Thoughts on construction?

[Willallison]

Well, if there's no alternative going to be thrown up to challenge the rough profile & arrangement sketch that I made, I guess we must assume that it is acceptable to everyone.....
Which brings us to the next step in the spiral - I guess that would be construction details. Alas, this is about where any expertise I might pretend to have starts running out of puff, so if O-1 is to progress any further, then someone needs to grab a hold of the torch and run with it.
We already elected to make O-1 buildable from a number of materials - ply, GRP over foam, or aluminium. That will make the construction desgin all that more difficult - perhaps we should think about limiting materials to one, or perhaps two types....my money would be on ply and GRP/foam core.....

[yipster]

not so long ago i checked on a price for GRP over foam for the glen-L 35'-3" by 13'-8" and 18,000 lbs. sea angler pictured here, local glas and foam was: $/E 5000..

ply and GRP/foam core for me (plus the construction details)

yipster

[yipster]

on construction of a hull i've been wondering why i havent seen stich and glue with hardfoam instead of plywood.

for bigger boats like 0-1 it seems to me a good idea to keep things workable..? again the cost? just a thought, any coments?

yipster

[yipster]

more cost and thoughts on construction at http://www.boatdesign.net/gallery/sh...sort=1&thecat=
anyone now for a cat of some sort named O-2?


yipster

[Tom Lathrop]

Yipster,

Interesting. One of the builders of my Bluejacket 24 pilothouse cruiser is opting to do just as you suggest. He plans to vacuum form the panels on a large table from glass/foam/glass and then fit them together as if they were plywood panels.

I like the idea and think it will work out well. There are some areas of the construction that I do not see clearly but they can certainly be solved. The bending characteristics bother me a bit since the composite panels will be thicker and therefore stiffer. My major concern would be in forming the forefoot which may need a design change to accomodate the material, but maybe not.

The insulation, floatation and sound deadening should all be improved by use of this technique. Since the finish surface can often be incorporated with the panel construction, there should be a great time and effort saving there, perhaps enough to offfset the extra work of building the panels.

I will be fllowing his progress with interest.

[Willallison]

Nice to 'hear your voice again, Tom.
I'm 100% with you on this one. preformed flat panels would be reasonably easy for the home-builder to make - all you need is a large, flat smooth surface. There was a great deal of discussion about just such a system on the boards some months back. I think it was a New Zealand crowd that specialise in design and construction using this technique. Unfortunately I havent found the thread yet.....

[Willallison]

Found it!
Duflex was the stuff we were talking about see here.... http://www.atlcomposites.com/pdf/DuFLEX_brochure.pdf

and for our discussion on it.....

http://boatdesign.net/forums/showthr...ight=composite

[Willallison]

Another possibility is to use C-flex. I know little about it beyond that C-flex planking is a combination of rigid fibreglass rods held together with unsaturated strands of continuous fibreglass rovings and a light f/glass cloth. Apparently it can be used in conjunction with foam core (though this would seem to negate its usefulness somewhat)

I couldn't find a web-site dedicated to it, only that it is produced by Seemann Composites (the same crowd that came up with SCRIMP) but did come across this:

http://www.bruceroberts.com.au/build...ods/c-flex.htm

[Jeff]

Here's another sequence of photos http://glen-l.com/methods/mthdfg34.html showing a small boat being built with C-FLex (click next several times and you can get a good idea of what C-Flex is like to work with.) I thought about trying it a few times, but have yet to do so. One potential drawback is that you have to use polyester resin with C-Flex rather than epoxy. Also I wonder about the overall weight of C-Flex plus the mat layer they recommend following it compared with a foam core.

It's too bad the "C-Flex Manual," the book by Seeman themselves, isn't online (I haven't seen a copy)

[Willallison]

Good link Jeff.
I agree with your concerns over weight without a foam core. Apparently you can use the C-flex with a core, but I can't quite see what the advantage would be.
Actually there's quite good sequence showing the construction of a foam core boat on the same site:
http://glen-l.com/methods/mthdfg01.html

[Willallison]

Calling Tom Lathrop!!

One of the builders of my Bluejacket 24 pilothouse cruiser is opting to do just as you suggest. He plans to vacuum form the panels on a large table from glass/foam/glass and then fit them together as if they were plywood panels.

Any news on progress of the construction Tom?

[IOVH]

I suggest to use Ply-Epoxi for the hull and deck and GRP for the pilothouse.
Regards
Ignacio

[Tom Lathrop]

Will,

I have not heard of his progress as yet. I will let you know when things get going. I think he has done this kind of laminate before.

I have looked at your specs for your cruiser but have not had time to digest any of it. Off the top though, I suspect that the bottom loading is too high to allow early planing. You obviously prefer to run faster than I, even in your "low speed mode". I don't feel comfortable in any small boat, other than a good cat, running in significant waves above 15mph. Used to do that but it is just not fun anymore for more than a few minutes.

[Willallison]

Good to hear from you Tom. Nope - I think we are in agreement as far as the target planing speed goes. I've had a quick look at the hull model:

at 1000kg (unrealistically light I believe) AWP = 8.75 m^2, giving a bottom loading of 114 kg.m^2

at 1500kg (a good target weight in my mind) AWP = 10.43m^2, giving 143 kg/m^2

at 2000 kg (probably getting too heavy?) AWP = 11.58 m^2, giving 172 kg/m^2

Based on your earlier suggestion that the bottom loading needs to be kept under 240 kg/m^2 , all these seem ok don't they ?
Having said that, I recall that you've previously said you take 65% of the (at rest) AWP for the calculation. If that's correct, then bottom loading @ 1500kg would be 220 kg/m^2. Still within your requirement, but are we getting too high?