carbon boat repair

HI
My carbon fibre yacht has been badly damaged after its mooring failed and she went on the rocks. She is uni directional pre preg with a nomex core and foam below the waterline.
I will begin the fix next week and just wanted to get some feedback on my proposed first stage work plan.

1. Cut out the damaged section of outer layup and remove the old core
2. Prepare and clean the inner skin for acceptance of new core
3. Insert and shape the new core
4. Tack on layers of uni directional carbon fibre at 0 & 90 degrees
5. Prepare a vacuum system for resin infusion
6. Complete the resin infusion process

Does anyone see any fundamental errors here?
This will be my first constructional fix so I would like to get some feedback
I have some questions that some of you guys might be able to answer

1.Becasue the boat is in its cradle I am not sure how to tack on the dry reinforcement so it wont fall off the side of the hull
2.What to use to bed in the core cell. Should the reinforcement and the core cell get infused at the same time

Thanks for the ear and advice

 

You need to talk to either the designer of the boat or a composite engineer. A sophisticated hull is no place to practice your first structural repair. Beside which an amateur job may make it difficult or impossible to get insurance.

 

Could I ask a few queastions ?

I'm sorry for your tribulations, and I don't begin to know enough to offer advice. I hope you could report the type of damage as I am considering a similar hull. Did you say you had nomex and foam under the waterline ? I was wondering the thinkness and which withstood the greatest damage from the impact. Again I'm sorry to ask but I am really intereasted in how these cores would work together.

Mark

 

Caution needed

One of the reasons I shy away from small carbon damage repair jobs is the scarf angle required to maintain integrity of the carbon to carbon interface. Can't remember when/where I picked up the info but to the best of my recollection the required scarf ratio was 1:32, now this may have been on an aeronautics spec job and may not be totally necessary for a boat repair.

These days it's more trouble than it's worth (for me personally), I'd take off the whole skin and put a new one on.

Get an estimate from a professional yard that's used to composite repairs and then ask why it costs so much. If they're competent they'll explain all the factors involved in composite repair. If they're not they won't explain and you'll be better off not using them or their advice.

Also check with original builder/designer if prepegs underwent postcuring (can add significantly to strength or lose significantly if not post cured after repair).

You'll find using prepregs will save you a lot of hassle.

Buy yourself some Gougeon Bros publications - "Fiberglass Boat Repair & Maintenance" for $3-5 each, from W.E.S.T. distributors it's a great little publication to walk you thru most repair jobs. There's also one on vacuum bagging - "Vacuum Bagging Techniques" - Don't believe it touches on resin infusion tho'. If this is your first repair, you'll probably want to pick up their "Final Fairing and Finishing" as well.They are great little "bibles"

 

Carbon Repair Job

I understand viewing your location that it might be difficult to find an adequate yard to repair your boat.
Earlier, you are advised to contact designer and/or builder. Probably you have received the advise to stay away from such a very complicated and difficult repair. The Nomex/Foam construction below the waterline sounds to me illogic, save for the fact that the boat is a racer, or ex-racer.
Most pre-pregs are heatcured after moulding so, you might have to use another kind of construction method. As already described earlier to you by another poster, the scarfing is extremely important as well as the overlapfactor.
The cosmetic affair, after the repair-job has been executed, might be another item.
In your case I would contact SP Systems. They might be able to give you a proper advise as they know probably the designer and builder of your boat. I think I should start there.
If you are for whatever reason left on your own to execute the job, then come back with an exact description of the actual damage.
I am in touch with one of the best composite-builders in Holland, so I might be able to give you some physical support, be it by this way.
Good Luck!

 

If you have access to it, there is a great article (June/July 2000) on such a repair that Eric Goetz did on Young America down in New Zealand. It does not give scarf reccomendations but that is available in some other articles. I would not be too afraid of the actual process but I would hire a composites engineer to help with some of the decisions on laminates and resins chosen. Even a few hours of advice from somebody like John Fox would add considerable confidence to what you are attempting. Clean and dry are paramount so you would need someplace indoors to do a decent job. Another option is to get everything as ready as you can and import a pro for a few days of help. Someone who is good with grinding, fairing and neat layup and bagging can reduce your frustrations. It is well worth the few hundred dollars per day that he/she would cost you. Remember that it is not a very big effort between a "good as new" confidence worthy hull and a piece of garbage. A few hours of prep and just a little more money spent can make the difference.

 

Mr. Aughney. Is the boat damaged because of design weakness, storm conditions, or not enough berthing protection? If it is a tear out due to design or manufacturing- they should make good. If your error ,you make good. So far I have been lucky on berthing.----- 1 in 32 ratios, Yipes. Carbon fibre does not like to wet out , new. You are really asking a lot of yourself. good luck.

 

Was going to give some advise But DGreenwood says it best. That is good advise...

 

I hope this helps you Carbon Fiber guys. I own a small Carbon Fiber shop and to be honest the most info I have learned next to trial and error comes from this place http://www.fibreglast.com/
On there home page you will see a link at the top in the blue bar it says fibre talk great forum lots a carbon fiber people.

 

Such a shame the topic starter never leaft a massage here again...