Structural engineer about?

[Monique]

I am considering a Kevlar hulled yacht from a reputed builder. However, I spotted what looks like hull de-lamination abeam the stays. (I want to circumnavigate beginning next year... a solid boat is needed)

The owner says the seemingly flawed hull is because the dark painted hull displays more of the underlying layers than if the hull was white. He says this will disappear when I repaint the hull from dark to off white. (Repaint is needed)

Any thoughts? The boat is excellent in many aspects and I do not wish to "Run Forest, Run" if the reality is as stated by the present owner.

 

[Neil_Y]

I'm no expert but have experience of a range of yacht builds/materials.

The fact that it is kevlar or has kevlar in the layup doesn't change that way it is made. Kevlar was sued in cruising and racing yachts for strength and or impact protection (Bavaria). If it's a light weight race boat it may be carbon kevlar.

The point is though with any laminated hull built in a mould the exterior should be true / flat and show no signs of layup changes in the hull. Dark hull colours do show up irregularities better but I would suggest or guess that this means the hull has flexed or perhaps been repaired from the outside? I've just had a hole repaired in a thin kevlar/carbon foam hull and you can't see it.

The strengthening thicker layup is visible from the inside but you shouldn't see any irregularities on the outside. I'd want to investigate more before deciding the hull was sound. That's what you pay a good surveyor for, just make sure you ask them to investigate this area in detail if it concerns you.

 

[boatmike]

Be cautious of any answers to that question without further info. A photo would be useful but still difficult to determine without direct examination. Most experience on here is related to polyester glass. I am charterered engineer with direct experience of designing and building structures in kevlar and carbon using many different resin systems and layup methods. Kevlar is much more difficult to "wet out" than glass and needs more care in choice of resin and layup.
Be very cautious. Delamination is a serious fault and if one area is faulty others may be too. Don't run away but don't accept that painting over it will cure it. It won't. I always insisted that non pigmented resin be used so that any defects could be seen. Get a good experienced surveyor to ultrasonic test it. Tell the seller he must foot the bill if it is faulty but if it's OK you will pay. That should call his bluff.......

 

[Monique]

Thank you to both. I cannot load a photo... can someone help?

 

[TQA]

Use photobucket and link to it.

 

[Monique]

Good idea...

http://s540.photobucket.com/user/phedm188/media/Hull2.jpg.html

 

[lw395]

From the photo, it's hard to see what is 'print through' where you can see the weave of the reinforcement due to resin shrinkage, and what might be stress due to core detachment in a sandwich construction.
Is there a top skin loose from the core?
Get a reasonably technical boatbuilder to look at it?

 

[TradewindSailor]

It looks like it may be a significant fault to me, but you'd need an experienced qualified surveyor to check it out. Photos are too limiting. Find a surveyor that is very experienced with that sort of layup. I've come across some that really could not assess a hull properly.

 

[Monique]

Thank you all. I will ask a surveyor to look at the boat. I know a good one in mainland SP.

 

[oldsaltoz]

I suspect that given your plans, I would be looking for a hull made of a material I could repair myself, this is not the case with Kevlar.

Also note Kevlar repairs are not easy and not cheap.


Good luck and fair winds.

 

[Rigger Mortice]

I suspect that given your plans, I would be looking for a hull made of a material I could repair myself, this is not the case with Kevlar

I was thinking much the same.
At one time RTW cruisers often opted for steel on the basis that it could be bashed back into shape or welded up in just about any corner of the world. I imagine these days that GRP is just as easy to repair. But a high performance material like Kevlar? Imagine trying to get a repair in some isolated spot when its been damaged on a reef.

 

[Deleted member 36384]

The picture for those who might want to comment.

Monique in the section links to share this photo, just copy the the link at the lowest option called "IMG" and paste the link. Only keep the text between the

delete everything else.

 

[Daydream believer]

I think you are being conned - it is not a yacht it is a car
You need a garage not a marine surveyor

 

[30boat]

You can find out if it's delaminating by tapping it with a plastic hammer and listening to the sound it makes.A hollow thud means delamination.

 

[Monique]

Thank you all; my plan now involves another vessel. Too many concerns to have festering in the back of my confused mind

I have 2 back up boats in contention. BIG BUYERS market out there. Apparently, most boats sell 25-40% off the asking price except those which are smack at the top condition for their price bracket. Almost time to pull the trigger.

Thank you everyone for your comments.