HVLP kit

[Nick Allen]

Has anyone perchance had any experience with this cheap(ish) HVLP kit?
http://www.hvlpshop.co.uk/Apollo+Spraym ... eb4198c377

[JimCrawford]

Hi Nick,

I've been investigating HVLP kit for a while with an intention of getting a set for glider work, fabric and composite. Since we live so close it may well be worth sharing the purchase cost, drop me an email if you are interested. I've also got a couple of ideas re spraying which may interest you even if you don't want to sydicate.

Jim

[Nick Allen]

Hi Jim

PM sent....

Cheers, Nick

[cholmondeley]

Hi Nick

Also v interested in that bit of kit. Did you buy it? Any good?

[Nick Allen]

No...immediate plans for its use got overtaken by events (the syndicate decided to have the wings completely recovered next year, and the fabricer will do the paintwork -- so no need for "restorative" work). But I'm still interested in how good they are for future use!

Nick

[JimCrawford]

Hi Nick,

I bought the next unit up - the spraymaster 1500 - and will be spraying the fuselage of a K13 in the next week or so. I'm using the Ceconite system; nitrate, butyrate & 2 pack polyurethane and I'll keep you up to date with progress. I've used it a bit with 2 part epoxy for painting the fuselage tube structure but that wasn't completely successful as the spray pattern is rather wide for spraying tubes without shooting most of the paint into thin air. I contacted the HVLP shop about this and the helpful chap there suggested fitting the smallest needle rather than the standard. It might work but I had a freshly blasted frame and no time to experiment so I hand painted a second coat. I couldn't find an alternative gun that runs on this turbine, I would have been happy to get an extra gun for detail and tube work. We will soon see how it performs when the fabric needs it's paint.

I discovered that there are several detail guns that are called HVLP but this is misleading as they run at pressures of ~ 2 -3 bar whilst this turbine runs at ~ 0.5 bar. I may still get one as another factor has come into play. For the 2 pack polyurethane I need a air fed mask. No problem but they run off high pressure air so I'll need a compressor anyway. On purely economic grounds you may conclude that it would have been more sensible to sink the HVLP cash into buying a really good compressor and using high pressure kit. Time will tell.

If I had been doing only fabric work and using paints that could be sprayed with a normal organic solvent mask then the HVLP set is an attractive stand alone kit.

Jim

[Brian Hope]

I used to spray cars and lorries for a living - long time ago now admittedly. Then I used the traditional compressor and high pressure guns. Later I bought one of these 'amateur' type HVLP sets, I think it's an Apollo but it's up in the hangar so I'm not sure without going see. I'd certainly recommend HVLP to the amateur painter as my 'relatively cheap' set does a perfectly good job. Considerably less overspray, though you should still use an air fed mask if you're using two pack poly or similar. These guns will handle nitrates and butyrates very well indeed, two pack needs to be maybe slightly thinner than you'd get away with with high pressure. Keep the gun moving, and keep the wet edge but practice and then practice some more on stuff that doesn't matter before painting your precious aeroplane. Like many things, spray painting does require a degree of skill but anybody can master it with practice. Dopes are more forgiving for the amateur than two pack so if you're a newbie and want to paint (new) fabric, stick with dope. It flashes off faster so you'll end up with less dust in it, and you can flat back runs and polish out less than perfect areas. Be very careful with dopes if you are over-painting. You must be absolutely sure that the original finish is compatible or the dope will pickle it up and you’ll have a right mess to deal with.

[JimCrawford]

Brian,

Thanks for your gen. Your remarks have boosted my confidence in the face of the looming task. As a rank beginner I'm building a frame to practice on before I point the gun at the aircraft. I would prefer to have used dopes (or maybe polyfibre) for the whole process but our traning gliders are very heavily used (~1000 launches / year) and each launch involves much clambering in and out and ground handling - often by inexperienced crews - so the robust 2 pack finish is necessary. A dope finish would soon become grubby. Also most glass gliders are supplied or refinished in 2 pack to get away from the problems associated with gell coat so, as I intend to refinish my LS4 in the near future, I'll have to take this particular tiger by the tail!

Jim

[Brian Hope]

Hi Jim, I should have mentioned that butyrate (colour) dope is pretty poor adhesion-wise on other than fabric so would not be a good choice for a glass glider. A two pack polyurethane would be a better choice.
Rgds, Brian

[Terry Lee]

Sorry to butt in on this but I just wonder if any expert has experience with spraying poly 2K on to Ceconite fabric. Two years ago I recovered the doors on my Terrier, I'd done some research and concluded that the best route was Nitrate dope followed by butyrate and UV coat then the poly 2k top coat with flexible additive added.

I was then advised, 'by someone on here, 'if I remember correctly'' to apply the poly top coat directly onto the Nitrate coat and omit the butyrate, this I did by mixing aluminium paste in with nitrate dope to serve as the uv coat.

The reasoning for doing it this way was that it was suggested the polyurethane would absorb into, and adhere better to the Nitrate. And my conclusion is that it was good advice, as 2 years on the finish is as good as it was the day they were sprayed, also I achieved a less wet look high gloss finish, which is what I wanted, I assume thats because the top coat absorbs more into the fabric whereas the Butyrate would act as a seal on the fabric. And to reinforce my theory I've seen a couple of aircraft that I know have been finished with poly 2k onto Butyrate where bits of paint have flaked off.

Just wondered if anyone has view on this, as I'm planning to recover my Elevators next.

[JimCrawford]

The more comments the better is my opinion.

I'm using the Ceconite system exactly as per the Ceconite manual, if for no better reason that I hear so many conflicting different ways of doing things that RTFM is a more consistant way to work. A few notes on Terry's post.

One comment I've heard, and can believe, is 'Don't mix systems. Get the whole scheme from one supplier and stick to it'. If you are adding a flexible additive to the 2K it implies you are using a base which was really designed for a solid substrate, metal or grp, and not for fabric. The Ceconite manual goes into chapter and verse about this being a very bad idea. Of course this may be influenced by the fact that they would prefer you to buy their 2K product (at greater expense), but it is a coherent rationale. I'm not convinced that the 2K is absorbed into the underlying dope, nitrate or butyrate, because the chemistries are completely different. I would think that the 2K sticks by mechanical bond. Also the first coats of Nitrate should seal the fabric so there is no question of the 2K being absorbed into the fabric.

I can see that it could be reasonable to use just nitrate right through with no butyrate, as the butyrate is only used because it is less flammable than nitrate. This isn't a factor in a glider but, as the Ceconite UV layer is only available as butyrate, this would mean violating the 'don't mix systems' rule.

At my club I have repaired several examples of paint flaking but I cannot attribute it to any particular cause as each aircraft has been painted using different schemes over the years. At least, as an innocent abroad, I can resist all the homebrew opinions by just following the manual which involves stages where old hands have told me "you don't need to do that" or "it is quicker this other way".

I researched the alternatives and probably would have gone the polyfibre route as all the layers are based on the same vinyl formulation and so should consolidate well. However I pretty well have to use a 2K finish for it's robust nature and as I'm only doing the fuselage of this aircraft, the wings were done by somebody else ~ 5 years ago in Ceconite and dope, then I'll stick with dope to keep the aircraft all the same.

We shall see!

Jim

[JimCrawford]

More gen on this old thread:

http://services.lightaircraftassociatio ... f=4&t=1921

Jim