i am verying highly considering modifying my duraplane in a few months. how are the wings offset(incidence) on normal bipes.

do i need to have the top wing with a little less incidence? should i stagger the wings slightly?

It all matters how you want to fly, by the look of your planes, you might want to stick with incedence of a Aeromaster or Pheaton 90. There are a lot of posts on these planes.

A Ultitmate is set 0°,0°,0° and is the truest flying. I would pick a 25% Edge or similar plane at this point. They can be flown gentle or unlimited, but do what you want. If you cannot build very lite, you will be dissapointed with any choice.

I started out wanting a large P-38, after 9 years, I'm still not ready and am just at 35% aerobatic planes, go figure that I wasted a lot of time with small planes. 73" and up wing spans planes are definately better flying and will improve your skill expodentially

My other suggestion would be a Sig 4 Star 120 with a G38 or a US 41. This is a great step with a easy flying plane that makes you grin everytime you fly.

If a air molucule is like a tennis ball to a full size, then the air is like a over filled basket ball at 60" wing span. The larger the plane, the closer to the tennis ball it is and the better flying the plane is.

Just remember to build lite!!!!!!!!!!!!!!!!!!!!!!!!!

Brschmid,
Suggest consulting the wing incidence thread on this forum.
Good info on biplane set up explained there.
OK?

Hal [email protected]

Full-scale wind tunnel tests conducted back in the early 30s showed that biplane wing efficiency was affected only very slightly by playing around with different incidence between the upper and lower wing. According to theory, induced drag should be reduced, and maximum lift increased, by giving the upper wing a little less incidence than the lower wing. This was not borne out by the tests, which showed just the opposite effect - a very slight improvement in drag and lift by increasing the incidence of the upper wing by one to two degrees, particularly if the wings have positive stagger.

I experimented with differential incidence (called decalage) a few years ago, and found that aerobatic line holding was slightly improved by using a little negative decalage (slightly less incidence in the upper wing), at least, in my model that had about 40% positive stagger (upper wing ahead of lower wing by 40% of the mean chord). I now give the upper wing one-half to one degree less incidence than the lower wing.

I wrote a bipe aerodynamic series for M.A.N a few years ago that went into this, plus a lot of other bipe fine tuning stuff, that is still available in Air Age's book "How-To's", under "Biplane Secrets", by Carl Risteen.

Is the amount of negative incidence in the upper wing a function of the wing stagger??

Getting an average wing incidence (not a precise way of doing it) it would give you a horizontal tail with a positive angle relative to the average wing. This is very close to what Hal Debolt proposes for a pattern ship.

Is the better line holding due to this or something else. I know it is difficult to guess based on no data but I have no experience in this area and wonder.

Hi Ben: I don't recall that optimum decalage versus stagger was investigated in the rather expensive full-scale wind tunnel tests. The wing combination of a bipe with positive stagger, and negative decalage (upper wing at a little lower incidence than the lower wing) would generate a negative pitching moment, just like adding positive camber to its airfoils. It would thus tend to require a little more negative horizontal stab incidence, or a little "up" trim, to maintain level flight.

Some other investigators did small scale wind tunnel testing of all sorts of weird biplane wing combinations. With positive stagger about equal to the chord, large negative decalage, and gap about 1/4 of the chord, maximum lift coefficient was found to be greatly increased. The combination was similar to a highly cambered slotted wing, and only suitable for flying at high lift coefficients.

Going a little further, some people played around with greatly decreasing the chord of the upper wing and the gap. Out of this came the wing with fixed auxiliary airfoil (very impressive maximum lift to minimum drag ratio), and finally, the fixed slot, which is really just a biplane evolution to a vestigial upper wing, tiny gap and large negative decalage.

Hi Rotary,
An explaination>
Over many years I investigated biplanes, mine were "Bipes".
In R/C the first reason was at the time R/C gear was heavy
and we had the craft flying ala free flight and simply guided them
The arrival of propo changed that approach.
A light wing loading was desired and with the weight that meant
a large monoplane.
My concept was that a biwing provided the needed area in a
much more compact size which aided maneuverability.
I found a working combo that put me on the US World Champ
team and the World champs.
The knowledge gained has allowed many more Bipes since that
time.
I provided the set up on another spot in this forum for your info.
One item not included was that a 2/3 Bipe proved most efficent.
That would be one where the lower wing is 2/3 the size of the upper.
Bipes have a charisma of their own and are most enjoyable.
Good luck and ask if you would like more, OK?

Hal [email protected]

Hi Hal: As a long time admirer of your designs - I particularly remember your Over and Under R/C aerobatic design from 1953-4, when I was in junior high, and your Speedwagon series (was a serious ukie speed nitro-maniac for awhile). I, too, saw the bipe layout as a path to getting lots of wing area in a compact and lightweight envelope, and began devouring all the bipe design lore I could find in the dusty back stacks of the university library here. Bipes attracted me, not for their merits, but for the challenge they presented, in getting good lift to drag ratio (normally bad) while retaining their flat-out fantastic maneuverability, particularly in knife edge. I learned to fly seriously crazy 3d-type aerobatics at very low altitude with a self-designed bipe weighing 5 pounds, with 1350 squares. This thing was just a blast to fly, with top speed around 65 MPH, but stall speed just a crawl, so it never crashed, and although an R/C neophyte, I managed to win a bunch of barnstormers events with it, and have been a bipe junkie ever since.

Hi Hal, great to see you here helping everyone. Congrats on a great life of R/C and being a part of it's legacy. I am scratching a bipe, mostly foam. I understand what I have read from your posts re: stagger incidence and wing spacing.


Of all the bipes you've flown (Or built better yet) what was the "optimum" overall dimensions.

Stagger:
Incidence:
Spacing:
Whatever:

and how can this be loosely applied to a general scratch design of any size?

On my scratch, loosely (very loosely) based on the old timer ELF2, I have this situation. (2/3 bipe) Have you had a favorite cabane wing mounting over the years?