How many layers of fiberglass?

[ondarvr]

I'll add that I frequently used my cats in shallow rocky rivers, I carried duck tape in case I hit some thing hard and created a leak, but never really needed it. One of my Kayaks was run over by a car, it crushed one end and a couple of other places. Because fiberglass tends to spring back into shape, the duck tape worked fine as a temporary fix, so the day wasn't ruined.

 

[TANSL]

Thank you @ondarvr, for so many explanations. Now we know who you think you are and we can evaluate your knowledge regarding ship design, boats structural design, and the creation of shipbuilding companies.

 

[fallguy]

Wow. I cannot imagine a 10 oz cloth and csm being stiff enough without other structural elements like coamings and tabbing. I’m used to building so the boat cannot fail in 39F water, so maybe I have a bias to strength.

Not trying to be disagreeable with old wisdom. OP said skin was the only structure, so that gets pretty flimsy is all, knowing zero else. Probably some version of both is needed for local reinforcing for beams or other features.

Polemics are likely on this thread and NOT my wish at all.

 

[ondarvr]

Thank you @ondarvr, for so many explanations. Now we know who you think you are and we can evaluate your knowledge regarding ship design, boats structural design, and the creation of shipbuilding companies.

I'm not seeing "ship design" being discussed anywhere. We are talking RC boat stuff here. I have first hand knowledge of exactly how this stuff is, and has been built. Please explain in detail your first hand knowledge and the products you've built.

 

[ondarvr]

Wow. I cannot imagine a 10 oz cloth and csm being stiff enough without other structural elements like coamings and tabbing. I’m used to building so the boat cannot fail in 39F water, so maybe I have a bias to strength.

Not trying to be disagreeable with old wisdom. OP said skin was the only structure, so that gets pretty flimsy is all, knowing zero else. Probably some version of both is needed for local reinforcing for beams or other features.

Polemics are likely on this thread and NOT my wish at all.

As I said, panel shape comes into play. Many things could be built thin and survive just fine, but may have a core added or maybe additional glass just to stiffen them. People perceive flex as a lack of strength, but it depends on how the panel is loaded.

I have customers that use spray foam on the backside of flat surfaces to reduce flex because people will be touching those surfaces. There is no laminate on the backside because it doesn't need it. The foam is just a quick and easy way to reduce flex in an affordable and light weight method.

I worked with Jeld-Wen in their door building plant. One of the biggest hurdles was making the door feel like wood. A high end composite door was stronger, better insulated, had great FR properties, was lower in cost and looked great, but the feel was different when you closed it or handled it. This resulted in extensive testing to make it feel and sound the same as wood, and this aspect added nothing to it structurally.

Cars use very thin metal, a flat panel of thin metal flexes a great deal. Add some contour lines or sweeping compound curves and the flex is significantly reduced and/or eliminated. A kayak with that thin laminate doesn't flex due to the shape. And they aren't designed for running into a shipping container at night in bad seas.

Your molds would probably have been better if built with CSM, but you used epoxy, so you would have needed to source the correct CSM. Plus they were temporary and probably for one-off parts, so it makes little difference.

 

[TANSL]

I'm not seeing "ship design" being discussed anywhere. We are talking RC boat stuff here. I have first hand knowledge of exactly how this stuff is, and has been built. Please explain in detail your first hand knowledge and the products you've built.

Perhaps you can't understand, but to advise on or accept that a hull has the correct lamination, it's very helpful to have some knowledge of ship design, or boat design if you prefer. It's necessary to be able to analyze the boat's shape and structure and its intended use and, based on that analysis, perform certain calculations that provide a degree of assurance that the boat will withstand all the situations it might encounter. I assume, perhaps I'm wrong, that you're unaware of all these calculations and studies (I'll correct myself, no problem, if I'm wrong).

Perhaps I have a certain professional bias, but I don't like to advise people haphazardly. I can give wrong advice, of course, but I can correct myself if I see that I've made a mistake.. This is a very important aspect: having the humility to correct oneself and having the necessary knowledge to offer a new solution.

You will have noticed that I haven't said anything about whether the lamination proposed by the OP was sufficient or not (the first thing I said was that it wasn't prudent to answer that question). Therefore, I don't need to support my advice with well-founded reasons, as I believe you should.

Two similar boats are never identical, and copying scantlings from one boat to another is not advisable. What you did on some other boat is simply not applicable to a boat that you neither know nor have bothered to find out about.

With all due respect, all the experiences you have shared, while admirable, do not qualify you as a boat designer or builder. You haven't claimed to be a boat designer or builder, but you have tried to convince us that your experience allowed you to know how to build the OP's boat, a boat you still haven't seen.

One of the problems with the internet is that anyone can present themselves as something they are not, but they can't expect others to believe it.
Best regards.

 

[ondarvr]

Perhaps you can't understand, but to advise on or accept that a hull has the correct lamination, it's very helpful to have some knowledge of ship design, or boat design if you prefer. It's necessary to be able to analyze the boat's shape and stgructure and its intended use and, based on that analysis, perform certain calculations that provide a degree of assurance that the boat will withstand all the situations it might encounter. I assume, perhaps I'm wrong, that you're unaware of all these calculations and studies (I'll correct myself, no problem, if I'm wrong).

Perhaps I have a certain professional bias, but I don't like to advise people haphazardly. I can give wrong advice, of course, but I can correct myself if I see that I've made a mistake.. This is a very important aspect: having the humility to correct oneself and having the necessary knowledge to offer a new solution.

You will have noticed that I haven't said anything about whether the lamination proposed by the OP was sufficient or not (the first thing I said was that it wasn't prudent to answer that question). Therefore, I don't need to support my advice with well-founded reasons, as I believe you should.

Two similar boats are never identical, and copying scantlings from one boat to another is not advisable. What you did on some other boat is simply not applicable to a boat that you neither know nor have bothered to find out about.

With all due respect, all the experiences you have shared, while admirable, do not qualify you as a boat designer or builder. You haven't claimed to be a boat designer or builder, but you have tried to convince us that your experience allowed you to know how to build the OP's boat, a boat you still haven't seen.

One of the problems with the internet is that anyone can present themselves as something they are not, but they can't expect others to believe it.
Best regards.

Maybe you never noticed, but I've said before, I don't get involved in engineering and design, that isn't the part of the market I live in. But I do work extensively with people very qualified in those areas, that started back in the 1970s, so I know how important that is.

What you seem to miss, and it may be intentionally in this thread, is that I have personally done this work, and it was prior to when any actual engineering was done on small boats like these. And then continued on doing this work when well educated experts in these fields got involved. That includes aerospace, where stuff actually goes to the space station.

You seem to ignore that this is a very small RC boat, he says robotics, same thing. And that I have slightly larger boats with similar laminates that hold people and outboards

The hulls on my 8' (7'4" at the waterline) are 19" tall and 12" wide at widest point near the top, narrower as you go down. You can get a sail kit, which I have for the 10' model, and both are set up for an outboard motor. So the question he asked has already been answered decades ago and proven to be successful, a thin laminate will work on such a small catamaran.

I've also worked with the UAV market on military projects. They needed light, low cost, and easy to build models, with rapid prototyping. I did no engineering, but did work with the engineers on the products and methods of construction that would meet their requirements. They were amazingly light and strong, plus low in cost and easy to build. And I'm in the room where these discussions take place.

This is significantly different than a 150' work boat or yacht, and I also work a great deal with that market. So yes, I understand the difference.

You still haven't presented anything in an attempt to show you have experience in any aspect of this, or have any first hand knowledge of producing anything similar.

I do think you are very qualified in the field you work in, and are very protective of that space.

 

[TANSL]

@ondarvr ,
Dear friend, with all due respect, I must tell you that nothing you say proves you are qualified to engineer the structure of a boat, be it large, small, or a toy.

I'm not going to recount my childhood to prove I can design boats. I will say that, just as you are surrounded by great boat engineers and designers, I have always been surrounded by doctors (my ex-wife, two of my brothers-in-law, one of my brothers, several of my best friends), and you won't hear me claim to know how to cure the sick. Knowledge and experience are not transmitted by osmosis, my friend, from one organism to another. You have to work hard to acquire them.

I repeat, I have never tried to make people believe I am something I am not, and therefore I don't have to prove anything to anyone, least of all to you, who wouldn't understand. You can think whatever you want about me, but your opinion will depend on what my opinions or advice reflect about me. I will never flaunt a degree so that you or anyone else will respect me a little more. When someone has to detail their degrees, their experience, etc., it's because they aren't convincing people and they have to add things to their resume. And those things aren't always entirely true.

Yes, I am very protective of what has taken me so many years and so much effort. I can't stand professional encroachment and I fight it whenever I think I should.
Cheers.

PS: Let me say that, generally speaking, the scantlings of a monohull, of a kayak, cannot be correct for the entire hull of a catamaran (big, samall or toy one, or a RC one). I would ask you, but do what you want, not to insist on this subject.

 

[ondarvr]

@ondarvr ,
Dear friend, with all due respect, I must tell you that nothing you say proves you are qualified to engineer the structure of a boat, be it large, small, or a toy.

I'm not going to recount my childhood to prove I can design boats. I will say that, just as you are surrounded by great boat engineers and designers, I have always been surrounded by doctors (my ex-wife, two of my brothers-in-law, one of my brothers, several of my best friends), and you won't hear me claim to know how to cure the sick. Knowledge and experience are not transmitted by osmosis, my friend, from one organism to another. You have to work hard to acquire them.

I repeat, I have never tried to make people believe I am something I am not, and therefore I don't have to prove anything to anyone, least of all to you, who wouldn't understand. You can think whatever you want about me, but your opinion will depend on what my opinions or advice reflect about me. I will never flaunt a degree so that you or anyone else will respect me a little more. When someone has to detail their degrees, their experience, etc., it's because they aren't convincing people and they have to add things to their resume. And those things aren't always entirely true.

Yes, I am very protective of what has taken me so many years and so much effort. I can't stand professional encroachment and I fight it whenever I think I should.
Cheers.

PS: Let me say that, generally speaking, the scantlings of a monohull, of a kayak, cannot be correct for the entire hull of a catamaran (big, samall or toy one, or a RC one). I would ask you, but do what you want, not to insist on this subject.

Again, no first hand knowledge of building or being involved in any kind of project like this. And when I talk about my two cats, you seem to exclude or forget them, you focus on the kayaks.

And it appears the OP hasn't been back since posting his question. So lucky for him he won't see the terrible information I gave him.

 

[TANSL]

And it appears the OP hasn't been back since posting his question. So lucky for him he won't see the terrible information I gave

I completely agree with you.

 

[Boat Design Net Moderator]

Some humor is great, but let's not get too snarky please as it can sometimes go off the rails and ruin the thread.

The second post did begin: "With that limited information, and assuming this doesn't need to survive in harsh conditions" so when I read it, I did not get the impression that specific engineering advice was being given for this project, but rather an idea was being given as "food for thought" only "With that limited information, and assuming this doesn't need to survive in harsh conditions"...

(Years ago we did add a statement at the bottom of every thread to be clear: "Forum posts represent the experience, opinion, and view of individual users. ... When making any potentially dangerous or financial decision, always employ and consult appropriate professionals. Your circumstances or experience may be different. ")

 

[Ad Hoc]

.... so when I read it, I did not get the impression that specific engineering advice was being given for this project, but rather an idea was being given as "food for thought" only ...

Indeed...there is no other way to take than as noted.
Except if one is wishing to belittle someone for no reason.

 

[TANSL]

(Years ago we did add a statement at the bottom of every thread to be clear: "Forum posts represent the experience, opinion, and view of individual users. ... When making any potentially dangerous or financial decision, always employ and consult appropriate professionals. Your circumstances or experience may be different. ")

I think it's very important to remember this from time to time.

On the other hand, saying "With that limited information, and assuming this doesn't need to survive in harsh conditions, one layer of 1708 would be more than sufficient" , someone, in my opinion, is giving very unfortunate and reckless advice.

But, to refute my comment and discreetly scold me, Boat Design Moderator, in post #22, wrote : "The second post did begin: With that limited information, and assuming this doesn't need to survive in harsh conditions" so when I read it, I did not get the impression that specific engineering advice was being given for this project.... "
(Why reproduce only half of the sentence, taking it out of context? That's distorting the truth, imo)

 

[Ad Hoc]

...On the other hand, saying "With that limited information, and assuming this doesn't need to survive in harsh conditions, one layer of 1708 would be more than sufficient" , someone, in my opinion, is giving very unfortunate and reckless advice.....

So, easy to clear up then.
If you think this is in error, please state so exactly and clearly where and what it should be.
Otherwise, why comment ?

 

[TANSL]

So, easy to clear up then.
If you think this is in error, please state so exactly and clearly where and what it should be.
Otherwise, why comment ?

Dear @Ad Hoc, you're always twisting language to make it seem like something it's not. I never said 1708 was a mistake, nor did I ever mention the type of fabric or its weight. What I am saying is that it seems unprofessional, inexperienced, and perhaps even dishonest to give that advice without knowing the boat or what the OP wants to do with it. If you like, go back and reread my posts, and if what I'm saying now isn't true, then tell the whole world from this platform or any other you choose.

Thank you, as always, for your invaluable contributions to this forum.
Given your attitude, I will refrain from replying to you further in this thread. Our conversations, you and I, are pointless, and I'm sure they're already boring everyone.