Originally Posted by skybattle

I think I will try with epoxy for future.

You won't look back, with the caveat that don't go cheap with your epoxy.
"Quality is remembered long after the price is forgotten."

D.

Originally Posted by skybattle

I think I will try with epoxy for future. ...................................

I don't think you will regret it. That then opens up another series of choices and considerations about what method of construction you use. Factors influencing this decision are:
1. Size of the mould.
2. How many pulls are anticipated from the mould.
3. What materials are available locally without incurring high freight charges.
4. If you have welding skills, steel framed, light shell moulds are on option. Like I did for my Entropy. Also, Larrikin Dave and Co did for the Sniper. (I may have even got the idea from them, can't remember that far back).

An example of # 3 is the so called: "DIY Corian" as described by Timbuck and others. It is obviously a very good and quick method for smaller sized moulds. If it is good enough for Tim, it is sure good enough for me! ATH is not available locally where I live and transport costs would be expensive. That is the only reason I have not tried it.

https://www.rcgroups.com/forums/show...-corian-moulds

As a relative beginner, it might be best to do what I did when starting out (and I still do). That is to open a build thread with as much information as is available at the time when starting a new model design and build.

Originally Posted by Larrikin

You won't look back, with the caveat that don't go cheap with your epoxy.
"Quality is remembered long after the price is forgotten."
D.

Great quote Dave!

Originally Posted by Larrikin

You won't look back, with the caveat that don't go cheap with your epoxy.
"Quality is remembered long after the price is forgotten."

D.

Yes, price and effort are forgotten after a good result. Totally agreed with you!

I don't have welding skills, but fore sure I will try epoxy moulds. Epoxy gelcoat is about double of expensive than polyester one, but... (Dave told everything that can be told).

Thank you!

What size model are you looking to build? How many parts are you likely to make from the moulds?

It is about 1 m. of wing span.

I thought in making at least 10 models from these moulds, but it was only a personal and unreal estimation.

How many models can you produce from your epoxy moulds?

Originally Posted by skybattle

..................................

How many models can you produce from your epoxy moulds?...............

I will never find out. That is because it is few. The reason that I asked, is that this is one of the factors that will influence your decision about what you make them in and how you make them. Just trying to draw out more details from you so we the readers can assist better.

Thanks, Jim.

To the extent that I am making progress I will tell all of you.

I will end the wing mould with vinylester, and, after the result, using wax+VPA this time, I will decide definitely if continue with that or not (I'm sure that no).

Cheers,

Vinylester is excellent for mould making. Make sur that you postcure the moulds properly, or at least let them age enough before use to make sure they won't release any styrene vapours anymore. This will ensure a proper product release with only a (good) wax treatment.

I think styrene migration and wax only has already been covered.

I am making the first half of the wing mould and I have found again these 'little caves'. Are they made from air bubbles? It's strange because I am very careful applying the gelcoat...

Have you happened any time the same?

The only thing I can suggest is that they are in fact air bubbles. Darned annoying for sure!
Have you arrived at a conclusion yourself yet? What do you think caused them?

When applying the epoxy based gel coat that I have used, the method suggested is to push the material along the surface, rather than painting it in the normal way you would when brushing on paint. I don't know if this explanation is clear enough or not, but a special technique is certainly required for thick gel coat application.
I have been meaning to do a simple drawing of trailing edge mould and part treatment for maintaining a thin TE and to post it here. Have yet to do it!
I'll see if I can get it done tonight.

Jim.

It hopefully demonstrates two ways of mounting a wing plug in a parting board.
In the top drawing, the plug is supported by wedge section shaped strips, possibly hot melt glued in place to support the plug with the chord line coinciding with the parting plane.
The second one uses chamfered and/or routed edges on the parting plane to support the plug.

This is the stage that affects directly the thickness that the trailing edge will be between the two mould halves.
I hope this might still be relevant to the discussion.

Hi, Jim:

Yes, I think it can be bubbles, and 'pushing' can improve the result. I use this method for resins, but not for gelcoats, so I will try to 'push' the gelcoat too.

Very interesting draw of how to 'adjust' the thin trailing edges.

I'm afraid I am using the first one, and I think the second one could be much more precise, although more complicated to make it. A lot of sanding .

I think I will finish the wing mould during the next days. Hope to have luck with the wax+industrial talc+PVA combination.

I saw that, accidentaly, the mould was receiving heating from the sun during the curing process, so I hope this doesn't damage the wax and in general the demoulding system.

Cheers and thanks,

Originally Posted by skybattle

.......................................
I saw that, accidentaly, the mould was receiving heating from the sun during the curing process, so I hope this doesn't damage the wax and in general the demoulding system............................

If the epoxy was at least partly cured, I would not expect any problems, even though it is summer in Spain! Probably best to avoid strong sunlight (heat) during any moulding process.

I will do another drawing of the layup of parts in a wing mould, with special attention to the matter of "thin trailing edges".

Originally Posted by skybattle

.......................................
I saw that, accidentaly, the mould was receiving heating from the sun during the curing process, so I hope this doesn't damage the wax and in general the demoulding system............................

If the epoxy was at least partly cured, I would not expect any problems, even though it is summer in Spain! Probably best to avoid strong sunlight (heat) during any moulding process.

I will do another drawing of the layup of parts in a wing mould, with special attention to the matter of "thin trailing edges". The short explanation is to stagger the fabric layers, leaving only one layer at the last 5 or 6 mm of the actual trailing edge.
More about that later...................