SK14 extra floatation do or don’t

[Edd]

I’m thinking about adding flotation pods on the back of my sk14. Like those on aluminum boats

It’s completely foamed under the sole. But when I stand in the back to pull start or whatever I get a ton of water coming in.

Would it be worth it to try adding floatation pods. I’d add them on and follow the lines of the hull glass it and make it seamless. Maybe about a foot off the back of the transom. Fill them with flotation foam. Probably would end up with about a cubic foot of foam on each side. I was about to freshen up the paint and fix a few things anyway.

[Dougster]

My SK14 doesn't ship water when I'm in the back. Maybe because I have a bunch of weight on the bow (troll motor, 50AH AGM battery). Before you add those pods I'd try to do some math. The only flotation would come from the lower portion of the pods that submerge, say up to the water line. When running you would of course get some lift, but as I read your post it sounds like you are talking about when you move to the stern when at rest. So, the flotation would be only the volume of the pod that is submerged. Dunno the details of the calculation off the top of my head, but someone will. That would then be offset by the weight of the pods and added foam. May not gain much.

Dougster

[Edd]

My SK14 doesn't ship water when I'm in the back. Maybe because I have a bunch of weight on the bow (troll motor, 50AH AGM battery). Before you add those pods I'd try to do some math. The only flotation would come from the lower portion of the pods that submerge, say up to the water line. When running you would of course get some lift, but as I read your post it sounds like you are talking about when you move to the stern when at rest. So, the flotation would be only the volume of the pod that is submerged. Dunno the details of the calculation off the top of my head, but someone will. That would then be offset by the weight of the pods and added foam. May not gain much.

Dougster

Yeah at rest is the issue. I do have a heavy 9.8 2 stroke tohatsu plus lm my weight equals a lot of weight when I’m standing in the back. I’ll keep thinking about it.

[OrangeQuest]

The 2 pound foam will only add less than 60 pounds of floatation per cubic foot, if I remember right. And that is them completely submerged.

[Edd]

The 2 pound foam will only add less than 60 pounds of floatation per cubic foot, if I remember right. And that is them completely submerged.

60 per cubic foot should be right. If I'm thinking right, adding about 1.6 cubic ft of foam below the water line would offset the weight of the engine.

[Dougster]

Seems like that would require pretty big pods. Water line on mine is maybe 4", so for me a square foot pod would only be 1/3 of submerged volume, or 20 lbs (40 for both of them). Done quick in my head, maybe wrong. Fool around with a pen and pencil and see what you get with whatever size pods you'd make. I don't see the need for foam, it adds weight. The foam is there to prevent sinking if holed. A flooded pod wouldn't sink the boat so foam seems not needed to me. Also, have you tried putting some temporary weight in the nose to see what that does?

Dougster

[Edd]

Seems like that would require pretty big pods. Water line on mine is maybe 4", so for me a square foot pod would only be 1/3 of submerged volume, or 20 lbs (40 for both of them). Done quick in my head, maybe wrong. Fool around with a pen and pencil and see what you get with whatever size pods you'd make. I don't see the need for foam, it adds weight. The foam is there to prevent sinking if holed. A flooded pod wouldn't sink the boat so foam seems not needed to me. Also, have you tried putting some temporary weight in the nose to see what that does?

Dougster

I might mock it with cardboard. If it’s not too ugly I might try it with leftovers from my lm18 build

[Dougster]

Well, here's a crazy idea. Glue up a couple of pods with cheapo thin ply, open at the top. Then clamp 'em in place on the transom and float her. Climb in and see what they do. If they don't lift the stern enough get out and clamp 'em further down (below the waterline) till they seem to do the job. Then mark where they are and you'd know the immersed volume required.

Dougster

[Edd]

Well, here's a crazy idea. Glue up a couple of pods with cheapo thin ply, open at the top. Then clamp 'em in place on the transom and float her. Climb in and see what they do. If they don't lift the stern enough get out and clamp 'em further down (below the waterline) till they seem to do the job. Then mark where they are and you'd know the immersed volume required.

Dougster

That’s a great idea

[fallguy1000]

Get flotation out of the head as a concept.

Displacement is what you want to do. Well, have to do, that is.

For seawater, 63.9 pounds of seawater is one cubic foot.

Stealing from the other poster and using a 4" waterline, that is 1/3 of a foot. A 12"x12" pod 4" deep adds 64/3 pounds if displacement less its weight. Obviously, you'd make the pod say 8" deep, but that gains you nothi g other than it won't ever submerge. Two of these pods is 64•2/3 or about 40 pounds added displacement versus the weight of adding them. They would be best made no float foam and hollow boxes. Now, let's say you get creative and find a way to make them 16x16x4""", this is 0.444 cuft and about 56 pounds added displacement less the weight.

It would be far wiser to do some testing and put 56 pounds of weights in the bow of the boat to see what happens.