22-24 feet power catamaran

[garrybull]

hi everyone. im new on here. im from england. i used to work for a company over here called catapult catamarans who make 40ft x16ft fast offshore fishing boats.

look on the website www.catapultcatamarans.co.uk

i no longer work there and i am going to design and build a 22-23ft x 8ft 9in .
i will be building a plywood plug and then moulding it so i have got a mould to make and sell the boats on as well.

what im after is pictures or drawings of similar sized boats were i can get ideas from for my boat. i want to design it so it can be used with either outboards or inboards. needs to be a fast planning design.

the reason for the beam being 8ft 9in is it can then still be towed on the road if needed.

im only after hull designs at the moment as i know what wheelhouse/cabin i want to build.

any info on design would be much appreciated. also doe's anyone know of a free download program where i can draw my designs.

hope i have posted this in the right section.

thanks everyone

[Mr Efficiency]

The requirement to run with either outboard or sterndrive ( presumably twin sterndrives ? ) might be a bit difficult with your dimensions, as there won't be much room in your sponsons to accomodate the general run of sterndrives. Plywood plug means you are working with developable shapes, which is not really limiting for this type of vessel. My preference would be sponsons with plenty of vee, as much as 45 degrees, but with a triangular flat pad starting at the forefoot and widening all the way to be around 9" wide at the transom. 25" outboard legs would be essential. I'd say no more than 24" wide (at chines ) for your (symmetrical) sponsons, a well raked bow and a drawn out forefoot. Lovely ! There really is nothing like them, shame about the occasional tunnel slap to jolt you back to reality.........

[garrybull]

thanks for the info. i was hoping to keep the hulls and tunnel roughly all the same size. im roughly going to make the boat 105" wide which gives me 35" hull , 35" tunnel 35" hull. will this work? overall height of the boat at the bow will be 5'6"-6' high so plenty of clearance to the water and the stern will be roughly 4'10". again plenty of clearance from the water in the tunnel. the tunnel it self will not be like your traditional style. it will be like a reversed s style tunnel to give more clearance from the water.

i know the sizes i've given for the boat may not be well proportioned but im not to worried about that.

im hoping to start building the plug early in the new year.

[Mr Efficiency]

Google "Sharkcat 23" (23 foot length, beam 8' 2.5" ) and you should see plenty of pix of a proven vessel that should give an idea of the sort of proportions that have been successful over time. You can see a video here with them in action as rescue boats.......

http://www.youtube.com/watch?v=0CtedRYVF9U

[michael pierzga]

Safe haven marine build smaller working cats..Might be some good pictures to help your design process.


http://www.safehavenmarine.com/BEST%...T%20PHOTOS.htm

http://www.safehavenmarine.com/TEES%20NAVIGATOR.htm

[garrybull]

cheers for the links guys. i do like the sharkcat with the wheelhouse towards the end of that video. given me some good ideas and i think what i have pictured in my mind will work ok.
if i have to run outboards i will be fitting pods to the back of the boat so that they don't take up space inside the boat.

[garrybull]

this is the sort of hull i want to build. only 1 or 2ft longer and 6" wider
if the link don't work its carat 21 built in poland

http://www.boatdesign.net/gallery/sh...php/photo/2633

[MooringProJeffL]

The catamaran you want to build is supposed to be fast so you should look at these boats and yachts from M2.
http://www.m2motoryachts.com/index.html
I took a test ride in the M2-21 and it was smooth is rough water. The items that are not exposed are fore and aft hydrofoils that raise the boat above the waves. This small cat can reach 72-mph with a single 225 outboard. I would like one like the M2-21 but, bigger in the 24-26-ft range.
8' 6" is the maximum width for trailering a boat in the USA without a permit.

[garrybull]

very intersting that m2-21. i have got a friend who will doing some 3d drawings on his computer for me later this week to see how my idea will work out. if i get some pics i will upload them on here for you all to look at ok

[Mr Efficiency]

Asymmetical tunnel hulls don't have a reputation for predictable handling in this part of the world. It is something of a " how bad does she run off course in stern quartering seas ?" thing.

[Stumble]

The Twin-Vee 24 and 26 may meet your requirements, though the company went out of business a few years ago. I think their molds wound up being bought by Glacier Bay, but I am not sure.

[garrybull]

mr efficiency that type of hull design is fine over here in england. quite a lot of catamarans used for fishing over here are like that. i helped design and build the plug and moulds for the catapult catamaran which is 40ft x 16 and am getting some of my ideas from when we did that.

[Mr Efficiency]

Originally Posted by garrybull

mr efficiency that type of hull design is fine over here in england. quite a lot of catamarans used for fishing over here are like that. i helped design and build the plug and moulds for the catapult catamaran which is 40ft x 16 and am getting some of my ideas from when we did that.

Well, your intended vessel is much smaller than 40x16, you might find that makes a significant difference, there exists the risk that a tunnel hull with the flat slab sided tunnel will experience steering forces in certain sea conditions, particularly where you have deep deadrise forward.

[garrybull]

there are few companies over here that build cats as small as 5.5mtrs. there is a company called cheetah marine who build cats from 6.2 mtrs with a 2.4mtr beam which is smaller than what im looking to build. there cats use identical hulls and there tunnel seems quite low. they have sold over 250 boats so the ymust work ok.
my tunnel will be a reversed s type tunnel to give me more clearance from the water. if you look at the tunnel on the catapult catamaran it will be similar in design to that with a smaller wave breaker built in.

[Mr Efficiency]

Symmetrical sponsons as in the Carat 21. is the safe way to go, IMO. Those Cheetah cats look like they too have symmetrical sponsons . It was flat-sided box tunnels I was worried about......you know the type of thing, like a mono cut in half along the length, the two pieces then separated by a narrowish tunnel. You seem to be on the right track.