Okume or Doug Fir Transom?

[ccx2]

Hey ALL , building a Garvey of Okume Ply that will be epoxy encapsulated and can save a coulpe hundred if i build the for and aft transoms of Doug fir, would i be making a mistake or should i use the Okume? Sorry for anoyther plyboat question, my next boat will be wood planked i allmost promise. Thanks:)

[TerryLL]

When you say Doug fir do you mean solid lumber or DF ply? I've mixed okoume ply and DF ply in the same boat and had no problems. DF has a big problem with surface checking, which won't be a problem on the exterior if it's glassed, but might show on the interior after time. I'm assuming you're painting rather than finishing bright. I'd think finishing bright with the two ply types would be a bit of an eyesore.

If you're using solid lumber DF transoms, and okoume ply planking, then I can't help. I did put a solid DF transom in a Swampscott dory with meranti ply planking and had no problems, but the dory transom is a much narrower item than the garvey transoms.

[RFNK]

Is it going to cost so much as you'll need to buy full or half sheets of the thicker ply? If that is the case, why not just laminate the transom up from the thinner ply you've used for the rest of the boat? You can easily use epoxy or several other glues for this, especially as you're glassing over it anyway. Rick

[ccx2]

When you say Doug fir do you mean solid lumber or DF ply? I've mixed okoume ply and DF ply in the same boat and had no problems. DF has a big problem with surface checking, which won't be a problem on the exterior if it's glassed, but might show on the interior after time. I'm assuming you're painting rather than finishing bright. I'd think finishing bright with the two ply types would be a bit of an eyesore.

If you're using solid lumber DF transoms, and okoume ply planking, then I can't help. I did put a solid DF transom in a Swampscott dory with meranti ply planking and had no problems, but the dory transom is a much narrower item than the garvey transoms.
Sorry , Df ply. Surface checking wouldnt be a problem if encapsulated before exsposure/use would it ? or could it check under epoxy and be a problem?

[ccx2]

Is it going to cost so much as you'll need to buy full or half sheets of the thicker ply? If that is the case, why not just laminate the transom up from the thinner ply you've used for the rest of the boat? You can easily use epoxy or several other glues for this, especially as you're glassing over it anyway. Rick
I can get both transoms out of one 4x8 sheet of 1inch DFply for about a third the cost of two 1/2 inch Okume.

[JimConlin]

Sorry , Df ply. Surface checking wouldnt be a problem if encapsulated before exsposure/use would it ? or could it check under epoxy and be a problem?
Just an epoxy coating might not restrain checking. I'd add a sheathing of (at least 6 oz.) glass cloth.

[SawmillBrook]

I built my Garvey out of Meranti, which cuts and sands like Ok.. it's a joy to work with. 5 years later I built a center console out of marine fir ply. Hated working with it, sanding, etc.

Invest in the best materials and invest in piece of mind

[JimD]

Ditto Jim Conlin. You must glass the fir plywood. Epoxy alone will not prevent checking.

[James McMullen]

"Encapsulated" is just a lie/wishful thinking unless you're also using glass cloth or dynel or something on both sides. The fir ply is going to be heavier and possibly even weaker and more rot prone than the multi-lam occume if it has any voids in it--and it most likely will. Unless you've got a source for some kind of Wonder-Fir plywood these days, I would just suck it up and pay for the occume. The good old fir plywood that was made from old-growth fir logs is gone, along with the forests that supplied it. Modern fir plywood in boatbuilding terms is best used for station molds and jigs--not planking.

[TerryLL]

Agree with all the above. In my experience fir ply will show checking unless glassed, regardless of multiple coats of the best sealers and paints.

[ccx2]

Just an epoxy coating might not restrain checking. I'd add a sheathing of (at least 6 oz.) glass cloth.
Im going to Sheat inside and out, does that prevent checking?

[Clinton B Chase]

I've done inexpensive Meranti transoms (which is similar to DF but considered a better plywood) and Okoume transoms and regret the Meranti jobs, which had to be thoroughly epoxy coated (3 coats) and fiberglass sheathed in some cased. The Okoume transoms were about 30+% lighter b/c the wicked encapsulation process was not needed so much.

To answer the Q, from what I have seen, yes checking can eventually make its way through epoxy coatings. A light f'glass sheathing will solve the problem. Again, all this epoxy coating and esp. the glassing adds a lot of weight as well as hassle. If it were my project ccx2, I would definitely suggest using a goood quality Meranti as a minimum or go with Okoume. I have always regretted using the cheaper plywood! No more of that...it is like getting cheap tools...eventually you will regret it. Now, budget is always a realistic factor, so I would suggest trying the Meranti...it is not too much more than DF ply but holds a finish much better, esp. with some epoxy coats to seal up the outer layer of ply. On most boats that I did not do this epoxy coatings, I have found within a year or two of launch that the checking comes through. 3 coats of epoxy would certainly slow this down considerably. What you need to look out for with the Meranti (as well as DF) is the filler they use (often pink) to repair splits and voids in the outer plys of these plywoods. That pink filler lasts about as long as elmers glue would in the marine environment. The Paint is not protection enough. This is why epoxy coats would be a good idea. At least 3 coats!

Good luck,

Clint

[HarryH]

Clinton-

I am using some Meranti on my build, and am knocked out by its quality. 13 plys, absolutely no voids anywhere, and after sawing up several sheets into a variety of shapes, looks to me as if it will last a long time. Is it possible the stuff you had may be of a different quality? This stuff has the 1088 stamp (here goes a debate). I purchased it from Maine Coast Lumber a few years ago, will buy more soon. Okoume is lighter, granted.

[ccx2]

I've done inexpensive Meranti transoms (which is similar to DF but considered a better plywood) and Okoume transoms and regret the Meranti jobs, which had to be thoroughly epoxy coated (3 coats) and fiberglass sheathed in some cased. The Okoume transoms were about 30+% lighter b/c the wicked encapsulation process was not needed so much.

To answer the Q, from what I have seen, yes checking can eventually make its way through epoxy coatings. A light f'glass sheathing will solve the problem. Again, all this epoxy coating and esp. the glassing adds a lot of weight as well as hassle. If it were my project ccx2, I would definitely suggest using a goood quality Meranti as a minimum or go with Okoume. I have always regretted using the cheaper plywood! No more of that...it is like getting cheap tools...eventually you will regret it. Now, budget is always a realistic factor, so I would suggest trying the Meranti...it is not too much more than DF ply but holds a finish much better, esp. with some epoxy coats to seal up the outer layer of ply. On most boats that I did not do this epoxy coatings, I have found within a year or two of launch that the checking comes through. 3 coats of epoxy would certainly slow this down considerably. What you need to look out for with the Meranti (as well as DF) is the filler they use (often pink) to repair splits and voids in the outer plys of these plywoods. That pink filler lasts about as long as elmers glue would in the marine environment. The Paint is not protection enough. This is why epoxy coats would be a good idea. At least 3 coats!

Good luck,

Clint
Thanks Clint, Ive decided to go ahead and use the Okume and laminate them to get the thickness i need and i had intended to glass inside and out, thanks for the opinions.

[ccx2]

Clinton-

I am using some Meranti on my build, and am knocked out by its quality. 13 plys, absolutely no voids anywhere, and after sawing up several sheets into a variety of shapes, looks to me as if it will last a long time. Is it possible the stuff you had may be of a different quality? This stuff has the 1088 stamp (here goes a debate). I purchased it from Maine Coast Lumber a few years ago, will buy more soon. Okoume is lighter, granted.
I may use the Meranti yet as per suggestion and price/avalibility but will prob use the Okume, Thanks

[TerryLL]

Meranti comes in at least two grades rated marine, the good stuff and the crappy stuff. Crappy stuff has fewer plies and some voids and should be avoided.

[SawmillBrook]

and finally... Meranti is 20% heavier than ok, but more "bullet proof", and, it was about 15% cheaper when I bought it 5 years ago, so my cost advice is way out of date.

[RFNK]

Glass gives you a little more UV protection than neat epoxy resin but not enough. In any case, the epoxy resin will break down through UV exposure. You need good UV protection over the glass sheathing - varnish with UV inhibitors, or paint.

[RodB]

http://i40.photobucket.com/albums/e239/Prestoboat/transom.jpg

http://i40.photobucket.com/albums/e239/Prestoboat/stitched-square-bw.jpg

http://i40.photobucket.com/albums/e239/Prestoboat/transom-edge-sheerdeck-72dp.jpg

You can't go wrong with a sandwhich construction of Okoume skins and doug fir core... or merranit skin would be tougher... the core can be Doug fir "one by" material rather than the "two by" material in the photo above.

My 18 foot skiff has a 90hp outboard on it, so I went with a Doug fir core throughout... you can use cedar as a core for lighter weight... depending on the degree of use... it may be a good idea to at least use doug fir solid lumber precisely where the outboard will bolt through or clamp to the transom. Just glass (encapsulate) the transom well and double the glass in the area where the motor will subject the surfaces to abuse. Remember, Okoume is not very tough... Merranti is tougher. On my hull, my designer suggested building the hull of Okoume but on the bottom, I added an additional layer of 1/4" merranti for a tougher hull surface. I also sheathed the hull well with xynole.

I think a properly built transom with any reasonable care should last many many years... just scale down the scantlings to fit your needs. You can easily make a bullet proof transom with sandwhich construction and glassing... remember, doug fir solid lumber is hard to beat for strength to weight ratio compared to most any boat builidng wood.

Good luck,

Rodb

[ccx2]

Great idea Robd, i will consider that for the rear Transom, my plan calls for 1" plywood and right off the bat i thought that was thin and weak. THANKS

[Clinton B Chase]

ccx2, one inch ply transom sounds fine, don't add too much weight by increasing scantlings. Sometimes you'll see boats with a thin transom and framing to get strength and extra faying surface for the planking. A 1" garvey transom would be really heavy!

Someone mentioned having some nice Meranti...it exists. Shelman's meranti is pretty nice stuff. I am using Hydrotek b/c it is expensive and we are a non profit so we try not to spend too much unless it is on a commissioned boat, then I get the owner to spring for the okoume. I'd use the Shelman Meranti on one of my own boats if weight was not as big a concern.

Cheers,
Clint

[ccx2]

ccx2, one inch ply transom sounds fine, don't add too much weight by increasing scantlings. Sometimes you'll see boats with a thin transom and framing to get strength and extra faying surface for the planking. A 1" garvey transom would be really heavy!

Someone mentioned having some nice Meranti...it exists. Shelman's meranti is pretty nice stuff. I am using Hydrotek b/c it is expensive and we are a non profit so we try not to spend too much unless it is on a commissioned boat, then I get the owner to spring for the okoume. I'd use the Shelman Meranti on one of my own boats if weight was not as big a concern.

Cheers,
Clint
OK, but its a 16ft Garvey and im going to put a 25hp on it and 1" just seems thin for a Transom, but i really havent looked to check the thickness of any production boats yet for a comparison, but then that was the designers job so i should probably stick to his design, Ha Ha, maybe i should get my first boat built before i start changing things up. Thanks for the reply.

[RodB]

You won't be sorry increasing the scantlings a bit for the transom... ending up with a stronger...and mostly stiffer transom... that will take lots of abuse an stay sound.

I'd rather have a sandwhich construction with standard "one by" for the core (DF) and the exterior 1/4" ply... epoxy all together and glass it all.


RodB

[pipefitter]

1" transom is a bit thin if it is stand alone without knees or a raised deck to tie it in. If you use the 1", you could always use a 1/4" aluminum plate as a backer for the motor. Depends on what the glass schedule is too because most composite transoms can have up to an 1/8" to 1/4" of fiberglass on each side which brings it up to 1-1/4 to 1-1/2".

You could also get away with an inch if you have horizontal bracing which could be battens to stiffen it too. What else is there in the way of framing there?

[ccx2]

1" transom is a bit thin if it is stand alone without knees or a raised deck to tie it in. If you use the 1", you could always use a 1/4" aluminum plate as a backer for the motor. Depends on what the glass schedule is too because most composite transoms can have up to an 1/8" to 1/4" of fiberglass on each side which brings it up to 1-1/4 to 1-1/2".

You could also get away with an inch if you have horizontal bracing which could be battens to stiffen it too. What else is there in the way of framing there?
She's gonna have Quarter knees, Transom knee , and the rear seats extend all the way to the Transom , and the plans call for a 1/4inch plywood motor plate but i prob will use aluminum.

[pipefitter]

She's gonna have Quarter knees, Transom knee , and the rear seats extend all the way to the Transom , and the plans call for a 1/4inch plywood motor plate but i prob will use aluminum.

Well that certainly makes the cheese more binding. It now seems more than adequate with the entire picture.

Also agree that it's not worth using the fir ply. You will spend at least as much getting it fair if you intend on finishing the hull slick.

[James McMullen]

I think you're getting ready to make the classic beginner's mistake of fixing something that ain't broken. . . . .

One inch thick high quality marine plywood is amply strong and stiff enough to hold a 25 hp outboard when it is braced with the quarter knees, transom knee and rear seats which extend to the transom. You could waste a lot of time building that ungodly lash-up of a fiberglass "encapsulated", occume-skinned, solid-lumber-cored panel which is way heavier, more complicated and expensive than just using the correct materials called out on the plans.

Heavier="bad" with respect to planing hulls, you know?

[TerryLL]

You can't go wrong with a sandwhich construction of Okoume skins and doug fir core...

Rodb

Actually, you can go terribly wrong using this construction technique. The plywood skins are dimensionally stable and the thick lumber core is not. If water gets into the lumber core it will swell, and the forces generated within the sandwich will be huge. The glue joint may fail, or more likely, the surface veneer on the glue line will fail. More water will enter, more swelling, more failure. Not good.

A much safer route is to use a less expensive ply core with an outer layer of okoume ply, then the entire sandwich is dimensionally stable.

[RodB]

Balderdash... properly encapsulated as described above will be around lots longer than you and I ... The assumption here is that the construction is done properly... and water is kept out of the core of the transom. That is why the top edges and the motor mount area are double glassed.

I don't think my skiff pictured above is going to self destruct any time soon.

Overall the plans should be followed and things should be fine... but if one errs on the side of stiffness and strength and the weight is not increased all that much, its not any big deal.

This type of construction has been used thousands of boats and stands up fine. It ain't like the polyester glassed transoms of yesteryear that rot and have to be redone due to water intrusion.

RodB

[TerryLL]

RodB,

You misread my post. I said "if" water gets into the core there could be problems. If the core forever remains dry, then no problems.

I've certainly been guilty of taking shortcuts to save money and time. But when a new builder asks for advice, I think the best we can do is tell them to follow the plans. Making grand assertions that a particular technique is foolproof often leads the new builder into trouble.

If the encapsulation is not perfect, a transom built as you suggest will have problems. A builder with your experience may be able to use this method with 100% success. A new builder, maybe not so much.

[RodB]

TerryLL,,

You are absolutely right. Don't take my balderdash too serious...

Merry Christmas


RodB

[TerryLL]

Nor mine.

Take care, and happy holidays.

Terry