Irwin 25 Floatation

[seasailor55]

I have an Irwin 25 that sunk during Hurricane Laura. Displaces 5500 lbs. How much flotation will be needed to raise it off the bottom for towing to shallow water. I know it sounds obvious but I've had two mechanical engineers give different answers. One says 5500 lbs. The other says it will take less since the boat weighs less when it's submerged. Who's right?

 

[Heimfried]

As long as the boat is completely submerged, the needed buoyancy is less than the displacement. But will you be able to tow a fully submerged boat? It could be a bit difficult and risky. As soon as a part of the boat rises out of the surface of the water, the needed buoyancy will increase.

 

[bajansailor]

Here is some background info on the Irwin 25 for reference -
https://sailboatdata.com/sailboat/irwin-25

How deep down is the poor Irwin presently?
I am wondering if it is within snorkelling range, or if you will need scuba tanks?
Will you be using standard commercial salvage air bags that can be filled with air from eg scuba tanks?
Or maybe 40 gallon plastic drums that are sunk and then filled?

And how far will you have to tow her to reach shallow water?
Once you reach shallow water, will you be able to lift her out with a Travel Lift, or put her on a trailer?

Has the boat got any positive buoyancy already built in? The wood trim (and bulkheads?) will contribute some slight positive buoyancy, but it's effect is probably fairly negligible.
Does she have an inboard engine? I am thinking probably not, as the drawing shows an ice box where an engine might be.
And does she still have the rig attached?
If you can salvage the rig separately, that will reduce the submerged weight of the boat a bit.

 

[Blueknarr]

I wouldn't try to lift it with less than 10,000 available.

Bottom suction

Will probably surface at an extreme angle of heal. It will take extra air bags to level it up.

Need to raise it full of water high enough to start pumping.

 

[seasailor55]

I wouldn't try to lift it with less than 10,000 available.

Bottom suction

Will probably surface at an extreme angle of heal. It will take extra air bags to level it up.

Need to raise it full of water high enough to start pumping.

The boat is in a slip in 6 feet of water. The main hatch is exposed at low tide. I need to get it off the bottom to move it to the launch ramp approximately 100 feet away.

 

[bajansailor]

Thanks for this additional info.
Where did the water enter the hull - was she holed below the waterline?
If so, would it be feasible to put a temporary patch over the hole, and then try to pump her out on a very low tide (re the main hatch being exposed then)?
Re how she is in a slip, I presume that you can get her fairly upright with lines on each side?

 

[seasailor55]

Thanks for this additional info.
Where did the water enter the hull - was she holed below the waterline?
If so, would it be feasible to put a temporary patch over the hole, and then try to pump her out on a very low tide (re the main hatch being exposed then)?
Re how she is in a slip, I presume that you can get her fairly upright with lines on each side?

Not sure where the water entered The bow was floating and the stern was on the pier. When the pier gave way the boat went down with it. Listing slightly to port, mast standing. How much flotation would I need to get her off the bottom? 5500? 10000?

 

[bajansailor]

Re how much floatation is required - I don't know.
Can you possibly post a photo or two of the boat in her slip?
Perhaps one at high tide, and one at low tide?

I presume that she is on Lake Charles (?) - in which case I am guessing that water is rather muddy, and not conducive for snorkelling to have a look underwater?

 

[seasailor55]

Not sure where the water entered The bow was floating and the stern was on the pier. When the pier gave way the boat went down with it. Listing slightly to port, mast standing. How much flotation would I need to get her off the bottom? 5500? 10000?

Photos: before and after.

 

[Blueknarr]

The keel and prop are certainly stuck in the muck. This can amount to lots of resistance.

I would:

Strap as many plastic pickle barrels as I can. Too much bouyancy is not a problem.
Attache a long plastic pipe to a high pressure water pump.
Shove the flowing pipe down along the keel ect to break the muck's suction.
Use the tides to your advantage.

 

[seasailor55]

Re how much floatation is required - I don't know.
Can you possibly post a photo or two of the boat in her slip?
Perhaps one at high tide, and one at low tide?

I presume that she is on Lake Charles (?) - in which case I am guessing that water is rather muddy, and not conducive for snorkelling to have a look underwater?

Visibility 1 to2 feet. I have a nephew that’s a diver but he’s working in Texas right now. Harbormaster wants the boat removed by this weekend.

 

[bajansailor]

Can you take a photo showing how much of the boat is above water at low tide please?

Here is the tide chart for Lake Charles - it looks like your lowest tides will be Monday and Tuesday next week, although they are still not much lower than today (the low tide is forecast to be 0.17 m. (approx 7") lower - but every little inch will help you.
Tide Times and Tide Chart for Lake Charles https://www.tide-forecast.com/locations/Lake-Charles-Calcasieu-River-Louisiana/tides/latest

As per BlueKnarr's suggestion re plastic barrels, can you easily get hold of some?
If yes, then you could lash pairs of barrels (one on each side) together via ropes or straps going under the hull.
Do this at low tide, and then you will have a few inches of 'buoyancy' available at high tide - that might help to 'unstick' her if the keel is stuck in the mud.
You might then be able to tow her to a slipway perhaps - if so, could you then put her on a trailer, and very slowly pull her out, allowing time for the water to drain through through the hole(s) in the hull that caused her to sink in the first place?

Do you have a local scuba diving club nearby? If so, it would be worthwhile contacting them to see if they might help in exchange for a cooler of beers and petrol money?
If you partially fill the plastic barrels with water before lashing them in pairs with straps under the hull, then the divers could use compressed air in the diving tanks to blow the water out of the barrels, thus enabling you to lift her a little bit higher.
A gallon of water weighs about 8 lbs; a 40 gallon barrel would thus have approx 300 lbs of buoyancy. If you can manage to fit four barrels on each side, and almost fill each barrel with water prior to lashing them in place (such that the barrel is almost neutrally buoyant), and then blowing the water out of them, that will provide you with approx 2,400 lbs of buoyancy.
And if you can find some divers to help, they shouldn't be too fazed about going into the water to disconnect the turnbuckles on the rigging wires so that you can remove the mast first - the more weight that you can take off initially, the better.

 

[Blueknarr]

Forgot

Is she still tied to the sunken dock?
Other debris could prevent her refloat

 

[seasailor55]

Forgot

Is she still tied to the sunken dock?
Other debris could prevent her refloat

Tied to 2 pilings. Stern lines only. These will need to be cut. She is resting on top of the collapsed dock, so the the stern at least is not in the mud.

 

[Blueknarr]

Tied to 2 pilings. Stern lines only. These will need to be cut. She is resting on top of the collapsed dock, so the the stern at least is not in the mud.

On top of is better than under. But could still be tied too. Or a line under.