Epoxy or Polyester Resin

[Erfolg]

I have been busy trying to find what I have, no longer have, all leading to what I need.

I have no experience of moulding UC. My aluminum UC are very stiff and about 3/16 thick. Are FG undercarriages stiff, or is some attempt made to be flexible?

Any way more questions. I have now taken some photos of what I have.

I have some CF woven roving, which I am guessing is far to stiff to get to drape over the mould. Next to it is some Kevlar which is probably much the same, plus near impossible to cut, after glassing. The Woven roving at the front may drape. But is this the weight of cloth that is normally used?

The next box contains at least a few bed sheets of cloth which I used for wing skinning at 1 1/2oz per Ft^2. Is this to light using several layers? If not, would I be looking for 1/8" or so thick.

In the past the GF string was something I used to use to make wing spars. these were placed in a "U" trough ( a mould) then squashed down with a clamping system. It produced lightweight very strong flanges for a "I" spar. I am tempted to use some of this in part of the UC. This method was superseded by CF tape later, much quicker to do, no mess, although generally not as strong, although fractionally lighter.

In the bottom of the top picture is the brown packing tape I am thinking of using to create a surface from which the moulding can be released. I think, only think that i have read that some have used this in the lost foam method. What I am not clear about, is it just a barrier to the polyester resin used, or can it also be stripped out after the foam has been melted out?

I came across something called R.A.2 in a big bottle. I put it to one side to throw out. I was thinking it was part of a Epoxy bottle set, as I had thrown out some large bottles of resin, when I moved here. Just in time it dawned on me this is PVA, then sold as Release Agent number 2.

I have a large can of release agent wax, which I may try, on however i decide to finish the mould in Picture 2.

I also stumbled upon some remnants of Z Epoxy, which may do for one UC.

Does any one remember Tylon, which I think was the companies name, how to make canoes, a bible back in the 60s. There is not race of my copy.

Anyway guidance and thoughts are now needed.

[Erfolg]

Again I suddenly realised whilst in bed, I had not seen hide nor hair of my consolidating rollers whilst just mooching about in the garage looking for other things. I feel i know i would not have thrown out my big roller. Although I am not so sure with respect to my small detail roller.

I thought I could pick something up in Poundland or Budget Bargains (I think it is called) like one of the edging wall paper rollers that people used to use. It seems that it is a used to be used, in that neither sold them. Nor did ASDA where I went shopping. I am now thinking what can i use that is cheap, probably throw away? Hmm.

However I did find an original GF wing spar, that never got used. I guess it never will now. Particularly that the spar press has long since been committed to the bin.

[Nigel R]

Piers, have you seen this article about laminating U/C?

[Bruce Collinson]

Erfolg,

I thought the disposable foam rollers from Buck’s Composites were reasonable. Good service too. He’s called Graham.

Did you know that predictive whatnot has you as Errol somebody?

BTC

[Geoff S]

Posted by Nigel R on 10/12/2018 17:07:29:

Piers, have you seen this article about laminating U/C?

That's a very interesting site, Nigel. Quite apart from the article you point to there's a lot of other good stuff even though the owner insists on Imperial units which always throws me. As a convert to magnetic building boards his piece on how he makes the parts he sold before the Amazon store system changed is excellent.

Geoff

[Former Member]

[This posting has been removed]

[Nigel R]

Well he is American so we should excuse the imperial units

It's a great site. Hadn't been updated for a while though and I don't think he's been active on the forums for a year or two.

[John Stainforth]

For a release agent, I have successfully used Pebeo Gedeo Demoulding Vaseline, which is like a colourless oil, i.e., much more fluid than ordinary vaseline. (I stumbled across this by chance while snooping around a local Hobbycraft store.) I have used this with or without brown packing tape, depending on the application.

Edited By John Stainforth on 11/12/2018 00:35:18

[Martin Harris - Moderator]

Posted by Nigel R on 10/12/2018 23:24:13:

Well he is American so we should excuse the imperial units

I spent the first 11 years of my life learning to gauge distances in feet and inches and was only introduced to the S.I. when I started senior school in the mid 60s - where our metalwork was conducted in inches and thou's throughout my time there...

I'm still happier visualising distances in Imperial terms - after over 50 years I still tend to make mental approximations when someone gives me a measurement in those funny French units.

Funnily enough, I'm happy to use Celsius for weather temperatures below about 20 degrees - above which I prefer to do my mental calculations back into Fahrenheit!

I find a strange comfort in using "proper" sizes with US sourced/market model equipment and when working on pre-70s cars and motorcycles - perhaps this is what happens when you are forced to make such a radical change at a vulnerable age...

Edited By Martin Harris on 11/12/2018 01:05:04

[Erfolg]

Bruce

The roller I am looking for is for consolidation, rather than to act as either a mop or applicator.

In the past my method was to apply resin onto the mould. In the case of canoes using polyester, onto the gel coat, then roll and stipple until the cloth looked under wet, but with evidence of being wet. Then use a sponge roller that was essentially dry, to get a wetted appearance, without a sheen. The problem is that when there is a sheen there is to much resin, plus it apparently floats on the subsurface.

When i started doing glider pods, I used no gel coat (as it is added weight), then essentially used a tiny roller to draw the resin through. There being no need to mop or use a credit card to squeeze out the excess resin. That was my method.

Now there are two issues, the first is I suspect that more than one layer is needed or I have to device a way of applying pressure to allow a single thickness to be used. I am sure that the pressure moulding would be better, but requires a much stiffer mould than I have fabricated.

[Erfolg]

Ah! It looks like John Stainforth uses Brown Packing Tape as a the mould release surface?

The blue PVA works fine (as an additional release agent, if compatable with the wax or tape), and just washes or flakes off.

[Stuart Z]

Erfolg

The roller I am looking for is for consolidation, rather than to act as either a mop or applicator.

This sort of thing perhaps?

**LINK**

[Piers Bowlan]

Posted by Nigel R on 10/12/2018 17:07:29:

Piers, have you seen this article about laminating U/C?

Er, no, but I have seen others and some with laminating the main landing gear on light aircraft with a considerable weight saving . I believe Burt Rutan's VariEze had composite main landing gear legs. One of the advantages is that you can reduce the length of the wood/carbon/epoxy laminations so that the leg is tapered, providing maximum strength and stiffness at the top and more give towards the wheels. Cheaper than casting or machining a solid billet of aluminium alloy. I have never tried it in a model aircraft but perhaps I should.

A nice clear, informative article Nigel.

Edited By Piers Bowlan on 11/12/2018 12:06:07

[Erfolg]

Stuart

That is the sort of roller I am looking to use, although much shorter. I had one, which I made specifically for model aircraft. I guess it was about 3/4"or 19mm lg. I may have something about which I could make into a bespoke roller.

I am starting to think about a mini paint roller frame, some suitable bar, preferably pre drilled, then banding together some hacksaw blades, to produce the slots.

It is surprising what started out as a little job. Partially as the full size aircraft uses a bent steel spring UC and the other issue being it is not easy or convenient to buy spring steel wire, where I now live.

Still the big unknown to me is what and how much cloth should I use.

You have all helped me find a source of resin. Although, the number of laminating resins available from the sane sources, still leaves me with a degree of confusion. To think, with my naivety, i would go along to the BARCS AGM and just buy a couple of large bottles of Epoxy from the traders present and never worry about is it the right stuff. The same with cloth, I just looked at it, gauged what I needed in weight and would purchase a few meters. Generally I would buy plain weave or surface cloth.

[Bruce Collinson]

Erfolg,

Serves me right for not reading the entire trail.

If a decorator's seam roller will do it, Google has heaps, down to £1.09.

BTC

[Martin McIntosh]

Can someone please explain to me where brown paper packing comes into releasing a mould?

[Former Member]

[This posting has been removed]

[Levanter]

Martin

I think what Erfolg said was brown packing tape otherwise know as parcel tape. When I was laminating professionally we used it as a parting surface for non-critical surfaces but still important to wax and use release agent as belt and braces.
For the undercarriage it should be perfectly acceptable presuming the moulding will be dressed and painted. The only thing to avoid is getting the tape creased as this makes a male feature in the mould and a female feature in the moulding that will need filling.

Levanter

[Erfolg]

Yep, the parcel tape I am referring to is the plastic stuff like a wide Sellotape.

I am still at a loss as to how many laminations of what weight could work?

The more I think of the issue the greater is my conviction, that there will be methods that come out of the mould and just need a miniscule of cleaning up. Then there is the position where I probably am, where a lot of work is still required to produce a usable and aesthetically acceptable UC.

[Nigel R]

"Then there is the position where I probably am, where a lot of work is still required to produce a usable and aesthetically acceptable UC."

One of the plus points for wire gear. Heavy duty bender, dremel with grind wheels, all that is needed. Allow a 1/2 hr per leg to cut and bend, plus some time to solder a washer or spat support on. A front and rear leg with wood fill and covering looks smart if you need a "wide leg". Or the wire can be painted if you like. But, au naturel, still looks good to my eyes.

Although if you are quite skilled with resin methods in general, perhaps the laminated gear is a good option.

[Levanter]

Erfolg

The more sophisticated the mould tools, the less cleaning up their will be to do and with a closed mould you can have finished edges as well. The problem with that is will make only one size and would be overkill anyway.

Looking at you photos you have got the basics and after you have finished the moulding it will be an easy job to dress the edges smooth and you have some license to vary the chord, curve the edges and even adjust it to an aerofoil section if you wanted to go really mad.

A larger number of thinner fabrics will be much better than a few thick ones. If the weave is coarse, the layers are held apart and fill with resin. This will have a poor strength to weight ratio. The other advantage of using multiple layers is that you can taper the thickness. The layers can be successively stopped short as you get closer to the wheel fixing. This will be efficient and give you a greater deal of suspension.

Your parcel tape will be fine but don't get any creases in it. It will also help achieve a good finish on both side if you could clamp boards to the outside surfaces. You could use the tape again as a release surface but wax and apply release agent anyway. The clamping pressure nd settings can be adjusted to keep the arms equal thickness and excess resin will be squeezed out with considerable benefit.

Don't use the Kevlar as it does not "wet out" easily as well as being hard to cut. If you have a diamond disc cutter then fine. Kevlar is great material with extreme toughness but needs special techniques to benefit from these properties. Carbon can be made very light but is very stiff and unforgiving. That's why I don't like it for undercarriages and I am willing to bet you make something that is well over strength anyway.

It will be messy nd I would definitely use epoxy following the good advice in earlier posts.

Levanter
It is likely to be messy

[Erfolg]

Levanter

Come on, my background is in heavy engineering and chemical plants, there is no room for light weight, flimsy stuff here.

One of my problems is that I have no recent experience. Which can easily mean that the UC will be far stronger than necessary and almost as easily, far to flexible.

As to messy, I hope not, when making canoes, then later when making FG fuselages, I was (and my then girlfriend or was it fiance) pretty neat. For canoes i would have a number of mixing pots available. A number of lightweight rubber gloves. A few mixing sticks. And for me an essential thinners/cleaner.

You are probably correct, I will not recognise that i should have something to hand, until I need it and my gloved had has some sticky residue on it.

The question will be can i keep things neat now, Hmm, you could be right. Then i knew what was required before I started. Now I have to think and plan.

[Levanter]

Erfolg

Sometimes the hardest part of a job is simply starting. I should get stuck in if you would pardon the pun.

The beauty of epoxy is that it is an adhesive so if you end up on the flimsy side you can always add another layer or two and exactly where you want it. If on the other hand you have reverted to heavy engineering then simply grind a bit off. You are going to paint it anyway??

I am a shipwright by trade and that was building steel ships up to 10,000 GT. Heavy stuff indeed with equal heavy bits. Delicate is just the other end of the same spectrum.

Levanter