Copydex

[Martin McIntosh]

Just tried gluing a 2mm Depron skin to a balsa wing frame with Copydex. Despite giving it plenty of drying time before bringing the surfaces together it virtually fell off the next day. I have used this many times before without any problems. Re did some using a fresh piece of Depron with UHU POR and it sticks fine, so has the glue formula maybe changed in some way? £18 quid for nothing!

[Engine Doctor]

What did the glue lift from , the wood or the foam ? If foam suspect release agent used in manufacture is the culprit . If its the wood then ? It could be duff glue or as you say a fomula change. "New improved  formula" usually equates to cheaper to produce and not as good .

Try wiping the foam with some isopropyl prior to glueing.

[Martin McIntosh]

That is a thought. Every scrap of it easily lifted off the foam and I rubbed it off the balsa. The foam is from a large batch I bought a long time ago so should be the same. The Copydex bottle roes not appear to be any different to previous ones. I shall `stick` with the POR.

 

Thanks.

[Paul De Tourtoulon]

Glue's, paint and even Acetone has been got at by the 'greens' now all useless,,,,😈

[Cuban8]

Apologies for veering off topic a tad, but has anyone else noticed how Methelated spirit smell so very much different to how it did years ago. Always remember the distinctive odour from the wonderful old Mamod steam engines filling the house and mum doing her nut with me!

Modern Meths smells very much like IPA now - strange.

[Don Fry]

Are you sure it’s not the smell receptors are not wearing out. 

[PatMc]

2 hours ago, Paul De Tourtoulon said:

Glue's, paint and even Acetone has been got at by the 'greens' now all useless,,,,😈

I don't think it was anything to do with the Greens, it was simply realised that a lot of easily available adhesives etc were using chemicals that were harmful when being used without proper precautions being taken.

[Cuban8]

3 hours ago, Don Fry said:

Are you sure it’s not the smell receptors are not wearing out. 

No, the aroma of old style meths is very distinctive and is clear in my memory from camping burners used on fishing trips as a kid, burners in toy chemistry outfits, and the good old Mamod engines.

I did lose all sense of taste and smell when I caught a dose of Covid a while back, but I'd already noticed that Meths seemed very different way before that.

BTW, what an extraordinary experience losing ones senses of small and taste was (now all back to normal for well over a year now). Even my favourite hot chilli pickled onions (my secret home made practical joke on unsuspecting guests) just tasted like balls of damp paper to me for a couple of weeks.

[leccyflyer]

Old fashioned meths smell is very familiar from the dreaded vaccinations in school- get flashbacks every time I open the bottle!

[PatMc]

2 hours ago, leccyflyer said:

Old fashioned meths smell is very familiar from the dreaded vaccinations in school- get flashbacks every time I open the bottle!

Was the school nurse an alcoholic😄

[Jon H]

17 hours ago, Paul De Tourtoulon said:

Glue's, paint and even Acetone has been got at by the 'greens' now all useless,,,,😈

 

I have to admit i am somewhat in agreement. I cant get decent slug pellets any more as the good ones were apparently toxic if you ate them. Who knew? a poison being toxic? knock me down with a feather. 

[Gary Manuel]

24 minutes ago, Jon - Laser Engines said:

 

I have to admit i am somewhat in agreement. I cant get decent slug pellets any more as the good ones were apparently toxic if you ate them. Who knew? a poison being toxic? knock me down with a feather. 

I'm not a greeny by any stretch and generally agree, but I must admit that I think that slug pellets are the devils work and need to stay banned. Slugs eat pellets then hedgehogs and birds eat the slugs. All die a painful death, then other animals feed on their carcasses and die too. On that cheery note, I'll leave you to clear your shed out and dispose of your old slug pellets carefully. 💀

Edited May 3, 2023 by Gary Manuel

[Jon H]

Sadly my garden is slug/snail central and its carnage without slug pellets. There are no hedgehogs near me and i havent seen a thrush in years 😞 if there were i probably wouldnt have a slug problem to begin with.  If these natural predators were still around i would gladly lay off the slug pellets, set up a hedgehog dinner table and watch from the window. For the birds, i left the dead stalks of last years sunflowers up so they would eat the seeds all winter. I watch them from the kitchen window. 

 

The other day when finally clearing them up this guy came to visit and was catching spiders all over the place. He had no fear at all and as soon as i turned over any earth he was in there. I almost bashed him with the trowel accidentally he was so keen. 

 

 

 

In any case i do try and keep the place animal friendly, and in fact its the local cats that cause the most problems as they think my flower bed is one giant litterbox 😡

 

I guess that is enough tales from the garden for now, back to the glue chat. 

 

 

 

 

 

 

[leccyflyer]

2 hours ago, PatMc said:

Was the school nurse an alcoholic😄

Discussed it with my wife this morning, in case it was my memory playing tricks - she remembers the same - they gave the needle a sloosh in meths and then dipped a cotton wall ball in the meths before rubbing it on your arm. No such thing as  disposable alcohol wipes in those days. The smell was very distinctive.

[PatMc]

Are you sure it wasn't surgical spirit ? Meths is antiseptic but (AFAIR) it also prolongs bleeding time.

[leccyflyer]

Definitely meths - purple in colour.

[Don Fry]

I’ve just had a wander on the net. JD8 is right. 
Old fashioned meths was ethanol, methanol to make it poisonous, something to make it bitter and unpleasant, dye, and other refinery bits.

In 2013 the formula changed. No methanol, different and more complex bitter flavours mix, and refinery bits,  no longer poisonous per se. No longer has a harmful substance label. 
I wonder how we slept without that knowledge. 

[Martin McIntosh]

OK back to the glue. Tried washing down the foam with IPA on a test piece. Same result, the whole lot simply fell off. Should be alright on polystyrene though.

Slug pellets? When I read that they would become green I wondered about the ones I am already using and found that they are indeed `green` but they work fine. The things dry out very quickly once dead so no self respecting bird would look at them. Copper grease painted around access areas to pots stops them in their tracks before they can get near my chilli peppers.

[Engine Doctor]

Sounds like its the copydex thats changed then. Use the POR or Deluxe Materials Foam2Foam thats brilliant.

[MattyB]

19 hours ago, Engine Doctor said:

Sounds like its the copydex thats changed then. Use the POR or Deluxe Materials Foam2Foam thats brilliant.

 

So in summary, Copydex for wing skins.... Never that good originally, and now even worse than it used to be! That about cover it?  😉😄

 

PS - If you really want wing skins to adhere, the best way is to stick a thn layer of glass cloth on the foam, wet it out sparingly with skinning resin, then vac bag the lot. Cores done this way adhere very well, though you have to be careful not to use too much epoxy or it can come through the wood or go into the foam giving a heavy result.

 

Edited May 4, 2023 by MattyB

[Jon H]

Dont you risk warping a soft foam core with the vac bag? 

[MattyB]

No, it's a completely standard construction method amongst slopers, though a lot less common than it used to be.

 

If you use s strong pump like a nebulizer or commercial job you do need a regulator to not go beyond your target pressure, but I have used a reversed fish tank pump for doing skins like this which provides a perfect (not as low) pressure for wood skins. You can just turn on and leave overnight with impunity.

 

I've done a few models this way ~10 years ago when I had workshop space, but the only one I documented online was the Limit EX. I don't think I added glass underneath the skins on that one though, it was just on top with some fake laminating pouch based "mylars")...

 

https://www.rcgroups.com/forums/showpost.php?p=21050310&postcount=252

 

 

 

 

Edited May 4, 2023 by MattyB

[MattyB]

DIY setup

 

Old vid on how to do it (quite long and detailed):

 

 

 

 

[Mike Chantler]

5 hours ago, MattyB said:

 

 

I've done a few models this way ~10 years ago when I had workshop space, but the only one I documented online was the Limit EX. I don't think I added glass underneath the skins on that one though, it was just on top with some fake laminating pouch based "mylars")...

 

Do you put skins + glass on all in one go, or in two stages?

[Mike Chantler]

I use a cheap 12v vacuum pumps with veneer skins on EPS cores (see link below). On that model I added 25gm glass separately after bagging the skins, took me ages to get a good finish - never thought of using laminating pouches. I had tried bagging glass directly onto foam using thin mylar or similar - but got a very dimpled finish. Using it with glass/veneer combo sounds good though 🙂