undercured laminate / gelcoat

Hi,

Latest disaster. Boat has been out of mould for approx 5 weeks and barcols through gelcoat are getting from 35 down to 25 - a bit on the low side.

Our temperature in the workshop since release was approx 16 - 17 degrees C which is on the less warm side but nevertheless we have not had hardness problems before.

I plan to postcure at 40 degrees for 24 - 48 hours the complete boat.

My question is this : If boat has been out of mould for 5 weeks already and possibly has some laminate that is slightly undercatalysed, is there any chance of getting the barcol readings up a bit with postcure heating at this stage?

I guess im looking for a bit of reassurance !


Thanks Neville

 

It should increase some, But you may end with some surface profile issues due to more shrinking as the resin continues to cure.

 

Is it possible to get the boat back into the mould ? Reason being it will have changed shape a little if its a softy and putting back in te mold to cure will help it get back to the origanal shape . Plus warming the mold will hep to retain the heat longer as it will cool slower .
36 hours at the hi temprature not getting up and cooling down fromShould make a big differance to the hardness . Always when using resin look for the minimum catalyst ratio and never go below !! If you do go be low then theres a chance the laminate will never ever reach it true hardness . . Boat building during the winter months will only cure when they are in the hotest day of the next summer even if it 6 months later .

Just to add if the right amount of catalyst has been used all throught the job then Heating and cooking will fix but if the catalyst level has been lower than the minimum recomended then you have a soft boat for ever and even if you cook it so its well done or over done nothing will change .
I have a sample sitting on my table that like a piece of rubber from over catalysing . Sits in the sun on the window sill each day and is 4 month old and has never changed in all that time .

 

You might want to change catalyst / peroxide, especially during the winter. Instead of an MEKP you might want to use an AAP peroxide, or a mixture. These have a better cure rate.

 

thanks all. we cant put it back in the mould - its nearly finished.

i have finally bought a barcol, some areas are not too bad - 30 plus, other areas are below 20.

We have never had this before but it does highlight the need for proper conditions, proper measurement of catalyst and no cutting corners.

Also I will look in to different catalyst . In winter we are on the low edge of moulding temperature.

I think post cure in the mould for 24 hours at 40 degrees as Lloyds rules should be done as per norm - we used to do it but havent on this occasion.

The proof will be in the pudding in 2 days after some localised heating I will test with the barcol again.

Cheers

Neville

 

Hi
Do you make boat for a living ??
Theres some real basic things that you should never step out side of no mater what country you are in . I travel around mainly asian countries helping to sort manufacturing problems and showing simple and better ways to do everyday glassing .Just simply set the basic rules and problems disolve and never come back again . .

 

Put the boat in bright sunlight.
UV cures polyester resin just as good as peroxide catalyst, even on a cold day.

The big question is: do you have bright sunlight in Scotland?

 

Tunnels : If our employees obeyed the basic rules Im sure things would be easier! The rules have been set a long time ago........

CDK : You are correct, not much sunlight over here. Its interesting the barcols are going up a little after heating (although they drop immediately after for quite a few hours before rising as the gel is softened).

We are going to hire UV heaters on monday to see if that will help.

MEKP was 2.3 % at 15 - 16 degrees.

Manufacturers doing tests on batch.


Regards Neville

 

To get an accurate barcol reading on gel coat you really need to do it in a casting, otherwise the resin and laminate can influence the test and give a false number.

 

ondarvr:

Yes, from what I have learnt recently a barcol is not a definative test and can be easily fooled by whats underneath.

However, unfortunately the surveying authority for this particular vessel insists on it.

Most annoying is the several hundred pin pricks that we now have !