High density polyurethane plastic frames - ribs

[sdowney717]

I like this idea a lot. It solves the rotting cracking oak frames problem.
The worst part of my own hull rebuild was dealing with bent frames. The planks were not any problem. Infact I was able to reuse all the mahogany planking. Did use new bronze screws.

 

[Old deckhand]

Cool

 

[Scary]

How strong do you think the foam is

Laminated oak ribs are way stronger than foam . the ribs do more than keep the planks fair, they also distribute the load over many planks . I don't think I would go this route. It is just too easy to cold bend strips in place glued with epoxy.

 

[sdowney717]

It is extremely strong this plastic framing.
HDMW polyethylene. I can tell he likes the stuff.

 

[Old deckhand]

Thanks for videos.

 

[Lepke]

I am a former shipwright. Without going into how we did it in the old days, laminated oak strips, epoxied are probably the easiest for owners to do and have a solid hull. I would check with a couple good wood surveyors before using plastic. The plastic could make that part of the hull stiffer and cause other parts to work too much in a sea. Plastic could shatter, fasteners pull out and so on.

 

[Lady soft]

I am not an expert, but I believe that mixing materials like this, is no good, because wood is a live material, and plastic is not, so when the wood actually getting its strange,from being able to move with the element it is forced to work against, like waves. The plastic will not. So I am convinced, this will cause stress to the wood, exactly were the plastic is attached. If you look at the way Coronet built their boats. The wooden interior was never attached directly to the plastic hull. They used a frame.

 

[GoneFarrell]

I used to be an expert, 30+ years mechanical engineer, designed all sorts of bending/cantilevered things.

IMHO, UHMW is way less stiff vs. oak/oak laminate. That means the boat will likely flex/work more for a given load.

Data: UHMW, E (modulus of elasticity) 110,000 psi
Oak, E, about 10x that above.

And yeah, I've made all kinds of stuff out of both. Stay with oak. UHMW is amazing stuff, but it is not structural grade material, not for my boat!

 

[Simi 60]

I am not an expert, but I believe that mixing materials like this, is no good, because wood is a live material, and plastic is not, so when the wood actually getting its strange,from being able to move with the element it is forced to work against, like waves. The plastic will not. So I am convinced, this will cause stress to the wood, exactly were the plastic is attached. If you look at the way Coronet built their boats. The wooden interior was never attached directly to the plastic hull. They used a frame.

Can't say I agree with you there.
How do you explain strip planked boats where the core is timber, usually western red cedar or balsa covered in a fiber reinforced plastic skin?

 

[GoneFarrell]

Simi,
I can explain it with a formula that has served me and my customers for over 30 years: I=B*H^3/12.

The FRP skin you reference is on the outer fibers of the "beam" and that is a cubic with distance from the neutral axis effect. So the FRP far from the neutral axis does a great job of adding stiffness. As does the outer strip planking, which is stiffer than UHMW, it is efficiently used because it is far from the neutral axis.

With a simple UHMW beam, there is no stiff material far from the neutral axis, hence it cannot be as stiff and strong.

 

[Right rudder]

Shipwright Sauzed used this on a working boat. A fishing boat to be exact, one that he did the same repair to the starboard side two years prior to the YouTube take listed above.

I have known a few guys that make their living by fishing and I find that like any self employed working man that they (most of them anyway) know the value of a dollar, or as one told me " don't say dollar....say work credit". He went on to explain that every time he contemplates divesting of some of his "work credits" it goes through his mind just how hard he works to accumulate it in the first place and it causes him to scrutinize just a little closer the true cost of outlays to his business.

The Owner of the workboat in question is apparently satisfied with the pervious repairs to the point of doing the same thing to the port side.

A rib with a little flex
won't draw water
won't conduct electricity
won't grow mildew
won't rot
What's not to like?

Let's all check back in here in a hundred years and see what's going on.

 

[uralite]

Tips from a shipwright Louis is seriously right on guy.

 

[Slowmo]

Jensen Motorboat in Seattle used composite (more like Trex), not foam, to sister a couple ribs on our old 40' wooden boat. The composit becomes easy to form when heated and then sets to the curve of the hull. They also hold fastenings well. Our repair is five years old with no issues at all. It is a good way to do repairs but like everythign I'm sure it has limitations.

 

[bridaus]

Not all plastics are the same, for that matter neither are most woods. That's what engineers and experienced boat builders get paid for...

At the same time, just because something works one time, doesn't mean it will work the second or any other.

The key here is: this has either worked very well in the past multiple times (experience), OR the engineering has been done. Pick one.

Oh yeah, one third factor: Luck. Not to be counted upon, but some people get away with it...

 

[mgardner]

As a life long wooden boat mag reader, dreamer, researcher yet fiberglass boat owner I am both shocked and intrigued.