Polyester basics

[Michail]

I pretend to build a single skin hull using isoftalics poliester resin, and for the most part it will consist of a 300 mat, followed by three layers of (Mat 300 with roving 600).

The main question (may be quite obvious for some) is what the sequence between these layers should be. The mould is about 18 m2, so that one can reasonably work through one layer (MAT plus Roving) in about 2 - 3 hours time. The gel time is about 30 - 40 minutes with the formulation suggested by the supplier (the maximum safe working time).

The local supplier suggested that I can start with the next layer without sanding, but wiping the surface with styrene monomer.

I have heard opinions suggesting that the next layer must be put almost immediately, i.e. just at the end of the gelling period of the previous layer, at most its double time, but without any wiping with styrene. And if I pass this time frame, it will be a secondary bond, and in that case I need sanding and wiping with monoesterine...

So basically the question is:
If I have a gel time of 30 minutes, and I can place the next layer not before 3hours after previous one, what is the best treatment for the previous layer (nothing, estyrene wiping, sanding and wiping). Or should one try and reduce the 3 hour time to maybe an hour by getting more helpers?

[dialdan]

Hi Michael
Make sure you use unwaxed resin and you won,t have a need for sanding , wiping etc.
Cheers
Al

[m3mm0s rib]

No need to wait 3 hours to spend in the next hand. You can do immediately. This way you will win because they use less resin. But so you want many people to do it. The biggest difference in time from one side to another without sanding is 12 hours. necessarily after sanding.

[ondarvr]

Skip the styrene wiping step.

With a straight ISO you have plenty of time to lay down the next layer and still have an good bond.

While doing the entire laminate at one time would be best, you don't need to rush the next layer, coming back the next day to finish it is fine.

Temperature and humidity will have big affect on how quickly the surface will cure to the point where the bond will be compromised. High temps and low humidity will speed the cure, low temps and high humidity will slow the surface cure.

Like has already been said, don't use a waxed resn, if you do use a waxed resin, wiping it with styrene won't help much.

[Michail]

I am going to use isoftalic F737 from AOC. It does not contain wax. It seems not certified for marine use, and is resilient resin for use in corrosive environments and for heavy duty piping. I was told by the tech department of the supplier that it comes closest to the use for boat building . In Chile it is impossible to find certified naval use resin, since everyone uses the cheapest stuff.

Actually, today I got an answer from tech department from AOC and they confirmed that no styrene wiping is necessary and the working window is about 12 hours between layers.

[m3mm0s rib]

Actually, today I got an answer from tech department from AOC and they confirmed that no styrene wiping is necessary and the working window is about 12 hours between layers.

EXACTLY

[tunnels]

Originally Posted by Michail

I pretend to build a single skin hull using isoftalics poliester resin, and for the most part it will consist of a 300 mat, followed by three layers of (Mat 300 with roving 600).

The main question (may be quite obvious for some) is what the sequence between these layers should be. The mould is about 18 m2, so that one can reasonably work through one layer (MAT plus Roving) in about 2 - 3 hours time. The gel time is about 30 - 40 minutes with the formulation suggested by the supplier (the maximum safe working time).

The local supplier suggested that I can start with the next layer without sanding, but wiping the surface with styrene monomer.

I have heard opinions suggesting that the next layer must be put almost immediately, i.e. just at the end of the gelling period of the previous layer, at most its double time, but without any wiping with styrene. And if I pass this time frame, it will be a secondary bond, and in that case I need sanding and wiping with monoesterine...

So basically the question is:
If I have a gel time of 30 minutes, and I can place the next layer not before 3hours after previous one, what is the best treatment for the previous layer (nothing, estyrene wiping, sanding and wiping). Or should one try and reduce the 3 hour time to maybe an hour by getting more helpers?

If you are using 300 gram chopped strand matt you will be there forever . lay 3 layers of 300 gram one after the other while each layer is still wet . 900 grams is ok Keep your catalyst so you have 40 minutes or more gel time . Work with amall areas till you get used to what you are doing and then increase the area you lay each time . If you are making a mould csm is best till you have at least 5 or 6 layers of you 300 gram down before you start and use any woven glass . Woven has a habit of showing the weave of the matt on the surface of your mould if its to close to the gelcoat . The sanding and wiping things is a waste of time just get into the job and do it !!

What are you making ????