Excellent Article In Bass And Walleye About The Comparisons Of Wood To Composites In

boat construction.
Very well written, and if you read between the lines, very enlightening!
Shocking to see some of the boat manufacturers admit how much is marketting versus fact.
As I've said and believed from day one (article agrees), it makes more difference how it's intsalled than anything.
Also amazing to me at how many people think all that foam core will not rot or saturate with water like wood does.
Pound for pound, wood, especially ply, is tough if not impossible to beat if "properlly" used.
One of the manufacturer's even stated that they tested all available composites for its ability to hold a screw w/o stripping.
None worked as well as wood.
Some are using a method called "pulltruding" (I think) where they use multi layers of multi types of cloth/mat, then saturate it with resin before running it through a combo press/oven.
It comes out very strong and will hold a screw comperiable to wood but is heavier and much more expensive.
When most of the top race boat builders (have to be the lightest and strongest) are still using plywood (some for the complete boat) for m.boards and stringers, and balsa core for skins, that's all I need to know.
Check it out, is an excellent read.
They also have a shot of the new Merc 4 stroke which I think is uglier than a box of rocks! Looks like two cowlings stacked on top of each other, yuch!
They divuldge more "beliefs" than I've read before. That small article along with the Merc written "guide to O/B's" (very well written also)as a pull out in the magazine, here's aprt of what they say/think:
It's an in-line six but all Merc instead of the new GM as many thought.
Although it didn't sound like it, Merc said it was "pressure injected" meaning super charged, or turbo.
In their O/B guide, they said that since the 300X won't pass the '06 EPA/Carb rules, it's going to be all Opti and four stroke, and they thought that 300+ HP's would be easy in the forseeable future.
The next 12 months may be interesting in deed.
I find it very ironic and kind of neat that their future may be with an in-line six! how appropriate would that be??
Gary

Concerning the strength of wood...........


A Trident II D5 Submarine Launched Ballistic Missile weighs approx. 130,000 lbs. It is lifted and moved from place to place vertically when necessary. The lifting fixture is attached to a structure known as the Nose Fairing. The fairing is made from laminated Sitka Spruce less than 1/4" thick. The wood core structure of the fairing is covered with a substance similiar to gel-coat. No question about the strength of wood here. There have been nearly 100 test launches of these missiles and not one single failure. The whole structure is subjected to extreme forces during launch impulse and subsequent hydrodynamic as well as aerodynamic peturbations. Now if we could only figure out how to get the wood to not be hygroscopic we would have it all.

huh?
I'm guessing, porus, or susceptable to water?

able to absorb water. Dot 3 through 5 brake fluid is also hygroscopic. Not sure about the higher grades. :cool:

Readily taking up and retaining moisture.

It's easy to make 300 hp with a 4-stork OB the trick is making it light.

If you want to make wood non- stroboscopic just add an air pump. Water can't get in unless the water pressure is greater than the air pressure. Just make sure the intake for the compressor isn't near water.

...are designed to penetrate the wood, and make it impervious to rot. Might be kind of painstaking to treat all the wood before laminating it, but it is a solution. :cool:

As you learn in materials science classes at engineering school, wood is actually a composite in itself and a laminate of wood and polyester is a composite of a composite (wood) and polyester.

So the whole wood vs. composite discussion that is popular in boating circles is scientifically incorrect...

And I agree with the points above: Wood is an excellent material.

Quote:

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Originally posted by Rickracer
...are designed to penetrate the wood, and make it impervious to rot. Might be kind of painstaking to treat all the wood before laminating it, but it is a solution. :cool:

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Is this the other stuff? http://www.rotdoctor.com/boat/Bmain.html

Is that a sign of aging? Let's see, there's wrinkles, gray hair, and I forget the other ones........:D
Actually CPES (Clear Penetrating Epoxy Sealer) is what I was trying to remember.

still being able to glue/galss or paint it after treatment.
When I was building hydroplanes we tried everything.
The best "wood preservetive" we found was a product called "cuhprenohl" (sp?) and it went on like water but staurated very deep into the wood.
The negative was, nothing would stick to it afterwards.
I built one and used the new "miracle" epoxy everyone was talking about, but it was too thick to saturate vey far, and peeled easy.
My favorite is and always has been thinned varnish. Glue still won't stick to it but you can apply it to the inside of the hull before installing the deck. We would use polyurethane (not actually varnish) and start off with it thinnned like 50% for the first couple coats, and then reduce from there.
On rot specifically, they say it actually starts as a fungace in the wood from the start. It needs heat and humidity to spread, almost like mold.
The "Git-Rot" I have seen has been more for repair than prevention??
My dad used to have wood cabin cruisers when I was a kid and I remember my dad always joking about buying stock in the company as long as he owned a wooden boat.
The stuff saturated the wood surrounding the damaged area and turned it rock hard and then you filled in the damaged area with a "Marine Tex" type epoxy filler.

As for the 300 HP 4 stroke, yep , I know.
Been saying that for yerars! Be interesting to see how far they can take em??
wonder how much a turbo or super charged 250/300 4 stroke I/O, Imean O/B :D will cost:eek:
I still say too, give them 2 or 3 years of use in the field and the neglect and abuse that our motors go through!
Going through one of our motor's is bad enough, but wait to get a quote for one of those bastards!!

when I started the re-coring project on my Vector, I researched the alternatives quite a bit.
Someone on this board (Techno?) turned me onto a marine website that did a study on it and it was very educational.
Basically what I/article said at the begging of this post.
That site showed pixs from storm damage of many high dollar yachts that were built with various cored construction.
The first myth they blew away was that the "foam" would not rot/deteriorate.
They were showing the sides of hulls with 2 and 3' holes in them but after being inspected, they found the majority of the area in the hulls to be totally de-laminating! (and not from the storm damage)
They/it basically said for strength vs weight, it's almost impossible to beat balsa.
I really appreciatted the people in the Bass/Walleye article having the stones to tell the truth on part of the myths involved.
Several of the company owners said that they much prefered wood construction but that the market had been brain washed (sounds kinda like the 4 stroke O/B gig doesn't it) into thinking wood was bad, period!
One owner quoted I beleive $600. additional cost for the same boat with no wood.
Several also hi-lighted the strenth per lb myth of composite vs/wood. Basically they said if both materials are of the same strength, wood is the lightest and that most of the claims contrary to this was purely marketing! (they also pointed out how some of the composites are described vs reality, again, marketing)
They also taked about the variables such as storing a boat on-shore with a drain plug in, or with the tongue down and the plug out and allowing it to fill full of water.

Great post, how do I get Bass and Walleye Mag, and do they have a websight?

Thanks

http://www.amagarea.com/Detail/NS-QPHH&LPAATNTQDPIH

later.sid

I've never known wood to be a problem as long as the transom holes are sealed up good, unless the manufacturer did something brilliant like leaving exposed wood without glassing it in, like they did under the transom cap on the Glasspar G-3. I have seen a couple of boats with rotted wood floors that got lumpy after about 20 years. But it's hard to say what the true origin of the problem was; the life of boats is typically directly proportionate to the IQ of the owner(s). I see a lot of boats sitting outside in snowstorms with no cover, gee I wonder if stuff like that contributes to these types of problems.

I have a 1960 Norris Craft with almost no rot in the transom even with a few holes through the glass cap. A little get rot and away I go.

On my Formula V race boat it was an Allison 1983. The bottom broke. The bottom used thin plywood from the transon to the seat area in rectangles of appox 4" X 10". They were all rotted. from the seat area forward was balsa in small squares. Appox 60% of this was bad.

I re did the bottom with foam inbedded in epoxy cut into small 1 1/2" squares. I used the foam for the weight. The epoxy mixture formed minature I beams and made the bottom very strong.

However after being involved with capsules and accident investigations as an inspector and referee I chose balsa core for the capsule I put in. It is 3/4 balsa, end grain. I would put my capsule aganist any built. When we put it in we cut the nose section off and glassed the capsule into the boat. We then ran a 18 wheel tractor over the nose section without even a deflection. A foam cored section could not hold up to this. It did weight more, but hell it is my butt in it.

We kept the transom of wood core.

So it depends on what you are trying to achieve, and how you do it that will determine the material used.

One interesting part of the article is some manufacturers use pressure treated wood for their boats. All the resin manufacturers I have worked with always said it was a no-no. Something to check out.

Klegecell is a PVC-based, rigid, closed-cell foam with high thermal stability and structural integrity similar to Divinycell.

In addition, Klegecell foam is impervious to moisture and unaffected by rot causing fungus and mold.


Klegecell is resistant to oil, fuel, and cleaning solvents and completely compatible with polyester, vinylester and epoxy resin systems.

It will not support combustion and is self-extinguishing.

Also, since Klegecell is a closed cell foam it will not absorb water.

Klegecell has a high strength-to-weight ratio like Divinycell. Therefore, it is ideal in applications such as boat transoms, LNG storage tanks and many others


Foam vs. Balsa Wood and Honeycomb

Balsa wood and more commonly plywood have been used extensively in boat construction for many years.

While these materials provide excellent compression and stiffness properties for a relatively low cost, they can be heavy, susceptible to water absorption, and will eventually rot.


Foam cores can be much lighter, fungi resistant, and do not absorb water or any other fluids encountered in a marine environment.


There is also evidence that foam cores have better fatigue resistance than balsa wood. Laminates made with foam cores can last longer and weigh less than wood cored laminates, while producing adequate physical properties. Wood is still a viable material to be used in areas where highly localized compression loads or through fittings are present (such as engine mounts and around cleats), where the appropriate high-density foam core may be too expensive.

Balsa's drawbacks are that it is at least twice as heavy as foam, and can become heavier still by absorbing large quantities of resin (sometimes called wicking) along its grain during lamination - and water too if the skin should later be punctured, whereas PVC foam with its closed cells is virtually non-absorbent. Balsa is also vulnerable to impact, so it should not be used under a thin skin in areas where it might get dented, with consequent delamination.


As stated, NO ROT, NO ABSORBTION AND no FUNGUS and self exstinguishing...

I think the website your talking about that surveys boats is called yacht survey…here is the link.

Yacht Survey

When I started my own project I looked at all the alternatives; epoxy, marine ply, kevlar, vinylester, foam etc, etc, etc.

One big advantage to plain ol’ polyester resin is that you can reduce it by 10-15% with styrene monomer…it really becomes quite thin and really soaks into the ply. After it sets you can come back and lay down an un-thinned coat for glass or as a final seal coat.

Bottom line is that you don’t have to get too exotic to have a perfectly sealed and strong wood design that will in most cases out perform other materials.

The entire back half of my boat was designed with cheap CDX ply and poly resin…nothing fancy, very strong and light.

You could see in my Bayliner how the rot started at the motor bolts and went out. Then again, it was on there since 1983, and sealant only lasts so long. So I drilled the holes big and epoxied in there twice, then pumped 5200 everywhere around/under the clamps. I might have tried the pipe method had I known, but I am sure the boat will die before this transom if it lasts as long as the stock one. I did 5200 the inside nuts, and even forced it down the bolts. I did this in case it ever flooded on the inside for some reason as the bolts are not that high from the floor. I would guess you should reseal it every so long.

I also found since then, that at the local Menards you can buy small peices of oak plywood, like 2x2'x3/4". Supposedly better wood I would have used, even though the oak is only the outside the plys are high quality. Cost would have been ok for small chunk.

I just painted the wood with epoxy and it seemed to soak in pretty good, not knowing how far. Had to use two coats as the first soaked away. After second it had a shine, and a couple spots took three. Did floor panels that way too, and carpeted.

Several people interviewed mentioned the problem of the engine mount bolts not being sealed durring re-power as common problems.

I too was shocked to read of the use of pressure treated plywood with glass, and have read it is taboo!
Very much rot resistant but, can't glue it, can't glass it, can't paint it, humh?

Hehehe, ya the Force has a nice bright aluminum block in it, and the rest of the motor is painted, bolts all scratched up!!! Wonder what dealer did that?? I was done before I got it, but I found no sealant at all on the bolts when I pulled that big anchor off the rotten transom.

Does anybody use cyprus for anything? I know thats what they build water-wheels out of, like for grist mills , and they last for 50 or more years. However they stay wet. I think it makes a difference, getting wet and drying out over and over.

we were building the race boats. Spruce for all stringers and any kind of blocks. One of the strongest woods there is for its weight.
Lighter even than pine.
On low budget boats I have used (with good succes)clear white pine in place of the Spruce due to cost and availability (actually close in weight and strength).
For plywood we used Okume which is an African Mahogany and is still in popular use today.
I found out the hard way long ago that there is a big difference in "Marine" plywoods also.
On one of the budget builds I found what I thought was a great deal on 1/4". (They actually go by metric sizes)
Once it was deliver'd I found out why it was so cheap.
It was 3 ply (normally 5 ply in that size) luan which is the same stuff they sell as "under layment" in the local DIY centers.
It was crap!
Another time I ended up with 3 ply 1/4" fir (with the football plugs in it) instead of Okume.
The real deal was 5 ply with no voids, but was around $90. for a 4' X 8" sheet back in the '80's and I think has more than doubled since then.
We used to use 3 ply 1/8" (3mm) for decks, the stuff was amazingly strong for how thin it was.
Built one "A" Stock Hydro w/a 1/8" bottom and doubled the last 2' to make it a 1/4" thick. I think that boat was about 9' 3 or 4" and weighed 57 lbs un-rigged.
Try that with glass:D

I had a guy who does house trim make me a sub box once. It is 1/2" and looks like 9 plys. They use it for the sides of drawers in kitchen cabinets. How would that work in a transom?

Wood is the classic boat-building material. That's why you can find boats approaching 100 years old still in regular use that are made from wood. Pound-for-pound it is stronger than steel and far stronger than glass fiber (much lighter too). It has many, many good points going for it, and if used correctly, works better than just about any other material.

As astutely pointed out previously, it is itself a composite material. However each species of wood has its own "performance," and, therefore, the correct wood must be chosen for the appropriate usage. Decks on WWII (and previous) naval boats were teak which is nearly impervious to rot and deterioration. However, teak would not be the wood of choice for something like engine stringers or frames for a variety of reasons.

The problem with most wood used in boats is that it is not treated correctly. It needs to be epoxy encapsulated whether using Smith's CPES or a hard epoxy like those from West Systems, System 3, or MAS. The encapsulation barrier gets broken down when someone drills a hole through the wood and then forgets to encapsulate the edges of the hole - and that's where rot will start if the wood is exposed to water. Encapsulate the hole's edges, and you again have a totally rot resistant material.

An epoxy sealant like Smith's CPES makes a perfect "prime coat" for any type of paint or varnish. Hard epoxies can also be painted or varnished with most marine materials. In most glass fiber boats using balsa, the wood rots because the glass fiber materials have failed first and allowed water to get to the wood. The wood then has the task of hold the boat together while the glass fiber continues to fail further (think about that one). If the balsa was CPES treated prior to its use within the boat, it is probable that the balsa would not rot at all and the boat would be intact until the final total failure of the glass fiber material surrounding the balsa.

As far as gluing encapsulated wood, there are two methods. You can use the hard epoxy as a glue, or you can use 3M 5200. Regular glues such as PVA types (like Elmer's), or urethanes (Gorilla glue) won't work because they cannot penetrate the wood surface pores because the wood is sealed.

It all comes down to knowing and understanding the material, choosing the correct material for the expected performance/use, and treating the material to ensure longevity.

That did it, I'm dumpin my Allison (that I thought was tough as nails) & buyin a 20 footer built with a WHOLE ****LOAD of WOOD ! I've seen the light !! Scott :D

No wood has got to be the Hottest selling point on Recreational boat now...So many people will buy a boat solely on that even though its a piece of crap..The only thing they know is wood rots and composite doesnt..So many people are buying boats and getting loans for 10yrs or more, when it doesnt matter if its wood or not it is still going to be a piece of crap after 5yrs regardless!!
Wood has its place and composites have there place each just needs to used correctly..

Hey Scott Gilmore just buy a Allison drag boat / to my knowledge they STILL use WOOD in those. Lets hear it folks am I wrong!

Well if I did buy an Allison Drag boat (2001) , I sure as hell wouldn't POUND it for 100's of hours up & down the lake , tearing up powerheads & lower units running it on the ragged edge, through HUGE water & expect it not break into little pieces !! Scott :D

Franki- Hmm. Just how well does that 5200 bond? I glued my whole motor on with it, hope it will come off if I need it to. Never thought about it, but I was thinking it seemed like urethane....the stuff they glue car windshields in with.

So many people are buying boats and getting loans for 10yrs or more, when it doesnt matter if its wood or not it is still going to be a piece of crap after 5yrs regardless!!





This hull just turned 11 yrs old. I can testify that the seats, floor and transom are solid.....knock on....wood. (no pun intended) It has been pounded pretty good and has been dipped twice. The problem I have with wood is keeping it attached to my damn trailer. The bunks sure dont seem to last long. Maybe I should try glassing them.:D

I don't know if I'd want to mount a motor with it though. You mean seal the bolts? That would be ok. :cool:

Are you using PT for your bunks? If you countersink stainless carriage bolts into them and use nyloc nuts, that's about as good as it can get. :cool:

5200 is dah ****!!
When I re-rigged my Sonic I had to pull off the old Gil Tube set back brackets.
I pulled all of the bolts out and the only thing holding them on was the 5200.
I set a floor jack under the brackets and lifted the damn boat (24' Sonic!!) off the trailer and they wouldn't break loose!
I Had to use another jack pushing between the transom and brackets while lifting with the floor jack to break them loose, and then the damn things pulled half the gel coat off with them!!
Nasty Stuff indeed!
On the bunk issue I always thought the pressue treated was the hot ticket until getting my Sonic trailer re-habbed.
The trailer builder said that they don't use p.t. because it expands and contracts so much that bolts are always coming loose.
They use plain pine.
I would suggest pine, with the cuprehnohl treatment and then the nylock fasteners like RR suggested.

SHO305, good idea, but I don't think that ply has water proof glue.
In reality (what I'm told) the only two differences between plain and marine ply is the glue and no voids in marine vs the plain.
Although I have bought the cheaper marine fir that had the football plugs in it, so by vids they must mean that it has the football plugs vs the "open" voids as some of the plian ply does.

I have always used clear cedar for my bunks, and had good luck, Stainless bolts countersunk, nylocks and BIG washers.

RT

If you have to remove anything that was glued on with 5200 just use a little heat like from a heat gun it will come right off.

For transoms we use cdx plywood, have for over 20 years. As long as any holes are sealed and no water gets to the wood it will last forever. Marine ply is better when the finished surface is important or high strength and low weight such as the above referenced okoume for race boats.

one of the main risks when using non marine ply is the chance of voids in inner plys that are impossible to see or seal.
In the kneel down boats we used to laminate two pcs of 3/4" A/C rated Exterior for 1 1/2" motor boads and also never had any problems.
Matter of fact I built several boats for testing purposes only and then destroyed them to prevent being copied and the motor boards never came apart!
Another major difference in marine ply vs standard is the number of plys. The more plys the stronger.
3/4" Exterior (I believe regardless of grade) is five ply, while marine is seven (if you ask for it).
I do have to agree though on a motor board due to the dynamics of the loading applied, you can get away with almost any plywood assuming adequate numer of ply's and total encapsulation (sp?).
One manufacturer in the Bass/Walleye mag even said they used standard plywood in their transoms since they were totally wrapped.
Not sure I'd agree with that??
Gary

What I meant was many of the boats that people are buying on these 10 yr loans are cheap boats to begin with..It doesnt matter if they are built with wood or composites they end up with stress cracks, interior trashed and so on..I know there are plenty of quality boats out there that will last for many years wood or no wood.. By the way thats a sweet looking Ally you got there:D

The internal voids inside a piece of plywood are completely insignificant to the performance of the product.

The bending forces are always concentrated on the outside skin of any material, the inside portion is basically just there for the ride. This fact allows us to use lightweight cores like foam or balsa to create some of the lightest and strongest panels possible.

Marine grade has more plys per inch making it slightly stronger but generally heavier than cheap CDX. When you factor in the weight, the real world performance difference ain’t much to talk about.

Whether or not you seal the voids is also not important…if water is actually present inside a piece of wood your f*&ked. Also, if water continually permeates the outside layer of glass or gel coat or paint and reaches the wood you’re f*&ked.

Marine grade ply will definitely last longer if it does get wet…most CDX is nothing more than sugar pine which has practically no ability to resist rot. Luckily most of us have the time and inclination to make sure our wood is completely sealed.

Here is my 100% CDX wood working project…:eek:

if you have a void in a inner ply of plywood, it not only weekens that ply but also both of the sandwiching layers to it.
If this ends up being a high stress or flexing area, it will crack.
As far as the outter skin providing all of the support that means we could use foam and bals cores for motor boards??
Again, I have to dissagree.
To this you would have to make the outter and inner skins thick enough to become a load bearing laminate which would more than negate any potential weight savings of using a core.
On a deck or hull skin, that's where the cores would shine.
Also anywhere where you could wrap it in glass using it as a mold combined with rigidity that the core would add to the skin.
On the other hand 3" of plywood in a motor board made up of 4 layers of 7 ply 3/4" ply sanwiched together and wrapped in glass is far superior in strength to "any" core in that application.
Ask any O/B or I/O race boat builder.

P.S. I like your CDX project, it looks great! What did you use for your filleting around and in your corners??