Hull construction

Petterml said:
I would like to know more about the transparent gelcoat Princess uses under their boats, below the waterline. What advantages does it have? I noticed that the field in the bow between the sandwich and the hull below, where the stair strips end, is often somewhat uneven with a slightly poorer visual quality than the gelcoat that is on the sandwich, what causes this? Why does not Princess manage the same finish as the sandwich part here? I myself have a V39 where this is the case.
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I was told the the clear gel coat on the bottom of our F55 was as an insurance to ensure the integrity of the hull. N mention was made of additional strength compared to white gel coat.

The clear area is roughed up and antifouled whilst on the production line.
 
Question from an old Steel yacht owner.
Does modern Gelcoat still get Osmosis through it's porosity. of have they fixed it??.
Just wondering.
 
Fixed many years ago by the use of special gelcoats, and special resins in the outer hull layers. Usually called Isophthalic resins.

It was always an exaggerated problem that people in the UK worried about much more than people in other countries.
 
Pretty rare occurrence though, and needs builder to make a mistake in a process that is now incredibly well tried/tested for well over a decade. Plus, the vac bag is translucent on the top side.
 
Petterml said:
I would like to know more about the transparent gelcoat Princess uses under their boats, below the waterline. What advantages does it have? I noticed that the field in the bow between the sandwich and the hull below, where the stair strips end, is often somewhat uneven with a slightly poorer visual quality than the gelcoat that is on the sandwich, what causes this? Why does not Princess manage the same finish as the sandwich part here? I myself have a V39 where this is the case.
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The transparent resin is used to find resin starved areas before the product is delivered. To be honest using only in the bottom is not enough IMO.
Resin starved areas is what causes delamination and a near to (or) catastrophic failure in resin infused construction.
It can also happen in the old hand laid method by the way but is much rare occurrence (-1%) because of it's made manual and visual method.
RI delamination is also very costly to repair, though I would imagine costs to be going down nowadays as the knowledge in it is improving.

The problem with resin infusion is quality control, and that is difficult to detect, so transparent resin is used to find the resin starved areas.
Its nice to see Princess embracing the method.
Resin infusion is a precise building method, to precise for what frp boat building was about before RI arrived.

If you start digging deep the Diab Divinycell (used by the majority of mainstream boat builders) is not the best and for example Core-cell is a much better core in absorbing resin.
Though Divinycell has improved in this regard in the recent years as well with its new generation of cores.

A perfectly build resin infused hull is better to a hand laid one in reality, from weight savings, to a cleaner product, less resin wasted, to a clean perfect profile.
The problem in doing this way it needs a high end expertise in the field which is not easy to find and or train.
The old hand laid method is forgiving (very) to say the least.

To learn about the subject I would suggest you subscribe to ProBoat and read some of the back episodes you can download about the subject.
For example there was a story on one of the mags, from about two years ago, for a delaminted high end custom sailing boat and how it got purchase and repaired and the cost of the job.
 
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I paid a visit to our work new build today and was chatting with one of the managers whilst watching some guys doing hand lay-up on a mould. Turns out I was mistaken - their hull above the waterline isn’t resin infused. They hand lay the outer layer of GRP on to the gelcoat in the mould before bonding the core to that outer layer. The bonding process uses vacuum bags but it draws the bonding substance through the foam core, which has holes dotted around so the bonding stuff is also pulled through the holes and forms a mushroom, which acts like a rivet, adding a ‘mechanical‘ fix to supplement the bonding stuff. An inner layer of GRP is then hand laid on the inside of the core.

The core varies throughout the hull so some parts will allow a smaller amount of bonding to be drawn through whilst other parts will allow a lot more. This means that the hull is very strong (and heavier) where it needs to be and not quite so strong but lighter in other places.

They have looked at the resin infused process and experimented on a small scale but have yet to go with it. They recognise the benefits but if it goes wrong it is not salvageable when building commercially coded boats so high risk.

The clear gel below the waterline is not just so they can see any issues with the lay-up, it is also more water resistant than coloured gel coat so osmosis is a lot slower in theory. But that is a bit of a moot point given current materials and the fact that they epoxy coat the hull as well!

Every day is a school day! 😁
.
 
Around 40ish yrs ago, a large Cheoy Lee Motor Yacht ran into the side of Southern Breakwall at North Haven (Adelaide.)
Stbd side of hull up and out of water mainly.
The bow that side was above water when tide dropped/ Exposing the Impact point/area. Paint, Gel, then near 3 inches hick of medium blue colour strands separated mainly. Showing virtually NO Resin nor cloth in that area just gun blown mat thickness.
I hope the rest of that hull. And it's sisters had a bit more Q.C in them than that??. It would have been a '70's model.
My mate was a Hull fibreglass tradesman from a local Farr Yacht builders. I took him there and he said. Wow. I'm surprised that boat still floated. Big seas could fracture that lot. NO torsional rigidity/strength in that at all Just the stranded mat. He reckoned, Female mould. Gel to it;s thickness. Gun blown to required thickness then probably a thin layer of cloth over inner surface to make it look good?. Not a boat he would go to sea in at any cost.
Makes you wonder about things don't it.
 
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Macka1706 said:
Around 40ish yrs ago, a large Cheoy Lee Motor Yacht ran into the side of Southern Breakwall at North Haven (Adelaide.)
Stbd side of hull up and out of water mainly.
The bow that side was above water when tide dropped/ Exposing the Impact point/area. Paint, Gel, then near 3 inches hick of medium blue colour strands separated mainly. Showing virtually NO Resin nor cloth in that area just gun blown mat thickness.
I hope the rest of that hull. And it's sisters had a bit more Q.C in them than that??. It would have been a '70's model.
My mate was a Hull fibreglass tradesman from a local Farr Yacht builders. I took him there and he said. Wow. I'm surprised that boat still floated. Big seas could fracture that lot. NO torsional rigidity/strength in that at all Just the stranded mat. He reckoned, Female mould. Gel to it;s thickness. Gun blown to required thickness then probably a thin layer of cloth over inner surface to make it look good?. Not a boat he would go to sea in at any cost.
Makes you wonder about things don't it.
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I am surprised about this as CL has usually a good reputation State wise, at least nowadays they do. Though personally I have never had anything to do with any of there vessels.
 
Macka1706 said:
Question from an old Steel yacht owner.
Does modern Gelcoat still get Osmosis through it's porosity. of have they fixed it??.
Just wondering.
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Nordic Tug (US made) has laminated some outer layers with vinylester resin to prevent blisters.

They granted a 10-year Hull warranty against osmosis or other manufacturing defects.

Now the boat has started its 14th season without any hull troubles.

NBs
 
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Colin Chapman was experimenting with different methods of building hulls in the JCL period 1970, one of these was the vacuum assisted resin injection system.
Many of the boats are still around today over 50 years later.
For those interested in the early history of hull production systems Sara O Brians book on Chapmans adventures in boats is still available.

IBSN. 1-84280-076-0
 
Are you sure they are real boats ?
It looks like you can actually go forward from the helm without risking life or limb or needing the agility of mountain goat. ....... and those windows..........you can actually see out of them. :)
 
Resin infusion was invented and patented by Scrimp USA. Some of the first production builders to use Scrimp where Pershing and Franchini (1998) from Italy and Horizon from Taiwan.
Altough a sort of Resin infusion was being used in the seventies by some of the custom builder shops in some small parts around the seventies in USA.
Unlike the current resin infused method the first version of Scrimp did not allow resin savinga but more of a precise resin to area distribution and better profile finishes.
 
NBs said:
Nordic Tug (US made) has laminated some outer layers with vinylester resin to prevent blisters.

They granted a 10-year Hull warranty against osmosis or other manufacturing defects.

Now the boat has started its 14th season without any hull troubles.

NBs
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THANK YOU.
 
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