Sharing A BAD Idea

[John G. Jedinak]

Starting on a Stuka 500 series and experienced, as we all do, breaking off edges when cutting the notches. My idea was to coat the back side of the entire sheet with 50/50 Elmers....looking for some strength. WRONG!!

The result was warping of the sheets. Now I have coated the sheets again and laid weights on top in hopes of removing the warps.

Anyone have any ideas on how to eliminate/minimumize breaking off the edges when notching??? Thanx, JGJ

P.S. I build for display, so weight is not an issue.

[Xanadu]

I cut my notched differently than what Guillows shows. It might seem a tad "dangerous" to some, but I have never cut myself yet.

I use a single edge razor blade.
Holding the former, rib, or whatever part I need to trim, in my left hand, I have the blade in the right hand, since I am right handed.

I take the blade and slice into the cut, pushing into the former. Do both sides of the notch, then flick it out with the blade edge. I have about a 99% success rate of no broken edges.

The drawback to it, is that you are pushing the blade towards your finger and thumb while holding/supporting the balsa you are cutting. But having patience and being careful is utmost.

I will try and post a pic of how I do it, hopefully sometime later today.

[moostang51]

In an earlier post "fuselage formers" some members posted their techniques such as 50/50 glue, sanding sticks even tissueing the back side prior to cut outs. I too experienced some breakout when first building but have since been using a single edge blade and with the former lying on the instruction template on a hard cutting board, just first plunge cut at the former edge where the instruction lines are located. It seem to relieve the pressure when I make the next cut to the Guillow's supplied depth of stringer cut. It's never a problen when you cut with the grain, it's always the cross-grain cuts that posed the problem. My system actually creates a previous "kerf" that allows a little flexing in the fibers. I often use this system at work when when plywood or even straight grained lumber needs to be curved to create a form. I also plunge cut with a #11 exacto blade the "crushed" Guillow's depth of stringer cut prior to side cutting the notches. Can't wait to experience a laser cut kit.

[John G. Jedinak]

Xanadu.....a single edge blade TOWARD the hand is tricky for a 74 yr old, but I will give it a try.....thinking it need be pretty sharp. Looking forward to the possiblity of a pic.

Moostang51.....I see where the first kerf cut would be advantageous in relieving stress. I use a #11 blade and generally make the depth cut first. I've done the laser parts already...really great overall, but still you run into "some" problem with the notch cutting.

Hey Guys, Thank you both for the input........JGJ

This message board is great, isn't it???

[Xanadu]

A sharp blade is a must!
Much easier to cut yourself with a dull blade than a sharp one.

Steady hands, brace your elbows on the workbench, and take your time.

I am sure you will find a way that works well for you!

[kittyfritters]

I haven't used a single edged razor blade since my first Cleveland kit. I still make the "Cleveland notcher" they suggested (and in some cases provided) in their kits.

For 1/16 inch wide notches you take a two to three inch length of 1/16 sheet stock about an inch wide and carefully glue a 1/16 in wide strip of fine sand paper to the long edges. All you have to do is sand the notches! I use a metal straight edge and a #11 Exacto blade to cut the strips of sand paper. Cut on the back side of the sheet. I still use Testor's "green glue" to glue the sandpaper on. One of these things will last through several models.

An alternative that I have just started using is my Dremel tool. If you put two fiberglass cut off wheels side by side on the same mandrel they cut a slot 1/16 inch wide. Your hand has to be really steady, but if you have accidently gotten some C/A on the edge of the former (Don't ask.) the Dremel is about the only way you will cut a notch through it. If my hand isn't feeling really steady I go back to the Cleveland notcher.

The notch markings on the plans and die crunched into the formers are more like guidlines than absolutes. If you put the fuselage keel and former assembly into a simple fixture to hold it straight than you can start with the notch markings in former #1 and run a chalk line back to get the exact notch positions. Fuselages come out a lot straighter that way.

Howard

[John G. Jedinak]

Kittyfritters...........great idea with sanding stick. I usually use the sanding stick to finalize the notch. On sticks, I have found that medium grit (or there-abouts) does not work well. The problem I see, is that with a 1/16th strip there are fewer particles of grit and it wears out quickly....that is for me. Next time I make them I'm going to try a fine wet-dry sandpaper. Any thoughts..........Thanx, JGJ

[John G. Jedinak]

Kittyfritters....I forgot. I have not guts to fly my models and a 74 yr. old with short stubby shakey fingers has even less guts to try the Dremel. A really great way to go about it though, if one has a steady hand....Thanx, JGJ

[cdwheatley]

My method for cutting stringer notches is as follows:-

Firstly I mark either side of where the notch is to go with my scalpel blade. Then, using a triangular section needle file, I carefully start sanding between the two marks until the section between them has been removed. This is simply to create a guide for a file I have that not only just happens to be 1/16" wide, but also has a sanding edge on the thin 1/16" side too! . It's then a simple matter of using this file to turn the 'V' shaped 1/16" wide notch into one that is also 1/16" deep.

If at any point the wood begins to disintegrate (or even before if I can clearly see that the wood is a bit weak or 'crumbly') I stop what I'm doing and immediately apply liquid cyano to the notch to either repair or strengthen it so as to continue sanding after it's soaked into the balsa and set. Using this process I would probably say that I have around a 99% success rate in avoiding the dreaded broken notch problem.

[supercruiser]

Kittyfritter's idea with the sanding stick is a good one. I use that method a lot.

JGJ, I'm fairly young and a dremel tool in my hands with a piece of balsa is not a good combination in many cases. I have heard of a notching method
of taking two hacksaw blades. Tape them together, side by side, with the tooth cutting direction of the blades opposite each other. I would think small, toothed blades for metal cutting would be a better choice. I've not tried this method, yet.

The chalk line idea sounds good, too.

[moostang51]

I use the dremel and sanding stick method when i cut the extra stringers ala David Duckett. It works great for this, but with the Guillow's crunched die-cuts etc... I have yet to try it. Mind you, the kits I've worked on were older kits that I haven't touched after I purchased them long ago. A newer kit (post 1990's might yield a better balsa former.

[John G. Jedinak]

SUCCESS!!!! The second coat of 50/50 Elmers covered with wax paper and then heavily weighted down worked likea charm.......the cups and warps have been removed. Maybe it wasn't such a bad idea afterall. Just have to approach it in the proper manner. Metal cutting blades placed opposite sounds like another great idea. Also, have to figure out where to find a square 1/16th file...not noticed them around here. Do I find them ina Hobby Shop???........Thanx, JGJ

[kittyfritters]

John,

Try any good tool supply for the file. It's called a Swiss pattern file and they come in various sizes and shapes. Hopefully, you can buy the size you want, individually, without having buying a whole set.

I bent up a little metal guard for the front of my Dremel tool that prevents me from going deeper than 1/16 inch with my notches. I still have to be careful not to go sideways.

As far as my sandpaper notchers not wearing out too soon, I don't know what to say. I'm just using 3-M, 220 grit, open coat paper.

Why not try flying one? We've got a guy in the Black Sheep Squadron who is over 90 who builds them to fly and usually shows us young 60 somethings a thing or two.

Have fun,

Howard

[Xanadu]

Try some sanding twigs.

Scroll down near bottom of page for picture of how to.
http://www.smallflyingarts.com/cgi-bin/ ... 0015/15#15

You can buy them from:

http://www.hobbypeople.net/gallery/649905.asp

or

http://www.taubmansonline.com/Tools.htm

[John G. Jedinak]

Xanadu.......your resource locations are always outstanding!!!Thanx,JGJ