stunthanger.com
Building Tips and technical articles. => 1/2 A building. => Topic started by: Dane Martin on October 20, 2018, 05:02:55 PM
-
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 design / build
-
Fuse
-
Fuse build
-
Fuse build
-
Sanded smooth for inspection. I got a light chunk of 1-1/2" balsa!
-
Building the wing to get a tail figure.
-
Adding a strip of basswood
-
Finished wing design
-
Tail design, seeing what it looks like.
-
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.
-
Engine mount install. 3/32 ply. Tite-bond with masking tape to hold it while it dries.
-
Fuse shaped, not hollow yet. Hinges on the elevator.
-
I had mounted the engine to find the CG location. The wing is butted all the way up against the engine mount. I was kinda shooting for that, to make the tail longer. So, I guess I did good.
-
More wing attached pics
-
Geeeez! Here we thought you was a quick builder. Now we find out that you let Jagermeister the Cat do most of the work. Hooked him up with some Friskies, then set him on the counter with the handdrill and some new batts and voila, the fuse is now hollow. We don't want to hear any more BOM stories out of you, buddy!
Divot
PS--Does Jager do engine work, too?
-
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.
-
So now that I've got the building technique down, I'll make two more. One for Joey, one for Dan. I will make plans available, based on next weekend's maiden flight. Lol.
First coat of dope
-
If we see cat hairs in the finish, we're gonna know who did the real work....
Divot
-
If we see cat hairs in the finish, we're gonna know who did the real work....
Divot
And you guys all thought camel hair brushes were the cats meow.....
-
#^ 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 CLP**
-
Since this one is simply the prototype, it'll be nothing but clear. I've sanded it down to 600 grit. So it'll be ok looking. It's very light. So much so, that I didn't hollow out a portion of the tail, and it's still going to end up nose heavy. After the controls are installed, if it's nose heavy I'll see about altering the plans. If all goes well, I would like to get plans and a build published in AMA!
-
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.
-
Is that wing 1/8"? If the plane gets up any speed the tips will wash in and put on the brakes. Should be 3/16" medium balsa with .56oz fiberglass for a speed plane.
Motorman 8)
It is, but for reed valve, I haven't had an issue with this type of wing construction. I honestly think with the harder wood being that close to the leading edge, it discourages twisting. Well, that's my uneducated guess anyway.
When I monoline this thing, wing constructing will change.
-
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 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!
The sub rudder helps in proto events. You must take off, get to level flying altitude and stay there. So it's all about acceleration, and of course a good to speed. With the rudder on top, and all that engine power, from a dead stop, the plane wants to come in. Just like taking off in a full scale piper cub. You'd need to stand on the rudder while you take off. So the sub rudder just helps fix that when you're not able to use a take off dolly
-
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
-
Interesting points there Divot.
Also, for the folks not familiar with speed.....
Proto is a timed event from a standing start. So dead stop, the clock starts when the pitman let's the plane go.
Speed events, you take off, and you're flying. The laps are timed when you put your hand in the pylon, presumably when you're up to speed.
-
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....
-
I can't find the completed pics, but here's some of the profi powered 1/2a. Perhaps I was too inexperienced to feel those affects while flying this? Past tense. My cousin Butters found a way to crash the stuffins out of it. Lol
-
Does everyone have a cousin named "Butters?"
Divot
-
Does everyone have a cousin named "Butters?"
Divot
One can only hope
-
Control system neutral.
-
Deflection up, and down. Nice high resolution controls, and super smooth.
So I'm not sure I like my elevator horn / attachment. I needed a little tail weight, so this made sense to not hollow out the tail. However, I may look into that for number 2. At this rate, I'll end up competing with number 3..... haha.
-
Measured out the LG to get the stance I wanted. Not much left to do.
-
More LG
-
And glued in
-
Looks great
Sent from my SAMSUNG-SM-G891A using Tapatalk