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Old 21-05-2007, 13:52   #31
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That might be true sully, but Gord does ask some very good and very warranted questions. He is not a mind reader, so he is suggesting that these are possibles issues YOU need to do some homework on.
Maybe the hull will carry the weight. I would be suprised if it didn't. But the important question is HOW does it carry the weight. Remember, weight on deck is still lower in regards to CofG. A structure up higher IS going to change the roll slightly. Maybe it won't capsize, but it will change the motion.
The next issue, without knowing the boat, is how does the existing structure offer strength to the hull underneath it. Some are part and parcel of each other. Removing the top can reduce the intergrity of the hull below. Maybe you are leaving the orginal compleatly untouched. Once again, we are not mind readers, just suggesting you consider all situations.
Will the new structure meet those same needs.
Will the new structure be strong enough to take a big sea. I realise you aren't going to be out in big seas intentionaly, but hey, you nuts if you think it can't ever happen. So will the construction be strong enough to suit green water. What if you did ever get rolled. Can it handle a roll. All questions to ponder and to build to. If it is a day boat only, it doesn't matter. But you are considereing taking extended coastal passages. Prepare and build for the worst. Oh and trust me, a sailboat can handle bad seas far easier than a boat like this. The sails add so much stability and ride comfort that these boats never have. You need to design and build with that in mind.
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Old 21-05-2007, 15:09   #32
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Quote:
Originally Posted by Alan Wheeler
That might be true sully, but Gord does ask some very good and very warranted questions. He is not a mind reader, so he is suggesting that these are possibles issues YOU need to do some homework on.
Maybe the hull will carry the weight. I would be suprised if it didn't. But the important question is HOW does it carry the weight. Remember, weight on deck is still lower in regards to CofG. A structure up higher IS going to change the roll slightly. Maybe it won't capsize, but it will change the motion.
The next issue, without knowing the boat, is how does the existing structure offer strength to the hull underneath it. Some are part and parcel of each other. Removing the top can reduce the intergrity of the hull below. Maybe you are leaving the orginal compleatly untouched. Once again, we are not mind readers, just suggesting you consider all situations.
Will the new structure meet those same needs.
Will the new structure be strong enough to take a big sea. I realise you aren't going to be out in big seas intentionaly, but hey, you nuts if you think it can't ever happen. So will the construction be strong enough to suit green water. What if you did ever get rolled. Can it handle a roll. All questions to ponder and to build to. If it is a day boat only, it doesn't matter. But you are considereing taking extended coastal passages. Prepare and build for the worst. Oh and trust me, a sailboat can handle bad seas far easier than a boat like this. The sails add so much stability and ride comfort that these boats never have. You need to design and build with that in mind.
I couldn't agree more, Wheels. A careful evaluation is always in order (including stability testing) when modifying a vessel. I also agree about the motion of a power vessel at sea (that doesn't have a sail up to damp the motion). It will surely be annoying as heck when I have a beam sea in that thing. But... as was stated originally, it's a platform to work and live from. Won't be taking her out in any rough stuff. We'll sit tight for bad weather at anchor.

No "top" will be removed. I am ADDING a bit of length to the EXISTING wheelhouse, which already has a good 5-10' or so to it on most models.

Considering they build enormous double-decker yachts onto these hulls, I think my skimpy little addition to the wheelhouse will be light enough. I've seen these with "additions" all the way back to the stern. Just saw a tour boat one today with about 40 people on it. It was 30-35ft. I'm getting a 40.

Only thing: Where I'm from, saying, " I fear your specification for “capsize safe”, may prove a self-fulfilling prophesy."

Means: I think it's a good idea that you specified "capsize safe", since it is likely the boat will capsize. (selp-fulfilling prophesy means it WILL happen)

So... I am addressing Gord's comments, not promoting a big modification without doing homework.
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Old 21-05-2007, 16:25   #33
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Originally Posted by ssullivan
”… Any idea which is most appropriate and which would be the least expensive? Thanks for any tips ....
“… The object will be to make as cheap and light (and WATERPROOF!) a structure as possible ... I need to find the cheapest and lightest material that will be waterproof and hopefully be able to take a capsize without detaching from the vessel or falling to pieces.. I have time but I have a shoestring budget. I don't want to spend any money …”
Sean was not soliciting counsel on the wisdom of his proposed modifications, so I should apologise for my slightly off-topic comments.

It seems to me, that although Sean has specified several important characteristics of his proposed modification, his overriding concern is cost. This seems to be a common theme.

My self-fulfilling prophesy jibe, was a cute attempt to reiterate my earlier comment to the effect that appropriate, light, waterproof, and able to take a capsize, are features not likely to be compatible with cheap.

I doubt that Sean has the either inclination or the skills to perform an engineering study – not even his own stability testing (a la 50 gal drums). When would these drum tests be carried out – prior to, or after purchasing the boat?

Others have suggested some construction methods.

I suggest, Sean begin by estimating the costs those of alternatives, then calculating the weight of each technique. This may provide some information upon which to make some rational guesses as to “appropriateness” for his purposes.

How did the guy, whose work impressed you, construct it/them?

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Old 21-05-2007, 16:36   #34
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Originally Posted by GordMay

I doubt that Sean has the either inclination or the skills to perform an engineering study – not even his own stability testing (a la 50 gal drums). When would these drum tests be carried out – prior to, or after purchasing the boat?

Gord... are you KIDDING me? What happened to the PM you sent me about not attacking people (Flying Pig/Skip)??

You just told me, a guy with a degree in Physics, who worked for NASA and has untold credentials in mathematics and computers that I "have neither the inclination or skills to perform an engineering study??"

You basically just called me stupid. Nice one.

Just because you are a moderator does NOT give you the right to insult people and put them down. If it was any other user, I could defend myself against your never ending attacks. Of course, I can't defend myself since you'll threaten to ban me or delete my post. How very hypocritical of you.

It seems all are subject to the forum rules except our leader himself.

What's next? Another PM from you telling me I'm out of line for defending myself?
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Old 21-05-2007, 16:41   #35
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Anyway... back to the matter at hand if (hopefully) GordMay has butted out:

I did a lot of reasearch on painted canvas and it looks like the way to go. It is supposed to last 5-10 years if done properly and can very easily be re-done for very little cost. (Waterproof, Light AND Inexpensive - go figure)

I am probably going this route since it does indeed meet all requirements and should last as long as necessary. Thank you for that suggestion as well as the suggestion on the techniques needed for building the structure out of wood.

I am reminded of a project I had a long time ago where Wheels suggested I use tung oil on my cabin sole. Everyone scoffed at him and I for using "old technology" and said how superior varnish is. Well, that's what the varnish makers want you to think. I tung oiled them and they are looking like they day the were installed, even after chartering for a summer.

Gotta love those old techniques.
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Old 21-05-2007, 17:11   #36
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Suggesting that you may not have the skills to perform a complicated naval engineering/architecture stability study, on a boat of indeterminate design, is NOT an insult.
Few people do.
I certainly do not, nor do the (5) Professional Engineers (construction disciplines) I work with.
I author engineering opinions, nearly every working day. It’s not uncommon for me (on behalf of the firm) to decline comment, citing “outside our expertise”.

I have never used my position as moderator as a shield to hide behind, nor a sword to attack (ban threat) with.
I’ve never threatened to ban anyone that disagreed with me.
I have recused myself from Admin/Mod discussions, wherein I believed it might be perceived that I had an emotional or personal investment.

I suggest you transmit your fears of (my) unreasonable retribution to AndyR. He will not permit such personal misuse of his forum.
Likewise, feel free to lodge your complaint, regarding what you perceive as my personal attack on your intelligence.

If you see my cautionary comments as an attack on your ideas, then please defend those ideas.

BTW: I would be mildly offended at being called a hypocrite…
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Old 21-05-2007, 19:28   #37
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Stepping away from who said what, to whom and why, I will just comment on another earlier poster's comment that foam core / fibreglass skins probably would be a better choice than timber frame / plywood panel, fibreglass skin when considering strength / weight. However I think the former choice is more costly and requries more expertise. Basic timber framing, panelling and simple firbeglassing of the resutling structure is probably within the compass of most amateur shipwrights. Working with foam and glass (and the associated mold making) probably is not. Additonally, while the materials themselves may not be more expensive in going the foam/fibreglass route, adding in the costs for tooling and molds I suspect might tip the balance...
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Old 23-05-2007, 14:15   #38
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Sean!! get a grip man. Stop being so paranoid. Gord cares about you enough to give you suggestions to ponder. If he didn't, I know Gord well enough to know he would be telling you very clearly and coldly your an idiot looking for a village somewhere. The subject is a difficult one to answer when NO ONJE here on this board would know anything about this boat. Gord makes a very good comment. When can you cary out any testing to know true answers?? Before you purchase? not likely, so it would be after you purchase. Then it's too late. Maybe you know more about the boat and know enough to make an informed decision. We don't, and can opnly assume you don't, or you would not have asked the question in the first place. By asking, you open yourself to answers. Some maybe good, some bad. At the end of it, they only serve to arm you with as much knowledge as possible to work out if you shoudl take a step forward or back from such a project.
You mabe a great NASA guy, no arguing with that. But you ain't no boat builder. Yes you have the skills and can make a beautiful job, that has already been proven. Yes you maybe able to crunch numbers and work out info yourself, but no where in what you have said so far has suggested such and so ones here can only presume by what you have surrended and what you have not. We can only read between the lines.
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Old 23-05-2007, 15:28   #39
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I'm going to disagree with the plywood proponants. Plywood is one of the least desirable materials to use in boat construction, IMHO. I still think that good boat building foam (not polystyrene) and glass laminate would be the ideal. Light, strong, easy to construct, durable and warm. I would build it in panels and then join them in place to save the cost of a crane rental.
Using "Good Boatbuilding Foam" that'd be Divinicell, Herex, Airex,Corecell etc will be way more expensive than Ply and stringer's.

By the time you add a substantual glass layup to the core it can sometimes be no lighter than useing ply.

Ply only has a problem when a poor job has been done in construction.

Because of the relative cheapness of the material, idiot's sometimes use it and a crappy job reulting in future rot problem's is done.

The ply/foam/ply with urethane or polystyrene has been used with great success by the designers I supplied links to.

This is not something I made up.

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Old 23-05-2007, 17:01   #40
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I'm going to disagree with the plywood proponants. Plywood is one of the least desirable materials to use in boat construction, IMHO. I still think that good boat building foam (not polystyrene) and glass laminate would be the ideal. Light, strong, easy to construct, durable and warm. I would build it in panels and then join them in place to save the cost of a crane rental.
I agree. If you are concerned about problems later on, avoid plywood. Moisture is the big deal. Repeated saturation/drying of moisture in plywood will weaken glass tabbing. Moisture will cause rot if not addressed (even in marine ply, if you wait long enough).

The are a lot of composite alternatives out there. Coosa, Nida-Core, and various foam sandwich-core panels. Not as cheap as plywood of course. As always, the decision is a compromise.
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Old 23-05-2007, 17:14   #41
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Think what you like guy's.

I have worked on well built 1970's ply boat's that are as good as the day they were built.

I have worked on poorly built 2002 production boat's with delamination problem's on the foam.

This does not mean foam is worse or better than ply, it just mean's there are crappy builder's out there.

If ply is done right, it will last indefinetly.

Rot is caused by lack of maintenance, which is a crappy owner fault, not the fault of a material.

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Old 23-05-2007, 17:32   #42
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Cat-Man, I agree. Most core problems are caused by poor build or bad after sales practice. I do know however that if water gets into plywood it will travel along the fibers of the wood and cause significant damage. Especially in northern climes where a few freeze/thaw cycles can cause delamination.

I am a fan of Vacuum Infusion, and have seen examples on the web of excellent amateur build using that method. I disagree that it is beyond the means of amateur builders, or even not feasable for one off projects. It should ensure an excellent glass/core bond that should last for a very long time.

The URL that I posted earlier is an example of excellent home builder use of the method.

However, it might not fit into Sean's budget. But certainly within the skill level of a NASA Engineer...
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Old 23-05-2007, 17:58   #43
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Think what you like guy's.
If ply is done right, it will last indefinetly.

Rot is caused by lack of maintenance, which is a crappy owner fault, not the fault of a material.
Yes, but if it can't rot in the first place...

Yes, plywood "done right" (whatever "right" means) might last indefinately. But that can be said for just about anything.

I use a lot of Coosa in my building.

Not because it is light...
Not because it wont rot...
Not because resin, paint, and structural adhesive sticks to it like you wouldnt believe...

But, because it is SO Much easier to handle than plywood (the former are definate plusses, however). Just gotta keep those carbide blades sharp.

But I can afford it.

I have also done some vacuum infusion and have had pretty good success (for non-cosmetic pieces). Just takes time and practice. VIP materials are readily available and arent that expensive. The only thing "pricey" might be the vacuum pump.
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Old 23-05-2007, 18:33   #44
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Coosa, is this the stuff you are talking about ?

Coosa Composites, LLC - Manufacture of high-density, fiberglass-reinforced polyurethane foam panels


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Old 23-05-2007, 20:34   #45
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Yep, thats the stuff. Very versatile.
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