small catamaran plans needful

[pulsar]

Hi,

I'm trying to design small catamran( not more than 5 meters). I'm not educated and have not experience in designing multihulls. From materials which I have found on net for this moment, I can't draw shape of hulls. I don't mention about calculations of hulls, because it's abstraction for me. I would like to built such boat by myself, I would be very satisfacted.
Is anyone could help me to get such plans of catamaran?

Peter

[frosh]

Hi Peter, have a look at the K design 435. It is a little smaller than you asked about but it is ideal for a first boat project and looks easy and cheap to build. Looking at it peformance should be fairly good also.
http://www.ikarus342000.com/SC435page.htm

[pulsar]

Thanks a lot Frosh. You are right that it's ideal project for first boat.

Best regards

Peter

[bhabanism]

I have a 10 m foil borne catamaran and I have it's linespan & offset table.
Will you like to go for this 10 m boat?

[pulsar]

Originally Posted by bhabanism

I have a 10 m foil borne catamaran and I have it's linespan & offset table.
Will you like to go for this 10 m boat?

Hi,

Yes, of course. It could help me also. For this moment I have only some russian plans, which are not complete and have some mistakes.
Have you got maybe any pictures of that boats? Can you send your plans by email?
I tried to send you a private message but I'm to "young" on that forum....

BR

Peter

[Seafarer24]

check out www.sailingcatamarans.com. They have the Pixie, Quattro 14 and Quattro 16 which you may be interested in.

[Troutcatcher]

Check out the Trident 15 plans at
www.johnsboatstuff.com .........it can be powered by either sail or an outboard. The buildiing method is stitch and glue.

At www.boatplans.dk they sell plans for a 15 ft rowcatamaran also build in stitch and glue.

Best regards,

Troutcatcher

[cleblanc]

You could also consider an alternate plan from K-design:

http://www.ikarus342000.com/DUO425page.htm

Basically it is the same boat as the SC 435 but it is equipped with two windsurfing rigs.

If you can get access to cheap windsurfing rigs, this will allow you to make huge savings on the total price of the boat.

Even two brand new entry level windsurfing rigs could be cheaper than a mast and sail and all of the associated hardware.

Also I am willing to share a method to fit two regular windsurfing rig on this boat without custom masts.

[Chris Ostlind]

Charles,

Have you actually had success with windsurfing rigs on cats in this manner before? If you have, could you post a couple of photos to illustrate that potential?

I ask because these rigs are highly tuned foils for specific wind ranges with very little ability to add roundness to the sail surface in other wind conditions. Instead, a windsurfer simlpy gets another rig of larger sail area out of his quiver that suits the wind strength. This is not an option on a sailboat where, as you know, the sail has to be adjustable for camber, downhaul and leech tension.

I do see the simple advantages of having twin, freestanding rigs on a cat, so the interest is more in how the windsurfer rig scenario has been solved.

Chris

[cleblanc]

Hi Chris

I an a beach catamaran sailor and I have owned 3 different boat so far. I also used to windsurf extensively and I still have alot of my windsurfing gear.

And NO, I never tried to installed windsurfing sail on a beach catamaran...

However, I tried to install one on a trimaran built out of one canoe and two windsurfing board but this was never intended to be a serious boat. And you are absolutely right, a windsurfing rig cannot be stayed like a conventional mast.

The information that I think should be incorporated in the Duo 425 is to used the Iceflyer rig setup:


Picture of two Iceflyers

Iceflyer site
Another Iceflyer site (in french)


The way I see it: Install a post buried in the hull and install a clip at the top of the post for the wishbone. You put a standard windsurfing mast track aft of the post.

You setup your windsurfing rig normally and simply install the mast base into the track. Because you still have the universal, the sail will lie down in the water or on the trampoline. Once you are ready to go sailing, simply raise the windsurfing rig in upward position and attach the wishbone to the post and attach the main sheet at the back.

With this setup, the mast is free to flex normally and doesn't have to support the downward compression generated by the stays.

In the case of the Iceflyer, it is important to have an extra stiff mast because the iceboat can reach speeds in the range of 60mph or 100 km/h but with a normal catamaran, the regular mast should be OK.

There is a efficiency problem with this configuration, the windsurfing sails are designed to be raked back and this setup will require to have the sails raked forward. The original K-Design plans also call for a vertical mast position.

This could be improved by replacing the post with a three leg stand that would allow the mast base to be moved forward compared to the position of the wishbone and would allow the sails to be installed in a raked position and increase their efficiency.

An alternate solution would be to have two "A-frame", on each side of the mast. If you are really interested a could draw a few sketches and send them.

On a more personal note, I have been watching the K-Design boat for a few years now and I became very interested with a few designs. I am thinking about building the P95 catamaran (I have already purchased the plans set) and I am also looking at the Manta catamaran.

[frosh]

Hi Charles, I also have experience in windsurfing and sailing, and being a tinkerer, have read and thought about your posting with much interest.
I just can't see how the single rig on the Iceflyer can be readily adapted to a catamaran hull and twinned. The rigs would be difficult but not impossible to stay. Unstayed masts generally are too soft to stand up to the RM generated by a catamaran configuration.
Windsurfing masts and sails are designed for high speed and low power in relation to the sail area. Ideal for a sailboard or an ice yacht, but where they have been put on regular sailcraft they have been invariably disappointing.
There is also the real risk that without excellent engineering the posts, if not stayed will eventually be ripped out on a catamaran.
All in all I think it is much more efficient, cheaper, less work, and less likely to break by staying with a conventional arrangement.

[Chris Ostlind]

I've had pretty good results using unstayed windsurfer masts on trimaran rigged canoes and sea kayaks. Typically, they aren't anywhere near as heavy as a beach cat and I dumped the windsurfer sail in favor of a 5 meter hoisted sail after glueing-on a mast track. I also buy them longer than does a windsurfer for bury in the hull and sometimes I add the 2 foot extension at the mast base.

These boats can scoot reasonably well and when one considers that they are usually paddled at 3-4 knots, any sailing speed around 7-9 feels like gang busters. The hulls usually fizzle-out after that as they are normally very low Cp values and just have a hurtin' time trying to carry much speed.

I tried windsurfer sails and dropped them as an experiment when they wouldn't generate any boat speed, were bitch to rig compared with a conventional, hoisted sail and they are fragile for rough handling.

[cleblanc]

Sorry about the picture not showing up, I have copied them on my personal space.

Here is another try


Here is the picture of the two Icefliers

Hi Charles, I also have experience in windsurfing and sailing, and being a tinkerer, have read and thought about your posting with much interest.
I just can't see how the single rig on the Iceflyer can be readily adapted to a catamaran hull and twinned. The rigs would be difficult but not impossible to stay. Unstayed masts generally are too soft to stand up to the RM generated by a catamaran configuration.
(...)
There is also the real risk that without excellent engineering the posts, if not stayed will eventually be ripped out on a catamaran.
All in all I think it is much more efficient, cheaper, less work, and less likely to break by staying with a conventional arrangement.

Hi frosh,

Fist of all, the Duo 425 is a design of K-Design, several have been built and they all seem to work with unstayed mast with windsurfing sails

I lost count how many DUO 425 are sailing worldwide, but it has to be more as 1000

K-Design Duo 425 page

There are several boat with unstayed mast that had a real commercial success:

For example, you could look at the Laser I and even the Sunfish. I am pretty sure that these are the two best selling sailboats of all times and both relies on Unstayed mast. This means that it is possible to engineer an unstayed mast... or post that will be strong enough not to "be ripped out on a catamaran"
Also the bury depth is much greater on the hull of the Duo 425 than on the Laser boat.

However, I agree with you that unstayed mast are not the best solution when used with windsurfing sails.

My suggestion is simply to keep a genuine windsurfing mast and install a post to support it like on the Iceflyer.




The post could be a stainless steel or aluminium tube and you would put an ABS pipe in the hull. At the top of the post, there would be the mast clamp

[frosh]

Charles, nice pics, however the Duo 425 cat shown looks like it fills a niche, but is it a better solution than say a cat like a Hobie 14? (discontinued I think now) I suppose it comes down to individual preference. Personally I would take the Hobie for the following reasons. One sail is easier for singlehanding.
Can mount trapeze on single mast. Hobie rig is more robust. Two windsurfing rigs would not be cheaper if bought new.
Regarding the post that is supporting the front of the wishbone. I would make it 50mm diameter carbon tube and angle it backwards about 20 degrees.

[EZcat]

Hi,

I'm going to promote sailing in a place far beyond water sport especially sailing, and planned to start with small, easy build, and material cheap/easy available catamarans so, K-design's windsurfing rig cat sounds suitable however, I can never access their web site. Can anybody help? Similar plans are welcome, too.

Thanks and regards