Design

[DoctaDave]

For those of you who are not building out of the kit, where are you guys buying your leading and trailing edges? and also what do you guys do to taper the tailboom?

[retired1]

For leading edge, I think that most people will use balsa sq's or rectangles. Carbon rod / tube is also an option, but a bit more difficult to find. With the 8g weight, thin bass wood is an option for a tough LE.
Tapers can also be bought or hand cut with a heavy straight edge. If someone has a Harlan micrometer slitter, it is very easy.
If someone has a micro table saw, it is not difficult to make a jig for cutting them.

[jander14indoor]

I cut all my own parts from sheet stock. Much cheaper and gives you the ability to control grain much better resulting in stronger parts.

I have a fancy Harlan cutter I use when I'm building hard core indoor planes where I need to control dimensions to the thousandths of an inch. But at $150 or so that's overkill for SO planes.

For SO planes I use an inexpensive Master Airscrew Balsa stripper. With a little practice and a few simple mods you can get VERY good results. With good, straight grained wood, I can cut piece after piece to within a couple of thousands of an inch in thickness. Just a little harder to pick the thickness than the Harlan stripper. This doesn't bother me too much since I cut lots of pieces and then select by weight and stiffness. The width will be close enough at that point that the other two factors are more important. Since I've described the process several times on this forum, do a little digging and searching to find it.

For tapered parts I use a good steel straight edge and more or less free hand cut. I have a big cutting board with a grid cut on it. I tape the sheet stock down so it won't move and then use the measurements at the edge to give the taper needed. Every other cut is straight across and in between tapered. By using the edges of the board I can increase the accuracy of the taper on the relatively short (12-14 inches) tail booms I use. Again, more than adequate for Wright Stuff planes.

Jeff Anderson
Livonia, MI

[retired1]

I have better luck with the Master Airscrew stripper on 3/32 and 1/8" balsa than my Harlan stripper. You can not beat the Harlan for really thin or thicker balsa.
I do not see how you could cut a taper with the cheap one.

[jander14indoor]

Sorry, not clear. I use a knife and a straight edge to cut tapers, not the Master Airscrew. There is probably a clever way to do it, but I have enough success that I haven't had enough motivation to figure it out.

Master Airscrew stripper is only for straight strips. I can strip any thickness and hardness, but thicker/harder takes a couple more tricks to do right. Big thing is don't PUSH it to hard, let the blade do the work it is designed to do. If you do, the blade will bend and the strips won't be consistent.

Same is true of the Harlan stripper on thicker stock. Don't try to cut all the way through the first pass.

Jeff Anderson
Livonia, MI

[torqueburner]

Here is a new design topic for discussion - the bonus wing for state competition, which has a 7 cm chord.

Our team has usually qualified for states, so we decided to start with the 7 cm wing. Our best time under a 19' ceiling is 3:09. But recently, we built a wing with 8 cm chord. Same fuselage, prop, rubber, and the best time is 3:28. Well, the math is pretty easy; this is almost exactly a 10% difference in times. So for us at this point, the chord bonus seems to be a wash.

Just wondering if anyone else has experience with the bonus wing. And also this question: if the times with and without bonus are essentially the same, is there any reason to prefer one over the other. Obviously, we will use the wider one for Regional competition, but is there any other benefit to a larger or smaller wing chord, other than what is shown by the stopwatch?

Dave D.

[DoctaDave]

Well for the leading and trailing edges found in the Freedom Flight kit, they use a very thin, tapered, triangular strip of balsa but I can't seem to find the same type of wood in any hobby shop or website. I've only found balsa leading and trailing edges that are 1/4"x1" at the smallest on sites like national balsa and specialized balsa.

I do have a masterscrew balsa stripper which I commonly use for bridges, but I can't see how I could possibly strip balsa to an angle as steep and as thin as the wood provided in the kit. Saving money isn't a huge issue since I probably won't need more than a couple wings to sustain me for the rest of the season so is there anywhere to just purchase the leading and trailing edges without having to strip or cut them myself?

[bjt4888]

nxtscholar,
Attached are pictures of the Harlan prop hanger/"pigtail thrust bearing" and custom prop hook and rear hook that my students are using. Both hooks are made from .018" guitar string. The Harlan prop hanger/"pigtail thrust bearing" shown is the Penny Plane bearing. This bearing needs to be drilled-out to .020" to accept the .018" wire. It appears that Ray Harlan (Indoor Model Specialties) may be manufacturing a Science Olympiad bearing now that is a little bigger overall (eliminating the need for the 1/32" balsa spacer shown) and that already has a .020" hole.

Also pictured is a modified Ikara wide-bladed "flaring" propeller that my students are testing. Note the sanding marks on the front half of the blade. It only took about 30 minutes to sand the blade thinner for better flaring and to readjust the pitch to our desired starting point. Notice that the "back" portion of the blade is cut off at the propeller spar. This is copying a design idea from Cezar Banks Leading Edge plan from a few years ago.

Good luck with the torque burner.

Brian T.

[bjt4888]

DoctaDave wrote:

Well for the leading and trailing edges found in the Freedom Flight kit, they use a very thin, tapered, triangular strip of balsa but I can't seem to find the same type of wood in any hobby shop or website. I've only found balsa leading and trailing edges that are 1/4"x1" at the smallest on sites like national balsa and specialized balsa.

I do have a masterscrew balsa stripper which I commonly use for bridges, but I can't see how I could possibly strip balsa to an angle as steep and as thin as the wood provided in the kit. Saving money isn't a huge issue since I probably won't need more than a couple wings to sustain me for the rest of the season so is there anywhere to just purchase the leading and trailing edges without having to strip or cut them myself?

See the attached design by Bill Gowen that has diagrams and notes for creating shaped leading and trailing edges. Some variation on this method would probably serve to create the wood shapes you are trying to make.

NOTE: this overall design is labeled "09" and is not legal for the 2015 Wright Stuff event as the wing chord is too wide. However, design ideas like LE and TE shaping, airfoils, Propeller shape (not propeller diameter), etc.

Brian T.

[DoctaDave]

Thank you guys for the help!