|Jan 23, 2013, 01:28 AM|
Hoping the paint is coming out some now Jim and looking better in the Morning.
Jim perhaps it is where you have keyed it up, but is that RHS plated ? A bit hard to tell from the photos.
|Jan 23, 2013, 02:35 AM|
The RHS is plated and of the variety called here: "Duragal". (spelling?) It's not quite up to hot dipped galvanised quality, but fairly good.
I chose it above black or primed as it was offered on special - cheap. No other reason. Judging by the force and persuasion I had to put into splitting these two halves, I'm confident of the bond with the vinylester resin is very good.
All things being equal, I would have chosen black mild steel.
|Jan 23, 2013, 03:18 AM|
It's great to see you've got a usable mould despite the stickup.
|Jan 23, 2013, 04:48 AM|
2 pack primer.
Thanks for the details about the use of 2k primer. I understand all your reasoning about the acrylic primer. For the very reasons of solvent retention etc., I left the plug for days between coats, and then for 10 days or so before spraying with 2 pack after the last application.
While I still don't think this is the explanation for the stick up, I'll defer to the experience of yourself and Tim and use it next time.
I did spray it on lightly, but some spots would have been thick, that is for sure. No solvent smell was apparent when I finally split the mould.
I completely fail to see how it would cause a 2 pack finish over the top of it to stick so well to the mould.
Maybe I'm missing something, but that is what I'm thinking.
Conversations with three of the pro's this afternoon with the evidence in front of us, combined with my recall of applying the PVA in such hot conditions (42 deg.), have convinced me (and them) that it was a problem with the PVA.
Like I have posted above, my plank wing plugs pulled very easily and they were done with acrylic primer and 2 pack finish. They were done in cool conditions though. Otherwise, exactly the same procedure.
Correction: the plank wing moulds were epoxy. This fuse mould is vinylester tooling resin/glass.
It's good to know that I can leave some primer in the gun for up to 2 hours. Thanks for the tip.
edit: The other four plugs (2 wings and 2 tail surface plugs), are also primed with acrylic lacquer and finished in 2 pack paint. It's now out of the question to completely strip all these and start again with 2 pack primer and filler. So, I will be continuing on with them like they are. The results of these will reveal something one way or the other. If you and Tim are correct, they will all stick up and be ruined!
I'll start with one of the small tail surfaces. Less to rebuild if it sticks and cannot be fixed etc.
By the way, is the "Dolphin Glaze" filler a single pack solvent based product? Or a 2 pack product?
|Jan 23, 2013, 02:42 PM|
Have you been able to obtain Duratec primer/surfaces in quanitities less than 5 litres?
I would still like to try some if I could get small amounts.
A couple of the comments that my Woopi pro friend said when he was looking at my disaster were interesting. He said that he has gone off using any paint for plugs and now uses only polyester based spraying gel coat. He also is looking at Duratec.
He also said that "I may have cooked the paint". A combination of the high atmopheric temperatures and some unavoidable exotherm, more significant than what would occur with epoxy, could have done it. As well as a poor film of PVA.
But I know you think it was the primer, you may be right - I have noted that and won't use it again under paint. I'm hoping that I don't have to use paint again actually!
|Jan 23, 2013, 02:54 PM|
Tail surface test strip.
As a result of the above stick up, I have a plan to do a small test with one of the tail surfaces.
I'll sand the 2 k finished plug to about 800 grit. Set in the parting board etc. Wax at least 3 times. Then apply the PVA very early in the morning when the temp is around 18-20 deg.C or so.
I will then do a small test strip across the plug using some scrap veil and epoxy.
Just for safety sake.
Also, it will clarify some things.
The plugs have to be completely stripped if Tim and Sean's conclusions are correct anyway. So nothing will be lost if this test fails than is already. If it succeeds and the test strip releases, I'll clean it up with water, wax and PVA again and continue to build a mould around it.
|Jan 23, 2013, 04:04 PM|
I've just finished duratec coated poraver epoxy molds. very happy with the results so far.. I'm polishing today so time will tell on Finnish I can get.
Sean will probably use what I have left over from this 5l batch if we are happy with Finnish.
It is a bit of a process...harder than normal epoxy molds. Very short spray time
1. Spray high gloss top coat
2. Vinyl ester primer
3. Hot box for 12+ hour @ 55+ great rid of solvents (shrinkage)
3 make mold.
4 hot box
5 pop mold , and sand with 800..... Then hot box @ 50. 12hrs +
This is to release all solvents from mold surface.. (shrinkage).
6 , wet sand 1200, 2000, polish...
|Jan 23, 2013, 05:02 PM|
Is the top coat @ step 1 Duractec Primer/Surfacer? or another one of their product range.
Is the mould @ 3 a conventional epoxy mould?
Did you finish the plug with one of the Duratec products? If so, which one?
|Jan 23, 2013, 05:11 PM|
Pics are on my GIZMO 36 thread....and info.
Plugs are epoxy.
Mold surface is high gloss duratec top coat.
backed with duratec vinyl ester primer.. ( gives something for the epoxy to stick to)
Then I build normal poraver molds. I'm making multiple sets of molds.
Resason I did it this way is to have repairable and polishable molds.
And to keep learning...
|Jan 23, 2013, 09:44 PM|
I've removed most of the stuck paint in the moulds, they will be completely recoverable and just need a few small repairs. Much relief in this camp!
Meanwhile, I have set one of the tail surfaces in it's parting board and started to wax it up. When I have 3 coats of wax on it, I will do it with PVA in the cool of the evening.
I plan to do a small test strip across this surface with some scrap glass and L3600 Araldite resin.
Guess what? I expect it to pull without problems. And furthermore, I think it will vindicate Tim and Sean's claim that the primer is the problem, and not disprove it!
Sound counterintuitive? Yes, I agree.
Here is my reasoning:
John from JT Fibreglass up at Woopi made an observation that I may have "cooked the paint". This suspicion is supported by the appearance of bubbles under the remaining paint on the plug. If that occured, it could have only been the result of the exotherming of the vinlyester. I did each side in 3 sessions thinking that was prudent enough, allowing it to cool between. Perhaps they should be done in even more smaller/thinner sessions.
The epoxy is not so prone to exotherming, especially the LC3600 with it's long pot life etc. Nice stuff to use!
Furthermore, as I have posted previously, the wing moulds for my moulded plank pulled cleanly; they were constructed using the LC3600 resin.
Adam of WWWorks has a thread specifically for posting the performance reports on combinations of resin/release system/paint etc. to further the understanding that combinations of these can work, while changes to one may result in a stick up.
I did not pay it much specific attention at the time as it was specific to US available materials and had little relevance to what I can get here. However, the principle is what is most important and of relevance here.
So, I will be revising much of what I have done here for future projects, if there are any!
Epoxy resin throughout will be the first and most definate thing to change over to.
No more vinylester. In the right hands, it would still be good I believe. But my 5 attempts at fuse moulds, all of which stuck, has made me a bit shy of it. Note here too: all 5 had varying kinds of paint, polyester spraying gel coat and some I've forgotten. All of them stuck!
edit: Note that the ambient temperatures were extremlely high while I was doing the layup of the vinylester in the mould. We had a heat wave over much of the country at the time. For a starting temp of 40 deg. C, plus, let's say, 20 deg. of exotherm above that, the resin might have been up to 60 deg. C. These are only estimates, but my point is a high starting point leaves much less margin for a rise in temperature.
|Jan 23, 2013, 10:52 PM|
Maybe one like yours. Or better still, one of yours (that you build of course).
It's a bit small for a visually challenged old bloke like me though! I have difficulty seeing my Cobra or Speedo flying at times. I lost sight of the Cobra completely at Borah, and Pismo Jim saved it!
|Jan 24, 2013, 01:00 AM|
This tip is totally new to me and I have not read about anywhere.
My proffessional fibreglasser friends at Woolgoolga suggested dusting the well waxed (as usual) plug or mould with talc before applying the PVA. The excess is dusted off and/or blown off with air.
Then apply the PVA with your preferred application method.
I tried it today with fantastic results! The PVA goes on continuous and homogenous without any surface tension problems like fisheye development and such. I have just done a plug with it and it looks like a nice even coat of clear varnish. Hardly even a wipe mark in it; I applied it with a kitchen sponge.
I've bumped the PVA application thread with this post.
|Jan 24, 2013, 04:42 PM|
Release test(s) successful!
The small release test that I did yesterday on the tail surface lifted off with almost no effort.
I'll now clean it up with water to remove the PVA entirely, dry it, wax again and then dust with talc/PVA as previous. I want to re-establish a nice seamless film of PVA.
I'll do both the surface together for obvious efficiency now I've regained my confidence after the setback with the fuse.
While I was at it, I did some release tests on an old plug that has been hanging in the shed for some years. It is painted with cheap rattle can paint that is, needless to say, totally cured. I prepped it as with the tail surface above. Then when the PVA was dry, I wet out two strips of cloth, one with epoxy and one with vinylester tooling resin, and stuck them on the fuse. Both released completely easily this morning.
Several things can be concluded from these extra-curricular test results (I think). It (at least) seems to confirm that a combination of heat (atmospheric + some exotherm) will cook the paint, especially if it not either all catalysed paint, or alternatively, totally cured (aged for a long time). The cooked paint will then release any remnants of volatile solvent which then sabotages the release system.
Alternatively, it does show that both resins release similarly, all other things being equal.
The project is going ahead after all. In the finall analysis, it's only my pride that is permanently damaged! It took five fuse plugs stuck to learn the above.
Not a nice record to have.
|Category||Thread||Thread Starter||Forum||Replies||Last Post|
|Build Log||Astro Flight Super Monterey: Build Log!||hugofly||Sailplane Talk||92||Dec 08, 2014 06:40 PM|
|New Product||Nanoshark ARF- Build Log - High Performance Depron Airplane||NanoDave||Foamies (Kits)||139||Jun 04, 2014 11:04 PM|
|Question||"Modular" EasyStar build... (And log).||Incendium||Foamies (Kits)||38||Nov 30, 2010 08:13 PM|
|Build Log||Dumas Eindecker build log?||mcjustis||Scratchbuilt Indoor and Micro Models||17||Nov 26, 2010 09:04 PM|
|Build Log||Slo-mo-shun build log on Scale Boats||JeremyBB||Racing Boats - Electric||3||Nov 04, 2010 08:18 PM|