Savannah John just landed.... overheated

[IBob]

I am going to have a look at a Sealey HVLP gun tomorrow with a view to using to learn on hopefully it will be good enough for the primer at least.I am worried about the volume of air my compressor can produce it is a twin piston direct drive Mcfee no idea what model it is though. We only have one size of quick fitting so that should be ok. What internal diameter hose line did you use? My whole setup is based on 6mm.

ICP mrentioned the yellow because of the amount needed to get an opaque finish but I think a lot is also to do with the skill of the sprayer. I cant remember how much extra weight she mentioned but I think it was 5 or 10 kg

Most compressors seem set to run between 8 and 10bar. Riveting uses 4 to 5 bar, approx the same as HVLP painting, but much less air.

 

Is there no label on your compressor? The compressor does have to be able to 'keep up'.

 

My airlines are cheap 3/8" 20bar, which seems to be the standard here.

 

I don't think 6mm will be big enough for HVLP, you will get significant pressure drop along the line, which will also make it more difficult for you to adjust the gun, and may mean it won't deliver properly at all. Or to put it the other way round, adjusting the gun is much easier if the pressure at the gun is steady regardless of how much air is being taken.

 

 

[IBob]

I got the compressor, lines, gun up front because I opted to prime all interior parts and surfaces during construction.

 

This was a personal choice, and just one of several popular options. Depending on which way you choose to go, you may not need any more air gear than you now have until final painting time.

 

 

[rmorton]

I am sure I will need bigger hose. Definatly worried about the volume of air and the length of hose I have between the compressor and the paint room.

 

 

[IBob]

Just to be clear: the Savannah kit comes complete with a can of black primer (and the air rivet gun). The manual says to apply the primer at all aluminium joins and laps during construction. It goes on with brush or roller or pad.

 

While some builders choose to use other materials and systems, I would think this basic system is quite adequate, and very many Savannah have been built using it.

 

 

[rmorton]

I had seen this on a few of the build logs and it seems to be a minimum starting point. The black paint seems to act as a seal and protective coat to stop corrosion between layers. I was going to prime the surfaces first and do the black gunk. Almost decided that the first few months will be spent sorting cleaning deburring and priming all the parts (aluminium ones that is.

 

 

[eightyknots]

On one of the Zenith threads some time back the oft quoted weight to paint a Zenith CH-701 is "12 pounds" to "16 pounds". That equates to 5.5 to 7.3 kg. The 701's fuselage is smaller than the Savannah XL/S is and the wings are shorter. I think the Savannah probably has 10% more surface area. Using the above estimates that would be (rounded) 6.1 to 8.0 kg.

 

Do others with completed planes think that is about right?

 

 

[planesmaker]

Extra 5 to 10kg for yellow paint! I don't think so. Out of interest I recently stripped the fabric off a skyfox and weighed the lot including the paint, 6.5 kg for the whole airframe paint and fabric!

 

 

[facthunter]

Treating the "Laps" would seem like a good idea. I worry about 2 pack on planes. Some day you are going to want to repair the paint. if initial painting is a daunting task what is repainting like? most paintstrippers scare me when Aluminium is being considered, especially the laps. A thin coat is best. Do you consider acrylic lacquer which can be touched up and repaired? Nev

 

 

[rankamateur]

I had seen this on a few of the build logs and it seems to be a minimum starting point. The black paint seems to act as a seal and protective coat to stop corrosion between layers. I was going to prime the surfaces first and do the black gunk. Almost decided that the first few months will be spent sorting cleaning deburring and priming all the parts (aluminium ones that is.

I used the approach you have described, but spend a few dollars on three or four rolls of easy peel masking tape to keep the Black of the face surface of your parts outside the joint or it will be a real pain come time to do your painting prep. It takes a bit longer to prime, assemble the joint, mask, dissemble, Black, dry, unmask, assemble, then rivet each exterior joint but I would do the same again. Once the Black dries it is very hard to shift with GP thinners or Prepsol, both of which mess up your base coat of primer.

 

 

[rankamateur]

I also put a strip of Etch primer down under each line of rivet holes so that there was primer under each rivet head.

 

 

[rankamateur]

Do others with completed planes think that is about right?

It is probably quite right and also the reason so many European planes get polished and just have the Wingtips and caps and the engine cowl painted. Oh what a joy it would be polishing around all those rivets. Wouldn't give much protection from corrosion for beach fishing.

 

 

[rmorton]

Yes I think you are right the 5 to kg I remember from my discussion with ICP was probably the total weight to allow for painting and not the difference when using yellow or other thicker paints.

 

 

[eightyknots]

Yes I think you are right the 5 to kg I remember from my discussion with ICP was probably the total weight to allow for painting and not the difference when using yellow or other thicker paints.

I always thought that the range of colour pigments would have been fairly close in weight. Is there really a difference in colour versus weight? And, if so, which are the lightest colours??

 

 

[SDQDI]

I always thought that the range of colour pigments would have been fairly close in weight. Is there really a difference in colour versus weight? And, if so, which are the lightest colours??

Your whites and pale colours are definitely lighter than dark colours, they are even lighter than their darker versions of themselves hence the names 'light blue' 'light green' 'light red' ect

I learnded this in art class at big school.

 

 

[IBob]

Your whites and pale colours are definitely lighter than dark colours, they are even lighter than their darker versions of themselves hence the names 'light blue' 'light green' 'light red' ectI learnded this in art class at big school.

I can't disagree with that (having neither weighed paint nor seen weighing results), and it is 'received wisdom' that some colours weigh more than others, so we all go round telling each other this. Also some colours and paints cover better than others, so more or less paint is required.

 

But surely the key question here is how much more or less? And this seems a lot less clear.

 

For example:

 

If using yellow paint will increase my 7Kg paint job by 5%, that's 350grams, and all I need do is empty my pockets before I go flying.

 

If it's 50%, then maybe I have to start eating less breakfast.

 

As with many statistics, it's not really the 'more or less' that matters, it's how much more or less.

 

The above conversation is an excellent example of the confusion around all this: we have people suggesting a 5Kg increase for yellow and people suggesting 5 to 10Kg for paint all up.

 

Planesmaker gives us 6.5Kg all up, paint and fabric, and that's one very useful figure for fabric covering.

 

So does anyone else have any hard figures on all this???

 

 

[rankamateur]

I know of a couple of yellow planes that required a third top coat to get the yellow to cover, so it is heavier by one full coat anyway.

 

 

[IBob]

I know of a couple of yellow planes that required a third top coat to get the yellow to cover, so it is heavier by one full coat anyway.

I know of a couple of yellow planes that required a third top coat to get the yellow to cover, so it is heavier by one full coat anyway.

I was about to say that's another good solid bit of information, and it probably is...then I thought 'but were they putting it on thin because they 'knew' yellow is heavy'.

 

I know what I am going to do when I get back out to the shed: spray a measured amount of the primer I'm using onto card, and weigh it before and after. Which won't account for overspray, but will be some sort of starting point.

 

Far too late to change tack on how I'm priming my build, but still I'd like to know...

 

 

[rmorton]

It certainly provides food for thought. I think that some colours do not cover well and so need to have more coats and therefore weigh more, there must also be some differences in density of the various pigments and carriers that go into making up the paint. It would certainly be interesting to do the tests before and after as you suggest.

 

 

[rankamateur]

You may need an analytical balance to measure the difference reliably. I doubt your electronic kitchen scales are going to give you what you need.

 

 

[IBob]

I just realised we have inadvertently hijacked Savannah John's arrival thread, yakking about all this.

 

Sorry John, that wasn't the intention.

 

 

[IBob]

Hi Steve. Not to be an argumentative son of a b****, but as luck would have it I recently bought a set of kitchen scales. And my printer paper says on the packet it's 80gms (per square meter), so an A4 sheet (21 x 30cm) is just over 5grams...and my scales are reading another 5grams for every extra sheet I put on them. I'm surprised too, but there it is: modern technology.

 

So, provided I spray a significant amount of paint, say 50ml, I should get into the ballpark here.

 

I hope.

[eightyknots]

I agree, but by that time there will, hopefully, a dedicated Savannah paint thread.

 

 

[hihosland]

Me thinks that:-

 

If there is any significant difference in paint weight due to the pigment then weighing two different coloured unopened 1 litre (or larger) containers would demonstrate this difference.

 

 

[IBob]

Me thinks that:-If there is any significant difference in paint weight due to the pigment then weighing two different coloured unopened 1 litre (or larger) containers would demonstrate this difference.

Seems entirely reasonable to me.

 

And i'd hazard a guess (but it is only a guess, nothing more) that at the amateur end of things, how much you put on has a far greater bearing on weight than colour....though since some colours cover better than others, the likely coating thickness (and so weight) is potentially linked to colour that way.