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Old 30-03-2010, 10:29   #1
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Are Ten Layers of Fiberglass Strong?

I just wanted to get a feel from the crowd...

Do you think a hull made from ten layers of 24oz roven hand layed fiberglass is strong?

Can you compare it to any other hulls ? My boat is a challenger 32, fin keel skeg rudder.

Thanks for your response.

v/r

gb
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Old 30-03-2010, 12:11   #2
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Quote:
Do you think a hull made from ten layers of 24oz roven hand layed fiberglass is strong?
Strong is a relative term and to say it isn't strong makes explaining how many of these 40 year old boats are still around difficult. Number of layers is not alone enough to say much since strength has a lot of factors. There were 1980's boats that were more over built. It is not always to be considered better to be over built. Many of the older boats had far more layers than they do today yet are not as strong. The process of construction and materials makes the issue far more complicated than number of layers. In a long list of things to consider before you would purchase this boat, I would say the strength issue is not on the list unless it is damaged.

Condition and comforts would probably make or break the deal. I wouldn't pay a lot for one. Much over $25K would need to have extra ordinary features. The elctrical system might be quite limited so use caution if doing any expansion. Marine electrical standards had not been invented in the early 1970's. There is a limit to how much I would put into a boat like this. You may find a newer boat will cost you less to acquire and make ready.

A 12,000 lb displacement 32 ft boat would be pretty stout and carry a lot of stuff. Cruising is about hauling a lot of stuff. This boat while not as big as a Westsail is still a larger 32 ft boats than average. Tankage is a tad light. If you look at a Westsail you'll see the differences. Could be a good boat, but the age may have hidden adventures. I would expect a few things need to be refit and will be reflected in the lower price. Don't let low boat prices confuse you into thinking it will be a better deal. This won't be a fast boat but for a cruiser in the 32 ft range that can carry a lot of stuff you won't get one that is in this price range. We had a CSY 33 and it was a larger boat at 15,000 lbs displacement and larger tanks.
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Old 30-03-2010, 20:13   #3
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Ten layers properly wetted out yields about 3/8" thickness...
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Old 31-03-2010, 08:53   #4
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Well, I've got a Challenger 32 and it is a pretty tough boat. I've never worried about the hull construction. Would I say that 10 layers are strong, on my boat they are.

A tip 'o the hat to Pblais. What he says is spot on. It's how you build it. Your 32 is overly built strong.

Enjoy it. We won't win any races, but no port is out of reach.
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Old 31-03-2010, 09:20   #5
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Hull thickness is really the only thing I worry about taking my boat off shore...everything is tabbed 4", through hulls are backed and beefy, tankage is great but with a hull at only 3/8" thick it is not very reassuring to me...give me 1" any day...speed comes at a price....and that price is security IMHO.

Thanks for this thread...I have often wondered how many layers my was...now I sort of know.................................about 30 to few...
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Old 31-03-2010, 19:03   #6
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[QUOTE=Stillraining;428700]Hull thickness is really the only thing I worry about taking my boat off shore...everything is tabbed 4", through hulls are backed and beefy, tankage is great but with a hull at only 3/8" thick it is not very reassuring to me...give me 1" any day...speed comes at a price....and that price is security IMHO.

If a 32' boat has a 1" thick hull, it will be tough to float. 3/8" is relatively thick for a 32' sailboat...
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Old 31-03-2010, 19:12   #7
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Reality check. Boats sail around the world, in the southern ocean, in conditions far worse than our boats will ever see, with less than 100oz of glass in the hull. That's like four layers of 24oz roving and some foam, balsa, or whatever. Your builder used ten layers because then they didn't have to figure out any structural issues....and they knew they could drop the boat in the yard a few times without losing it. Insane overkill...it will never be of any use to anyone.
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Old 31-03-2010, 20:07   #8
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[QUOTE=silverp40;428976]
Quote:
Originally Posted by Stillraining View Post
Hull thickness is really the only thing I worry about taking my boat off shore...everything is tabbed 4", through hulls are backed and beefy, tankage is great but with a hull at only 3/8" thick it is not very reassuring to me...give me 1" any day...speed comes at a price....and that price is security IMHO.

If a 32' boat has a 1" thick hull, it will be tough to float. 3/8" is relatively thick for a 32' sailboat...
I was talking about my boat which is 41'
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Old 01-04-2010, 00:36   #9
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You can't compare the amount of glass used for solid and cored hulls. Computer designed boats have different thickness everywhere, calculated tapers, flow from cored to solid etc. You can't compare that to old hulls that basically made everything stronger than needed for the strongest point (and thus carrying much more weight than needed).

On our hull (not deck) we have solid laminates ranging from 3/8" around the hull-deck joint to tapered 1" to 1.5" around the keel and engine to over 3" at the bow (!!). We have 1" balsa core everywhere else and the laminates range from 3/16" to 1/2" on the outside and 1/8" to 3/8" on the inside. A huge range but even at 3/16" outside plus 1/8" inside with the 1" balsa core, total 5/16" glass, I think it's stronger than 3/4" solid.

A point not discussed yet is that besides strength, abrasion resistance is also important for parts of the hull like the turn of the bilge (think groundings). You want a lot of fiberglass there, some even use Kevlar.

For the old hulls: as long as there is no delamination it is way stronger than needed. The biggest problem with these hulls is that they lost stiffness if they ever had it to start with (not too important for cruising). But if you punish it hard enough, the lack of stiffness leads to quicker delamination so the two are linked somewhat. Blisters are the other problem but are fixed relatively easy.

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Old 02-04-2010, 07:41   #10
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Nick, x 2 your comments.

From 1972 to mid- eighties I was a member of a group building custom commercial boats using Airex PVC foam. There was not much data available at that time on foam-core construction, other than that the Dutch and Norwegians, ITIW, were building Pilot cutters using the material. We used a Tandy Radio-Shack PC to build our spread sheets.
Some of these boats, up to 83ft, were fare-paying passenger carriers, so we had to provide test results to our Govt licensing people.
In short, after many sizes of test panels, we always came back to the same ratios for construction.
70%/30%

Hull thickness 70% core/ 30% FRG skins.
Skin distribution 70% outer/30% inner.
Laminating mix 70% glass/30% resin by weight.
During those early years it was all polyester resin, almost all hand rolled-out, 24oz roving and 2oz mat. Later we used Fab-mat, stitch-mat and Bi-axial stitch-mat. Later on a Ransberg 4-bobbin chopper gun with colored tracer bobbin.
All of these boats are still working today here in Bermuda, except for 1 of the 83ft models, which went to Cuba on her own bottom, 2 round trips ITIW, and is still there.
I dont think Paul Johnson, of Venus fame, would mind me saying that he developed his cored line of boats, after working here with us.

One interesting point. When we were doing the destructive tests on the panels, we used the docking light cut-outs from a famous solid lay-up, 31ft deep-V sportfisherman, and similar cut-outs from our 83ft boat. On the press table, with similar spacing of the supports, the cored sample deflected until it slipped between the supports with no separation of the laminate, and returned to within 90% of true in 6 hrs.
The solid sample fractured thru about 75% of its lay-up without slipping off the supports, and did not return to shape. The solid sample DID require about 4 times the load to fail, that the cored sample required to deflect to failure.
I say this to support Nick's comment about other conditions of use, being important considerations
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Old 02-04-2010, 08:07   #11
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Quote:
Originally Posted by Stillraining View Post
Hull thickness is really the only thing I worry about taking my boat off shore...everything is tabbed 4", through hulls are backed and beefy, tankage is great but with a hull at only 3/8" thick it is not very reassuring to me...give me 1" any day...speed comes at a price....and that price is security IMHO.

Thanks for this thread...I have often wondered how many layers my was...now I sort of know.................................about 30 to few...
Just curious, where was that thickness measurement taken? Like Nick said, it does vary throughout the hull. I measured mine at 5/8" (solid glass) at various thru hull openings between the keel and the turn of the bilge, surprising to find that the 41 would be a 1/4" thinner than than the 32.5
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Old 02-04-2010, 10:26   #12
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Thanks s/v Jedi & Blue Stocking (& others), for sharing your knowledge.
Its truly a pleasure to read such informed & expert contributions.
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Old 02-04-2010, 11:00   #13
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Quote:
Originally Posted by Mi2ndWind View Post
Just curious, where was that thickness measurement taken? Like Nick said, it does vary throughout the hull. I measured mine at 5/8" (solid glass) at various thru hull openings between the keel and the turn of the bilge, surprising to find that the 41 would be a 1/4" thinner than than the 32.5
Hey Mi2ndwind"

The only place I have had the opportunity to personally verify hull thickness is at the turn of the bilge, even with and about a foot Port of my shaft log....That is where my grounding plate is bolted to the hull...Its only 3/8" thick there....I was quit surprised to find it so thin in that area....but maybe its normal I have no Idea....This is perhaps 2' aft of the trailing edge of the keel.
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Old 02-04-2010, 11:18   #14
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3/8" sounds like plenty. I've taken thinner hulls thru conditions worse than you'd ever want to be in: Where tabbing breaks and the pounding is horrendous.

Nit picky detail: Cores do not increase strength. Cores increase stiffness without increasing weight, strength or total FRP thickness. Uncored boats, unless as thick as a cored boat, behave as if they are made of rubber. They bend under sailing loads. To make a hull stiff enough requires thicknesses like mentioned above... around an inch. To do this in solid FRP is far too heavy.

'Strength' prevents punctures, breakup, compressive failure, stuff like that. 'Stiffness' keeps the running rigging tight, and interiors from untabbing....a geek detail...

You'll want strength if you plan on parking on coral, or taking gunfire, or close racing against newbies...
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Old 02-04-2010, 11:23   #15
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Thanks Daddle...that's comforting to know.
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