Bestevaer 49ST

[dannc]

Regarding a generator....

It does seem that with a LiFePo house bank of a size to match the main engine HP/alternator capacity, and a engine that has just the right amount of HP, that it would be possible to use one, or more likely two, big alternators to properly load the engine while quickly charging the batteries and/or running other heavy power loads on the boat.

I looked at this for the boat family we are interested in getting but the engine, while small by most standards, still seems to have too much HP to run alternators to properly load the engine during charging or running heavy power loads. The smaller engine being discussed here might work.

Later,
Dan

[estarzinger]

Anodizing will not work for two reasons - need huge bath, way too expensive; and if you scratch it, as you certainly will on top sides, no good way to repair it.

Kevlar is actually pretty crappy for hulls. It is difficult to work with (MUCH more so than carbon). In impact, while the fibers may hold, the matrix (resin) will shatter, which will sink the boat. Also it's technical strengths are "contrary" for boat building - the abrasion resistance you want on the outside of the laminate but the compression you want on the inside of the laminate. If you want a "sophisticated" composite hull, you will use thin ply carbon pre-preg. Better in essentially all regards. Properly engineered (unlikely in a pleasure yacht) it can be extremely tough - attack helo blades, golf club shafts and tennis rackets are pretty hard to break.

That all said you can make an adequate boat of Kevlar.

Personally, I have always wanted a titanium boat - machined out of one solid block Or perhaps 3d printed (no welds)

[paulanthony]

Originally Posted by Polux

On case of the Comar we are talking about a full kevlar hull that is rare on production boats but used on hard duty boats, like military Patrol boats.

I do agree with you that the Comet web site do imply they use full Kevlar. Maybe their blurb is simply not written up properly.

It could be they have found a way to fully exploit compression strength. I have no idea really but if it is Kevlar then to get the same tensile strength they would need two fibres for every one of glass so weight would be negated anyway and the only way round this would be to have a very clever engineered design.

We will find out in due course but if it is kevlar max then it will be very expensive and I would not like to have the job of repairing it in some far flung place.

It would be interesting to discover how and why they want maxed out kevlar.

[noelex 77]

Originally Posted by poiu

I don't know about the clear coating, but how about anodising the hull? It should give better protection than bare aluminium.

Anodising is a great process, but as Estarzinger has said it is not practical for the hull side.

K&M will anodise some parts. I think this can be used to good effect. It avoids the use of dissimilar metals.

Here is an aluminium anodised cockpit grating that I liked. (Sorry for my blurry photo):

[robert sailor]

I've always seen the Kevlar thing to be an excellent marketing game

[estarzinger]

^^ nice if the chainplates are anodised, helps protect them from the stainless bushing, pins and toggles near them. You fabricate then anodise, then have to grind some of the anodising to weld them into the hull, but most all the above deck portion can be left anodised. Look nice also.

[Polux]

Originally Posted by estarzinger

..
Kevlar is actually pretty crappy for hulls. It is difficult to work with (MUCH more so than carbon). In impact, while the fibers may hold, the matrix (resin) will shatter, which will sink the boat. Also it's technical strengths are "contrary" for boat building - the abrasion resistance you want on the outside of the laminate but the compression you want on the inside of the laminate. If you want a "sophisticated" composite hull, you will use thin ply carbon pre-preg. Better in essentially all regards. Properly engineered (unlikely in a pleasure yacht) it can be extremely tough - attack helo blades, golf club shafts and tennis rackets are pretty hard to break.

...

I don't know about that but I do know that the US Navy had changed the Aluminium hull of their 82-ft 57-ton SEALS patrol boats for a Carbon/Kevlar one and I don't think it was for a question of marketing, as says Robert, or because the material was crappy or worse than aluminium.

They have changed from aluminium because Kevlar/carbon absorbs a lot better slamming loads and because " It is actually 50 percent stronger and slightly lighter than its aluminum predecessor"

Composites take the hit in U.S. Navy patrol boat : CompositesWorld

Yes, that is an expensive way to make boats but an outer skin on Kevlar is not only used on military boats but on several other high quality boats among them the Hinckley that today make their hulls in Carbon/kevlar with vinylester resin, even on their classic models. The design may be hold but the building and materials are the best.

https://www.google.pt/url?sa=t&rct=j...F5dg8dpbjSyOuw

[estarzinger]

^^ did you actually read the laminate details? They used only one ply of Kevlar, just on the outside, for abrasion resistance, and the rest was carbon - pretty much exactly as I suggested.

It's actually a pretty low tech structure. And the design objective (to reduce panel modulus to reduce high speed slamming acceleration) is not very relevant to cruising boat design.

And hinckley building and materials are certainly not "the best", even in boat building (which is a long way behind aerospace). You will not find a modern AC or vendee or g class boat built that way. Kevlar is used in those boats in part of the decks in order to make it transparent to sat com signals, but nowhere structurally important.

[robert sailor]

Originally Posted by Polux

I don't know about that but I do know that the US Navy had changed the Aluminium hull of their 82-ft 57-ton SEALS patrol boats for a Carbon/Kevlar one and I don't think it was for a question of marketing, as says Robert, or because the material was crappy or worse than aluminium.

They have changed from aluminium because Kevlar/carbon absorbs a lot better slamming loads and because " It is actually 50 percent stronger and slightly lighter than its aluminum predecessor"

Composites take the hit in U.S. Navy patrol boat : CompositesWorld

Yes, that is an expensive way to make boats but an outer skin on Kevlar is not only used on military boats but on several other high quality boats among them the Hinckley that today make their hulls in Carbon/kevlar with vinylester resin, even on their classic models. The design may be hold but the building and materials are the best.

https://www.google.pt/url?sa=t&rct=j...F5dg8dpbjSyOuw

Now you are adding carbon fiber in the mix which is entirely different. I still believe companies like Jeaneau use the Kevlar thing because people associate this product with bullet proof vests and the average entry level sailboat buyer does more due diligence on buying a flat screen TV than he does when he buys a new boat.

[paulanthony]

If you want a clear coat then a wrap has to be a serious contender. 3 times cheaper, sticks very well to aluminium. Can be reversed.

http://vinylboatwrap.co.nz/boat-wrap-case-studies/

[Dockhead]

Originally Posted by dannc

Regarding a generator....

It does seem that with a LiFePo house bank of a size to match the main engine HP/alternator capacity, and a engine that has just the right amount of HP, that it would be possible to use one, or more likely two, big alternators to properly load the engine while quickly charging the batteries and/or running other heavy power loads on the boat.

I looked at this for the boat family we are interested in getting but the engine, while small by most standards, still seems to have too much HP to run alternators to properly load the engine during charging or running heavy power loads. The smaller engine being discussed here might work.

Later,
Dan

I think this idea has great merit. I think many sailors overestimate how much load is needed by a diesel engine to keep it healthy. It depends on the RPM. If the alternator is set up to produce most of its rated power at low engine revs, then it wouldn't take that much. You could even install a third, shaft-driven alternator of very large size, which you would only engage at certain RPMs when using the main engine as a generator. Main drawback is you lose the redundant diesel engine, but it's probably a tradeoff worth making in very many cases.

If I had a catamoron, that's exactly what I would do. I would never want a third diesel engine on a vessel which by design is so sensitive to weight. I would use one of the mains to drive a really big alternator, and use that as the genset. Set up right I don't see any problem for the health of the engine.

You can buy alternators up to 10kW, consuming up to 20 horsepower from the main engine:

http://www.americanpowerinc.com/imag...20Cutsheet.pdf

How to arrange the drive for such a brute is a different question, but in a new build project I'm sure it's not unsolveable. With lithium batteries and their huge charge acceptance rates, you can use this power, too.

[weavis]

Originally Posted by Dockhead

I think this idea has great merit. I think many sailors overestimate how much load is needed by a diesel engine to keep it healthy. It depends on the RPM. If the alternator is set up to produce most of its rated power at low engine revs, then it wouldn't take that much. You could even install a third, shaft-driven alternator of very large size, which you would only engage at certain RPMs when using the main engine as a generator. Main drawback is you lose the redundant diesel engine, but it's probably a tradeoff worth making in very many cases.

If I had a catamoron, that's exactly what I would do. I would never want a third diesel engine on a vessel which by design is so sensitive to weight. I would use one of the mains to drive a really big alternator, and use that as the genset. Set up right I don't see any problem for the health of the engine.

You can buy alternators up to 10kW, consuming up to 20 horsepower from the main engine:

http://www.americanpowerinc.com/imag...20Cutsheet.pdf

How to arrange the drive for such a brute is a different question, but in a new build project I'm sure it's not unsolveable. With lithium batteries and their huge charge acceptance rates, you can use this power, too.

That would be Catamaran.

Given your family lineage for penmanship, It is pertinent to point out the mistake.

[Dockhead]

Originally Posted by weavis

That would be Catamaran.

Given your family lineage for penmanship, It is pertinent to point out the mistake.

You are correct, sir! Sorry for my mistake and thanks for the correction. Obviously a Freudian slip

[weavis]

Originally Posted by Dockhead

You are correct, sir! Sorry for my mistake and thanks for the correction. Obviously a Freudian slip

I read it and it made me laugh. I know you are not anti multihull so I concluded it was an error of keyboard or whatever.

But then, I wondered if you had moved over to the dark side............

[Dockhead]

Originally Posted by weavis

I read it and it made me laugh. I know you are not anti multihull so I concluded it was an error of keyboard or whatever.

But then, I wondered if you had moved over to the dark side............

I have flirted with the idea of cats, even though I am at heart definitely a mono guy. They have a few clear and notable advantages for the kind of sailing I like to do.

And I am definitely over standardized plastic cruising boats with open helm positions, made for weekend sailing and two week Med cruises, not for hard core long distance sailing. That includes "high end" "blue water" boats -- none of them are really made for what I do.

At the end of the day, though, I think something very like the boat discussed in this thread is what I need. Something more workboat-like, heavier duty, and with a pilothouse. This thread has been a real inspiration for me.