Metal plate instead of plywood core for transom? Not the bandaid thing..

[ondarvr]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Skip the metal, acrylic, Kevlar and carbon, stick with stuff that works well with fiberglass in a marine application.

Use any type of core you wish (typical products, I would use 4-8lb foam) in most of the transom and then use solid glass where the transom clamps are located.

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Skip the metal, acrylic, Kevlar and carbon, stick with stuff that works well with fiberglass in a marine application.

Use any type of core you wish (typical products, I would use 4-8lb foam) in most of the transom and then use solid glass where the transom clamps are located.

I've seen a few vids of guys using the 1708 mat+weave...

I'm for sure going with Coosa.. I've seen it's best to use epoxy resin for better elongation before break results than vinyl or poly resins.

Though you say the carbon/aramid fiberglass shouldn't be used for marine applications?

 

[ondarvr]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

What you need to determine is not what the "best" products are, but what makes sense for this repair. If you want the absolute best, then throw this boat away and have one custom built, the cost will be crazy though.

Any resin will work to rebuild it and hold up for decades, although some are stronger than others, they all work. Carbon and Kevlar have their place in some marine applications, but to rebuild an old transom to hold a 115 HP OB it's not needed. Now if this was a high performance, well engineered, mega HP, scary fast, with an unlimited budget project, then fine, go with those products.

The advantage of using the high dollar products is to save weight, the amount of weight you save in doing a typical transom repair may be about the same as a six pack of beer (or less). Now those six extra beers on the boat may be very important to some people, but the weight savings doesn’t justify the cost and hassle of using them. Some people like the thought of having those products in their boat and that’s fine, just don’t expect to notice a difference in anything but your pocketbook.

Coosa and VE resin (or even normal polyester) is fine and will never fail, that is if you do it correctly, which has more to do with attention to detail than the products used.

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

What you need to determine is not what the "best" products are, but what makes sense for this repair. If you want the absolute best, then throw this boat away and have one custom built, the cost will be crazy though.
QUOTE]

Bah, someone is opinionated! hehe
I appreciate the feedback though. And yes, I actually have thought about just using my current cap and hull as a mold for a carbon/aramid build.

Though I understand 1708 and other normal fiberglasses are just fine for a repair like this, it doesn't hurt for longevity.
I would guess Kevlar and carbon fibers last 10-20x longer than glass fibers. I am indeed after a weight savings, but I know what I'm riding in now, will still be the same after I do a repair with those products. Though I will have a bit of extra peace of mind because I just didn't use the "minimal components."

I really do like the boat design itself, and hey, since it's old enough as is, I might as well make it something special in case I ever decide to resell it. And the components will make the difference between "restored boat" and "restored boat using Kevlar and carbon fiber".

You mention though that VE or poly resins will never fail... I've read elsewhere they're weaker when it comes to sheer force? (iirc)
I mean, ultimately, if the motor gets caught up or hits a log etc, it's going to be a huge blunt force on the motor which in itself is a lever, so epoxy resin would be best? Because it would break last of the 3 types?

I was considering getting some of the pure aramid, pure carbon, aramid/carbon mix, and then the 1708 and glassing a few panels of certain size to stress until break. Then calculate the total forces that could be withstood on a panel the size of the transom.

I know most would think what I'm talking about is overkill, but it would be more than just a cosmetic change, it would be entirely functional for both strength (beyond regular glass) and I have no doubt they last longer than regular fiberglass. The real question becomes, how many years until the original fiberglass in the boat is degraded to the point where the stress would fracture the boat in the rear end because the stress would just bypass the aramid/carbon glassing in the transom and stern area to the weaker glass up front of that. (I'm sure it would happen no matter what I use, but ya, that's physics)

 

[ondarvr]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Now that you have sort of changed the parameters of the project from just a rebuild to possible modifications of the entire boat for personal and aesthetic reasons the products you choose can be whatever you like for whatever reason you choose. Will it be a better fishing boat….for the money and time spent not really…..will you enjoy it more…..possibly, and that’s what really matters.

What you gain with the pricier products is the same strength with less weight, the glass and poly laminate can be made to be about as strong, just heavier, which in a rebuild doesn't amount to much. The poly and/or VE and glass laminate can typically take more abuse too, carbon holds up well right until the point it fails, then it's normally a catastrophic failure. Which means instead of the transom just cracking, it falls off. Look at the history of America's cup type sailboats, they are very light and strong, but snap in half and sink in the blink of an eye, this is typical of a CF laminate.
How did the current construction fail, did the laminate fail, or did the wood rot? If the boat held up for 30 plus years being made with the lowest cost products and methods possible then a slight upgrade, possibly just in your care and attention to detail should make the rebuild last even longer using the same materials.

If you want to take advantage of everything epoxy, carbon and Kevlar have to offer then hire a composites marine engineer to design the laminate schedule, otherwise you are just guessing at how much of what fabric you need and where to put it. This is where the DIY crowd tends to fail when going to epoxy and other fibers, they end up rebuilding the hull back to the same thickness and weight of the original build, but with very expensive materials. So they end up spending far more money with greater hassle at the same weight. It is stronger though, but since the laminate doesn’t typically tend to fail in the original build the extra strength isn’t needed.

 

[jones01m]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Something else to consider, unless you vacuum bag your work it will be difficult to see (through the black fibers) if all the air bubbles are out and can compromise your laminate without you knowing it. I am not an expert, but this is what I have found.

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Thanks for the heads up Jones

On another note Ondarvr, I have found similar circumstances for the use of the Kevlar/aramid and CF mix instead of what you describe, as is what carbon based things do, break before bend. Concerning Goop Coat-it, speaking with one of their chemists, he admitted they've never conducted a test such as using it for a bonding agent ie: resin for glassing, and the resulting longevity under such high stress.(it's technically an epoxy "sealer" though it can be used with glassing) This is where the aramid excels though, and these mixed with even a single layer of glass I'm sure has a fairly decent ratio compared to plain glass.

I guess one thing that might be misleading my train of thought, is I'm planning on getting a fairly decent setback in the form of a jackplate, or at least, leaning towards that resolution. So as it is a 19" transom with a ~300 lb motor, already set back 6" to increase general weight to 1.5x, and in having the base of 450 lbs, with a top speed of a about 45 mph avg (with PTT 6" setback), I'm sure the actual force will be indeed a good amount. I also came to find out recently, the shaft is a 22" shaft on a 19" transom. So I'm sure the angle of force and resulting pressure is beyond what was calculated for this boat. Of course this is all before shock values!

On your other note, I have no idea what the transom core looks like, I'm looking to open that here within the next week or two. There is some inconsistencies in the stories from the PO, who I still talk to today on "good" terms. My concern started to grow as I recently discovered about fiberglass boats being produced with wooden objects in the back where they tend to get wet.. :| (brand new to boats with more than oars btw lol)
I discovered a screw coming through the hull at the left front corner of the square deck. It almost feels like it was hollowed out and new glass over the back because there is a ridge on the top side under the carpet. The PO said when I mentioned previous restorations that maybe the guy HE got it from did something, but never noticed a screw through the hull. But then he sent me a pic of the boat with a different hull color when he bought it.

Either way, I'm quite happy with the boat and the motor, so I'm doing what I can. The transom area does sound differently than a 'thud' and it does sound rather similar to the foam filled area in another section next to it... heh luckily there's no visible damage as of yet, but there is several bends on the top transom cover so water/etc can makes it's way into the top area.

 

[ondarvr]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

This keeps changing, now a jackplate.

There is nothing wrong with these ideas, they just cost money, money that may be spent in a more useful way someplace else, like a different motor.

You don't want to use Coat-It, it is not designed for that type of use, use a product that is formulated as a laminating epoxy if that's what you plan to use, there are plenty of them out there. There is a reason why very few boats use Carbon or Kevlar, it doesn't help much, it's very good for bragging rights and that Bling factor though.

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Can't it change? I'm here to weigh the odds and different ideas.
And if I was concerned about money, or buying a new motor, I would go that direction.

I have to disagree though, I see a lot of carbon and Kevlar used for whitewater boats. There's just no doubt about it that carbon and Kevlar together make glass look pretty sad. If you're unfamiliar with this stuff though, np. I know not everyone is an expert in everything..

 

[ondarvr]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

You have figured me me out, I know nothing about composites, nor do I know how boats are built and why. I'm just somebody that Googles stuff for my opinions

It comes down to the fact that you can rebuild it any way you please and if you won't be happy without those products, then use them. You asked for opinions and information on what works, you were given that, you can use it or not.

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

I don't doubt you're knowledgeable, but saying they're not appropriate for boat building is a fallacy.

Here's one I found quite interesting on comparisons of the materials.
Comparing the characteristics of Glass, Kevlar (Aramid) and Carbon Fiber

But yes, I've yet to see a reason not to use it, short of cost.

 

[pyrotek]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Why not just make the entire transom out of solid glass? I thought the main reason they put wood in between is for cost. If your not worried about cost, wouldn't making it entirely out of fiberglass be the best?

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

I have thought about that Pyrotek, but when I say I'm not worried about cost, I'm not trying to spend 10,000$ on the transom..
I find 1-3,000$ acceptable, but not 10..

Though I would bet long term, a solid core encased in fiber, would last longer as fibrous glass isn't that strong. It's also about spreading the force of the engine pulling on the transom, across greater area to alleviate the stress and bring the suspended weight down to a manageable amount.
If you built a glass transom and put the engine on, it would break fibers immediately around the bolts since they are not able to withstand such force. Adding the core, puts the pressure on the solid mass. And then the solid mass translates that pressure to the surrounding fiber strands.

You can observe this mathematically if you take say, 400 lbs. Now rest that 400 lbs on a 2x4 extended between 2 benches. (this is just an example of how pressure works)
Each side of the 2x4, if it's in the exact center of the benches, and the weight in the exact center of the 2x4, will be supporting 200 lbs. Now add a 2x4 next to it, level, and each under one side of the weight. Now it's 400 lbs divided by 4 = 100 lbs exerted on each "leg" of the 2x4. This is the way fibers work when encased in resin. They share the load. But if the load is not properly SPREAD, it creates an area of compression, and eventually leads to premature failure.
Of course if you move that 400 lb weight off center, of the 2x4, one half will be supporting >200 lbs.

These physics can be easily observed in architectural calculations for building construction.

 

[ondarvr]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

You bring up charts and graphs that list the specific properties of each product, not how they work in a laminate in combination with each other, this is where the composites engineer can design a laminate that will work. Since carbon has very little elongation compared to glass, when you combine the two the carbon carries the entire load until it breaks, when it breaks then the glass takes the load, but it wasn't designed to take the entire load so it fails too. Now you can increase the amount of glass or carbon to take the entire load by themselves, but then the other fiber isn't needed. Unless you understand how these fibers work and design the laminate to take advantage of the properties of each fiber it's sort of a waste of time and money. It sure sounds sexy though.

Since you're an IT guy we can put it this way. You have a cheap 15 year old ACER desk top computer and you want to upgrade it, where do you start and how much money should you really put into it.

 

[Watermann]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Ca mon Kung buddy, enough talk, just take that transom out or at least peel back some stuff to take a look at it! Next post better be pics of that thing tore down. Trust me it's fun as all get out actually working on boats.

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

I'm aware of the differences ondarvr, but the point is you can gain strength and longevity from combining the materials, compared to purely using glass. You hit it right on the head with 'the glass isn't designed to take that load.'
The failure you're talking about, you only mention carbon, which I'm not going to do. It will be a mix of carbon+aramid+glass(aramid+carbon weave specifically, layered with glass), and these three together in a solid matrix (resin) will complement each others strengths and alleviate the weaknesses of each. As you've stated, yes, purely glass is just fine, but it doesn't match the flexibility, rigidity, or longevity of the 3 components combined, let alone weight savings.

Watermann, I'll get those pics up, should have the motor off by next week and dig in, gotta build myself a stand first
The resin I'm leaning towards requires 77 degree temps, so I'm going to try to do it before winter, but depending upon what it looks like under the cap, I might have to reserve winter to the cleaning out stage.

Thanks for the responses, it's always best to challenge a thought to discover more. If this wasn't the case, progress would never be made in any sector of life. :ranger:

 

[ondarvr]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Sounds like you have it all figured out.

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Slowly but surely, a bit tedious, hopefully there's no surprises under the cap! lol

 

[Woodonglass]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

I have thought about that Pyrotek, but when I say I'm not worried about cost, I'm not trying to spend 10,000$ on the transom..
I find 1-3,000$ acceptable, but not 10..

Are you really being serious with the above statement. You find spending 1-3 thousand dollars on a transom replacement acceptable for a boat? Can I ask Why? It's a proven fact that a wood core transom, properly encased in resin and glass and then properly cared for and maintained will last 40+ years. My boat is still on the original transom and its 52 yrs old. If I had to replace it, It would be the same as it is and I would expect another 50 years out of it. The costs would be approx $300 dollars. The only reason I can see to use the NO ROT composites is when the boat will not be cared for and maintained.

I just don't get it. But as everybody on the forum knows,

I'm just an

 

[kungpaoshizi]

Re: Metal plate instead of plywood core for transom? Not the bandaid thing..

Because if wood and glass lasts 40 years when properly maintained, there's no reason replacing the wood (which is relatively weak compared to other material) and reinforcing the glass (which is stronger than purely glass) wouldn't yield a better range of service and allow for higher stress values before failure.

This is worth the cost to me.

There's a boat manufacturer that gives their boats a lifetime warranty structurally. Wouldn't this be worth the cost?

I know there's a right way and a wrong way to do things, but that doesn't exclude the terminology of 'better' and 'best' practices. And I don't doubt that many boats, including old styles of building them (wood may have been best before the advent of finer technology) are in fact "older" practices.

Saving money is one thing, but putting forth some extra for "better" materials isn't a dumb decision. /shrug Is it necessary? That's the ultimate question and where the divide is created between engineers.

I know for a fact, if I ever decide to sell the boat, my improvements will make it a better sale.

Had to find the quote (I love quotes!), but I believe you can see it displayed here. I know I've seen it on other sites where people debate the inclusion of materials that weren't available 30 years ago.

The advancement of all sciences, especially where there has been such a radical change, have been attended with persecution.
-Daniel Palmer

All in all, I see the validity of purely using glass, but consider the possibility of an engineer that grew up mid-century. You might describe a piece of electronics, and he agrees with every aspect of the device. But then you hit a crossroad. And his attention becomes irritation. You can't imagine why he's debating the subject, but after all, he has seen the evolution of technology. But he still prefers analog electrical devices and a big round disk. This would be the advent of the cd. And he prefers vinyl records.