Leaking Mould for 100' Hull Infusion

[VIKING]

Hello,
Does anyone have any ideas for sealing the underside of a ply hull mould as it is leaking badly. Bear in mind that it is 100' with plenty of crevices and corners. I have coated it with epoxy resin and radiused all joins with epoxy paste. It is still leaking like f..

I have put a new bag on and it is still leaking. The leak is definitely in the mould as have tested all the lines seperately.

Perhaps some form of rubber coating?

Any ideas would be most welcome

[John ilett]

Maybe the the coatings used to seal/reseal bathrooms/showers.

[wet feet]

I have never had to deal with the problem on such a large mould so take these suggestions accordingly.I would be tempted to apply a very low vacuum to the mould and to spray gelcoat over every part of the external surface,maybe more than once.The workshop would probably get very messy in the process.Several years ago I worked for a company that made racing cars and we had a power cut when the chassis mould was curing in tha autoclave.This left the mould a bit porous and in desperation the whole outer surface was covered with silicone mastic with a vacuum bag over the mould face.The mastic was brushed out a bit and left to cure.More than ten chassis were subsequently produced from the mould.The difference was that the mould was only six feet long,you have more of a challenge.Good luck.

[Dutch Peter]

Wet feet his approache is maybe a bit drastic. With a sound detector you can identify every leak separately and plug it locally, rather then treating the complete mold.

[Buckle]

Is the mould for a one-off infusion. If so perhaps do a envople bag. Seal all around with lots and lots and lots of pletes. It could be your cheapest option in terms of cashie and time.

I am no mould engineer. Why are you not using strips 1" wide by whatever long, as outer form TENSION TIGHTENERS? You can exert a lot of localized forces to close and then seal the leak. You epoxy anchor 1 end- wet out 1 foot of the other on a piece of ply that can be Come- Alonged till the leak stops. I have done that in industry- not SAE approved but very effective. Use as many strips as you need, as close as needed. 1 big-wide strip is less effective. Good luck. Rich ----- I know you have pulled apart the molds while you still can. I would hate to know you stopped the leak and then went ahead and cured the boat as it will bond perfectly to the form so completly that you will have to grind out the hull and mold for a very large area. Write off this casting as a loss and save the mold. I do not know your abilities. Rich

[lakerunner]

At that size it is time to STOP and do a serious inspection on your mould. I heard you say Plywood mould.... I would not move another inch of lay-up untill you found out Exactly where your leaks are coming from. It is a mould Made of wood . I am assuming it is a solid mold ? Strip ? Hard to tell from your description. But what ever means.
Sound detection will work. If it is solid Shut the lights down at night .. get underneath
have someone inspect the surface with a High beam light and it will show even the smallest of holes or cracks. Mark the spot or spots. Old school but it works

[Dutch Peter]

Viking,

Any results yet, are all the suggestions usefull!!??

Regards,

Does the light work on long angular, or is there a point that ultra sound takes over? I imagine his mould is quite thick. Every time a mould was damaged it turned out to be not enough RELEASE was used correctly.

[lakerunner]

I agree as to damage caused by insufficient release agents ( where she sticks is where she sticks! ) The Light is actually a hand held ie; Same as used for night boating spotlight 1 million candle light power .Very bright in a dark enviroment. Literally working the light as you would with an Orbital sander across the surface with a spectator below .
used directly on the surface to get ultimate penetration of light through the mould. again even the smallest of holes and the transparent nature of resin it will show up.
Seems for the size of his mould this is very little investment in time to energy to possibly find the problem. Sonar works well but will it pick-up small hole's ? Where light will penetrate and visually be seen. That is a huge waist of resin as he described and possibly a very easy way to inspect. I trust technology, But I still check the math You get the point. Good luck

[VIKING]

I went 'old school' and used a light as suggested and managed to locate a few major leaks which got the vacuum to a satisfactory level. The infusion went ahead and results have been satifactory although still want to seal all the minor leaks for the 2nd hull coming up- will do so once I have demoulded the first hull. Will probably just redo the surface of the mould then!

It seems chopped strand mat is the ideal fibre to facilitate sealing a mould as opposed to the few layers of twill we used so will go that way.

[lakerunner]

Viking . I'm glad that worked for you. Good luck With your next one

Originally Posted by Dutch Peter

Wet feet his approache is maybe a bit drastic. With a sound detector you can identify every leak separately and plug it locally, rather then treating the complete mold.

Viking, just curious. Are you listening to what is being said here? Are you using ultrasound detector?

[VIKING]

The Cost Of A Leak Detector Was The Issue. (shallow Pockets!)