New power cat - help please!

This is a cool project keep on posting !

 

I'm not trying to put you off from your project. I want you to realize that you could be running into problems. There are things that will work, and there are things that can be potentially hazardous. The reasons is the same why one cannot take certain suspension arms on a car, cut them and weld them together again, no matter how sporty or nice the outcome would be. In this case it would be best to weld the arms to what it should be, then have it made out of a one piece of the right material so the required strenth is achieved.

Wrt your project - I would suggest that you assemble your hulls with the tunnel in it. Once you're happy it is as you want it, finish it and use it as a mould. This way the whole hull would be one integrated piece of glass and would be of required strength.

You can easily do a test. Make two layups with glass. In the one you make a layup, let it dry out then add another layer halfway off it. The second layup you do the same, but do both at the same time so they go wet on wet.
Afterwards you would be able to pull the first layer off the second (delaminating it), while the second that went wet on wet you would tear the glass with great force, but it would not delaminate.

If you plan on doing a good and proper job then there are some things you will have to take into consideration. The glass types and orientation of the glass is also an important consideration, and also the amount of layers. It will determine if the hull is going to be stiff and rigid as it should be.

This is what makes building a boat alone so difficult. Boat builders either have a team of people that do the layups from start to finish, or they use vacuum infusion where one or two people do the final infusion. If you plan on doing this alone then I suggest you look at infusion. You can place all the layers and do the prep at your own time, then when you're ready you can infuse the whole hull in a shorter while. It would also be stronger and lighter than hand layups.

 

Do you think it would be of any benefit to either make an angle on the tunnel sides or step in the tunnel sides, will this stop water creeping up the tunnel?
Will a vertical side to the tunnel work just as well? (much easier to construct)

 

A few steps in the tunnel side have a buffering effect in you plow through a wave, while at the same time at speed it provide lift like a foil. You can check it in the article I posted a link for previous. It will also add to stifness in the hull.

 

this is an idea i have considered often i reckon it would be very doable, i would however make sure that i had good stringers installed and possibly put ring frames into the hull before i split it
sean

 

Northercat, I made numerous templates & took plenty of measurements before I cut the boat in half however the two halves are surprisingly rigid!
The original Phantom power boat was often fitted with 225hp motors but the hull is amazingly thin, I guess the boat was built on the limit of strength v weight.
The few stringers fitted have a sort of compressed cardboard form rather than the usual plastic pipe or hose pipe often used 20 years ago. The hull shows no signs of fatigue or osmosis even though is was kept in the water.
I am quite familiar with fiberglass as I have worked with the product for 30+ years, in fact I completed a 5 year boat building apprenticeship 29 years ago!
I haven't been a professional boatbuilder for the last twenty years so I am definitely not up to speed with the latest methods however I still work with composites & resins to this day.
Guernsey, my home is only 9 x 3 miles so the sea & boats play a huge part of all the residents lives, I have been boating, diving, surfing & building all the related equipment all my life.
I, like yourself, have often wondered about completing such a project as this one - so here we go! I am going to do it!!

 

Next issue for me is how to construct the tunnel, seems like two main options - make a frame & cover it with plastic coated board or formica to be used as a mould & then removed.
Make a ply tunnel & glass it in place & then encapsulate the ply from underneath with epoxy & fiberglass woving?

 

make some frames glue the 2 halves of the hull onto them and then glass and build the tunnel onto the frames
sean

 

Do think about adding some permanent floatation, something like a foam. It makes construction easy and the double skin adds to stiffness. Just don't use PU foam, it's a heat insulator and absorbs water.

Closed cell foam and use the right type. I like PE foam but there are others that is aparently also good. And they are all expensive. It is a nice thought though that if worst comes to worst the boat cannot sink.

I would never - after a nasty storm I was in - build any boat without permanent floatation ever again.

 

I have taken some templates from the back of the boat & made a full size template for the cats transom......what do you think?

 

Nice you can screw this against the transom.
Maybe you schould make some steps in the tunnel like you said.
Damn guernsey is so far, or i would come over to help.
Cool project keep the pics coming.

 

Ha Ha you would be welcome but wait for the summer first.
Yes I will make a step & radius the top corners.
I am still revising the final dimensions - I need to find where the water line was - the hull was recently spray painted so I cant work out the water level!
I might have to raise the tunnel height a bit as my finished cat will be quite a bit heaver than the original mono hull & I want 150mm clearance down the tunnel. (I think?)

 

Found this picture . might offer you an idea. That's all.
http://www.boatdesign.net/gallery/showphoto.php/photo/8916

 

Does anybody know where i can get UIM rules for racing cat hulls?

 

you can get the UIM 2008 Complete Rules manual here.