1/4 round?  So the ribs are fish-mouthed?

How do router blades hold up with balsa?  It's my experience that anything you use to cut balsa has to be sharp sharp sharp or it'll tear instead of cutting -- harder woods seem to be more forgiving for blades that you've let go too long, since they're more likely to burnish (or fry) a bit rather than ripping up chunks or skating over the wood entirely.

          Greg, I was just wondering about the process you used to make these leading edges. I find it funny that the conversation I had was in fact about the leading edge of a Mongoose that one of the club members fly. He in turn is a upcoming flyer who is going to be in need of a new leading edge when his bites the dust. He's just learning inverted flight and its not going so well. Also, we fly Ringmaster's by the handful at times with multiple flyers in the circle. We mainly glue the RIngmaster's back together which over time gets pretty heavy. It would be nice to make a new solid leading edge and maybe hollow the inside out. Realizing that the majority of kit manufacturers back then used a solid leading edge and our current source is drying up. You ask yourself what to do. Is it my understanding that you are making 2 quarter round stocks and gluing them together? I myself use routers on a daily basis but not much in turn of different set ups. I use them mainly for hinge gains and Corian installations. Most bits consist of bearing guided cutters in which were just doing a one sided pass along a straight edge. I figured the first pass would be the easiest but the second one doesn't allow the bearing to have enough area to follow. I thought I could always drop the fence back giving the bearing enough room to ride on the square stock then sand the rest of the radius in. This would probably suffice for the shape,  but not very time efficient. I also thought of getting a cutter made which would be the ultimate factor but the cost is nearing $160.00. This may still be the best option. I have a thumbnail bit which looks the closest to what I need but the radius isn't quite the same as it looks more like an elipse vs a radius. I just thought it may be a matter of playing with the depth. What do you use to hold the wood on the mdf? How is the weight once completed? Does the stock take off and warp afterwards?Ken

Not sure if this is what you mean but I trace the airfoil from the plans on card board and cut it out as a template and sand to fit using the template to check down the length of the LE.

If I could scan it.  The plans for the Brodak Jr Flite Streak show how they do the leading edge.  I think it is the same on the Baby Flite Streak and the Goldberg kits that Brodak is now doing. 

The problem I've had using a router bit to shape balsa parts is that the heat generated warps the wood badly.  The same problem using a table saw.  I get good results only with the band saw with a "skip tooth" blade, which carries away the heat in sawdust.

I've built several S-1 Ringmaster models using a 3-piece leading edge, and sanding after assembled.  This doesn't warp, and is light and strong.

Floyd

If you are burning the wood while routing, you are feeding too fast.  I just wonder how Goldberg and Sterling made their leading edges?

If you are burning the wood while routing, you are feeding too fast.  I just wonder how Goldberg and Sterling made their leading edges?

In my experience, feeding too slow will cause burning.  Feeding too fast causes roughness in the cut.

Thought using a router was pretty common but guess it isn't.. A cheap router and router table are real handy to have in your shop, mine came from Sears and seem to remember having less than $75.00 invested in both the router and table. I did buy a set of quality carbide bits that were a little expensive but Harbor Freight might be a good place to start.

I have never been totally sure what router bit and shape to get.  This Barton forum thread was very good about answering some of that:
http://controlline.org.uk/phpBB2/viewtopic.php?p=110335#110335
Where John told me to "bit you want is a carbitool round over fillet" but I have not found a source for those in the USA.  Also what size is needed?  If the plan calls for a 3/4" x 3/4" LE then is a 3/4" round over bit needed or is it 1.5"?  Also,  John did tell me that the shape is elliptical.


As for my router and table,  it was also a cheap Sears but they were about $100 when I got mine.

What I have gone to is making a couple of forms out of pieces of solid leading edge, and using them to make a molded leading edge.  I have a lot of 1/32 sheet,  I wet two pieces of the sheet with water with a spritz of simple green. I wet a piece of glass down with the water, lay the 1/32 sheet down and spray it on the top.  In maybe a minute it is like a wet noodle.  I wrap the form with plastic to keep it dry, put the two sheets in place, with some pins through to keep them centered, and wrap the whole thing with Ace bandage.  I let it dry over night. 

I take the top sheet off, and spread a really thin layer of epoxy on the sheet still on the form.  Maybe I run a couple of carbon fiber strips down the length, the put the top back on and re wrap.   Once dry, I trim the back edges of the sheet to suit, then glue it on the ribs, then D-tube it.  Gives a very strong, light leading edge.