Kit #604 Lancer build

[Sai1704]

Finished the model, after spending about 8 hrs yesterday and today on covering! I went crazy and covered the wing and fuselage in both white and grey, expecting it to look a bit more vibrant, but it still looks dull. I am satisfied with the covering, despite quite a few wrinkles. Horizontal stab warped and now has a slight dihedral; not a problem.
Frame weight is now a whopping 29g, and the propellor and motor together weigh around 9g! I pray that it flies, because I built this plane to get experience only in flying it.

[SpiceMan]

Sai,
Looks like your baby has turned out VERY NICE.
My bet is that she's going to fly just fine.
Keep us posted on how the maiden went for ya.

[David Lewis]

The landing gear on a model airplane must be able to bend back without transmitting too much force to the mount, so you can either use traditional hat shape wire with the mounting plate ahead of the the axles (i.e. gear legs swept back), or torsion bar design, which has better stroke efficiency. If the landing gear legs sweep forward, you will have problems.

[David Lewis]

"Notice how the horiz. stab. has an airfoil? I've been wondering how this affects the flying..."

A flat plate airfoil seems to work just as well. Some contest events years ago imposed a wing area limitation, so designers moved the CG back (typically to 40% or 50% of the chord), reduced the decalage and increased stab area. Static margin is low with this setup. The stab contributes to lift without contributing to wing area, and a cambered airfoil gives you higher L/D than a flat plate. Note that a cambered stabilizer airfoil and a lifting stab are two separate, independent design features. E.g., some designs feature a lifting stab that has a flat plate airfoil.

A lifting stab reduces nose up pitching moment at high speed, and it also gives you a better glide ratio. The disadvantage is when the model goes into a dive it tends to recover slowly or not at all.

In the more common longitudinal force arrangement, the stabilizer generates a down force (cancels some wing lift) and the CG is farther forward. These models are characterized by relatively smaller stabs, more decalage and CG around the 25% chord point. The advantage is it recovers from a dive more rapidly.

In the 1950's and 1960's, Clark Y stab airfoils came into style because a lot of contest winners had them and designers copied each other. Eventually the fad ran its course.

[Steve Blanchard]

That is considered a lifting stab. It really isn't necessary for a good flying model but it has been used extensively in the past on older designs. In effect it lifts the tail end during flight. I have built some models with this for old timer events only because it was required to build per plan to compete. The models by design flew very well but no better than the models I have built without a lifting stab. I'm sure there is a real reason for it but I do not know what it is.

Steve

[Sai1704]

.Thanks Spiceman. I believe the stab-airfoil enables the CG to be moved a little behind of the standard position?

Today was my first eye opening day of the result of free flight. I had extremely satisfying and amusing flights, lasting up to 20s in duration.
The lancer hit the ground and other obstacles VERY hard numerous times. I am proud to say that there is no breakage in any of the frames of the plane, but lot of the underside tissue has torn. I flew the plane in light to medium winds, and I'll say the wind made the flights just more spectacular . The model would rise at once to about 30ft, make a wide circle to the right and upon losing most of the power, it would dive and just flare before landing (BTW I flew without landing gear). Due to a warp in the rudder, it would always turn right, but not too drastically.
I had one flight where it flipped over in flight because of wind and began rapidly descending, when suddenly it flipped over again and flew a good 50 ft again before landing.
Again, this is only with kit rubber, which lasted about 15 flights before losing power delivery. I had no time to try with 1/8" competition rubber. The plane is still together, and by redoing the covering, I'll try again with the other rubber.
I have two videos, one showing a poor fail, and another showing a better and longer flight, but none of the more amusing ones.
Now I am encouraged to build more planes to fly

[davidchoate]

i posted a question about an stab with airfoil on my Javelin. I am currently rebuilding the fuse due to catastrophic motopr failure. I was considering building a horiz stab with less airfoil, but did'nt yet. I am also going to modify the fuse slightly. using plywood "F" parts, and maybe a built up configuration toward the rear of the fuse , behind the motor dowel ( which I am going to relocate an inch forward of whats on plan. my original fuselage had a lot of twisting after a few flights.OH, the landing gear is all but useless except for balancing weight & aestetics.