CA and fins

[gpoehlein]

I'm wanting to do some experimentation with coating (soaking in actually) some fins with CA. I want to keep them from warping while they dry, so I'll need to weight them down with something flat. Anyone have any suggestions as to what I can wrap around these suckers to keep the CA from bonding everything into one solid mass? BTW - I'm talking about thin cardstock fins, not balsa. At this point, I'm wondering about either wax paper or some kind of plastic. Anything commonly available that CA WON'T stick to?

 

[RangerStl]

I'm not sure you'll really have much to worry about since CA isn't water based. I have not seen an instance where CA causes fiber to swell and warp like water does. As long as they start out flat they should stay that way.

And as far as what doesn't stick to CA, the list is pretty short. Even stuff that doesn't bond well will get stuck because of surface roughness.

 

[troj]

The first thing that comes to mind is the white plastic cutting board material.

The trick will be to get a perfectly smooth piece, so that you don't have cured CA in grooves, valleys, notches, etc, that makes it difficult to remove.

As far as warping goes, when I've applied CA to materials, I've never had any problems with the materials warping.

-Kevin

 

[hcmbanjo]

Try the waxed paper.
I was amazed that CA wouldn't stick something as ordinary as waxed paper.
I use BSI Adhesives brand (thin, 1-3 seconds cure) and regular Reynolds Cut-Rite waxed paper.

I've used it on balsa and on cardstock laminated fins. After applying the CA, I'll fold waxed paper over the top and bottom of the fins and set them in a heavy book. The CA won't penetrate the waxed paper and after drying my books are fine.
To test, try setting a drop of CA on waxed paper. Put your finger under the other side of the paper, under the drop. You can't glue your finger to the paper, it doesn't soak through. The weird thing is, that drop of glue you set on the waxed paper doesn't want to dry. There is nothing for it to soak into.

 

[gpoehlein]

Thanks, guys - I'll give the waxed paper a try. I'll let you know the results.

 

[JAL3]

I have assumed that wax paper would be useful for something like this and have ended up with the wax paper stuck to everything including me. To make matters worse, it was a Christmas wax paper and transferred little star shaped tattoos onto the rocket and to me...and the tablecloth, and the tea pitcher and just about everything else that was in the kitchen that night.

SHE WHO MUST BE OBEYED was not amused.

 

[RangerStl]

All the model airplanes I've ever built with waxed paper over the plans successfully prevented the plane from being glued to the plan sheet, but the plane has always ended up glued to the waxed paper.

I'm not sure the waxed paper will just peel off. Try it on some scrap first.

 

[Micromeister]

Yeap Greg:
Waxed paper it the trick: Many a internats flyer as created a Laminated fin, wing and other parts with either weighted or vise compressed waxpaper sheeted outer layers.
You'll end up with a dried CA flashing that'll need to be trim sanded but it works off very easily.

CA shouldn't be your only choice either, you really should consider 30 minute epoxy as well. the Weight to thickness ratio isn't that much different on very thin compeititon fins

One of my Internat's buddies used to make .005" thick CarbonFibre/epoxy fins between to pieces of 1/2" aluminum plate in a huge bench vise using Waxed paper as the outer leafs. Thinnest I've done personally were/are .010". You need a triple beam scale to read the .000ths grams of the 3 fin sets.
Hope this helps.

 

[gpoehlein]

Tried it with a couple of pieces of cardstock last night - the wax paper peels off just fine. Actually, what I am experimenting with is whether or not CA soaked cardstock can be substituted for G10 as a lightweight fin material. Not having any G10 to play with, I'm just winging this here. One layer of 110# cardstock dries nice and smooth and flat and is about .011" thick. It is very flexible though - I'm afraid it might flutter too much as a fin. Two layers of 110" card is about .022 to .023" thick and is quite stiff. I'm going to try 67# stock next and see what two layers of that do. I just used the CA to stick the two halves of the fin together then coated the outside.

My next question is: just how flexible is .010" G10?

 

[hcmbanjo]

Hi Greg,
I just thought of something,
If any of the wax transferred onto your fin surface you might have trouble getting paint to stick to the surface.
Get some light solvent and put a little bit on a paper towel to remove any wax. Just be sure you don't use too much solvent at one time, if it gets too wet it may start to break down the cardstock. I would experiment on some scrap first.

 

[gpoehlein]

I'm not worried about paint - I am pre-printing the fins on the cardstock and this is for competition models anyway - we don't usually paint them. I'm mostly looking for a nice smooth surface on a very thin fin that doesn't have too much flex (don't want any fin flutter). Also, I am sanding the surface after removing the wax paper, so that should take a lot of anything that remains off. Oh, and I am not cutting away the cardstock at the fin root - I am using this as a handle while I coat the fin itself with CA then cutting it away after the fin is dried and sanded. So the root edge had no contact at all with the wax paper.

 

[Micromeister]

Tried it with a couple of pieces of cardstock last night - the wax paper peels off just fine. Actually, what I am experimenting with is whether or not CA soaked cardstock can be substituted for G10 as a lightweight fin material. Not having any G10 to play with, I'm just winging this here. One layer of 110# cardstock dries nice and smooth and flat and is about .011" thick. It is very flexible though - I'm afraid it might flutter too much as a fin. Two layers of 110" card is about .022 to .023" thick and is quite stiff. I'm going to try 67# stock next and see what two layers of that do. I just used the CA to stick the two halves of the fin together then coated the outside.

My next question is: just how flexible is .010" G10?

Greg;
Short answer is not much at all. lately i've been using .005" Waferglass or (G10) for most competition model fins. Both are pretty much the same thing composition and mass wise. Only real difference i've noticed is the former is sort of a milky clear, while the G10 is yellow to light green transluscent.
My suggestion would be to pickup a sheet or two to experiment with. The precision Garolite (G10) i've been using lately is from McMaster-Carr. .005" #1331T23 and .010" #1331T25. Each 12" x 12" sheet runs 9.18 and 9.77 each. and is available in 24" x 36" sheets as well, that take the Sq in price down a couple cents
For competition model fins, particularly the sizes we're concerned with here, mass really isn't the most important factor. Thinness and span rigidity are as you know what we're looking for. You might want to trade off a couple hundredths of a gram in mass to pickup span rigidity with some allowance for material flexiblilty before failure.
Because Dried CA does not flex at all, but Cracks under such stress I'd be very skeptical of using it as a Stiffener on just about anything for very thin fins. Silk or superthin fibreglass cloth might be exceptions. While CA soaked cardstock makes a pretty darn good airdried phenolic composite, it really has little strength in repeated flex area applications.

Ps: both Waferglass and G10 take magic markers pretty well for Coloring
Hope this helps a little.