Mark Wightman Posted January 19, 2021 Share Posted January 19, 2021 Hi Guys I'm just about to start the Harrier,RC 1462.The motor suggested is .40.I intend to enlarge the model by 50% and install an electric motor. I've made a few models,some from plans,and none them suggest a Down thrust of 6 degrees.Any ideas?The incidence for the wing and tailplane is zero.I don't remember any of my other models having down thrust.Maybe because the wing is annedraal? Any suggestions would be welcome.Cheers.Mark Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 19, 2021 Share Posted January 19, 2021 Welcome to the forum Mark. Anhedral is normally there to reduce lateral stability - compensating for the effect of sweepback. I don't know the plan or the designer - S. Newton - but maybe someone could put you in touch with him? Whether it's a function of the scale nose outline or as a result of trial and error during the design stage is a matter for conjecture! The long moment arm from the wing's centre of pressure to the propeller might be involved. Edited By Martin Harris - Moderator on 19/01/2021 14:46:09 Quote Link to comment Share on other sites More sharing options...
Mark Wightman Posted January 19, 2021 Author Share Posted January 19, 2021 Thanks Martin, Interesting. Didn't mention,the designer is P Bosak and it was designed in the 80s .Used to be able to get the plan from RCM&E.I got mine from Sarik.You can get the pdf from aerofred.com (I'd 96226),free.Wingspan is 36".I did think it might down to aesthetics because outline looks just like a Harrier.Cheers Edited By Mark Wightman on 19/01/2021 15:40:57 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 19, 2021 Share Posted January 19, 2021 Ah - assumed it was the Sarik one which shows a different designer. Looking at it the plan on Aerofred, the thrust line is well below the wing with a long lever arm so it may well be required to stop pitching up under power. Edited By Martin Harris - Moderator on 19/01/2021 16:23:11 Quote Link to comment Share on other sites More sharing options...
Ray Wood 4 Posted January 19, 2021 Share Posted January 19, 2021 Hi Mark, Pavel Bosak was a very prolific designer/builder back in the 80's & 90's he was the Tony Nijhuis of his generation Many prop driven jet designs to his credit, he knows his stuff, they are much easier to balance these days of electric, back in those days you had a heavy weight engine in the nose and Rx battery on the tail . Good luck Regards Ray Edited By Ray Wood 4 on 19/01/2021 16:44:04 Quote Link to comment Share on other sites More sharing options...
Mark Wightman Posted January 19, 2021 Author Share Posted January 19, 2021 Many thanks,that's so goods to know.Cheers Mark Edited By Mark Wightman on 19/01/2021 16:57:14 Quote Link to comment Share on other sites More sharing options...
Mark Wightman Posted January 21, 2021 Author Share Posted January 21, 2021 Hi I can find a folding prop (I'm doing away with the undercarriage)with a 2"spinner which would give a good scale profile but I intend to scale up the plans by 50%.I can't find a 3" folding spinner.Any ideas?I looked at the idea of an EDF but that is too complex for me,I think.This is the first time I've gone electric.Cheers..Mark Quote Link to comment Share on other sites More sharing options...
Mark Wightman Posted January 29, 2021 Author Share Posted January 29, 2021 Hi A question on the motor downthrust again.Do you think this needs to go up when I scale up the plans by 50%ie the motor points down more.Cheers.Mark Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 29, 2021 Share Posted January 29, 2021 You mean scale the plans up by 150% surely? 50% would be shrinking it! Downthrust is not dependent on the size of the airframe. If the reason for this model needing the downthrust was the large distance between the thrustline and the wing, then scaling the model will not change this relative distance. Also, amount of downthrust is not a definitive amount. If you are changing propulsion from a high revving two stroke glow that the original flew with (and a small prop say 10" diameter by 6" pitch) to a slower revving electric motor turning a prop with either more diameter or pitch (or both) you may well find the need to alter the amount of thrust offset after test flying. This is quite a tricky project - what is your current level of building and flying experience? Quote Link to comment Share on other sites More sharing options...
Mark Wightman Posted January 29, 2021 Author Share Posted January 29, 2021 Thanks Alan, I thought that might be the case,wasn't certain.With regard to the thrust offset,there isn't any on the plan,which I thought strange but I'll leave it like that because I'm putting in an electric motor but I'll see how it goes. Yes,scale plans up by 150%.I've made a few scale plans(by Brian Tailor) and they've gone well.My flying is so so but I have a very good test pilot.😀 Yes,a tricky project.I intend to test fly the model before the fuselage is planked fully to see if the thrust is ok.So I'll be me able to make any adjustments so the finished look is ok.I need to think about that for a bit.Manks thanks for the help.Any suggestions are welcome.Cheers. Mark Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 29, 2021 Share Posted January 29, 2021 There is thrust line offset on the plan - the down thrust you are falking about in this thread is it! Personally I would finish planking the fuselage before trying to fly as this will give you a realistic idea of the effect of drag caused by the intakes etc which you wont get if you dont finish the fuselage. If the thrust line is wrong then it's only the nose you will be altering so there is no penalty in not finishing the fuselage. Edited By Alan Gorham_ on 29/01/2021 18:00:59 Quote Link to comment Share on other sites More sharing options...
Mark Wightman Posted January 29, 2021 Author Share Posted January 29, 2021 Sorry,thought you meant right thrust line,in addition to the down thrust.Cheers. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted January 29, 2021 Share Posted January 29, 2021 I have been looking in my library of RCM and e mags and I think I have seen the feature in them. Would you know the month and year of RCM and e it was in ? If I have it a could photograph or photocopy the article, if that is any help ? Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 29, 2021 Share Posted January 29, 2021 The article is available online to download at aerofred.com Quote Link to comment Share on other sites More sharing options...
Mark Wightman Posted January 29, 2021 Author Share Posted January 29, 2021 Rich,Many thanks.Ive got that.Here Mark Edited By Mark Wightman on 29/01/2021 18:39:42 Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted January 29, 2021 Share Posted January 29, 2021 RCM and e August 1983 Paul Bosak BAe Harrier 4 channel 40 powered in nose. My phone will not open pdf files, god knows why, the lads does no problem. Edited By Rich Griff on 29/01/2021 18:46:37 Quote Link to comment Share on other sites More sharing options...
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