plywood choices for floor and transom

[Kracker Jack]

Do you necessarly need to use a marine grade? I have heard some things you can do to a standard plywoods instead of using marine grade. Can I get some positives and negatives on all different applications. Thanks in advance

[Kracker Jack]

can i get some positives and negatives on different types of plywood and techniques for prepping non-treated

[Kracker Jack]

Hedge i read a thread on here on "hot coating" a b/c type ply. By rolling on non hardened resin let it sit over night then roll on a hardened resin then sand and apply. by hardened I mean mixed and non mixed. Im not trying to cut corners im just looking at about 15 sheets of 3/4 birch cabinet grade that was made and china and is far from finish grade that was given to me.

[baconaneggs]

As a builder, I have used some of the Chinese 3/4 birch. It is much less expensive than the the US version carried by my lumber yard. The first time I used it was on a study/office renovation. We built up numerous built in cabinets and proceded to prime them in place after installation. You can imagine my delight when the vaneer began to delaminate and wrinkle after application of a oil based primer. We have used latex primer on the good stuff and have never had any problems I think I saved about 400 on the job. I figured I lost about 3000. I would strongly recomend you buy a marine plywood to do any repairs. A house is only as good as it's foundation. Why skimp on your boat. And he is right, treated pw is very wet and takes forever to dry. when it does, it looks like a potato chip! Or a taco.

[Kracker Jack]

baconaneggs same here with this ply!!thin veneer!!! I just figured it would be a little different using a resin and hardener on it rather than your issue using a latex or "water base" paint. once again not trying to cut corners. There are alot of threads on here were guys are using 3/4 untreated plys in fully encapsulated situations such as transoms and floors. im just trying to get every ones opinions. Is marine ply treated? or is it just the quality of glues they use to laminate the plywood that makes it marine grade?

[jeffmo]

every time i have used plywood on one of my boats i used marine grade.after cutting the pieces to whatever size i needed i would apply a couple of coats of helmsman spar for added protection.

[baconaneggs]

KJ, upon giving it a little more thought, the whole idea of encapsulating the wood is to prevent it from absorbing water. So using a piece of treated pw that has been in a warehouse drying seems like a good idea. However it is pressure treated, so it does tend to squirm around during the treatment process as the different veneers absorb fluid at different rates and move in different directions, leading to a sheet that is not totally straight or dimensioned properly. Is it as strong as it once was? I don't know. Marine plywood conforms to a much higher standard than regular plywood. It has waterproof glues and decay resistant wood species. You have to know in the back of your mind that if you used marine pw, you would never have to worry about the quality of your work. But everytime you saw a thread about stringers or transoms, there would be a twinge of doubt! What ever you use, just pay attention to any cuts, limber holes, and chase ways. ultimately it is the penatrations through the encapsulating cover that leads to the downfall. I'm ripping apart a 73 center console right now to replace the floor and stringers. I can't wait to see whats underneath!

[RidgeRunner]

Regular pressure treated plywood is a NO-NO. It will be so wet you will never have proper adhesion. Most treated plywood is Southern Yellow Pine which is not the best plywood to use in the first place. Pressure Treated Marine Plywood that has been Kiln Dried After Treatment is dry and will work. Marine Plywood is FIR and has a better grade of interior plies.(Less Voids) It is available with or without the pressure treatment.
All of the plywood of BC grade or better has a finish too smooth for my liking. I like to rough them up before laminating with resin. I do not know if the glue is different from regular exterior grade plywood. Most all of the delamination issues come into play due to lack of proper glue in the manufacture of the plywood. There are numerous brands and species. I wouldn't use a cabinet grade plywood for core on a boat. I would make certain that whatever I used it had Exterior Grade Glue. Look for the X on the end of the grade. (CDX, BCX, etc.) If you don't want to invest in the Marine Grade Plywood, at least go with Exterior Grade Fir. Okume is very nice but expensive. Happy hunting..

[Kracker Jack]

I just built a storage box for our duck decoys on my buddys Chincoteague scow. And we used salt treated he had laying around and the hollows in the layers and the soft plyable wood makes me nervous to use in structual applications such as a trannsom. And also resins and wet treated wood is like mixing oil and water. This salt treated plywood he had had been in his garage for like 6 monthes and it was all we had so we made due. As for the v20 im not wanting to put junk wood in my transom, but i am looking for functional money saving material that will serve my purpose. Thank you for all the info so far guys.

[spareparts]

I've used what I've been told is forming grade plywood with good luck, its the stuff with the red paint around the edges. Its not marine ply, but it doesn't cost like marine ply. resin seems to stick good to it, I redid the compartments on my Mitchell a few years back, that boat has been thru three owners since then, been used like a government mule. the work I did on it is still holding up last time I saw it

[Kracker Jack]

I know where theres a couple sheets of that form plywood at, but they slapped diesel fuel on it a couple times to reuse for concrete forms and keep the crete from sticking to it. I looked into some at my Grandaddys house after reading one of your thread responses.


Back to this "hot coat" technique one of you guys posted on here about treating a cdx with raw resin and letting it soak in and then putting a Hardener/resin batch over that then sanding then applying to transom. Is this true? this sounds fairly plausible to me. Im probably gonna go with marine ply. But just curious about materials that some backyard builders use and are sucessful with.

[spareparts]

I don't like the idea of having resin without any catalyst under cured resin. I don't think the under coating will ever kick, I could be wrong as I've never tried it. I usually lay down a thinned coating of resin with catalyst, thinned with acetone, (you have to add more catalyst when you thin with acetone), the thinned resin gets into the wood pretty good. Don't thin more than 10% as it won't kick

[RidgeRunner]

Yep, That is a hot coat. With Vinylester it helps to penetrate into the wood and gives it some bite. Essential on Kiln Dried PT Plywood IMO. With PT plywood the cells of the plywood that would ordinarily be open for penetration are actually full of preservative, metals like chromium copper and arsenic. It can give a case hardened effect making penetration difficult, that is why I recommended you grind it with some 40/60 grit before laminating with glass.(It helps the mechanical bond) Always wear Personal Protective Equipment when working with PT or any time you grind or sand on glass.
If you seal any type of plywood properly it will work for a long long time. I do not consider Wellcraft's glasswork to be that outstanding. My hull had lots of voids and buggers once the foam was removed.
ACX Fir seems to be a lower cost alternative to Marine Plywood and is available at most of the Box Stores. You need dry and without contaminants.

I have always mixed the hardener in with the resin. I'm like Spare, how does the resin underneath harden. I try to keep the ratios of hardener to resin consistent at the low end of the scale so I can have the most potlife and work on larger areas. (Mind you I glass in 95 degree weather) I threw out more kicked up in the bucket resin than I care to admit trying to find balance.

[Kracker Jack]

I will be glassing in a controled temp warehouse. but in va beach we are averageing 75degrees and high humidity. fellas thank you so much for the help so far, keep it coming im like a sponge soaking up info.

[spareparts]

) I threw out more kicked up in the bucket resin than I care to admit trying to find balance.
I know all too well about that, had to scrape off uncooked resin as well
Kracker, start making some small repairs, check temp and humidity, make accurate measurements of the hardener to glass. don't use the that looks about right method that my self and Ridge probably use. Check the time it takes for the resin to kick. Don't forget that you can cut off excess glass while "green" with a knife or scissors before it kicks completely. Once you get a handle on the time frame it takes, start making bigger batches. Keeping the batch together in a cup or bucket makes it kick faster, spreading it out over a surface slows it down, heat will get it to kick when its slow(hairdryer). Putting the mixed batch in the fridge will slow it down(makes your food taste funny to). Acetone will require more MEKP(hardener), don't go over 10% with the acetone. Wear gloves and long sleeve shirts, its better than picking resin out of your arm hairs later, and acetone makes your skin itch

[spareparts]

one other trick, if you have to reinforce something on the back side, take a piece of pvc, cut it in half down the middle, lay on it the piece your glassing after a layer or two, lay the next layer(or two) over the pvc, it will create a chamber that will make it stiffer. I know some guys that build racing sailboats(yes I used to race), they have a rubber oval shape hose they lay inside the molds, they glass over them, then after it kicks, they pull real hard, the hose gets smaller from pulling it, and it slides out, leaving only the glass in a shape that makes it stiffer.

[Kracker Jack]

I have a couple more questionn for you guys while we are on a roll here. What kind of cloth should i use for the transom and floor? 1708/45? how many ounces? waxed or non-waxed resin? I have noticed the non waxed is more of a laminating resin but stays kinda tacky even after it kicks. thanks fellas. Im asking these questions not because i have not done my research im asking them because im curious how different people do things.

[spareparts]

don't know the names or numbers for glass, I usually use what I find a deal on, if its thin, I use a bunch of it, if its think, I use less.
Yes, laminating resin doesn't have wax, it allows the next layer to stick better, keeps the glass in place

[RidgeRunner]

For the record I measured out the MEKP. Had a quart bottle with the measuring cup built into it. Still didn't help my dumb arse. The resin and hardener came with a chart of ratios. I worked under a pole barn. Resin was always in the 90's in the afternoon even when the outside temp was down to the low 80's. Cut the glass to fit prior to mixing any resin. I always buy 5 gal buckets of resin so I would give it a stir thru the dispensing hole. Pour the resin into a work pale big enough to use a roller. (Smaller jobs used a 3" roller) Add the hardener as per the guidelines and mix it up proper. In glass with Vinylester you can multiple layer with 1.5oz chopped strand matt and then add woven roving 24oz. over that. Wet on wet the way Wellcraft built the hulls. Or you can step into some technology and get fabric that has the matt stitched onto multi directional fiber like 1208/1708. Then there is all the super trick tri directional, carbon and kevlar varieties. Working with bi-directional fabric gives lighter results that are very strong with a better glass to resin ratio, sometimes a little harder to wet out. I have used both. I was instructed to use the old school layer on layer. If you mess something up or something goes wrong be prepared to grab a putty knife and scrape off the carnage before it gets dry OR be prepared to grind after it sets. I normally roll some resin on vertical surfaces to help hold the fabric in place, roll on some more resin and then go to it with a bubble popper.
Surface prep and having the basics is the key to glassing success. Anywhere you want to repair existing fiberglass needs to be prepped by wiping with prep solvent/acetone, ground with 40 grit until all the shine is gone and the surface is relatively flat, cleaned and then wiped again with acetone and allowed to dry. Spot repairs should extend out well beyond the actual problem spot. If that problem spot is the hull itself you try and minimize the grinding on the outside of the hull and make the majority of the repair from the inside. The outside will be 95% cosmetic and 5% structural. The inside of the repair will be 100% structural and typically not seen. You can glass over the top of gelcoat after proper prep and grinding but I wouldn't make it a habit. On rebuilding my transom, Wellcraft had gelcoated the inside of the boat from side to side. I wanted my glass to cover the transom and wrap around the sides a good 8" or more. I ground it out and prepped it but still had a few spots of gel showing. No issues..

[000's]

wait untill its hot as hell and the sun is baking(opens the pore of the wood up).Add 10% acetone to the resin,needs to be like water,it will saok into the wood .Stays a little tacky,but I promise it works.Same thing that stuff you see for sale what is it GET rot,got rot same thing.A 30 year fiberglass guy showed me that one. Good explanation on ply wood for boats.




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[Kracker Jack]

Well after doing some research I have found a ACX plywood called Arauco it is an Argintinian species of wood called Radiata pine. Of course it is not treated but the glues and lack of voids in the layers and surface being permeable make it a great canidate to be treated with a "hotcoat" seems like it would really soak up the epoxy or other resins and only $30.00 dollars a sheet at Lowes.

[Kracker Jack]

Well after 2.5 hours of research on this plywood i have decide this Aruaco plywood is the material im gonna use for my transom and floor repair. This plywoods only down fall is alot of guys say its very thirsty when it comes to treating it with a hotcoat. everyone says its very solid with no voids and is put together with a good grade exterior glue. I read some negatives also but most of the negatives came from the purists or the old school workboat builders(which means alot because these are our wise men) they simply didnt like it due to more use of resin and some inpurfections in the thickness of the plys which they consider make the panel not as strong, when i seen the material at Lowes today all the plys were very consistent with each other in my opinion. Alot of the guys on other forums have put samples of this plywood in there diswashers to do the BOIL TEST and the plywood has passed the test with flying colors all claiming no delaminisation what so ever. One guy even put it as his base floor in his pontoon boat like 4 years ago and the integrety of the plywood still remains the same. im gonna be bringing my v20 home this weekend after my morning deer hunt on saturday so I will make a new build thread and start documenting my demo and rebuild with plenty of pics. Thanks for all the help guys Im sure im gonna need alot more of before this is all said and done.

[RidgeRunner]

Good choice. The price is right. We pressure treat plywood on a regular basis. Arauco plywood is one hard plywood to treat. It has interior plys that are so dense we simply have trouble. The interior plys are also allowed to be hardwood which cannot be penetrated effectively by the pressure treatment process.
On the other hand, Radiata Pine boards and fence picketts are like a sponge. Due to the fast growth of the tree, the growth rings are not very close together so there is a lot of sapwood that is easy to penetrate with preservative.
I don't think you will have any issues. It has a great track record. Keep us posted.. Pictures too..

[inaforty]

Very interesting research.
The front deck of our V is soft and will need recoring at some point.

I used Coosa board to recore the cockpit hatches on the Bertram last winter but the Coosa was pretty $$$.

[Kracker Jack]

The first thing i searched when i joined this forum was core material. I was very interested in what backyard fiberglass guys and professional repair and boat builders are using besides the over price marine plys.Im expecting this boat to last me for a while and if my repairs with a 30.00 dollar big box store(lowes,home depot) last me 15 years then im gonna be happy. There are a few threads on here where guys push nothing but expensive marine grade ply wood I disagree with that. But I do agree with using fresh resin and quality cloth and a decent ply that is functional. I f anyone else has any more opions or has experience with the 3/4 arouca ply wood from lowes please share because im sure alot of budget conscious backyard repair guys would like know. Thanks for all the info in advance.

[spareparts]

I've seen a lot of the crap that boat builders use, most of it is barely cdx throw aways. the wood you've picked out is probably better than 50% of the boat builders out there, True marine grade wood is a rarity in the marine world

[RidgeRunner]

We stock and sell the PT marine grade plywood. I really like it for some applications but not all.. It is excellent for pontoon boat decks. Most of which never gets sealed. I have seen it rot in the worst of conditions, like pedestal seat bottoms where the foam gets wet and keeps the plywood soaked. Wellcraft used 1/2" CDX plywood for the foremost bulkhead on my center console. And they didn't bother to glass it 100%. Just tabbed it in place with some heavy roving.
Coosa is real nasty to work with and soaks up resin. The cost for major itch was $125 per sheet for 3/4" in 1996. I used it on my deck and hatches on my V. It is my understanding that it will never rot.

[bigshrimpin]

I used ACX Arauco in a bracket that I built 2.5years ago . . . I was very pleased with the product. Also used it in my transom on the 23 seacraft. Only time will tell . . . but seems like a decent lower cost alternative to Dougfir abx or Okume marine ply

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[Kracker Jack]

shrimpin did you make the wheel house on seacraft? That is one sweet set up!!!

[bigshrimpin]

Thanks Kracker . . . That's a seamark mini pilot house!! It's huge but it fits perfectly into the 23 . . . I can even standup in the console. I got it from Bill Potter who had it on loan to Piratecom in PA.

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