Composite construction challenge

[coopec43]

Originally Posted by stevead

A previous poster suggested making your own f/g channel using a piece of wood as a mould/form, coated with release agent or wax. Keep in mind that plastic brown parcel tape might be easier & less time consuming than wax as epoxy doesn't adhere to it. Also great for masking off areas.

Have you ever used release agent? What could be more simple than painting a liquid onto a mold?

Why would you use epoxy instead of Vinylester which is what the OP has stated he is using?

(Don't make the mistake of believing everything the Gougeon Bros (West System) have to say!)

[GILow]

Originally Posted by stevead

I've been following this thread with some interest. Pardon me for my ignorance. I thought honeycomb construction when used on its edge would have poor shear strength?



A previous poster suggested making your own f/g channel using a piece of wood as a mould/form, coated with release agent or wax. Keep in mind that plastic brown parcel tape might be easier & less time consuming than wax as epoxy doesn't adhere to it. Also great for masking off areas.



And as much as it might be an expensive purchase, perhaps a vacuum pump would enable you to vacuum bag some of your pieces which may achieve more uniform clamping pressure than clamps, or even get to places that clamps can't. You could even use vacuum bagging to form your f/g channel over the mould, without worrying about stray pieces of glass lifting.

For the stringers, the honeycomb won’t be in shear, it will be in compression from the cut edges. And the core itself shouldn’t be taking a significant load, it’s the fibreglass either side that is taking the load. The filler piece isn’t really needed in that part of the job, except to keep water out of the core as in this case as I’m using the floor stringers to form a water tank.

The cabin sole will also be in compression, this time the faces of the panel, but according to the supplier and a few guys I’ve met who’ve actually used this stuff, there will be no problems with the load.

I got to play with some panels on a motor boat being refitted nearby and I could not believe the strength of this stuff. He was using the 15 mm version and I could not bend or in any way deflect the panel he’d built for his fly-bridge.

Vacuum bagging to wrap the ends sounds like a good idea.

[coopec43]

Originally Posted by GILow

No, nothing against buying online. It's just a time and motion thing. Getting one in will take a few days, I'm already using the one I bought. It is adequate.

Plan ahead!

As far "as a time and motion thing" I save hours and hours buying online (and I'm not running up miles on my car odometer)

[GILow]

Originally Posted by coopec43

Plan ahead!

As far "as a time and motion thing" I save hours and hours buying online (and I'm not running up miles on my car odometer)

Hard to plan ahead when the idea is given to you mid way through the job. I was going fine without it but I could see the merit in the suggestion. I wasn’t about to put the job on hold while I waited for it to arrive in the post.

[GILow]

Originally Posted by coopec43

Have you ever used release agent? What could be more simple than painting a liquid onto a mold?

Release agents are a PITA. I’ve used them before, and I’ll use them again I’m sure, but in this case I’m using builder’s film. Much easier. The tape idea is pretty good too.

[coopec43]

Originally Posted by GILow

Release agents are a PITA. I’ve used them before, and I’ll use them again I’m sure, but in this case I’m using builder’s film. Much easier. The tape idea is pretty good too.

Matt and stevead

I don't know why you say "Release agents are a PITA."

Have a look at this 2 minute video clip and tell me why release agents are difficult to use. What do you guys think is the problem?

I'm not suggesting you use PVA Release Agent for your current job. (whatever that is)

https://www.youtube.com/watch?v=hr-GSpo1jbc

[stevead]

Matt and stevead

I don't know why you say "Release agents are a PITA."

I didn't say that release agents are a PITA. I just suggested that plastic brown parcel tape is an alternative to wax or release agents.

Depending on the task at hand, you use a cost effective and appropriate technique.

And now that you've got my gander up, the video describes using PVA release agent on a piece of formica covered board. As we all know, formica is a smooth, non absorbant material and in that example the use of PVA release agent is appropriate for the task.

On the other hand if using timber as the mould, depending on the timber species (absorbency), the machining performed (smoothness) beforehand, the desired finish and the time allotted to the task, PVA release agent may not be the most appropriate method

[GILow]

Originally Posted by coopec43

Matt and stevead

I don't know why you say "Release agents are a PITA."

Have a look at this 2 minute video clip and tell me why release agents are difficult to use. What do you guys think is the problem?

I'm not suggesting you use PVA Release Agent for your current job. (whatever that is)

Mate, I don’t need to look at videos. I use the stuff. Lots. For lots of jobs. But any time I can use builder’s film instead I will use it, it is much nicer to work with and much better for repeated processes.

Release agents are good for complex moulds, and preferably for moulds that are only used once or twice.

I’m going to try the masking tape idea too, I think it might be a very good addition to my arsenal.

[coopec43]

Originally Posted by stevead

I didn't say that release agents are a PITA. I just suggested that plastic brown parcel tape is an alternative to wax or release agents.

Depending on the task at hand, you use a cost effective and appropriate technique.

And now that you've got my gander up, the video describes using PVA release agent on a piece of formica covered board. As we all know, formica is a smooth, non absorbant material and in that example the use of PVA release agent is appropriate for the task.

On the other hand if using timber as the mould, depending on the timber species (absorbency), the machining performed (smoothness) beforehand, the desired finish and the time allotted to the task, PVA release agent may not be the most appropriate method

Well it certainly doesn't have to be formica surface. PVA release agent can be used on ply as well.

"PVA is a traditional mould release agent (not the same as PVA glue!) and can be wiped on or sprayed onto a wide range of pattern and mould surfaces to provide a very compatible and reliable release barrier for polyester, vinyl ester and epoxy composites".


I laid this up over a ply mould using PVA release agent. (Certainly not parcel tape!)

[Matt Johnson]

Originally Posted by coopec43

Well it certainly doesn't have to be formica surface. PVA release agent can be used on ply as well.

"PVA is a traditional mould release agent (not the same as PVA glue!) and can be wiped on or sprayed onto a wide range of pattern and mould surfaces to provide a very compatible and reliable release barrier for polyester, vinyl ester and epoxy compositesI know from experience".


I laid this up over a ply mould

That was raw unfinished plywood?

[coopec43]

QUOTE=Matt Johnson;3626070]That was raw unfinished plywood?[/QUOTE]


I laid that fiberglass moulding (using polyester resin) over a finished plyboard mould (using PVA release agent)