• Administrator
  •  
    Before your membership becomes valid, you will receive an email that must be answered.
    Please check your spam folder or this email.
     

Problem painting Diatex

Anything to do with gliders & gliding.
LarsWikstrom
Posts: 28
Joined: 06 Jan 2019, 09:09
Location: Reigate

Problem painting Diatex

Post by LarsWikstrom »

IMG_2495.jpg
IMG_2494.jpg
Hi,

I am painting my SHK and have a possible issue I wonder if someone else has experienced.

The wings are covered with Diatex and then doped as per their instructions, however, I did not add the silver paint.
I am using Skycrafts coloured dope to paint. I am using an HVLP gun and have thinned the paint to 50%.

The white went on just fine and I got good coverage but then it was time for the blue underside...
Day 1
I sprayed the topside white and got a good result.

Day 2
Now it was time for the underside which was to be blue.
I sprayed the wing and thought I had put on enough to get coverage; however, in the evening I could see that the coverage was not enough.

Day 3
I now added three additional layers and thought the wing looked "wet".
In total, I might have used about 1-1.25 litre

Now when looking at the wing I can see that the coverage once again not enough.
As you can see on the images, the coverage on spars and ribs are much better.

Questions
What do you think is the problem
Have anyone experienced the same and what did you do?
What would you recommend me to do

Thanks, Lars
User avatar
RobbieB
Posts: 547
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Problem painting Diatex

Post by RobbieB »

Lars, how did you apply the dope before the colour coats, brush or spray?
LarsWikstrom
Posts: 28
Joined: 06 Jan 2019, 09:09
Location: Reigate

Re: Problem painting Diatex

Post by LarsWikstrom »

Robbie, brush and several layers
User avatar
RobbieB
Posts: 547
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Problem painting Diatex

Post by RobbieB »

One of the problems with Diatex and other non adhesive backed covering fabrics is sealing the weave before painting. If you spray the sealing dope on, because it is thinned a lot in order to facilitate spraying, the volatile thinners flash off and push the dope out of the weave and therefore, the dope has not keyed through the weave and it will not be sealed. That's why it is important to brush the dope on as you have done to make sure it has penetrated the weave.

What isn't obvious, as I also found out to my cost in my early experiences with Diatex, you really should only thin the dope as little as is necessary to make it brushable - thus reducing the possibility of any thinners flashing the dope out of the weave. Even then, you are quite likely to have some 'pinholing' problems but nothing like you have experienced there.

It's a thin line between brushing enough dope through the weave to seal it and not getting some pooling on the inside of the weave although some full size inspectors like to see that as it is a good indicator of good weave penetration; but they don't have quite the weight considerations that we do.

You can see where the fabric is attached to the parts of the wing that have had adhesive applied to them the colour seems to have taken ok as the weave would have been adequately sealed at those points.

Would it be possible to apply another much thicker coat of dope over the paint?
LarsWikstrom
Posts: 28
Joined: 06 Jan 2019, 09:09
Location: Reigate

Re: Problem painting Diatex

Post by LarsWikstrom »

Robbie,
Do you mean dope and not less thinned paint?
Lars
User avatar
RobbieB
Posts: 547
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Problem painting Diatex

Post by RobbieB »

Yes, less thinned dope and again, brushed on.

When sealing this type of fabric I have one of Skycraft's doping brushes trimmed down a little to make it a little stiffer to force the dope through the weave - just be careful not to flood the fabric, brush it out well and try not to do too large an area with each brush load. Heaven only knows what the paint will look like after applying more dope on top but subsequent colour coats should deal with that ok - always try a small patch first!

Another thing I would have done, before applying the colour coats I would have one or two coats of grey or white primer, the last one rubbed down dry and the dust only wiped off, not blown or vacuumed. This way any remaining pinholes hopefully will remain filled.

The aluminium paint you mentioned is only a UV protection layer to protect the fabric.
LarsWikstrom
Posts: 28
Joined: 06 Jan 2019, 09:09
Location: Reigate

Re: Problem painting Diatex

Post by LarsWikstrom »

I have spoken to Skycraft and they will send me a new can of paint.
They say they will add more colour and then this additive that makes it not crack later on.

We will soon see how that goes. :?
User avatar
RobbieB
Posts: 547
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Problem painting Diatex

Post by RobbieB »

Ah, maybe they know something we don't..............
LarsWikstrom
Posts: 28
Joined: 06 Jan 2019, 09:09
Location: Reigate

Re: Problem painting Diatex

Post by LarsWikstrom »

Yes, especially as the white paint which is supposed to be the same worked just fine…
barrieburton34
Posts: 20
Joined: 05 Jul 2018, 13:52
Location: warwickshire

Re: Problem painting Diatex

Post by barrieburton34 »

I normally use water based clear varnish,brushed on to fill the weave,then spray with cellulose

Barrie Burton
Post Reply