john stones 1 - Moderator Posted November 29, 2014 Share Posted November 29, 2014 Hi All Here's a question I have asked and never got a answer for, but I reckon I will on here I like to build my own sports designs but have never done a bipe. How/what determines if I fit ailerons top and bottom or just top or bottom, which if any are the more efficient and why ? John Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted November 29, 2014 Share Posted November 29, 2014 One of the main reasons for building a biplane today is that the wing span can be shorter whilst keeping adequate wing area so the wing loading is reasonable. The advantage to having a shorter wingspan is that potentially the roll rate can be higher (less axial inertia and roll drag). To take maximum advantage of this higher potential roll rate you want very powerful ailerons - hence have four rather than two! The only advantage I can see in the opposite arrangement - ie only two ailerons - is the simplicity of the linkage. The reason why, when there are only two ailerons, they tend to be on the lower wing rather than the upper is basically the same - simpler linkage. However, aerodynamically there is possibly a case when only using two ailerons to have them on the upper wing as this contributes about 65 to 70% of the lift in a biplane - hence they would probably be more effective there. BEB Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted November 29, 2014 Author Share Posted November 29, 2014 Thanks BEB I didn't know there was such a difference between upper/lower wing in lift, but I do now John Quote Link to comment Share on other sites More sharing options...
J D 8 Posted November 29, 2014 Share Posted November 29, 2014 Most biplanes have the top wing further forward to reduce biplane interference and improve performance of the lower wing[a few have rearward stagger] and the larger the gap between wings the better. Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted November 29, 2014 Share Posted November 29, 2014 Many years ago, I had a "Stringalong" biplane which I modified to 4 ailerons. It flew very well and had a very reasonable roll-rate without being at all vicious. I also built a smaller "Pasadena Special" (I like biplanes!) with ailerons on the lower wing only. That also flew extremely well, but the ailerons were bigger as a proportion of the lower wing than on the "Stringalong". The extra complexity of 4 ailerons (all driven from one servo in the middle of the lower wing!) required more attention to detail when rigging at the field - wingtip struts were a "must" - but it looked better! I still can't decide whether it flew any better or not, so not much in it, really! -- Pete Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted November 29, 2014 Share Posted November 29, 2014 May be a dumb question - but why not use servos in the upper wing too? Cable would have to be routed down the cabanes but other than that......... Quote Link to comment Share on other sites More sharing options...
kc Posted November 29, 2014 Share Posted November 29, 2014 Presumably with tiny servos available cheaply it could be practical to use 4 aileron servos to get ailerons on both wings and avoid rigging complications by just plugging in the leads ? Peter mentioned Stringalong and this plan is still available from MyHobbyStores here Pasadena Special is another very old Radio Modeller design but is available here This has been a favourite model at my club with several being built and flown in the last few years. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 29, 2014 Share Posted November 29, 2014 There is perhaps one further issue considering what happens when a biplane stalls. It is usual to arrange that the top wing stall first - all things being equal it probably will anyway due to the upper wing providing a 'slot effect' to the lower one - so ailerons on the lower wing should remain effective even as the plane enters the stall. The DH Tiger Moth is an example. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted November 29, 2014 Share Posted November 29, 2014 4 servos also gives independent adjustment of all 4 control surfaces in both directions, which should allow for much easier tweaking of throws / differential to give nice axial rolls. You should be able to use smaller servos too, as the load is divided between more surface. There should not be much increase in the overall weight (or price) if you select the right servos. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted November 29, 2014 Share Posted November 29, 2014 Posted by Simon Chaddock on 29/11/2014 16:59:05: There is perhaps one further issue considering what happens when a biplane stalls. It is usual to arrange that the top wing stall first - all things being equal it probably will anyway due to the upper wing providing a 'slot effect' to the lower one - so ailerons on the lower wing should remain effective even as the plane enters the stall. The DH Tiger Moth is an example. .. Edited By Dave Hopkin on 29/11/2014 17:13:08 Edited By Dave Hopkin on 29/11/2014 17:27:16 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted November 29, 2014 Author Share Posted November 29, 2014 That's very interesting Simon it makes the choice of which trickier. It's just something I've wondered for a while Gary because of fullsize aeros, linkage apart why some top and some bottom? John Quote Link to comment Share on other sites More sharing options...
bert baker Posted November 29, 2014 Share Posted November 29, 2014 Hmm, read with interest, why does my tri-plane have ailerons on the top wing only. and it still performs rolls. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted November 29, 2014 Share Posted November 29, 2014 Posted by Dave Hopkin on 29/11/2014 17:11:53: Posted by Simon Chaddock on 29/11/2014 16:59:05: There is perhaps one further issue considering what happens when a biplane stalls. It is usual to arrange that the top wing stall first - all things being equal it probably will anyway due to the upper wing providing a 'slot effect' to the lower one - so ailerons on the lower wing should remain effective even as the plane enters the stall. The DH Tiger Moth is an example. Totally Misread your post!!!!!! But its a gorgeous plane.......... Edited By Dave Hopkin on 29/11/2014 17:13:08 Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted November 29, 2014 Share Posted November 29, 2014 I like the ailerons on both wings. Gives faster rolls. Models that I can quote from are "Yuppy Love, the scaled up Toot Sweet and Melody. I prefer to use one servo in each wing. with a Y lead on the Rx. By coincidence I have a half drawn cabin Biplane on the drawing board at the moment. IT will have 37" span, 8 1/4 chord and 1" wide ailerons. Power will be an OS 40 Surpass.. Area about 610 sq. in. Ideal for winter because it will go in the car in one piece Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted November 29, 2014 Share Posted November 29, 2014 Posted by Dave Hopkin on 29/11/2014 16:31:14: May be a dumb question - but why not use servos in the upper wing too? Back then (late 60's / early 70's) the cost of radio gear in relation to earnings was far greater than now Even one extra servo was a week's wages. On the other hand, piano-wire push-rods were cheap....! Nowadays, yes, a multi servo setup would make much more sense! -- Pete Quote Link to comment Share on other sites More sharing options...
Mike Smith Posted November 29, 2014 Share Posted November 29, 2014 John, I don't profess to have a great deal of experience, but I can vouch for the effectiveness of 4 ailerons on my Mini Panic. The roll rate is excellent!! The lower ailerons have a servo each and the lower ailerons are connected to the upper ailerons by dowels, terminated with ball joints. They pop apart easily enough, should you need to remove the wings for storage or transportation. Mike Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 29, 2014 Share Posted November 29, 2014 Bert The top wing of a Triplane had significantly more area so it made aerodynamic sense to put the ailerons there, coupled with Anthony Fokker's notorious reputation for saving money. Why have 3 sets when 1 will do! In any case the Triplane had a serious tendency to scrape its lower wing tip on the ground hence the 'pick axe handle' skids! Quote Link to comment Share on other sites More sharing options...
bert baker Posted November 29, 2014 Share Posted November 29, 2014 Posted by john stones 1 on 29/11/2014 14:33:19: Hi All I like to build my own sports designs but have never done a bipe. John Cool what fun, I suppose being an own design, it will depend on what you want it to do and look like. I think more info on how you intend to build it would help. Foam veneered wing, sheet wing, built up. depron. The little Toot is sporty and only has lower ailerons as do Tiger moths, the original Avicraft Panics had lower ones only. If it is intended as a quick to put together plane when weather is pants, i would stick with lower ones What size were you thinking of Bert Edited By bert baker on 29/11/2014 19:38:17 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted November 29, 2014 Author Share Posted November 29, 2014 Hi Bert It would be next winter before I started anything i'm a little busy with mass builds just now What would I build ? something Pitts like, 4 ailerons and just small enough to fit my car in one piece, only down side to them is rigging at field John Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted November 29, 2014 Share Posted November 29, 2014 i have a design for A 52" all depron bipe brewing at the moment. i was only going to have one pair of ailerons, but i think i will now go for four after reading this thread. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted November 29, 2014 Share Posted November 29, 2014 My take is that a semi-aerobatic model can make do with a simple installation with ailerons only on the lower wing, for something that is meant to be fully aerobatic you want 4 ailerons. Of my 7 bipes 5 have 4 ailerons with a servo in each lower wing and upper and lower surface linked by pushrods, one has 4 ailerons and 4 servos (try a Panic with switched coupled elevator>flaperons or crow braking ) and one is rudder/elevator/motor. My favourites are the 2 servo linked aileron setups as the link rods only take 10 seconds to fit - struts are far more of a nuisance. The 4 servo Panic is good to play with but there is a weight penalty from 4 servos and the top wing servo wires are a nuisance flapping in the breeze where they are prone to fatigue damage. My Baronette tripe has one servo driving both ailerons through pushrods and bellcranks, a system I do not like - too prone to slop and liable to suffer from an inconsistent neutral, but ok for a sport scale first war model. Of course if you are building a scale model such as the Tiggie above the decision is made for you Quote Link to comment Share on other sites More sharing options...
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