Myron Beaumont Posted February 7, 2009 Share Posted February 7, 2009 Have decided to use the "Rupert's Dad" (monoplane highly aerobatic 3-D type A/C ) as a starting point for designing what hopefully will be an exciting winter project . I have a few points I'd ike to clear up before putting pencil to paper .Can you help me --Never designed a biplane but just love their prescence in the air -like my puppeteer . # 1 I think the wing gap should be approx equal to one chords width ? # 2 Unsure whether to incorporate any stagger ( originally used to give the pilot a better view I read somewhere -the only "raison d'etre") # 3 As the original wing has large ailerons -will it perform well without ailerons on the additional top wing or is it a "must have "? # 4 Would it be best to sweepback the new top wing ( there is no dihedral on the original ) If so About 5 degrees ?9 SWEEPBACK THAT IS # 5 Should the new top wing be set at the same incidence angle as the lower one ?(or maybe about 1/2 to 2 degrees more ? ) # 6 I assume that the proposed top wing will be best being the same size ? Certainly easier to construct ! # should I increase the tail feather areas -I.d rather not ? I don't want the ultimate aerobatic capable m/c (too old for that ) but with the nice thick symmetrical well rounded LE section it should turn out to be a winner & docile enough for the title of Ultimate trainer no 2. Will now post this whilst 'er indoors tries to send a picture of the original ASAP . Would really appreciate advice before I get started -There's not much info I could find on the net to do with models _ only a little on full size jobs. Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted February 7, 2009 Author Share Posted February 7, 2009 Hopefully here is a picture of the Rupert's Dad build http://i44.photobucket.com/albums/f10/MyronBeaumont/DSC00034.jpg Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted February 7, 2009 Author Share Posted February 7, 2009 This is another picture of Rupert's Dad -the red and white one behind the Extra Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted February 7, 2009 Author Share Posted February 7, 2009 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 8, 2009 Share Posted February 8, 2009 Myron As far as I am aware the reasoning behind a biplane is Ailerons on both wings to keep the same roll rate. At least one wing chord gap to minimise inter-plane interference - thick wing sections will interfere more. Positive (forward) stagger helps delay the stall of the lower (further back) wing (slot effect) thus ensuring a positive nose drop at the stall. Sweep back on the top wing is normally to improve access to the front seat! Tail feather moment is proportional to wing area so it may need alteration, or reduce the total wing area. You may well find the slot effect delaying the stall on the lower wing is so strong that the top wing stalls long before the bottom one so top wing incidence may be set slightly lower to allow high alpha angles to be maintained. I hope this helps How do you intend to mount the the top wing? Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted February 8, 2009 Author Share Posted February 8, 2009 Simon Apologies for late reply .& thanks for comments Have been mulling over your advice & am wondering whether it's such a good idea -especially about the thick wing section ./ interaction factor.In the back of my mind was the way the Pitts' Special performs but don't know its wing sections If you can see the picture you'll see it has a generous tail & fin/rudder area as a monoplane (hence the idea ) Good tip about the Aof I of a top wing -Glad I asked about that -I was way out with my thoughts ! Are you suggesting maybe that if I make the angles of attack the same it would be a satisfactory compromise ?( or the top wing maybe a degree or two less than the ( original) bottom wing I was right about stagger anyway . The mounting will be done with a variety of pianowire / dural structures and/or laminated balsa thin proper ply near end of wing tip joiners . I see from your logo "Fokker triplane I guess"- that you must know something about multi wing set ups so appreciate your advice before I set pencil to paper .I've learnt a bit already Incedentally -the original is SC 52 Fs powered & the Bi-plane will have my SC 91 A up front with a 12 oz tank which hopefully will bring the C of G to the right position without any serious re haching. assuming no stagger ? Regards & thanks again Myron Quote Link to comment Share on other sites More sharing options...
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