[rv12iS-builder]

The Aircraft Spruce catalog says "NEVER use micro between glass layers." Is it acceptable to use flox or some other type of filler between glass layers?

Thank you,

 

[mdredmond]

How much build-up do you need?

You should alternate layers of cloth and mat. A bunch of mat or chopped or milled glass can be used as a structural filler. Not sure if you can use flox between layers of cloth, but seems to me it would not be nearly as strong as mat or chopped glass.

 

[gpiney]

The Aircraft Spruce catalog says "NEVER use micro between glass layers." Is it acceptable to use flox or some other type of filler between glass layers?

Thank you,

The basic answer is NO! The strength of multiple layers of fiberglass comes from them being together with no voids or other material between them. A composite sandwich (glass-foam-glass) can also be made very strong.
Flox mixture is Very Heavy. Sorta defeats the purpose. Flox is generally used where a hard surface or point is needed.

If you could describe your problem, a better solution may be given.

 

[f1rocket]

The Aircraft Spruce catalog says "NEVER use micro between glass layers." Is it acceptable to use flox or some other type of filler between glass layers?

Thank you,

You should never use micro between layers, but flox is sometimes acceptable. There are usually other techniques that are stronger and lighter than flox to build up an area that should be explored first. Describe your problem in more detail and pehaps we can assist you with a solution.

 

[David-aviator]

The Aircraft Spruce catalog says "NEVER use micro between glass layers." Is it acceptable to use flox or some other type of filler between glass layers?

Thank you,

Having been somewhat educated in the EZ world, the answer is NO.
I do not recall ever using a filler between layers of glass.

dd

 

[Finley Atherton]

The only time that flox is "sort of" used between glass layers that I am aware of is when two lay-ups of glass meet to form a corner over a foam core. In this situation the corner of the foam is removed after one of the sides has been layed-up and allowed to cure. The resulting void is filled with flox and the other side is then glassed over the wet flox. So you end up with two glass lay-ups joined by flox at the corner.

Fin
9A Australia

 

[rv12iS-builder]

You should never use micro between layers, but flox is sometimes acceptable. There are usually other techniques that are stronger and lighter than flox to build up an area that should be explored first. Describe your problem in more detail and pehaps we can assist you with a solution.

Thanks for everyone's help. I'm working on a fiberglass rear skirt for my 9A slider. There is one area where I think I can get a smoother shape if I add some filler. I was going to add some filler, and then do another glass layup over the original layups and the filler. Based on what you guys are telling me, it sounds like I should do all of my glass layups first, and then put the filler on top, instead of sandwiching filler between the different layers of glass.

 

[gpiney]

You got it.

 

[f1rocket]

The only time that flox is "sort of" used between glass layers that I am aware of is when two lay-ups of glass meet to form a corner over a foam core. In this situation the corner of the foam is removed after one of the sides has been layed-up and allowed to cure. The resulting void is filled with flox and the other side is then glassed over the wet flox. So you end up with two glass lay-ups joined by flox at the corner.

Fin
9A Australia

That's the primary one, but if you lay a bunch of plies to make a hard point, and you need to smooth the transition around the build-up, you can lay in some flox in order to avoid any voids in the layup. Generally, the use of flox between layers is avoided because of weight, not strength. It is extremely hard and strong, as you probably know, but weighs quite a bit. Glass cloth with grab flox quite readily and not let go. Not so with with micro, which will stick to the cloth, but has a very, very low shear value and the glass will easily seperate from the micro with just a minimal shear load.

 

[DanH]

He's talking about a canopy skirt, not a structural part. No problem with flox core between cloth layers in that application.

Dan Horton

 

[mdredmond]

Another thing -

I used micro between two layers of glass for a through-hull repair to my sailboat. I laid glass on the inside of the hull, filled from the outside with micro, then laid glass on the outside. Worked just fine. But 95% of the strength comes from the inside/outside glass bonded to the hull - not the very small areas of glass that have micro between them.

So if the micro is just used to bulk up an area & there is plenty of glass/glass bonding all the way around that area, should be no problem. Imagine a ravioli made out of glass. If the filling was micro or flox, it would still be real strong.

 

[f1rocket]

I'm not going to knock anyone that chooses to put micro between layers of glass. If you determine that it's fine for your application, then feel free to do so. My comments are based upon what I learned from Burt Rutan and Mike Melville when I built my Long-EZ in the early 80's. That doesn't mean it's the gospel or anything, but it does provide other readers a perspective on where my experience comes from. I'm just trying to help where I can.

 

[RV7Guy]

depends on application

I think it depends on the application. If it is a wing lay up I'd say no. If it is cosmetic and the fill is thin, there should be no problem.

On my cowl at the inlets where the top overlaps the bottom, I used some micro filler and epoxy to match them. After sanding to shape I "locked in" the work with a layer of thin glass cloth.

For cosmetics I'd rather use the filler underneath and lock it in with another layer of cloth. Epoxy technology has improved and I think we are in better shape than when it all began. Improved for the better.

 

[David Clifford]

The Aircraft Spruce catalog says "NEVER use micro between glass layers." Is it acceptable to use flox or some other type of filler between glass layers?

Thank you,

As a builder of two Cozy MKIV's, I can say that is is perfectly acceptable and common practice to add flox between the layers of cloth for building up hard points. No more that a 1/16" layer of flox between layers of cloth. This is for hard points only though. For sharp corners where glass meets, a 1/4" "V" filled with flox provides a great joint and protection against crushing the joint.