M'lud Posted August 26, 2008 Share Posted August 26, 2008 I have asked this ? before, but can t remember where, so please excuses me. is the dihedral factor as important in a scale model 1/18 as in a larger model. Forgot to tell you mine is rubber powered. thanks a lot Reg Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 26, 2008 Share Posted August 26, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
M'lud Posted August 26, 2008 Author Share Posted August 26, 2008 My god Eric you are a mine of information. I did not think that this game we play is so damn complicated,Perhaps I should return to woodwork,or nursing that was easy, spent a lifetime at both.Another reason my Puss Moth would nt fly . The covering tissue distorted the wings, such little thing that keeps one grounded. Please, how do I give a model more dihedral, that is not so much a ? as a plea I m 68 and confused, not only by the pc, but the things I have to learn to pursue my latest hobby Thanks alot Reg. Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 28, 2008 Share Posted August 28, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted August 28, 2008 Share Posted August 28, 2008 Better still y' all Build in a few degrees washout on the tips (purpose built in warp for those who dont know ) ie raise the TE of each wing half at the tip when doping My Trixie has extra ribs at angles to keep the shape without having to resort to "warping" & its virtually impossible to stall it Grumpy MyronPS just put a 'lektric thing in the front ---Mistake ---No likey ! Quote Link to comment Share on other sites More sharing options...
Rick Tee Posted August 28, 2008 Share Posted August 28, 2008 The addition of washout is usually used to reduce or eliminate tip stall, its side effects are to increase drag and reduce lift efficiency effectively increasing wing loading, flying speed and making inverted flight unstable. The exception is where a wing is specifically designed to have some washout, in which case the aerofoil section at the tip will be different to that of the wing root (aerodynamic washout.) I believe it's mainly used on thermal gliders as tip stall can be the result of highly tapered, high aspect ratio wings and inverted flight is not a major consideration with this type of model. In this case we are talking about a free flight rubber powered model (I think) so inverted flight is not a consideration, but the wings lifting and drag characteristics are. Though increasing the dihedral does reduce the wing's effectiveness, it should not increase the drag. I'd go with Eric's post, if instability is the problem, increase the dihedral by cutting the wing or building a new one. If the wing is twisted then pin down and re-dope, if your lucky the twist will be gone, if not it will be back in a few days. I remember having this problem with rubber powered kits, i bought a balsa stripper and replaced spars, leading and trailing edges (mainly spars) with ones cut from the same piece of wood, as inconsistency between them seemed to be the main cause (all looked fine untill the dope dryed.) If i've not got this right i'm sure someone will correct me. Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted August 29, 2008 Share Posted August 29, 2008 Rick Just a couple of points .Trixie is a 40 in span cabin type trainer high wing 5 to 1 aspect ratio parallel chord design for a 10 to 15 ic engine .Its primary feature is its slow speed capability . I made it about 10 years ago & cant remember where the plan originated except that it was a freebie . The ultimate predictable "evening" no hassle machine I ve known .I put this down myself to the built in washout .If only I could get this laptop to do photos as easily as it flies, I would be a very contented guy ! Not grumpy Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted August 29, 2008 Share Posted August 29, 2008 Trying photobucket procedure again-excuse pictures on the wrong thread. I'll get there! Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 30, 2008 Share Posted August 30, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted August 31, 2008 Share Posted August 31, 2008 How scale is your Puss Moth? The full size was built with absolutely no dihedral at all - but then it has a pilot on board! On the original each wing is simply pinned to the top of the cabin so the wing struts alone position the wing. If your wings are fixed in a similar sort of way, then simply longer struts will give you dihedral. Rubber power models tend to need quite a bit of it as they normally have big over scale slow speed propellers. The result of this is that if you trim it to glide straight then it will fly in circles when under power and vice versa. So they are usually set to turn one way under power and turn the opposite when gliding. This also has the benefit that It will hopefully stop it flying too far away! I hope this helps. Quote Link to comment Share on other sites More sharing options...
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