Hull Laminate Question

Towboat

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As a mechanic by trade having never really been exposed to the design, layup & assembly side of boatbuilding I have a couple questions - or more of a poll for the experienced builders on this site.

When I bought my boat last summer, I hauled it for an insurance survey but paid little attention to how she was built myself. I was more concerned with the systems, engine condition, layout, etc and figured it is a solid glass hull built by a local builder with a long standing reputation in the business so I didn't worry about it. Condition was good and I was satisfied.

Fast forward to the winter and she's in my shop for a couple months for new pilothouse windows, some much needed engine maintenance, wiring upgrades, etc. I pulled one of the seacocks and was surprised by what I would consider a relatively thin hull thickness layup. located between the starboard two full length longitudinal stringers, about midship and halfway between the keel and chine, the seacock has a pretty stout glass backing plate but the actual hull in this area was only about 3/8". I have not observed any other locations yet.

I understand the hull thickness varies and is thicker in high stress areas, but this seemed thinner than what I expected and certainly not the 1" solid glass I seem to hear about on many boats here. Is it common practice for a builder to vary how heavy the hull is built from boat to boat depending on its intended purpose? This boat was laid up in 1989 before the fire at MDI's original shop and finished in 1990 at Weldon's new shop once he got going again. It was built for the Norwalk boat show with gelcoated bilges and a finished cabin, but purchased by a couple halfway through the build.

So - while this particular hull was finished off for recreation, there are plenty of 30s and 32s out fishing, unless there is more difference than meets the eye

Anyway, because we still are measuring the snow depth in feet and I'm at work on a tug for another few days - I thought I'd get some insight. Of course, the boat is 25 years old, shows not a stress crack anywhere & has a nice ride I'm sure it's fine I'm just learning and would like some feedback. Like I really need something else to worry about :rolleyes:

Thanks for reading & happy spring? That's what the calendar says, anyway.
 

Powderpro

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3/8" thick on the bottom of a 30' recreational boat wouldn't be a concern to me, sounds like it's held up good so far. Although it's not a rugged layup, it's probably perfectly adequate for a boat that size used recreationally. The 1" thick bottoms you hear about are usually much larger boats that carry a big engine, lots of fuel, and are used in rough sea conditions. Commercial boats have to go out in all kinds of weather to pay the bills, so they are usually put under more stress than a rec. boat. Also, a 30' hull doesn't need as strong/thick of a layup as say a 44' hull.
 

Towboat

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Thanks for the reply! I totally get the reason for a tough boat - have been running commercial boats full time in all kinds of weather all over the east coast since my first license 15 years ago. I was more under the impression that builders around here laid up hulls more or less the same and finished them off for their intended purpose, but perhaps I am wrong about that and this boat is an example? Or maybe this is a typical 30' hull. I'm not a boatbuilder so I was just curious

I have a friend with an H&H 32 who claims 1" in a similar area when he pulled a seacock. I have yet to verify this myself.

How would this compare with other solid glass hulls say 28-32'?

I'm not overly concerned - it's mostly a recreational boat however I do intend to run some UPV charters mostly island transportation stuff, a little mooring work, move floats for some local customers and some dive tending.

Just wanting to expand my knowledge in this area - I have been very impressed with the skill and experience on this site in all areas of the industry

Thanks
 

jojobee

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I don't think hull thickness tells the whole story. 3/8" of chop is not the same as 3/8" of bi-axial. Hull thickness often gives us a false sense of security.
 

Towboat

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I don't think hull thickness tells the whole story. 3/8" of chop is not the same as 3/8" of bi-axial. Hull thickness often gives us a false sense of security.

I was thinking the same thing, actually. While it's nice to see a whole pile of glass under the boat, without actually knowing the material used it would be hard to generalize the strength.

These differences in building techniques are all very interesting to me.

Thanks for the input
 

Numasahake

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The fact is, if it hasn't developed stress cracks in that many years tells you, it's fine. Back in the cave man days, boats were built with a lot of mat and a couple woven rovings, some boats, I'm sure were chopper gun specials. Fortunately every boatbuilder in Maine that I'm familiar with, built good safe hulls.
 

nickyp

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My buddy has a 31 jc solid glass hull, and it's about the same thickness you found at about the same spot. Boats been fished hard since the 80 s. No problems
 

Keelboater

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Here is a tid bit for you guys to think about:

I just removed some unused through hull fittings on the bottom of my 24 DE, and am also relocating the seacock for better access to the strainer and ball valve via the motor box. What did I find? Inboard of the two main stringers, the bottom is 3/4" thick. Outboard of the stringers on both port and starboard sides, the bottom is only 3/8" thick. But that came as no big surprise to me. I did the same type of job to my 28 Bertram a few years back and discovered that the central part of the V bottom, in between the inner main stringers, measured a solid 3/4" thick. Outside of the main stringers on either side, the bottom was only 3/8" thick or even less. So I guess if you don't like the thickness you find in one place, just bore a hole in another place. :eek: :D Both are old boats and have already stood the test of time, so no worries here on laminate thickness. It is what it is.
 

backman

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I know there is no "right" answer here but what is considered "safe" when it comes to a debris strike? I'm not talking running up on the rocks at 20 knots but if you hit a floating piling at 10 knots - can 3/8" take it?
 

Brooksie

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I know there is no "right" answer here but what is considered "safe" when it comes to a debris strike? I'm not talking running up on the rocks at 20 knots but if you hit a floating piling at 10 knots - can 3/8" take it?

Again, depends on the size "mass" of the boat. Hitting a piling at 10K in a 9000lb 30 footer carries a lot less force than in a 35000 lb 40'.

I remember many years ago when I was a helper in a body shop, the man challanged me to beat my way through an old Corvette fender and handed me a hand sledge. Exhausted myself and could not do it. They are 3/16"-1/4" thick and all mat.
 
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