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Old 18-10-2012, 14:26   #1
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How to Assess Layup

Mainly, how does one check to see if a hull is made using a chopper gun or using hand lay-up technique? (On a 40+ year old boat)
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Old 18-10-2012, 14:30   #2
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Re: how to assess layup

i think you will find all grp hulls untill the 90's were laid up by hand,using csm and rovings.
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Old 18-10-2012, 15:30   #3
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Re: How to Assess Layup

Few boats were all chopper most of that age used alternating layers of 1-1/2 oz mat followed by a layer of 24 oz woven roving and so on. You could calculate the number of layers by knowing the thickness. There were a few Asian boats I saw that had all chop but I do not think it was chopper gun. Do you need to know for a repair?
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Old 18-10-2012, 16:24   #4
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I need to know for peace of mind. I want to know if it's worth to keep working on my boat or if i should give up on it for coastal cruising.
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Old 18-10-2012, 16:24   #5
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Re: How to Assess Layup

Boat hulls are layed up with alternating layers of roving and matt. The matt gives tensile strength resistance to shattering and puncture. The matt fills in the irregularities in the roving and stiffens the lay up.

Some manufacturers like Morgan and Cheoy Lee used Chopped matt mixed with resin dispensed from a gun to replace the matt sheets. In theory it works just as well and takes less labor but requires a gun operator who knows what they are doing and cares. The operator has to spray on a thick enough layer that is relatively uniform. Most manufacturers stopped using chopper gun layup in hulls because of applicator error. I had a Morgan hull that had no chop on one side which resulted in every thing that was tabbed to that 1/2 of the hull on the inside 'printing' through to the outside and flexing. I came out whole after the law suit but it cost Morgan way more than if they'd just scrapped my boat and built me another one with a properly laid up hull. That boat may still be out there. I kept the boat as part of the settlement and sold it cheap with everything disclosed. The new owner essentially used the hull as an armature and laid up a new hull on the outside of the defective side.

Without drilling holes in the hull, couldn't tell the difference in its thicknessl. Areas that didn't have an opaquing gel coat layer looked paper thin and almost transparent. When we attacked with the hole saw found they were actually the thickest areas of the hull. Other areas that looked fine were the thinnest. About the only thing that you can do is look at the hull and see that there is no print through of the bulkheads and other furniture tabbed to the hull. When you take it out sailing to weather, go below and feel whether the hull flexes as it hits waves. Some flexing is inevitable but it should be virtually absent. Also check that the bulkheads, etc. are still tabbed to the hull. If they've broken loose the hull has either had some rough handling, is flexing too much or the tqbbing was badly done when the boat was built.

Chop, because it's made up of short strands, has lmited reistance to puncture so is structurally weak. All chop layups typically are used in things like FRP skirts and the like for cars, liners in hulls, and other things where strength is not an issue. They are almost always done with a chopper gun because matt sheets are labor intensive and hard to work with.
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Old 18-10-2012, 16:32   #6
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Re: How to Assess Layup

Flo617 you do not say what brand but I am guessing that if the boat is 40 years old and still sailing, that should tell you something. Boats of that era were often overbuilt as far as laminate goes. Often the problems were in other areas like mast steps or hull deck joint or like was mention secondary tabbing. If it is that big a concern drill a hold and measure or remove a thru hull for the same. You could also hire an expert to help you
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Old 18-10-2012, 18:40   #7
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It's a Columbia29 from1967. The reason of my concern is that there is a depression in the hull around where the chainplates are attached. The chainplates are tabbed to the inside of the hull.

The surveyor mentioned something about the boat being taken out of the mold too early before the hull got its final set. I was eager to get a boat then and i bought the argument. Somehow that doesn't feel right though.

Also i found rumors about chopper guns used in columbia boats but there are just rumors. So that's why i'm looking for clues. Even if i were to pull a thru hull out, how could i make the composition of the hull?
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Old 18-10-2012, 18:56   #8
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Re: How to Assess Layup

I'd doubt there is anything wrong with the hull. Those pre '68 Columbia's were built exceptionally strong. Fiberglass was still an unknown commodity and they over did the laminate in their mistrust of the stuff. The pencil pushers didn't get involved till the end of the 60's and start thinning out the hulls.

Hulls are quite pliable till the bulkheads are in and the deck is on. Don't know how bad this 'wow' is but it is feasible that it could have happened. The cradle broke during shipping on our west sail and pushed one of the verticals into the hull making a permanent deformation even though the situation was corrected within a couple of weeks. If the hull isn't hogging and doesn't flex under sail, wouldn't worry about it. If the cosmetics bother you, grind off the gelcoat and epoxy layers of Biax cloth till it's flush, grind down, and regelcoat or paint.
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Old 18-10-2012, 19:04   #9
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Re: How to Assess Layup

Quote:
Originally Posted by roverhi View Post
I'd doubt there is anything wrong with the hull. Those pre '68 Columbia's were built exceptionally strong. Fiberglass was still an unknown commodity and they over did the laminate in their mistrust of the stuff. The pencil pushers didn't get involved till the end of the 60's and start thinning out the hulls.

Hulls are quite pliable till the bulkheads are in and the deck is on. Don't know how bad this 'wow' is but it is feasible that it could have happened. The cradle broke during shipping on our west sail and pushed one of the verticals into the hull making a permanent deformation even though the situation was corrected within a couple of weeks. If the hull isn't hogging and doesn't flex under sail, wouldn't worry about it. If the cosmetics bother you, grind off the gelcoat and epoxy layers of Biax cloth till it's flush, grind down, and regelcoat or paint.
+1,if any thing the likelyhood is your hull is over built for that era.
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