Cat Design - Cold moulded Wood

[fhrussell]

Does anyone know of a KIRI supplier in the US?

I remember ready other posts about kiri and, if I remember correctly, some very positive things were said. Dave, do you remember those posts?

[fhrussell]

By the way, there is a discussion taking place right now on:

The Multihulls February 2007 Archive by date

(scroll to bottom)

It is a comparison of foam vs. cedar strip.

[cat man do]

Originally Posted by fhrussell

Does anyone know of a KIRI supplier in the US?

I remember ready other posts about kiri and, if I remember correctly, some very positive things were said. Dave, do you remember those posts?

I know that I did a few re: KIRI

It comes into OZ via China, as they have old growth forest's there .

Paulownia [KIRI] is a dimensionally stable, light, strong, clear, durable, odourless hardwood with an air dry density of approximately 300 kg per m3.

Compared to about 340 kg per m3 for Western Red Cedar

Dave

[cat man do]

Have a look on this site, it appears that there may be some places in the US that may have some info on KIRI.

Paulownia.org Directory

Dave

[fhrussell]

Thanks Dave! That's great and I'll look into it.

Getting back to Steve's original post.... There is a 52' CSK plywood/cold molded (double diagonal) available in Florida. Also, in Brooklyn, NY is a 60' Gil's Cat (designed by Vince Bartolone of CSK) also for sale ...Both yachts need some work, but at the prices they are asking, they have great world cruising potential and both are plywood boats. You can find them oon Yachtworld.

Steve, if you are set on building new...you should certainly consider strip built or foam. Both are easy methods and you can create any shape desired.

That said, I agree with Gary Dierking's opinion that a plywood boat is still the lightest all around method for building. Having built a number of boats in all building methods (except steel and aluminum), I am still amazed at how light you can build with plywood (or cold molded) versus foam and strip. The amount of glass you have to lay up to give the foam any strength kind of negates its raw weight advantages. The other consideration is the rot resistance foam will have over plywood. So many plus and minus factors for each method...

Does anyone have any examples of two boats of the same design built of the dissimilar materials in discussion?

[cat man do]

Originally Posted by fhrussell

By the way, there is a discussion taking place right now on:

The Multihulls February 2007 Archive by date

(scroll to bottom)

It is a comparison of foam vs. cedar strip.

I have argued long and hard that foam is about the same weight as strip plank timber, especially if the foam layup is gelcoated compared to the stripper's paint.

The only way to go lighter is to start using Kevlar on the foam, and then it work's a treat, but the cost blowout is horrendous.

Dave

[fhrussell]

Copied from the Multihulls List from John Shuttleworth:

I have just done the calculation on the Shuttle 40 "Zazen"

If you make everything in foam sandwich except the hull and decks over
the
hulls the added weight is 500 Kgs even with the glass reduction.

Just doing the hulls below the sheer line in Cedar strip planking adds
340 Kgs.

regards

John

[Steven Prince]

I like the idea of the speed of construction that plywood construction allows, but i like the idea of strip planking from the point that if you use a clear gelcoat and clean the wood up nicely before applying then you have a nice wall to look at for the inside.

I need to speak to my other half and see how she wants to do the interior before I decide on a final construction technique. Either way the radius part will need to be strip planked I would have thought.

The exterior of the boat is to be painted black with tek dek to be used on certain area's of the deck space. Can anyone tell me whether there are any effects the heat (from solar radiation) will have on the gelcoat system over the wood.

Regards
Steven

[GordMay]

Despite Practical Sailor’s generally favourable comments, I am somewhat leery of synthetic look-alikes. Of particular concern would be heat build-up, and PVC’s high coefficient of expansion.
Practical Sailor “Synthetic Teak Test”: http://www.tek-dek-benelux.nl/ps_june04.pdf

[Steven Prince]

I'm more concerned with the heat build up on the actual hull than the Tek dek. I'm concerned about the epoxy coating on the wood expanding more than the wood will and cracks forming.

Any issues with the wood/epoxy and heat build up found by others would be appreciated.

I would also be intersted in ppl's opinions on my plan to fit the boat with a Gaff Rig.

[fhrussell]

Originally Posted by Steven Prince

I would also be intersted in ppl's opinions on my plan to fit the boat with a Gaff Rig.

Steven,
Take a look at the 'sliding gunter rig'. I've been contemplating using this rig to create smaller spars so that I can raise and lower my rig without the yard costs. The gaff acts as more of an extension of the mast than a true gaff rig. In 'Wooden Boat' (J/A '96) there is an article on the Sonder boats. 'Bibelot II' has a Gunter Rig designed by N. Herreshoff and is FULLY BATTENED! I think this is the best gunter rig for a multihull. The only issue with gaff rigs and gunters is the top roll-off of the main....not good for going to windward.
There is a cool little racing dinghy that Russ Brown is involved with out of Port Townsend, I think it's called the P-52 that also uses the gunter rig, but they have designed a way to prevent the top roll off. They have incorporated the use of a channel that the spar slides on at the top of the mast. It is a carbon rig, if memory serves well.
Finally, take a look at the Wharram rigs. He's been designing cats with very simple sleeved mains with gaffs, and boomless!

[mikereed100]

Steven,

I would be carefull about painting your boat with a dark color. The heat buildup in direct sunlight can be surprising. I have a dark blue stripe under my rubrail that gets very hot to the touch on the inside of the hull. If your entire hull is black you might feel like you are living in a toaster oven. In a composite hull you will encounter problems with different coefficients of expansion which I imagine could very well cause the problems you state. Also, even dry wood has moisture content which will cause it to expand and contract with temperature changes. I believe this is what led L. Francis Herreshoff to reply when asked what colors are suitable for a boat; "There are only 2 colors to paint a boat, white or black, and only a damn fool would paint his boat black". (His words not mine!)

Best of luck with your project,
Mike