New power cat - help please!

[foxfish]

Hi, I would like to build a small cat, about 5mts would be ideal for my use.
This will not be my first attempt New boat problems but I would like to get it right this time!!
So I am looking for advice, building methods, plans or any tips ect. I will power the boat with two Honda 50hp motors but will be happy cruising at 20kns. I did train as a boat builder but that was 30 years ago - still I am happy to work with either glass or wood to a reasonable level.
Mart.

[Fanie]

Hi Mart, befor jumping in the deep and and start waving the brush around, do some research on hull shapes, types and collect as many pictures as you can. All these would give you a good idea of what is out there and which is considered the best. One also pick up lots of tricks and get some good ideas.

I would also look at displacement hulls as to planing hulls...

[northerncat]

go for a displaning type hull that way you get speed and economy/low power
something like this but scaled down to 5m probably wouldnt need more than 2 20hp's
http://www.lizardyachts.com.au/designs/lizard_7-2.html

sean

[northerncat]

i should mention it cruises at 18 knots goes flat out at 23knots and burns 10l an hour at 18knots
sean

[foxfish]

Interesting! So a displacement catamaran can still get good speed?
I will be doing plenty revision before I start the build but does anyone know of any plans that I can study?

[Guest625101138]

There are some nice big cats around and the lizard cats look nice. I guess you need to get hold of plans for glass construction. Many of the designers are looking at efficient displacement hulls now. So a matter of having a good look around.

I think a boat that will punch through heavy chop at 18 knots is very capable. Probably average similar speed to faster boats that have to slow down once they get into heavy going. The thing about these cats is that they sit well at these speeds. They do not need to be doing 30 knots to level out.

Rick W.

[Fanie]

If I ever make myself another power boat, it will have a displacement hull, be longer (loa) and wider (boa), similar to sailing catamarans and trailerable.

Our last trip at Jozini we had to go out of the water due to the wind pushing up waves every day. We were there on my friend's bass boat, but even the small skiboats abandonned... similar to that one in Sean's picture.

Size does count - Godzilla.

[foxfish]

What I am interested in is the underwater shape, the transom shape & the distance between the hulls etc.
I have a 17' dory (Nab 17') in my shed & I am thinking of doing a similar conversion on this boat as I carried out on the aluminium dingy. I think I can build two hull underneath the dory using the same methods but I dont intend to start until I have more info on hull shape.
There are some pics of my conversion method on page three - New boat problems

[northerncat]

my next project will probably be one of these lizards
sean

[foxfish]

OK I am convinced I need a displacement design, I now need search for inspiration - I found this http://powercatamaran.typepad.com/ho...ustom_designs/

[Fanie]

You have to make up your own mind as to what will work best for you, our say-so is just to get you to look around a bit.

[foxfish]

Ok, well I guess that is one of the problems of an open, international forum!
What I meant was - thanks for the heads up on displacement hull catamarans, I think they would suit my needs very well.
What I now need is some basic info on how to design & build such a boat.
I would appreciate any basic info on how to start the build process?

[Fanie]

Do a google for catamaran build projects... many articles and pictures.

[foxfish]

Hmm I have been googleing for hours! Not many small power cats that I can find? However is would appear to me that a displacement cat requires quite a gap between the water line & the under deck?

[Fanie]

Only for hours ? You just skimming the surface. Every now and again you discover something new that will bugger up your preconceived ideas ... and get the creative juices flowing anew.