I just got a wild hare to design and scratch build a hollow log based on Larry's post. I haven't built a 1/2a speed plane in a while, so I'm over due.
It'll be 56 squares. About 18" wing. 14 squares for the tail. Still thinking about tail span, but maybe 4.5- 5 inch?

Fuse

Fuse build

Building the wing to get a tail figure.

Finished wing design

Wing and tail area.

Wing: 58.375 (to play it safe with the rules)
Tail: 14.1875 or 24.3% of wing area. I was shooting between 20-25% for stability. Let's see if my ideas work.

Fuse shaped, not hollow yet. Hinges on the elevator.

More wing attached pics

That cat has the most steady sanding technique I've ever seen.
Jaeger is throwing some cox engines together for these projects. There'll be 3 for the speed team.

If we see cat hairs in the finish, we're gonna know who did the real work....

Divot

  Hello Dane!

I've been following this build with a lot of interest, I have a question about the final sanding & finish. Do you use clear dope as a sanding sealer? What are you going to use for the finish?

I would love to see the plans for the "Zippy".

RK Flyer 

Bellcrank and leadouts are now done. Push rod z bend is done. I'd love to be done, flying it this weekend. But I don't know if that will happen without epoxy finish.

So for the solid lead out's on my 1/2a's I make a little P in the wire. Then I wrap and solder that.

I don't do speed...but why is the rudder in the bottom?
I'm just trying to understand.
Oh, and I envy the speed with which you can build!

I would expect the opposite effect with the construction shown. Here is my reasoning:

1.   The wing is developing lift, unless you are simply swinging a rock;
2.   This lift puts the wing into bending, according to the lift distribution; and
3.   The lift is caused by higher pressure and downwash under the wing, including the trailing edge; and
4.   The wing will deflect based on the constraints and the modulus of the materials; and
5.   The spruce(?) spar due to its higher density (more material in a given volume to take up load), will deflect less than the balsa adjacent; furthermore
6.   The spar, on first examination, is forward of the apparent center of the torque tube if the entire wing had been made of one material, causing the rotation axis to shift forward;
7.   The trailing edge is constrained at the trailing edge due to its attachment to the fuselage; therefore
8.   The wing will tend to wash out (TE goes up) progressively toward the wingtips, not wash in under flight loads.

I flew one OPP (Other Person’s Plane) extensively in Mouse I. It had an aerodynamic quirk that was more amusing than anything else. It was high aspect ratio, with a double-tapered planform. (The planform was “waisted.”) The chord at the tip was tiny. From memory, maybe only an inch or less. As it slowed down and you fed in up control as it was whipped back to the pitman, you sooner or later got to the point where the tips were stalling. It would then rock back and forth in roll all the way to the ground. The wing never quit flying due to the center section and the controllability was fine, but it sure looked like some strange four-legged animal trotting back to the pits, tilting back and forth. We could have gotten rid of this by washing out the tips, but then you have the drag of the twisted airfoil all the time. I know a lot of speed wings have gone with a semi-symmetrical airfoil with a progressive nose radius which causes washout and have probably done pretty well with it. I put a bit into all of my Quickie Rat wings, too.

Putting some fiberglass on the wing would certainly make it more durable. And if there was any tendency towards flutter it would help there too. However, the fastest 1/2A Proto I ever saw had a very flimsy balsa wing (around 40 sq. in.) with some MonoKote over it. The whole plane was incredibly light. It was running a GZ .049 with a glass prop. The acceleration was tremendous. When I let go, it simply disappeared….

Dave

I would expect the opposite effect with the construction shown. Here is my reasoning:

1.   The wing is developing lift, unless you are simply swinging a rock;
2.   This lift puts the wing into bending, according to the lift distribution; and
3.   The lift is caused by higher pressure and downwash under the wing, including the trailing edge; and
4.   The wing will deflect based on the constraints and the modulus of the materials; and
5.   The spruce(?) spar due to its higher density (more material in a given volume to take up load), will deflect less than the balsa adjacent; furthermore
6.   The spar, on first examination, is forward of the apparent center of the torque tube if the entire wing had been made of one material, causing the rotation axis to shift forward;
7.   The trailing edge is constrained at the trailing edge due to its attachment to the fuselage; therefore
8.   The wing will tend to wash out (TE goes up) progressively toward the wingtips, not wash in under flight loads.

Dave

Although I completely agree with what you're saying, I'm wondering at what weight and speeds do these things take effect vs what you can "let slide". Obviously I'm going for as fast as possible, but I don't see this going as fast as my bladder tank profi 049 powered profile proto. Same wing construction, similar squares and fiberglassed. It did pretty respectable. I believe I got a first place with it once at whittier. And, this is the prototype. I'm drawing up the plans with pencil, if ya know what I mean....

Does everyone have a cousin named "Butters?"

Divot

Control system neutral.

Measured out the LG to get the stance I wanted. Not much left to do.

And glued in