How much of a hassle would it be to replace the flat horizontal and vertical stabs (and rudder and elevator) with built ones on an uncovered DP Ultimate (or probably any other ARF)? I'd imagine it could improve handling and, if done well, might lower the overall weight a bit.

Are you talking about replacing solid sheet flat stabs with built up flat stabs, or replacing built up flat stabs with built up airfoiled stabs?

Jim

Replacing solid sheet with built-up airfoiled stabs.

It would sure make a lot of models more realistic! Especially H9 warbirds...

First, in case you didn't know, the full scale Ultimate Bipe has flat tail surfaces.

Airfoiled tail surfaces are almost always fully sheeted and are usually heavier that solid flat sheet tails. They are a lot heavier than built up flat tails, which are usually not sheeted.

Airfoiled tail surfaces are a little smoother around center in high speed maneuvers (precision aerobatics)but they don't do a thing for slow speed stuff (3D).

Mounting them at the correct incidence can be a challange because the stab saddle is not flat and decent looking tail fairings can be a nightmare.

But as Tailskid said, they do look good on scale models of airplanes that had airfoiled tails. (Back to the first sentence above.)

Jim

actually...because airfoiled stabs are airfoiled, and not flat, their efficiency creates far greater control response than flat surfaces. so they do make a significant different difference in handling. (try a knife edge loop with a flat stab rudder, it gets pretty exciting towards the end!) some airplanes have gone through design iterations that went from flat surfaces to airfoiled surfaces, (original Aerworks Edge 540 comes to mind) and that singular change resulted in an airplane with far greater tail authority for both precision and 3D. but getting back to the question....replacing flat stabs with built up stabs can be done, (on some airplanes) but it is a lot of work, and requires a pretty good understanding of how it is done on larger airplanes. good luck.

Paul

Yep I was fully aware of that. I'm not interested in replicating a scale aircraft. I'm interested in improving the performance of model aircraft. I've seen airfoiled tails that were not fully sheeted and were very light. I was thinking that it would be possible to do this and still maintain plenty of strength in the planes I mentioned above. I might see if I can design a vertical and horizontal stab that will work. I've never done anything of this size before that's why I was asking.

Keep in mind that the airfoil on the tail is opposit the wing on many designs, if not symetrical.

keep in mind that chip won the TOC with a flat stabbed ultimate...not sure you are going to improve the performance, and I personally wouldn't mess with it for those reasons.

P

If you want an airfoil, just use the 'slab stab' and install it. Then 'build' your airfoiled stab on that piece. Just my $.02 worth.

Good point.

What he said!

For a diamond airfoil, simply add a spanwise stick on top and bottom at about 25% of chord, then Monokote over the whole thing. Simple, light, behaves about the same as a curved airfoil. The Taurus and Orion models by Ed Kazmirski (circa 1962) used this technique. It still works. [8D]

I had thought about doing this, but wasn't sure of the effectiveness. Hmm I wonder...

When I repaired the damaged rudder and fin on my H9 Corsair, (stick built flat surfaces) I sanded the trailing edge of the rudder down to a feather edge, and thinned the leading edge of the vertical fin a bit, then sheeted both (yeah, yeah, I know the corsair had a fabric covered rudder) with 1/32 balsa, and then sanded the LE to a smooth radius and re-feathered the trailing edge. Made for much stronger unit at minimal weight gain. I also extended the fin sheeting slightly past the rudder post, and rounded the leading edge of the rudder to produce a coved fin/rudder joint. Plan on doing the stab/elevators next.

Based on what you described, I'm guessing you had a very thin airfoil. Do you have any pictures? How did this effect the handling characteristics?