MichaelRapp
Well-Known Member
- Joined
- Nov 9, 2014
- Messages
- 279
- Reaction score
- 38
When I last was working on a rocket (late February, it's been an unusual last few months, obviously), I swore I would never touch CWF again. I've always just had such problems with it. I abandoned it and switched to papering fins using Avery labels, which worked well, until I realized that they are easy for simple swept parallelogram shapes, but get trickier with more complex fin shapes.
I want to give CWF another try. In the small areas of fins in which I've done it well I do get that lovely plastic look after priming and painting. I've been doing some reading and video watching, and I think I know where I've been going a little bit wrong with CWF. My first problem is in my CWF to water ratio. I've been just eyeballing it, so my ratios change every time I make it. I stumbled upon Chris Michielssen's ratio of CWF to water of 2.5:1. I tried that tonight, and this is significantly thinner than what I've been using. It's still viscous, but it is not a paste either.
This leads me to my second problem. I've been putting this stuff on way-too-thick, almost like I was frosting a cake. CWF, of course, sands really easily, but I'd still have these (relatively) tall mountains I needed to sand down and in doing so I may have been getting too close to the balsa in other areas. In any case, I never seemed to be able to get it perfectly smooth and after I had primed and painted the rocket, these slight but visible shallow gouges were clearly visible.
So I've got a few balsa triangles I'm playing with tonight. I put on enough of a coat to cover the grain (and I didn't forget the edges, save the root edge), but not too thick.
I also switched my paintbrush. Historically, I've been using those 1" ultra-cheap disposable brushes you can get at Home Depot. I think the coarseness of the brush fibers were really causing me problems and creating some of those mountains and valleys. Tonight I'm using a 1/2"-wide artists brush with very smooth fibers and it is making a difference. It does seem to allow me to work the CWF into the wood without creating those ridges.
I'm going to let them dry overnight, sand tomorrow, and see how I did.
I want to give CWF another try. In the small areas of fins in which I've done it well I do get that lovely plastic look after priming and painting. I've been doing some reading and video watching, and I think I know where I've been going a little bit wrong with CWF. My first problem is in my CWF to water ratio. I've been just eyeballing it, so my ratios change every time I make it. I stumbled upon Chris Michielssen's ratio of CWF to water of 2.5:1. I tried that tonight, and this is significantly thinner than what I've been using. It's still viscous, but it is not a paste either.
This leads me to my second problem. I've been putting this stuff on way-too-thick, almost like I was frosting a cake. CWF, of course, sands really easily, but I'd still have these (relatively) tall mountains I needed to sand down and in doing so I may have been getting too close to the balsa in other areas. In any case, I never seemed to be able to get it perfectly smooth and after I had primed and painted the rocket, these slight but visible shallow gouges were clearly visible.
So I've got a few balsa triangles I'm playing with tonight. I put on enough of a coat to cover the grain (and I didn't forget the edges, save the root edge), but not too thick.
I also switched my paintbrush. Historically, I've been using those 1" ultra-cheap disposable brushes you can get at Home Depot. I think the coarseness of the brush fibers were really causing me problems and creating some of those mountains and valleys. Tonight I'm using a 1/2"-wide artists brush with very smooth fibers and it is making a difference. It does seem to allow me to work the CWF into the wood without creating those ridges.
I'm going to let them dry overnight, sand tomorrow, and see how I did.
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