A couple of great tools

[Rktman]

Just picked up 2 of the best building tools I've come across in years and wanted to pass on recommendations that make life so much easier.

If you need a real time-saver that gives you clean cuts, especially through thick balsa, thin ply, launch lugs, etc., you can't beat a Rotary Cutter. Hobby knives limit you to cutting at an angle, whereas a Rotary Cutter lets you use the strength of your entire arm to press down while cutting. It doesn't splinter or crush balsa (would probably work great on fomecore or foam sheets) and a stroke or two is all it takes. Found mine in the fabrics section of Michaels, though I'm sure any craft shop would carry it. They also carry replacement blades.


I've used fine tip Cyanoacrylate applicators for years with thin CA, but the drawback to them is that they clog real easy (usually after just one or two uses, and they're virtually impossible to clean) and it's not easy to precisely control how much comes out the tip. I found another type of micro-tip applicator that has a squeeze bulb at the end and it lets you precisely meter out EXACTLY the amount you need. No more accidentally flooding your surface with CA when you squeeze the bottle. Instead you dip the applicator tip into your bottle and draw out some CA where it's stored in the shaft. You can squeeze out REALLY small amounts of CA at a time, less than a drop, and put it right where you need it with unreal precision. I keep a container of acetone nearby and clean out the applicator by sucking up/squeezing out the acetone a few times, and leave the tip to soak for a few minutes. No more clogging problems so I can keep on reusing it instead of tossing it after every use. BSI sells it but I found a whole bunch of choices on Amazon.

 

[neil_w]

I must say I never would have thought of that rotary cutter, might just give it a try.

Also handy if you cook up a pizza while you’re building.

 

[manixFan]

Rotary cutters are great for cutting fiberglass for lay-ups, but never would have thought about it for balsa. Good point.


Tony

 

[AfterBurners]

Would you still use a steel ruler as a guide with the cutter if you are balsa etc

 

[neil_w]

The weird thing about the rotary cutter for balsa is that my impression is always that it is the *point* of the knife that is doing all the useful cutting, and the rotary cutter lacks a point. Can't quite imagine what it would be like cutting with one. Color me intrigued though.

It does sound great for cutting launch lugs, but I wouldn't buy it for that purpose only.

 

[SeanW78]

The main thing to think about with a rotary cutter is how the bevel will effect the cut material. With Fiberglass, which is relatively thin, there isn't much to think about. But a fin that could be 1/4" or thicker, by the time you get through it, you may have introduced an unwanted chamfer.

 

[Rktman]

Would you still use a steel ruler as a guide with the cutter if you are balsa etc

I would. But then my manual skills aren't what they used to be; too many years wrangling only a mouse and keyboard have left me with somewhat unsteady hands.

 

[Rktman]

The weird thing about the rotary cutter for balsa is that my impression is always that it is the *point* of the knife that is doing all the useful cutting, and the rotary cutter lacks a point. Can't quite imagine what it would be like cutting with one. Color me intrigued though.

It does sound great for cutting launch lugs, but I wouldn't buy it for that purpose only.

It has a razor sharp edge though, so instead of pulling a hobby knife across the material's surface, you instead roll a continuous edge along to cut. You can also press down with more force than with an Xacto blade. I've used it primarily to cut thick hard balsa, 1/64" ply and .060" carbon fiber rods (and apparently it can also be used on fiberglass) but as a strictly LPR guy I haven't had the need or opportunity to use it on anything thicker/harder. Would be interesting to see how it would perform on denser materials that you would traditionally use a hobby knife for. Guess I'll be finding out.

 

[Rktman]

The main thing to think about with a rotary cutter is how the bevel will effect the cut material. With Fiberglass, which is relatively thin, there isn't much to think about. But a fin that could be 1/4" or thicker, by the time you get through it, you may have introduced an unwanted chamfer.

The rotary "blade" is as thin (or thinner) than a hobby knife, and even #11 hobby knife blades have the same honed "beveled" edge. Happily, neither leaves a discernable chamfer as the honed edges are only microns difference in thickness from the rest of the blade.

 

[jqavins]

The weird thing about the rotary cutter for balsa is that my impression is always that it is the *point* of the knife that is doing all the useful cutting, and the rotary cutter lacks a point. Can't quite imagine what it would be like cutting with one. Color me intrigued though.

The point of a blade is, obviously, good for piercing, but it's not so goof for cutting; that's done by the edge. When you cut with the pointy end of a blade, the actual tip sinks in and down to the cutting surface (mat, whatever) and then, as you draw the knife along, it's the edge that encounters the thickness of the material along the way. And sometimes the tip can snag on the way, at the bottom face of thin material like balsa sheets or anywhere on very thin material like paper.

Try the following. Place a straight edge down on a piece of paper and cut a line with the tip of a #11 or box cutter. And do the same with a scrap of balsa sheet. Then do the same using the curved edge of something like a #10 or a freshly sharpened pocket knife. In my experience, the curved edge works much better.

Now, rolling a curved edge onto and down through a sheet is a different motion from dragging it along. The rolling cutter is good for more than just pizza when you're in the kitchen; I've rarely if ever used the pizza cutter outside the kitchen. I guess it's worth a try.

I would. But then my manual skills aren't what they used to be.

My manual skills are exactly what they used to be; I used to be an average an average seven year old.

 

[Rktman]

The point of a blade is, obviously, good for piercing, but it's not so goof for cutting; that's done by the edge. When you cut with the pointy end of a blade, the actual tip sinks in and down to the cutting surface (mat, whatever) and then, as you draw the knife along, it's the edge that encounters the thickness of the material along the way. And sometimes the tip can snag on the way, at the bottom face of thin material like balsa sheets or anywhere on very thin material like paper.

Try the following. Place a straight edge down on a piece of paper and cut a line with the tip of a #11 or box cutter. And do the same with a scrap of balsa sheet. Then do the same using the curved edge of something like a #10 or a freshly sharpened pocket knife. In my experience, the curved edge works much better.

Now, rolling a curved edge onto and down through a sheet is a different motion from dragging it along. The rolling cutter is good for more than just pizza when you're in the kitchen; I've rarely if ever used the pizza cutter outside the kitchen. I guess it's worth a try.
My manual skills are exactly what they used to be; I used to be an average an average seven year old.

Hope you were kidding about the pizza cutter cuz it's way too dull. The edge on the rotary cutter is as sharp as a razor (already found out the hard way when my finger got too close to the straightedge I was using to guide it).
Bet they'd make great ninja throwing star shuriken once they got dull. Just cut to the right shape and there you go.

 

[manixFan]

Hah, yeah, the fabric rotary cutters are dangerously sharp, not at all to be confused with a pizza cutter. They make tungsten steel blades that will cut carbon fiber cloth for fin lay-ups, as well as regular steel ones that work great for regular fiberglass.

No joke, you can very easily cut your finger just by casually rubbing it on the blade.


Tony

Not the best video, but here's an example of one cutting thru two layers of fiberglass cloth:

 

[jqavins]

My pizza cutter is sharp. OK, not sharp enough to do what the rotary cutters you're talking about are capable of doing, and its central bearing is much too floppy. Still, it's sharp enough to try on a piece of balsa scrap. I keep all my blades sharp.

 

[Rktman]

My pizza cutter is sharp. OK, not sharp enough to do what the rotary cutters you're talking about are capable of doing, and its central bearing is much too floppy. Still, it's sharp enough to try on a piece of balsa scrap. I keep all my blades sharp.

How do you sharpen your pizza cutter? Whetstone? Mine is pretty dull after of years of use.

 

[Greg Furtman]

Hmmm...I wonder if I should put a better edge on my Enterprise Pizza Cutter.

 

[jqavins]

How do you sharpen your pizza cutter? Whetstone? Mine is pretty dull after of years of use.

It's a somewhat annoying process but, yeah, whetstone. Tape the blade to the structure, hold the cutter still and move the stone working on an area, then move the blade to a new position and do another area. You can cover about a third of the circle at a time. I don't keep it nearly as sharp as my regular kitchen knives because it's such a pain in the neck and not as important. I get it pretty good once and it's probably good enough for life, where my other knives are generally maintained much better. (They're overdue at the moment.) If I really wanted the pizza cutter like a razor I'd grind out the central rivet so that I could put the blade in an arbor in a variable speed Dremel and work with the stone while the blade spins slowly under it. Then put it back together with a small bolt and nut. But it's not worth that much effort.