Re: Osmosis on a boat made of sandwich balsa polyester

[ Follow Ups ] [ Post Followup ] [ Osmosisinfo Forum ]

Posted by B.B. on February 14, 2005 at 03:56:15:

In Reply to: Osmosis on a boat made of sandwich balsa polyester posted by Chantal Perducat on February 14, 2005 at 03:53:19:

Posted by Bengt Blomberg on January 27, 2003 at 06:30:25:
In Reply to: osmosis on a boat made of sandwich balsa polyester posted by Chantal PERDUCAT on January 25, 2003 at 05:00:02:
Hello Chantal!
Balsa is a big problem as it is impossible to dry through the laminate. Also when the balsa mats are applied to the laminate the spalts between th small cubicles widens and are seldome filled up with the resin. This leaves empty enclosures which are filled with water within a few months after the hull is launched and then never dries.
The two available repair systems which normally provide sufficient heat to stop the hydrolysis process do not work on balsa laminates because the high amount of moisture in the balsa cools at least two of the nearest laminate layers as much as the temperature there never reaches the 80 degrees needed.
The areas you have found now where the resin has been hydrolysed will slowly spread all over the underwater hull. Trying to apply any kind of so called water barrier will speed up the process only and is wasted money.
Unfortunately this kind of laminate loses as much as 70% of its strength where the laminate does not stick to the core and something should be done in order to regain that loss.
The only way to get rid of the problem for good is to peel of all of the laminate outside the balsa under the waterline, dry the balsa with infrared heaters or hot air and then relaminate with epoxi and modern stiched biaxial fiberglass.
Half of the original polyester thickness will be enough.
If you can not afford that, drill holes about 20 cm spaced and of a size suited for inserting the tip of a normal filler cartridge into the delaminated areas.
Blew compressed air into the holes until no more water drops comes out of any of the holes. You will still have high moisture readings as tyhere will be water enclosed in the balsa spalts but the epoxy filler will glue the laminate to the core better than original anyhow.
Then mix normal laminating epoxy and make it a little thicker with micro ballons. Buy some empty filler cartridges and a cartridge pistol and press the epoxi into each hole until it comes out in the next. Next day use a normal epoxi filler to even out the holes. Sand and then apply antifouling only.
This will restore the strength but will not stop further hydrolysis and the hull must be checked for new delaminations yearly.
Regards Bengt

: Posted by Chantal PERDUCAT on January 25, 2003 at 05:00:02:
: Hi,
: Osmosis, with a few delamination problems, on a 9,50 meters cabin cruiser which is out of water for 17 months, and 7 months in boathouse.
: SOVEREIGN Control on the hull is stillbetween 21 and 24% of humidity, and saturation in the balsa. In the delamination part, not very big, we cut a part and the polyester is not sewed on the balsa, and there is no more resin on the textile face of the polyester.
: Have you a solution for my problem in France ?
: How much for the complete treatment ?
: Is there a french translation of Blomberg book ? Where to buy it ?
: Thank you per advance
: Chantal Perducat

Follow Ups:

Post a Followup




Optional Link URL:
Link Title:
Optional Image URL:

[ Follow Ups ] [ Post Followup ] [ Osmosisinfo Forum ]