plywood

why can i not use exterior ply to build a boat as its as waterproof as marine as i sat two bits of ply in a bucket for 6 months one of each and both were ok .the boat im thinking of building is coated in fibre glass anyway so why can i not use exterior ply ???????????help anyone know why not ...................................................................................................

 

Go ahead, it works. However, it won't bend in as fair a curve. Also, because of the voids, it is more likely to rot. I have built many skiffs that lasted over five years. They were stored outside in the weather too.

 

was thinking of building a 26 foot thunderbird or 32foot thunderbird was wanting more than 5 years from it uuuuuuummmm.

 

For a boat that size the cost of plywood is a small percentage of the total. A better quality is a good investment.

 

Voids in exterior grade plywood will speed rot and worse- delamination. The investment you will make(time and money) in a boat of the size you intend to build will be wasted after 3-5 years. Initially, during the build process, you will have difficulty achieving a fair curve with ex grade ply also. I have used ex grade for small, "throwaway" boats. I can afford to keep them afloat for 5 years by annually sanding and recoating with epoxy and paint, inside and out. I wouldn't want to do the same with a boat of 26' or 32'.

 

A 32' Thunderbird? Does such a beast exist?

If you are planning on scaling up a Thunderbox to 32', why not go straight to a 32 footer designed as such. Two I can think of are the Gulf 32 by John Spencer (Kiwi designer, famous for the Cherub dinghy and Transpac-winning maxi Ragtime) and the Nelson 32, by Peter? Nelson in NZ.

Both are very much in the big T-Bird style, BUT they are designed to that length and they are proportionately faster, especially the Nelson. The T-bird is a great boat, but in a chop and light airs their very full bows can stop them dead at times. Spencers are probably easier to build; I'm not sure about the Nelson. I've sailed T-birds, have a 28' Spencer which is sort of like a T-bird with less weight (good), better bow (good), more space (good) and narrower stern (bad) and would seriously consider the Nelson.

 

CANT FIND ANY INFO ON THE Nelson 32 ON THE NET Any help on it would be great thank for the help so far i have ordered plans for the thunderbird 26 but am still looking for plans for a 32 foot sloop thanks scott in scotland

 

You can use exterior ply wood with the same aspects as mentioned above. but you can get it to last longer but at a cost. you have to put as much glass n cloth on the inside of the hull as the outside. preferably b4 youbed the frames,stringers engine beds,etc. at that cost though its cheaper to go witha better ply.
Howard