Rudder Failures

[smackdaddy]

Originally Posted by minaret

Perhaps because he's not being paid large sums of money for his opinion, unlike the fellows who made that "study", you might consider he is being more honest?

Can you show me how you know these fellows were paid for this study - and what that amount was? That would certainly change my opinion of it.

[minaret]

Originally Posted by smackdaddy

This is your documentation?

What is the typical tab layup made of exactly? And why are these boat-builders in these reports saying the opposite (see image)?

You can find "documentation" on the internet to support anything. I don't value that much. For a guy who is willing to spend large quantities of time posting links to "documentation" which supports your ideas, you sure don't seem very willing to step away from your computer and do some research of your own. It's very simple and can be eye opening, all it takes is a desire to find actual answers instead of trying to support your poor argument at any cost. Shall I do it for you and post pics? I certainly have before...

[smackdaddy]

Originally Posted by minaret

Shall I do it for you and post pics? I certainly have before...

Sure - that would be helpful.

[robert sailor]

Any company flogging anything can have favorable reports on their product from so called experts, it simply is a normal part of business these days. Don't always buy into what you read or pick up on the net, remain a skeptic. Australia wants to mine more coal and has many studies showing how it will even improve the well being of impoverished nations. Russia says they have never sent any troops into the Ukraine and ISIS says if you become their next suicide bomber you'll get 72 virgins and you guys pull a study off the net showing "Plexus" is stronger than Superman AND Spiderman combined.

[smackdaddy]

Originally Posted by robert sailor

Any company flogging anything can have favorable reports on their product from so called experts, it simply is a normal part of business these days. Don't always buy into what you read or pick up on the net, remain a skeptic.

...you guys pull a study off the net showing "Plexus" is stronger than Superman AND Spiderman combined.

Oh I'm with you all the way. I'm definitely a skeptic...but very much an equal opportunity skeptic.

The problem is, so far I haven't seen much on this particular part of the internet that credibly counters what I've seen on other parts of the internet.

So what do we have from the experts here? I'm eager to see it.

[robert sailor]

Smack these guys are trying to educate you a little so you come out in better shape the next time you get boat work done. Common sense ain't very common as the great American humorist Will Rogers once said and studies promoting products are as old as the hills. The tobacco lobby and Hollywood had a ton of Americans convinced that tobacco would not hurt you and it might even be good for you and there were piles of studies from Doctors, yup friggin Doctors supporting all their theories.
Do the little experiment that the boys suggested, get some Plexux and lay a thin coat on wax paper and see how flexible it really is..you don't have to do that with fiberglass cause you already know they make bows out it(as in bows and arrows)

[transmitterdan]

As it happens I am an engineer and use composites both fiberglass and wood laminates for constructing lots of things. I don't build yachts but I have worked to rebuild one large catamaran with numerous large holes in the pontoons.

My opinions are not clouded by concerns about the cost. I don't know what motivates the proponents of adhesives but I suspect their need to save money without appearing to be giving up any structural ground is one possibility. Adhesives have their uses and few things can replace them in some applications but tabbing structural bulkheads and stringers isn't one of them in my opinion.

[smackdaddy]

Originally Posted by robert sailor

Smack these guys are trying to educate you a little...

Cool. That's exactly what I'm asking for. Who here has done (or has links to) actual studies like these to show, empirically and objectively, that glass tabbing is categorically better than adhesives like Plexus?

[robert sailor]

I'm not sure you could find studies that were not filled with opinions but use your common sense. If the better boat builders all use glass tabbed bulkheads and the cheap boats all use glued liners and glued bulkheads then your skeptic balloon should be flying. On the other hand if some really well respected builders of offshore rated boats are using Plexus glued bulkheads then maybe we should all have another look and please don't repost the new/old C&C (Tartan) 115 story as these were never designed for offshore use. Look into Polux's lists of top racing boats and top cruisers and see what they are doing, remember, not the cheap seats but the top of the line boats.

[Polux]

Originally Posted by minaret

Perhaps because he's not being paid large sums of money for his opinion, unlike the fellows who made that "study", you might consider he is being more honest?

Yes of course. Here you have another cheap boat that use bonding agents to structural work:

https://www.youtube.com/watch?v=9XSTmyl2tIM

"The hull and deck of every Shipman boat are chemically bonded, and the hull and the upper flanges of the bulkheads are chemically bonded to the deck using Spabond 345, an epoxy-based adhesive. Once this operation is cured, the final stiffness of the boat is achieved.
All main bulkheads are structural and built in female molds using the same technology as the hull and deck: carbon fibers, epoxy resin and a high-density core, vacuum bagged and oven-cured. The structure is made in female molds, laminated using Sprint and, after oven-cure, bonded to the hull with Spabond 345 material."

Build process - Shipman

[avb3]

Originally Posted by Polux

Yes of course. Here you have another cheap boat that use bonding agents to structural work:

"The hull and deck of every Shipman boat are chemically bonded, and the hull and the upper flanges of the bulkheads are chemically bonded to the deck using Spabond 345, an epoxy-based adhesive. Once this operation is cured, the final stiffness of the boat is achieved.
All main bulkheads are structural and built in female molds using the same technology as the hull and deck: carbon fibers, epoxy resin and a high-density core, vacuum bagged and oven-cured. The structure is made in female molds, laminated using Sprint and, after oven-cure, bonded to the hull with Spabond 345 material."

Build process - Shipman

So the bulkheads are not plywood. No mention of a liner either.

[Polux]

Originally Posted by avb3

So the bulkheads are not plywood. No mention of a liner either.

I don't understand your point. I have said: "we have seen already that when well made with proper materials and the proper way a bond can have advantages in what regards strength to a lamination. Bonded structural parts are used everywhere from buildings to airplanes to cars and boats. F1 cars are bonded ... Bonding if well done can be better than lamination stop talking about it as if it is always an inferior method regarding lamination."

Minaret had said: "Bonding with plexus is never as good as a laminate-never. Its strictly a money saver for the builder"

I think that the use, by a very high brand (with boats that use extensively carbon and cost millions) of bonding agents to bond structural parts on their boats, is a clear evidence that for some structural uses bonding is superior to lamination, or do you think they use bonding instead of lamination for budget reasons and not because it performs better on the boat structure?

[Polux]

On my blog I made a post about what is the best rudder option regarding cruising boats, quoting a opinion of a main NA that thinks like meWell OK, I think like him.

For the ones that are still interested on the original subject, have a look.

[neilpride]

I think no one here disagree about single or doublé spade rudders, i dont see the point, there is good spade rudders and bad spade rudders, good hung skeg rudders and bad hung skeg rudders, after all is a compromise, cons and pros!! i like the idea of shallow doublé spade rudders, maybe in a short future we start to see better rudders ...

[smackdaddy]

Originally Posted by robert sailor

I'm not sure you could find studies that were not filled with opinions but use your common sense. If the better boat builders all use glass tabbed bulkheads and the cheap boats all use glued liners and glued bulkheads then your skeptic balloon should be flying. On the other hand if some really well respected builders of offshore rated boats are using Plexus glued bulkheads then maybe we should all have another look and please don't repost the new/old C&C (Tartan) 115 story as these were never designed for offshore use. Look into Polux's lists of top racing boats and top cruisers and see what they are doing, remember, not the cheap seats but the top of the line boats.

Dude, Island Packet is still building freakin' full-keel sailboats. Just like on the internet, you can find virtually anything you want out there. Demand drives what's delivered. It doesn't mean it's great.

Even so, I see what you mean. I'd actually be more interested in know if/how Plexus is being used in racing boats. That's where strength matters the most.