Need Advise : Flat Bottom + V Seaworthy ?

We are thinking for a budget boat. Do you think this boat can be used on sea's with swells upto 3-4 feet @ 5-8 sec interval with winds of 8-12 Knots.

Boat is 18' Long & 5'5" wide

We are planning to use it as a dive boat and put up an 20Hp Yamaha 4 Stroke engine (already bought).

Sincere advise will be highly appreciated ...

 

Sure, I've been out in homemade skin on frame kayaks in "bigger seas".

But are you going to be overloading it, or loading it top heavy, or allowing everyone to gather on one side?

 

Agreed, that boat will do fine, though the boat's shape is less important than the skipper's abilities. 3' - 4' rollers aren't much to overcome, though it might be a wet ride, if powering very hard into them. The boat is fairly narrow for use as a dive platform, so she'll tend to roll around while parked over a spot in certain conditions, but hey, everything is a trade off of some sort. Most boats of that length will have 7' - 8' of beam, which makes for a more stable, static platform.

 

Sure, looks like Panga design type of boat, Google them for some incredible stories of seakeeping. The Pacific Islanders here use them for excfeptional voyages.

 

We have to put in
6 Scuba cylinders(20Kgx6=120Kg),
2 kit bags (80Kg)
4-5 persons Max (60Kgx4= 240)

Approx 500-600 Kg Payload .. I guess

 

The Panga is a great boat. you will be happy

20 hp is a bit small. you need a 40 to operate fully loaded

 

Well ... I under estimated this boat but still have doubts about it.
Thanks for Pin pointing the hull design

Do you think its worth buying for our purpose ... and would a 20Hp 4 stroke take it around 12 Knots with 600Kg pay load ...

 

I don't think this is a Panga and I think this boat is a wee bit small for you needs. Maybe you'd be better off finding one with either more length or more beam or both. I also think your weight estimate is low. You'll have a 410 kilo crew load alone and haven't considered running tackle, spares and other essential items all boats take along. A 5.48 m by 1.65 m boat is going to be darn crowded, with guests, tanks and gear on a calm day, let alone in a pitching sea.

 

Yes the deck might be cluttered with gear, but we are on tight budget here.
I think anything Bigger then this would render our 20Hp OBM useless.

If it can handle the sea conditions, we can use it. This New boat is costing us US $3000

 

I think its somewhat resembles the design features of this

http://www.starcoboats.co.nz/hull-design/

 

A lot of these things originated in Japan, for Third World/Pacific islands fishing and island hopping market. Too narrow gutted to be survivable in extreme conditions imo.

 

Particularly grossly under powered with a 20 HP outboard.

 

60 kg per person is a bit too low estimate, particularly if you plan to carry western tourist divers. 75 kg is a weight per person commonly used in design calculations, but that too is an optimistic value, imo. 85-90 kg per person would be more close to an everyday reality.

Sorry if I ask perhaps an obvious thing, but did you account for 7-10 kg of lead per each diver?

I also agree with previous posters that going into an open sea on such a heavily loaded boat powered by just a 20 HP motor is not advisable.

Cheers.

 

Agreed ... under-powered.... If we put in an 40-60 Hp diesel inboard .. do you think it will handle the sea

 

Too big a load for this boat.....

600 Kg will sink her 4-5", which is too large a freeboard reduction for the anticipated sea state. You need a bigger boat with higher sides. Also think about how you will get the water out once it comes in.....