Flotation

[jay_merrill]

I now have about 90% of the floor out of my new project boat, and am pleasantly suprised at the condition the stringers are in. I will have to rebuild the drain well, and sister in stringer sections where they seem to be missing (short portion, aft end), but the vast majority of the stringers seem to be OK.

There is no foam in the bottom of the boat and I would prefer not to put any in, so that I can build watertight storage boxes in the voids. That being the case, I will have no flotation unless I figure out how to get enough of it under the rails and along the sides of the boat.

So here's the question - how do I figure out what type of material to use, and how much of it I will need to keep a boat that will weight about 3,000 lbs loaded (engines, fuel, batteries, bodies, etc.) afloat? The boat now has saddle tanks and an average amount of area under the rails, so I'm not sure whether or not this is a realistic plan. If need be, however, I could get quite a bit of the stuff along the interior sides of the cuddy, as well as the underside of the deck in the cuddy.

Anyone have any advice on this?

 

[oops!]

Re: Flotation

uh......i would never say in open forum to forget the water sucking stuff....


so.....hows the weather jay?

 

[Ike-110722]

Re: Flotation

Before I can tell you that I would need to know, length of the boat, O/B or I/B, what's the maximum weight capacity and persons capacity. If O/b how big an engine, if I/B what does the engine weigh. and so on.

Look at this page on flotation and how to calculate how much you need. http://newboatbuilders.com/pages/flot.html You don't need to use foam. Air chambers will do, bladders, balsa, I've even seen ping pong balls and coke cans.

 

[jay_merrill]

Re: Flotation

It's a 19 foot Thunderbird Cheyenne trihull. Basic hull weight will right at 1,500 lbs, once I install the v-berth and cuddy enclosure. I will power it with a pair of 1972 Johnson 65hp outboards. Standard fuel is 36 gallons. I may add two more saddle tanks (12 gal ea) to boost total capacity to 60 gallons. That said, the only time I will most likely use them is when doing SAR missions, which occurs about 6 times per year. During those times, I am likely to only have one other person in the boat.

Following are photos taken on the day I brought it home, and after removing a good bit of the floor.

 

[jay_merrill]

Re: Flotation

Peter, thanks for that link. I am studying the formulas now and will do the math once I understand them.

I may have to guestimate the load capacity because there is no data plate on the boat and I can't find that info on the net. The 1,500 pound hull weight is based on an original brochure that I found on AOMCI. The basic version (outboard) weighed 1,430 lbs from the factory and the deluxe weighed 1,510 with cuddy bulkhead, porta-potty, etc. It is rated for up to 200 hp, although they described that as a twin installation, due to lack of 200 hp singles at the time.