Cutting a strip from a sheet?

What don't I understand about using a Master Airscrew stripper to cut a long thin strip from a sheet of balsa?

I lay the sheet on the work bench, line up the flat edge of the stripper and use the straight edge of the sheet to guide the stripper as I pull it along to make the cut.

The inner, cut edge of the resulting strip is never as straight as the edge of the sheet.

And of course it only gets worse as I use that edge to cut the next sheet.

How do I properly make a strip parts from sheet stock?

Cy.

Get yourself a metal yardstick. Put several pieces of double sided tape on the back and use it with your single edge razor blade. You can also cut tapered spars, etc. this way. I modified my MA stripper by mounting it on a piece of plywood and adding rails to extend its length. It does better now.

>
>What don't I understand about using a Master Airscrew
>stripper to cut a long thin strip from a sheet of balsa?
>
>I lay the sheet on the work bench, line up the flat edge of
>the stripper and use the straight edge of the sheet to guide
>the stripper as I pull it along to make the cut.
>
>The inner, cut edge of the resulting strip is never as
>straight as the edge of the sheet.
>
>And of course it only gets worse as I use that edge to cut
>the next sheet.
>
>How do I properly make a strip parts from sheet stock?
>
>Cy.

Ron B.
F4Fguy

You're probably trying to make too deep a cut.The tip of a #11 isn't very stiff and deflects easily.Try setting the blade to only half the thickness(or less)and making cuts from each side.Also,always use a "dead sharp"* NEW blade and change it frequently.Unless you have a means of mechanically controlling the edge angle,don't try to sharpen the blades used in the stripper.If the angle is off ,even slightly,the cut will try to go to the shallow side.
*If you wouldn't shave with it,don't use it in your stripper.
Be careful not to push the guide edge too hard against the sheet edge,as you will tend to compress the balsa locally and cause the edge to wander.
Remember:Deep Cuts Bad!!
Heavy Pressure Bad!!
Many Shallow Cuts Good!!!!!
Light Pressure Good!!!!
I have three strippers which I keep set at 1/32",1/16",and 1/8" for up to 1/16", up to 1/8",and up to 1/4" respectively.

Hope this helps.

Have you "TRUED" the edge of the balsa plank FIRST? Every plank has to be trued. I have a 48" stright edge to do the job.
On the cutter. Lay it down on a glass surface. Losen the blade untill the tip of the blade touches the glass. Tighten blade. Make sure that you'r blade is Less then a 15 degree angle to the cutting motion or direction. Go SLOW and watch.

Scott(works for me)Riese

Also, when you cut the strip from the sheet, you remove inner stresses in the wood. No doubt you've seen a piece of wood curl quite a bit as you take it off too. All part of the game. I like my stripper from MA, but like said above, multiple cuts little preasure, true the wood first.

From the old cabinet maker: Yea, wood has a personality. After we would straight edge on the jointer and send it thru the table saw--Opps, not straight!!! Like it has been stated very well in previous posts, some times a piece has internal stresses. Try the other side of the plank you are stripping. ALSO, I prefer to hold the cutting blade up just a smiggen so that it does not cut onto the surface (Glass or whatever))This way the tip of the blade does not become dull when you cut--they last a lot longer!!!

>From the old cabinet maker: Yea, wood has a personality.
>Like it has been stated very well in previous posts,
>some times a piece has internal stresses.

Which leads me to divert my own thread.

We talk alot about molding thin sheet for leading edges and such.

I'm currently working on a couple of strips on the trailing edge. When I put the webbing in, there will be an "A" tube, if you will spar at the rear of the wing.

Since my inch wide 1/16 strips insist upon snaking around, why not soak them in hot water, clamp them in place and let them dry into shape as the trailing edge parts I need instead of clamping them in place with stress lying in wait to warp later on?

By extrapolation, why not soak all the sheeting, fuselage sides etc, and then clamp into place to dry, predisposing all the parts to bend right into the shape they are to assume for the life of the airframe?

Cy.

LAST EDITED ON Nov-28-03 AT 04:41 PM (CST)
 
Here's a pic of one of my favorite tools from the '70's, a "Crockett Copy Cutter". It was made by Jim Crockett (yes, a distant cousin of Davey), and was sold to the Free Flight guys by his company, "Jim Crockett Replicas" (Fresno, CA?) which I doubt is still in business.

It's patented under #3,854,214, so you should be able to look up the detailed drawings of it. Essentially, it's a piece of chipboard with two pins (to align the straight edge to), and three hanger bolts, to clamp the locators for the edge of the sheetstock. The cool thing about it, is that it will cut straight or tapered strips. You start out by cutting along the straight edge with no balsa...this makes a perfect groove in the chipboard for your knife to follow. Unless you let the straightedge move off those pins, it will cut exactly in that groove, everytime. It doesn't prevent the strip from warping, nor does it make the edge perfectly square. But is is useful, especially for tapered spars. Steve

LAST EDITED ON Nov-29-03 AT 06:41 AM (CST)
 
"You're probably trying to make too deep a cut.The tip of a #11 isn't very stiff and deflects easily.Try setting the blade to only half the thickness(or less)and making cuts from each side"

I had a Master airscrew stripper that I had not used for years because the blade wandered. On one of the free flight boards that I read frequently someone (in an almost identical thread) mentioned using the bigger thicker blade, for the #2 handle, that looks like the #11 blade. Sorry I do not remember the Xacto number. I thought what the hell I have nothing to loose, so I tried it. Man what a difference!!!!! I now have a usable tool!! You can go through 1/8" wood in a single pass and the blade does not wander at all. Give this a try, what have you got to loose?

To get a straight part for a Trailing Edge, don't try to get two 1.5" pieces from a 3" sheet, and don't try to do it in one cut. You have to make several cuts, alternating sides as you go. Start big and work your way down to the correct dimension. This must be done with a straight edge, a sharp knife, and a cutting surface that will not guide the blade.

You will throw away some wood here, but if the two parts are not exactly straight and identical, you will build a warp into the wing.

>
>You will throw away some wood here, but if the two parts are
>not exactly straight and identical, you will build a warp
>into the wing.
>
>Curt

Well, a new process of using an aluminum angle as a straight edge and a single sided razor blade (which looks like it belongs in a plane--thick) has resulted in a pair of 1 1/16 inch wide 1/16 stock strips long enough install on the trailing edge.

They have been clamped in place and on one area, the wood pops up just a tiny bit as it is being bent. Apparently the stress showed up after I carefully cut these strips. Instead of laying smoothly on the ribs, the edge toward the front ripples up very slightly.

The plan is to glue these top and bottom 1/16th strips in place and then while the wing is still in the jig, install the 30 degree angle sheer webbing that will pin the front edges of the strips down and turn the assembly into an "A" spar.

The question is, will jigging everything and then CA gluing all the structure in place for a closed tube spar lock the trailing edge spar structure in place like I expect it to?

Or do I have to go cut myself another bunch of wood just to get parts that lay down perfectly flat in order to proceed?

Mind you the ripple is very minor or I would not be considering this.

But who wants to go through all this balsa wood just to get some parts fabbed?

How much waste is enough?

Cy.

>
>How much waste is enough?
>
>Cy.

It all depends on how much your time is worth and what your expectations are of this particular model. To me, the many hours invested in constructing a model is much more valuble than a two dollar piece of wood. Besides, are the ribs getting cap strips? If they are, then just shave a little more off the sheets until they are true. The little bit you trim will never be noticed.

Just bringing this up front, in order to better illustrate the point made in thread titled: "More unsolicited advice..."

>Just bringing this up front, in order to better illustrate
>the point made in thread titled: "More unsolicited
>advice..."

What Dan meant to say was:

There's a reference to this thread in my "More unsolicited advice..." posting at the link below:

http://www.clstunt.com/htdocs/dcforum/DCForumID1/7059.html

Cy.

Dont' as me why but...

Stripping wood with a blade pretty much always results in a bow in the resulting strip. For some reason, if you cut your strips on a jig saw or a band saw the stresses that cause that bow aren't formed and the strip stays as straight as the piece from which t was cut.

Probably the same reason that the strips made by using a plane are curls rather than straight slices.

I use a band saw with a nice fine cut blade and the rip fence for most all of my balsa cuts for exactly this reason.

>I use a band saw with a nice fine cut blade and the rip
>fence for most all of my balsa cuts for exactly this reason.
>
>Ted

The same thing applies to cutting out an I-beam spar from a sheet of balsa. It will often go wonky on you if you don't use a band saw. I found this out the hard way.

Eggy

Cy,

I strip a lot of 1/8x1/4" and some 1/4x1/4" using the same stripper. I usually cut up a 4" sheet of 1/4" 10 lb wood at a sitting. I make all cuts with one stroke. Usually, the only time I have trouble with a wandering blade is when I try to cut quarter grain balsa. Quarter grain never cuts straight. Occasionally, I run into a piece of wood that doesn't want to cut straight. When that happens, I don't fight it. I simply use that piece of wood for something else. By selecting my stripping wood for weight and grain, I seldom have any problem.

LAST EDITED ON Dec-03-03 AT 02:49 AM (CST)
 
Cutting up quarter grain wood into strips would be a waste of a nice piece of quarter grain wood, in any case..

I've heard of A , B and C grain, but never Quarter Grain.

How will I know it if I see some?

Cy.

I had similar problems with the Master Airscrew stripper. My solution was to clamp the stripper to a board and embed the tip of a #11 blade in the board. This keeps the blade tip from wandering. Instead of moving the stripper, move the wood - like ripping on a table saw.

For long cuts, I'd use a straight edge and a new razor blade.

-Norm Furutani

Amen to changing #11 Xacto blades often.

To get yourself in the habit, and make it, from an emotional standpoint, justifiable economically....

buy the little box with 100 blades. They are a lot cheaper that way.

Set that box in a prominent place on your workbench.

Also have at least three or four Xacto handles (with new blades attached) located in prominent places in your work area, whereever you contemplate use of the thing. Currell

Cy,
I've tried this with pretty good results - I overcut the wood by about a 1/16 of an inch and then use a long "L" bar with sand paper on the inside edge of the "L" to sand the edge straight. It helps with minor misses on the edge. It also cleans up the edge on the sheet you just cut from.

So far the only one to actually mention the grain in the wood is Al Rabe. When I was into free flight, almost everything was scratch built. I have the tru cutter that Steve shows, by Crockett. The one thing that most have mentioned is: first true the edge of the wood. But what only one has mentioned, and this is very important, is the type of grain you are cutting into. Pick wood with the absolute true parallel grain. This elimnates most if not all the tendency of the wood to curve. Also, I found that if the wood is slightly damp with isopropyl alcohol, it helps. Sal Taibi told me that his company wet all the wood before it was die cut. This made for very precise cuts and if you have ever built a Competition Models Star Duster, you know what I mean.