockwise unless you are on the other side of the earth. Also I put the mat to the inside for an smoother surface on the inside.

[searaytuna]

hmm. that sounds pretty good/convenient for a smaller tank, but the one I am planning is much larger and not sure if that is gonna be structrually sturdy enough(??). Wouldn't be too brittle with just the woven cloth alone even if I put additional layers of heavy cloth?
Here is a rough diagram(it's really not to scale) of what I am thinking. Each bait tank will hold at least 40~50 Gallons of water so there will be enough weight and pressure from the water there.. I would like to get this thing as light weight as possible without compromising the structural strength of it. Any ideas?

BTW. I agree with you about the rounding of the edges on the inside of the well with clockwise water rotation. I am thinking of rounding the exterior corners as well.

[gonzo]

Have you considered what adding 400-500 lbs to the aft end will do to the boat's trim. If the panels are flat like in the drawing, Baltek makes balsa 4X8' already glassed. You can cut them and join them with fillets and tape on the edges. Another thing to think about is that amount of water free moving. Without baffles the tanks will have to be very strong and have lids, hinges, locks, etc. that can handle the loads.

[FAST FRED]

With the wight of water your looking to carry any tankage will be under 2lb per sq ft of surface and hardly count.

FAST FRED

[wdnboatbuilder]

very good point gonzo. and as to the tank being brittle you must be refering to polyester resin. epoxy won't get brittle and as far it holding up without adding any extra glass should not be a problem. in my experience if you run your water in a clockwise rotation your fish will die.

[searaytuna]

Originally Posted by gonzo

Have you considered what adding 400-500 lbs to the aft end will do to the boat's trim. If the panels are flat like in the drawing, Baltek makes balsa 4X8' already glassed. You can cut them and join them with fillets and tape on the edges. Another thing to think about is that amount of water free moving. Without baffles the tanks will have to be very strong and have lids, hinges, locks, etc. that can handle the loads.

Yes. THis is my main concern. So I was/am trying to minimize the amount of weight possible, but I realize just on the water weight alone, at 8.3lbs to a gallon of water it's pretty heavy stuff. At about 5200lb dry wt. of my boat, is this even a feasiable thing to do or am I thinking out of my ass?? I would really like to get as much bait to this boat as possible without jeopardizing the trim as much as possible.. am I dreaming to make 2x20gallon tanks even?

I thought clockwise water rotation was suppose to be ok.. but I am an amatuer with this.. thanks for the correction.

[cyclops]

My biggest concern is getting caught offshore in a fast squall that causes the waves to hit at the bait wells and fill if the tops are at deck height. They can also provide the full area of their bottoms to a wave slamming up the bottoms . No course or speed will stop them from pounding the bottoms. Putting a 45 degree angled filler piece would stop a lot of the upward slamming action. Enough? I really can't say. Lots of sea conditions to think of with a loss of all power. Another is to mount the tanks with break away pins if things get scary. Let the tanks go and come home safe and with a complete transom.

[searaytuna]

Originally Posted by cyclops

My biggest concern is getting caught offshore in a fast squall that causes the waves to hit at the bait wells and fill if the tops are at deck height. They can also provide the full area of their bottoms to a wave slamming up the bottoms . No course or speed will stop them from pounding the bottoms. Putting a 45 degree angled filler piece would stop a lot of the upward slamming action. Enough? I really can't say. Lots of sea conditions to think of with a loss of all power. Another is to mount the tanks with break away pins if things get scary. Let the tanks go and come home safe and with a complete transom.

So in other words, I AM thinking out of my ass for trying to do this.. This thought just came to mind because, I do currently have a small tank (~15 ga.) on one side of the boat for fishing with a fairly large cooler (about 4' in width) tied to the swim step adjacent to the bait tank. Recently, I have been filling the cooler with overflow water from the current bait tank and have been loading additional bait for chumming.. so the thought came to mind to just make something that would be a bit more presentable.

What if I decrease the size of the bait tank to ~15ga. ea. the center "livewell" is essentially a box to put my catch. I thought it would be nice to have some water running through it to keep'em fresh, but I know weight is definitely an issue.

After reading cyclops's post, RE: "..making a break away pin" I am even more scared/hesistant to do this.. It would be a nice feature for me to hve on my boat, but don't want to risk my life in doing so. I am very new to fabricating stuff for my boat. I am currently making a hardtop for my vessel and it is coming out pretty good. And since I have some fiberglass fabric and resin leftover, I thought I would bang out an additional project this winter.. WOuld a 8'x2'x3'(wxdxh) box with 15 gallons of water on each side be that dangerous to mount on the swimstep? Thank you for your insight and any expert opinion(s)/advise.

[wdnboatbuilder]

correct me if i am wrong but thats about 360 gallons of water. thats quite a bit.

[searaytuna]

Originally Posted by wdnboatbuilder

correct me if i am wrong but thats about 360 gallons of water. thats quite a bit.

no. the overall volume of the box is 8'x2'x3'(wxdxhwith 15 gallons of water on each side. SO it would be a total of 30ga. with about 15 ga. on each side. the center portion (fish hold) would not be filled with water.

[cyclops]

Back to my original concern of filling the tanks in a squall. 8 x 3 x 2 = 48 cubic feet x 64 pounds for each cubic foot of saltwater = 3,200 pounds on the platform and brackets attached to the transom. It will pull the stern down till volume and weight is satisfied. How low? Can not even start a guess. You have some serious engineering to do.

[searaytuna]

Originally Posted by cyclops

Back to my original concern of filling the tanks in a squall. 8 x 3 x 2 = 48 cubic feet x 64 pounds for each cubic foot of saltwater = 3,200 pounds on the platform and brackets attached to the transom. It will pull the stern down till volume and weight is satisfied. How low? Can not even start a guess. You have some serious engineering to do.

OK. Let me try this again.

I AM NOT PUTTING 48CUBIC FEET of water!!! 8x3x2 is just the overall dimension of the entire box. Each ends will hold ~20Gallons of water making a total of 40 ga. at the most. The center portion is just an empty box. Now is 40 ga. that's approximately 320lbs of water weight which is in concern.