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jonannie@f2s.com · 15-12-2019, 06:19

I have been looking at self building a catamaran and favour ply glass as a method,length 10 to 11 mts with 5 berths must be able to dry out and most important have at least standing headroom in saloon.I have recently looked at Bernard Kohler designs but no little about him he does however make claims of close winded boat and also good cruising speeds . Who has built one and even more important sailed one

Chotu · 15-12-2019, 06:31

Don't forget Richard Woods and Bob Oram and such. Have you settled on this designer for sure?

Boatguy30 · 15-12-2019, 06:52

5 berths in the hulls of a 10 or 11 m Cat is going to be hard. I have seen a woods flicka with a forward single berth, but then you loose the watertight bulkhead. The Woods designs are probably the most economical plans price wise and excellent sailing boats.

daletournier · 15-12-2019, 06:53

I have no issue with ply but remember resale value. Imho building in ply is just as much work as other building methods but the market always sees them as inferior to foam or Balsa.

Maybe cc44 will comment, as a experienced home builder and knowledgeable cat sailor he maybe able to guide you better than most.

alumcat · 15-12-2019, 09:12

Self build cats.
I built my own cat. a sailing aluminium cat, 48 ft long. I bought the plans from an Australian, Tim Mumby designs. You could try googling him. If you want to see his plans, I only live in Gloucester.

DerekKelsall · 15-12-2019, 10:21

Quote:

Originally Posted by jonannie@f2s.com

I have been looking at self building a catamaran and favour ply glass as a method,length 10 to 11 mts with 5 berths must be able to dry out and most important have at least standing headroom in saloon.I have recently looked at Bernard Kohler designs but no little about him he does however make claims of close winded boat and also good cruising speeds . Who has built one and even more important sailed one

Ply is not the simplest, it is not the quickest it is not the cheapest in the full cost and it lacks insulation. Neither is it the most durable or the best resale value. I suggest you look further before making such an important decision. How you build will determine your future for a year or two, probably which year you will launch. DIY can be extremely satisfying. Happy boating,
Derek.
,

daletournier · 15-12-2019, 11:05

The poster should listen to the last post, doesn't get much more "expert" than that.

BobFord · 15-12-2019, 12:11

Happy days building a cat ! I've built (2) , one in glass , (Crowther ), the first in ply ( Wharram ). The Wharram incurred a big problem - Jim specified un-sheathed ply but , in my ignorance , I chose to sheath the ply . Big mistake - the sheathing traps water against the ply and causes rot.
The Crowther was professionally built ,Airex foam hulls and I finished the build. An excellent boat that did many , many ,miles.
If challenged again , i'd use sheet aluminium 5083 grade,but the skills of welding will need to be mastered. Current boat is aluminium but professionally put together.Good building !!

44'cruisingcat · 15-12-2019, 12:17

Quote:

Originally Posted by jonannie@f2s.com

I have been looking at self building a catamaran and favour ply glass as a method,length 10 to 11 mts with 5 berths must be able to dry out and most important have at least standing headroom in saloon.I have recently looked at Bernard Kohler designs but no little about him he does however make claims of close winded boat and also good cruising speeds . Who has built one and even more important sailed one

Have a look at Peter Snell's designs.

Mike Waller is worth a look too:

http://www.wallerdesign.com.au/

Edit: Peter Snell may have retired. Can't find his website.

Fore and Aft · 15-12-2019, 13:22

The one thing about plywood and the reason I like it is that it is a nice material to work with. That is a big factor when building a boat.
As for resale value the most expensive plywood cat in Australia I have surveyed sold for $250,000. Just check this link out for plywood cat prices.
https://yachthub.com/list/search.htm...rency=&poa=yes
As for plywood yachts check out the RM website. They are good looking boats. Did I read another post Dale where you said you had been on one?
Fora Marine - RM Yachts
Cheers

Simi 60 · 15-12-2019, 14:19

Then you get these type of plywood cat for sale for $1million usd

Dudley Dix DH550 Catamaran for sale by owner

blubaju · 15-12-2019, 14:37

I built 2 cats, first stripplanking/ply in West system, far to heavy, second a set from Schionning design/Australia, this balsa core is fine, your size I would look into Fusioncats.com they are 12m or 40' come in prefinished, (including paint!!!) parts in a container. No risk on overweight, no problem w quality surface, assemble, fit out & sail away. And no, no ply

billgewater · 15-12-2019, 14:40

Some years ago I observed a building technique that may be of interest. The catamarans were Wharram designs but maybe the technique could be extended or modified for other designs. No complex molds required.
On a workshop floor, a smooth surface of Masonite - a hard thin very smooth material -was laid and checked for "flatness". A release agent was applied and then fiberglass and resin (probably polyester, but vinyl ester or even epoxy could be used considering the relative merits and costs of each). I assumed the builders knew what layup was required. the glass was hand laid and long broom handled resin rollers kept the resin /glass ratio under some control.. The sheets were then lifted off the masonite with "perfect" surface finishes. Four sheets were produced and these four sheets essentially made up the two hulls. (Wharram hulls are slab sided). The hull frames were straight edged wood and the sheets were attached using glass and resin. The curved keels were glassed in PVC pipes about 200 mm diameter, which also served as water tanks. The hulls were built upside down. After inversion, some extra glass was applied to the inside where required. Decks for the hulls were then constructed using the same flat sheet technique.
The company making these hulls did it as a side line from making large industrial/farming water tanks. The large flat sheets made up the tank cylinders. The reason they used this method was that they could put many flat pack sheets on a truck and then attach the bases on site at the farms.
Wharram hulls don't necessarily appeal to everyone but I am sure the technique could be modified for multi-chine hull forms. For a multi-chine hull form, bonding at the chine joints may be an issue, but I am sure any reasonably competent glass supplier would have solutions.
Food for thought. The glass hulls over wooden frames gets around the wood/sea water problem but still allows a wood finish interior where wood rot is far less likely.
What this technique does provide is a good water tight hull form along with a perfect surface finish - minimal sanding or fairing.
Probably heavier than some other materials, but definitely very much faster and cheaper. Most bridge deck structures are also flat (ish) so this technique may also be used there if needed.