Which is better for Biaxial?

[JBas]

I want to use Biaxial as part of my re-fiberglassing the hull.
Does anyone know which resin is better for it? Epoxy or Polyester?

Cheers!

[Benz]

Biaxial with no mat sewn on is good with either, but I believe is more commonly used with epoxy. Biax with mat (usually called "1708") is a little difficult to wet out with epoxy, but wets out very easily with poly- or vinylester.
The 1708 gives you a more resin-rich product, which people are usually trying to avoid with epoxy construction.

I should add that you should determine what resin is right for the job first, based on budget and function, then pick a material to go with it.

[Singularity]

Originally Posted by Benz

Biaxial with no mat sewn on is good with either, but I believe is more commonly used with epoxy. Biax with mat (usually called "1708") is a little difficult to wet out with epoxy, but wets out very easily with poly- or vinylester.
The 1708 gives you a more resin-rich product, which people are usually trying to avoid with epoxy construction.

I should add that you should determine what resin is right for the job first, based on budget and function, then pick a material to go with it.

Just highlighting the bolded point from above. Mat usually (always?) has a binder that requires poly or vinyelster to appropriately dissolve. Definitely check with your supplier before using epoxy with mat.

And highlighting the second point, consider that a resin-rich layup is substantially weaker than a resin-appropriate layup. Always try to remove any excess resin from the layup before walking away. Never throw extra resin on a layup to "make it stronger" as it does the opposite. You want tightly packed sheets of glass with just enough resin....not resin soup with glass noodles floating in it.

If you don't have much glass experience and want to watch the world's first totally civilian astronaut and rocket ship designer show how hand layups should be done, check out the video:

https://youtu.be/p9GTYsNBiaE?t=2267

FWIW I'd use epoxy if it's a repair job.

[JBas]

Thanks you two!! A lot of good information =)

[Down East]

Agree with all above and I use epoxy for almost all glass work, but keep in mind epoxy doesn’t like UV. So if it’s in the sun it will need paint.

[JBas]

Cheers!

If you guys know of any other tutorials of laying fiberglass on the hull- especially multi-layers, that would be great!

[Spot]

JBas-Are you fixing damaged structure or just trying to smooth over other repairs?

[Benz]

Originally Posted by Singularity

Just highlighting the bolded point from above. Mat usually (always?) has a binder that requires poly or vinyelster to appropriately dissolve. Definitely check with your supplier before using epoxy with mat.

Because in 1708 the mat is sewn to the biax, they don't bother with binder, so epoxy can wet it out; it just soaks up a lot. Glass mat by itself certainly has binder, and ought not to be used with epoxy.

[motion30]

Biaxle fabric is much smoother than woven roving and holds less resin. It makes a much less resin Rich laminate. as far as using Matt with the epoxy you should check with your supplier. Some mats require styrene to break down the binder others do not and are fine to use with epoxy.. vinyl Ester cost less than epoxy and has a much better secondary bond strength 10 polyester. Secondary bond strength is very important for a repair

[s/v Jedi]

Originally Posted by Benz

Because in 1708 the mat is sewn to the biax, they don't bother with binder, so epoxy can wet it out; it just soaks up a lot. Glass mat by itself certainly has binder, and ought not to be used with epoxy.

+1 this info is correct: 1708 wets out perfectly with epoxy as well as polyester.

If this is for the underwater part of the hull then definitely use epoxy as it's a much better moisture barrier

[JBas]

Am reparing the whole hull from lots of blisters I've removed. So need to fill in the craters that they have left behind, as well as apply 4-5 layers of fiberglass as I had to remove a lot of the "skin" off.

Am going to use polyester resin. And use mat and biaxial sheets. I just wanted to know about how biaxial behaves with polyester resin.

[gmakhs]

Consider finishing the last or 2 last layers with vinylester , that will add some osmosis protection .

[Spot]

Originally Posted by JBas

Am reparing the whole hull from lots of blisters I've removed. So need to fill in the craters that they have left behind, as well as apply 4-5 layers of fiberglass as I had to remove a lot of the "skin" off.

Am going to use polyester resin. And use mat and biaxial sheets. I just wanted to know about how biaxial behaves with polyester resin.

If you want to get a flavor of how woven cloth does with polyester resin, take a look at videos from professionals in the surfboard glassing industry:

https://www.youtube.com/watch?v=_73JZE1B730

If you want your noodle baked full epoxy vacuum bagged composite sandwich style:
https://vimeo.com/3950466


I have never laid cloth on the underside of a hull against gravity. I have done 'wet-outs' where the cloth is saturated on a flat surface with gravity and then rolled up and moved to the project, unrolled, and laminated.

[thinwater]

Originally Posted by Benz

Because in 1708 the mat is sewn to the biax, they don't bother with binder, so epoxy can wet it out; it just soaks up a lot. Glass mat by itself certainly has binder, and ought not to be used with epoxy.

This^^. Regular mat requires polyester/vinylester resin, but not 1708. The thin mat is just enough to improve bonding between layers when laminating by hand (vs vacuum bagging). I've used both, hand and bagged.

[Spot]

Second video above s/b from the Nelson Factory:

https://www.youtube.com/watch?v=vDnRk31yW-o