1/35 Schnellboot Typ S-38 rc conversion

[Arjan]

Hi Stephen,  I have more or less followed the recommendations Vallejo provide for spraying Polyurethane surface primer :

 

https://acrylicosvallejo.com/en/category/hobby/surface-primer-en/

 

I read somewhere Vallejo recommend using an 0.4mm nozzle which to me is an indication that clogging is definitely an issue with this type of paint. . I use Vallejo Premium reducer (62.066) to dilute the Polyurethane stuff.  I really doubt if the normal Vallejo Airbrush thinner (71.161) is suitable for diluting  Polyurethane paint/varnish. I use an airbrush with an  0.3mm nozzle and it usually clogs up at some point. I have never tried the Vallejo flow improver so I don't know if this stuff is any good in preventing clogging/tip drying. Cleaning the nozzle afterwards is also an issue, normal enamel thinner and alcohol doesn't seem to affect the Polyurethane paint once it has more or less dried 🙂. I have never tried Vallejo airbrush cleaner but I doubt if it works well for cleaning the nozzle after having sprayed Polyurethane paint. To sum up, I really can't  recommend  Vallejo Polyurethane paint for spraying and whenever possible (especially for smaller surfaces) I apply it with a conventional paintbrush.

 

Regards,

 

Arjan

[Stephen Allen]

Thanks Arjan

 

A very full, frank and useful response about the properties.  I will do some experimenting on my test pieces to see what effect the flow improver has, and I was planning to use a larger needle/tip size, probably 0.5mm, before moving on to my miniature Iwata spray gun. The news about cleaning is worrying, but I will try some lacquer thinner, that usually shifts just about anything, and i understand that methylated spirits will dissolve the paint. I am still at the experimenting stage before I go anywhere near a real model.
 

This advice reinforces my views about the excellence of your work - great finish with a brushed coat.

 

cheers

 

Steve

[Arjan]

Thanks Steve, please keep me posted about your findings regarding the flow improver and cleaner.

 

Regards,

 

Arjan

[Stephen Allen]

Shall do. I use surplus white bathroom tiles for practice - being very smooth they help to show whether you are getting any orange peel or dusting, and they are easy to clean off and use again.

[Greg Law]

Arjan 

I had a big day today putting the S100 hull together. All went well with the boat. Unfortunately I spilled a new bottle of Tamiya extra thin over my coffee table. The table must have a very good clear coat on it as it wasn't effected at all. Probably smell for a few days. I also ordered the prop shafts for it.

[Arjan]

Hi Greg, better to spill it over a table than the model 🙂. I'm looking forward to seeing some pics of your models. 

 

Regards,

 

Arjan

[Greg Law]

Unfortunately Arjan it is going slow. I was planning to tackle the running gear on S38 this weekend,  but I got in two new work projects today, which means a weekend of work. These are good projects which I make good money out of, so they must be done. It's like that a feast or a famine.

I did get the screw covers on S100 today and finished sanding the covers on S38.

[Stephen Allen]

Arjan

 

I have now had the opportunity to have a bit of a play with the Vallejo RC Premium Matt Varnish. I sprayed following the recommendations in the Vallejo guide. I used a Paasche H external mix airbrush using a No.3 tip/needle. I used the ‘H’ because it is easy to break down and thoroughly clean, given the concerns about cleaning a polyurethane-based acrylic out of an airbrush. I used the Vallejo Premium Reducer (thinner) at the suggested ratio of 1 part Reducer to 3 Parts paint. I didn’t use flow enhancer, and I haven’t tried spraying it straight out of the bottle. My air pressure at the compressor was 38 psi, within the 30 to 60 psi range suggested by Vallejo in their brochure. I sprayed over glossy finish white ceramic bath tiles. One tile was half covered with a light grey enamel from Colourcoats, US Standard Navy Gray, and one with a strip of Colourcoats Night - just happened to be the colours I had ready for a Tug. As a comparison I also sprayed half of each tile with Revell enamel Matt 2, another matt clear coat I am considering. This was thinned 6 parts Colourcoat thinner to 4 parts varnish, as this seemed ‘about right’ for the rather thick consistency of the paint out of the tin. The Revell was sprayed at about 18 psi.

 

i didn’t experience any problems with either of the paints. I interrupted the spraying of the Vallejo to refill the colour cup, about two minutes, and the airbrush took up right where it left off without clogging.  Tightening the tip up, the Vallejo does seem to stop spraying a little earlier than the Revell, but opening the tip slightly again allowed spraying to resume normally again. I didn’t try the flow enhancer because I really didn’t need it.
 

Both the Vallejo and the Revell dried to an even, smooth, matt finish without frosting. Under raking light the Revell enamel looks a tiny bit rougher but this isn’t really discernable under normal light. The Revell is a touch more matt than the Vallejo. Subjectively, neither varnish has much effect on the look of the underlying colour, the Vallejo finish seems to slightly lighten the paint in comparison to the Revell but that could just be film thickness.  The white bits of the tiles remained white. After letting them dry for about 24 hrs I subjected both finishes to a gentle fingernail scrape test - both varnishes marked about the same with a visible shiny line and in neither case was the underlying paint scraped. The Vallejo didn’t seem any more resistant to the scratching than the Revell or vice versa.

I cleaned the airbrush right after spraying each time - the enamel just dissolved away with a bit of enamel thinner as usual. The Vallejo was starting to form skins on the side of the colour cup, but these came away using the Vallejo cleaner. You probably wouldn’t want to let it sit for too long before cleaning. The  Paasche is essentially all metal apart from some seals and if all else fails then Lacquer thinner clears anything. Cleaning may be a more significant factor for an internal mix brush or one with more delicate parts - I tend to use my ‘elephant guns’ for the final varnish.  Spraying over rigid tiles, I can’t comment on how tightly the Vallejo, as an acrylic, bonds to the underlying enamel if the surface flexes or if there is a big bump ( eg, running your boat into the concrete side of the pond). I really don’t think there would be much of a problem, short of a hit that is going to be catastrophic in many other ways😬.

 

For my current Tug project I decided to use the Revell enamel matt varnish. Given the comparative performance this was more a decision based on my comfort factor with enamels rather than any shortfall with the Vallejo, though being able to spray at lower psi is a benefit in limiting overspray when spraying indoors( I use a spray booth extracting fumes to the outside and wear a half face respirator). For future projects I would consider either, but will mix in a small quantity of gloss clear in both cases. For an operational RC model my sense is that both are too matt, and may retain watermarks, show shiny scratches, capture dirt,grease  etc, and a bit of gloss would help them wipe down better without impacting on the dull finish. Vallejo has a Satin varnish which may be an answer.  Both work over my favorite Colourcoat enamel paints which was my chief criterion, as other, hotter, lacquers don’t. If you are running IC rather than electric then the fuel resistant properties of the Vallejo would be a real benefit.

 

All this is utterly unscientific, but I hope it is of interest to you.

 

cheers

 

Steve

 

[Arjan]

Many thanks Steve for your comprehensive account. I used to have an external mix air brush (a basic Badger one) many years ago and clogging was indeed rare. It only took a very small amount of thinner to spray Tamiya paint with this air brush. . When I switched to internal mix brushes, however,  I had to add much more thinner and clogging became more frequent. Perhaps I should get myself another basic  external mix air brush for spraying polyurethane paints. Of course temperature is also an important factor in problem free spraying. In general acrylics seem to require a higher temperature than enamel (water doesn't evaporate as fast as enamel thinner)

 

Regards,

 

Arjan

[Stephen Allen]

No problems Arjan

 

Its currently late Autumn here in Canberra, and our daytime temperatures are often in the low to mid teens. I use an electric panel heater to get the room warm enough for good spraying.  Standing the bottles of paint in a bowl of hot water also helps, same trick for spray cans before use. Yes, there’s nothing particularly intricate about doing an overall clear coat on a largish boat, you want good coverage without drowning it and a smooth finish and thats about that!

 

cheers

 

Steve

[Arjan]

I have finally applied the "D" initials to the doors of the bridge. These letters were made by a fellow clubmember with some kind of cutting device.

 

 

Arjan

Edited July 20, 2021 by Arjan

[Greg Law]

Looking good  Arjan.  Bet you thought I had disappeared.  I've been tied down with my work projects and did something stupid and started in a group build with a Beaufighter which has ended up being four Beaufighters. Anyway my good friend reinforced my S100 hull this week, so now I will have to get back to the shipyard and make a bit of progress getting the running gear in both boats. It will be slow going because I'm a bit paranoid about cutting into the hulls.

[Arjan]

Hi Greg, good to hear you haven't abandoned  your S-Boot project. I used a 6mm rat tail file for the tube slots in the hull. I usually use CA glue to fix the outer tubes in the correct position. Finally I fill the gaps with Tamiya putty .

 

Regards,

 

Arjan