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Weight lifting competitions. - 2/5/2003 12:07:01 PM   
Zweihander


 

Posts: 18
Joined: 2/4/2003
From: Saskatoon, SK, CANADA
Status: offline 		I am in current design phase of a biplane. All previous design experience has been with tricycle gear on monoplanes. I have been trying to find out why there are mostly tail draggers for biplanes and very few tricycle setups. Any comments would be appreciated.

Thanks for the help,

EDIT: Feel free to add and questions comments on heavy lifting.

Tyler

< Message edited by Zweihander -- Feb 15 2003 8:26PM >
       Post #: 1

Weight lifting competitions. - 2/5/2003 12:38:04 PM   
BMatthews



Posts: 8949
Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		Because trike gear on a biplane is just..... just..... well, just.....

[SIZE=8]WRONG[/SIZE]



The only one in the full sized world that I know of is a Waco Cabin Special or something with a lot of odd letters. And it just looks odd.

Conventional isn't all that hard. I've flown both and conventional is actually easier in some cases. The cross wind takeoffs are just a bit harder than trike. And there's a few tricks to setting the toe in and stuff that you can do later if the ground handling is a problem.


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Bruce-
Proudly wasting balsa since 1965.

Free Flighters go that extra mile........

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       Post #: 2

Tricycle - 2/5/2003 12:54:11 PM   
Daniel Nelson


 

Posts: 87
Joined: 11/20/2002
From: Lancaster, CA,
Status: offline 		Oh come on. Ignoring the asthetics, is there any reason why a biplane can't have tricycle gear? Personally, I say go for the trike gear. Better ground handling, better crosswind, and easier landings.

If you really want to get wild, how about retractable tricycle gear? Just be sure to post a few pictures.

(in reply to Zweihander)
       Post #: 3

Re: Tricycle - 2/6/2003 2:40:48 AM   
BMatthews



Posts: 8949
Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		[QUOTE]Originally posted by Daniel Nelson
..Ignoring the asthetics, is there any reason why a biplane can't have tricycle gear? ..... [/QUOTE]

No reason at all. But you can bet the fashion police will shut down his flying field and all the people that saw it will need to go for special counseling....

I know, I know, so call me prejudiced but in my book biplanes just need to sit with their noses in the air.


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Bruce-
Proudly wasting balsa since 1965.

Free Flighters go that extra mile........

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Weight lifting competitions. - 2/6/2003 4:25:54 AM   
MinnFlyer



Posts: 19637
Joined: 4/22/2002
From: Willmar, MN, USA
Status: offline 		I'm with you on this one Bruce. A nose gear on a bipe would look like a training bra on Dolly Parton. Just plain silly.

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Weight lifting competitions. - 2/6/2003 12:30:29 PM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		I think there was a model bipe called a Bolero or something like that, can't remember who designed it but it was sold for a number of years that had a trike gear. I always though it looked pretty good.

Several years ago a bipe was flown at the RC world aerobatic champs by Tony Frankelwitz (please excuse the spelling) but I can't remember if it had a trike gear or not.

Most bipes are indeed built as scale models of full scale which use the conventional gear because it works good enough and is lighter than a 3 wheel gear. A nose gear to take any loads needs to be heavier than a tail wheel.

If there were a lot of ground handling maneuvers in pattern flying and a pattern that needed the qualities of a biplane you would see a lot more trike bipes.


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Ben Lanterman

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Weight lifting competitions. - 2/6/2003 9:50:06 PM   
Zweihander


 

Posts: 18
Joined: 2/4/2003
From: Saskatoon, SK, CANADA
Status: offline 		Thanks for the input.

Main reason for designing a biplane is for maximum lift on a small wingspan. I'm trying to get a 13kg lift out of 183cm wingspan.

From what I have seen conventional gear landings can be difficult with heavy loads.

I am not sure how heavy loads will work with conventional gear, stearing could be difficult on takeoff.

Asthetics are not a problem, as funtionality is 1st priority on this plane.

I'm not even sure where I would mount trike gear on a biplane, very little documentation on it?

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       Post #: 7

Weight lifting competitions. - 2/6/2003 10:35:54 PM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		--------------- I am not sure how heavy loads will work with conventional gear, stearing could be difficult on takeoff. -------------

With conventional gear regardless of weight because the CG of the airplane is aft of the wheel contact with the ground it becomes an unstable system. As the airplane is rolling it hits a bump which offsets the CG from the centerline and it tends to want to keep on going. The tail wheel helps stop this until there is a transistion where the tail wheel is not providing much steering and the tail is not providing much aero help.

When the motor is adequately powerful it can literally blast stability into the system through a thrust vector and the vertical tail. Of course the bigger motor brings torque problems with it.

With a heavy airplane the problem comes with the increased moments of inertia in yaw. Once the airplane starts yawing it takes a lot of directional stability to stop it. You tend to over correct and end up with a ground loop. Again lots of power and directional stability will help keep it going straight.

Trike gear is stable. When you get the airplane moving and a little ground bump hits a wheel the inertia of the CG tends to straighten the airplane out.

------------- Asthetics are not a problem, as funtionality is 1st priority on this plane.

I'm not even sure where I would mount trike gear on a biplane, very little documentation on it? --------------

Look at any trike geared airplane and copy it :-) My main approach.

The main wheels are perhaps 5 percent of the wing chord aft of the CG. Too far aft will make it difficult to rotate to take off attitude. Too far forward will not let the nose gear have enough weight on it to allow steering to occur. The nose gear should be located basically as far forward as structure allows. It allows steering with small side loads, something good for large airplanes but not a problem with models.

You want to allow enough clearance with the aft fuselage to allow rotation to the takeoff angles needed. There is a weight lifting contest held every year that some others may know about, I don't remember the name of it. Sometimes the tail cones are slanted upwards to 20 degrees to allow rotation of the wing. Conventional gear setups in this application can't rotate too far so the wings have to be set at a large angle with respect to the fuselage.

Weight lifting airplanes should probably go with a tricycle gear.

Was this any help???


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Ben Lanterman

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Weight lifting competitions. - 2/6/2003 10:51:43 PM   
BMatthews



Posts: 8949
Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		If you're trying to lift a heavy load with limited wing span be sure to watch out for the interplance spacing. For best performance they need to be something like 1 1/4 to 1 1/2 chord widths apart to minimise interferance between the airflows which will dampen the lift. Many of the racing biplanes of the 30's ignored this as a tradeoff for speed but they didn't much worry about higher landing speeds as long as they were tolerable.

And don't let my ragging about aesthetics put you off. It's YOUR model and YOUR hobby. I was just pulling your leg. Do what you want and enjoy it.

Sounds like this is meant for a weight lifting contest. Yes? If so then there are options for the interplane struts to be placed at the tips of the wing panels and act as fences to control tip loses.


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Bruce-
Proudly wasting balsa since 1965.

Free Flighters go that extra mile........

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       Post #: 9

Weight lifting competitions. - 2/7/2003 11:29:42 AM   
Zweihander


 

Posts: 18
Joined: 2/4/2003
From: Saskatoon, SK, CANADA
Status: offline 		Ben,

I thank you for the comments, great help. I will continue with trike design. You have confirmed my theories for take off with conventional setups being unstable especially having a small engine.

BMatthews,

I have current design plans as you mentioned. 1 1/4 chord spacing, and wing tips. It is a weight lifting competition.

Thanks again,

Tyler

(in reply to Zweihander)
       Post #: 10

Weight lifting competitions. - 2/7/2003 12:37:00 PM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		You are having all the fun. They didn't have this kind of thing when I was a kid. Well yeah they did, it was the old PAA .049 powered cargo event. There were some great models designed for it. I think Model Aviation or one of the magazines had coverage of a recent lifting contest a few issues ago.

The resulting airplanes are just plain homely. It is a great technicial challenge though. As Bruce said the lift goodness from the big end plate on the bidplane has got to be a lot. Plus some structural difficulties are made much easier. Be sure and make something that can fly well in addition to carrying weight.

Be sure and post a photo of the final result.


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Ben Lanterman

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Weight lifting competitions. - 2/7/2003 11:14:40 PM   
BalsaBum


 

Posts: 62
Joined: 9/26/2002
From: satellite beach, HI, USA
Status: offline 		HEY ZWEI ! What are you guys smokin up there ? Tri-Gear on a bipe would be uglier than home made sin !


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and your wife does not here it..

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       Post #: 12

Weight lifting competitions. - 2/7/2003 11:55:01 PM   
springer-RCU


 

Posts: 32
Joined: 3/18/2002
From: YORK, UNITED KINGDOM
Status: offline 		I'm involved with a British version of the American weightlifting comp, which latter is run by the SAE.

In seven years of competition, we have never had a biplane entry owing to the comparatively poor aerodynamics.

However, we have found the trike to be a far superior animal to the conventional u/c, especially as the weight piles on. However, don't fit a spindly bit of piano wire and hope that this will do the trick. You need to engineer the nose-leg or you will find that it collapses and/or renders the model impossible to control on the ground.

BTW, there have been quite a few full-sized aircraft with tricycle gear, I think , especially in the microlight world. Once you become accustomed to the aesthetics, you'll find that they look fine.

Springer

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       Post #: 13

Weight lifting competitions. - 2/8/2003 12:42:18 AM   
Ben Lanterman



Posts: 1284
Joined: 10/27/2002
From: St. Charles, MO, USA
Status: offline 		I had forgotten who put the competition on. I guess using a bipe or not would depend if there were wing span limits imposed in the design rules. There would be a set of aero tradeoffs that can be made based on the rules that should give a very clear design trend.

http://www.sae.org/students/ade99res.htm

is a picture of the open class winner. Four motors and lots of propwash will help. The aero layout is a perfect example of the ideal planform for the contest. Note the really big vertical tail to keep the nose going straight. They are ugly. I remember seeing somewhere the standard class had a one motor limit imposed.

To get more variation in the designs they need to make them fit into a box of a given size. It would get rid of that ridiculous tail boom angle.

http://www.db.erau.edu/campus/departments/aeroeng/students/sae_contest_98/sae_contest_98.html

http://home.cfl.rr.com/saeaeroeast/


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Ben Lanterman

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Weight lifting competitions. - 2/8/2003 3:57:11 AM