ok, i know i am going to start a huge debate on this but i need to hear some opinions. i am getting ready to replace my transom and stringers but i am not sure what wood to use. some people say use only marine grade plywood, some say use regular higher quality plywood, does it really matter? my stringers are 2x6s and 2x10s from the factory and i dont think they ae marine grade? the transom i dont know, i think it is 5 layer plywood but not sue yet. i called around town and one guy siad use marine grade and the other said regular, both are well known for good work. i understand that there may be voids on the inside of the regular plywood but we also found them in the marine grade.... so what if there ae voids? does it really matter? my thoughts are that if the wood is a decent quality and is sealed very very well with glass ad resin then i think i should be alright. marine grade wood ros just like normal wood also, the key seems to be keeping it dry! i am not building some stupid cazy motor and can not imagine ever having more then 450-500 hp so i dont think that i need to be super worried too much about strength. the old stringers where not marine grade and they made it 20 years with allot of spots that should have been sealed, if they had been sealed i think they would have still been good. the transom does not have much either but i figure if i have the rest of it out then why not? i can get all 3 sheets of normal plywood for less then one sheet of marine grade.... in a economy like this i need to cut costs where i can but i dont want to f*ck myself in the long run either..... some one please shed some light!!!!

Exterior grade plywood is OK, I prefer the marine grade, its a lot of work to save a few $$$$ on the ply, but I dont believe your stringers are 2x4's or 2x6's, they SHOULD Be laminated marine Grade Plywood!!! Please dont use 2x Lumber on the stringers!!!!

only marine grade is the way to go !!!!

all other plywoods will delam after a wile because of the type of wood (oil) ,and resin can not fully go in !!!!

U can also look at diffrent foam core or plastic materials ,,maybe more cost but defenetly lighter and easyer to work with ,,also never will root ever !!!


More info ,,, www.fiberglassservices.com

Put a value on your time and the differential cpst of the marine versus reg is a small cost of the total project cost

I have always had a theory of not skimping on things that are very hard to change later on such as redoing the srtringers in the future

I'm sure they were. My Baja has/had 2X for stringers, 2x6 for the engine, 2x12 from the rear bulkhead up.

But they are/will be replaced with laminated ply.

If cost effective yes, marine ply is the best. But again I'll disagree based on experience with year/build quality of a similar boat that marine ply was definitely not used when the boat was built. I pulled out my transom and it was not marine plywood, it was exterior ply as I saw the stamping on certain layers. It had the usual knot voids and where it wasn't wet, it was solid as a rock and biotch to take out. Personally I think the hub-bub about the knot voids is a little overblown but that's my two cents.

I'm using a decent grade of 3/4 inch ply I found at Menards, I think its a 9 layer ply iirc.

You said it yourself, the existing stuff lasted 20 years and the build quality was crap by todays standards. If you take the time to seal up/laminate everything correctly it should last at least another 20.

And also less strong, so you need the glass work to take take all the loads - which is fine as long as you design/build for it. Most people replace a good wooden component with foam thinking it;s a like for like replacement, when it's not.

I'm not suggesting 2x4 softwood is the way to go, it absolutely is not, but if we're talking "should" rather than "is", they should be a single length of something like douglas fir - the multi directional element of ply is wasted in a stringer and only half the layers are really providing strength.

Has anyone looked into using LVL wood beams ? I know there are a residential bulding product but I use them in my homes with great results . They come in various sises and stand up very well to wet conditions . And they are strong as hell .
http://www.gp.com/build/product.aspx?pid=1392
Paul

That is an interesting idea. Initial thought is that it would work good for stringers, I actually have a few pieces left over from my cousins house build. I'll have to give that a look.

so someone please tell me why to use marine grade rather then marine grade if the original stuff is not marine grade? this boat sat out side for at least 3 years with no cover, no interior, no engine and was full of crap when i found it and the wood was just now going bad. plus marine grade will rot just as fast as normal wood since it is not treated. so what exactly am i going to gain using marine grade besides it costing at least 3 times more, it will be almost 300 for 3 sheets of marine grade verses 80 for normal. the lumber store told me the only difference is the voids and not a strenth issue.....