Chris Bott - Moderator Posted December 17, 2011 Share Posted December 17, 2011 Hi Glenn. I think the roll to the left effect has two components, 1) The motor trying to turn in the opposite direction to the prop and therefore push the whole model that way, and 2) the rotating air behind the prop hitting the fin and rudder. My mind likes things simple so I refer to the combined effect as the torque effect. As I said earlier, my DH88 suffered most just on takeoff. I think this is purely because while the wheels are in contact with the ground, the port (left) wheel can't go any lower, but at lift off, the plane can suddenly roll. I've seen some proof of this when flying off snow. Most ski impressions show the port ski going deeper in the snow. This picture sort of shows that. The twin converted YT 3Demon did suffer from the torque effect when both props went the same way. This could be seen in the verticals or during my pathetic attempts to hover. Going to contra rotating just completely eliminated it. Partly, this was to experiment with using rudder mixed in, to speed one motor up and the other down. With a view to using this on the DH88. Also so I could have a play at trying to fly on one motor.With rudder it's great for taxiing but in the air there were all these other effects like extra lift on one wing and gaining some torque effect where there was none before. So I won't be adding that facility to the DH88. The other result from the experiment was finding the large difference between rotation directions. With "in at the top" being far better if a motor gave up. Oddly enough a Lancaster is now very high up my build list too. Mine will be having contra rotating props as long as I can find suitable pushers. It will be from the 100" John Ranson plan, but will be modified to replicate a particular one of the Lancs that my father crewed in. Meanwhile, I have to complete the last few little jobs and get out and fly the DH88 again. But I'm in no hurry and will probably wait for some nice spring weather. Edited By Chris Bott on 17/12/2011 17:34:27 Quote Link to comment Share on other sites More sharing options...
Nick Chudley Posted January 16, 2012 Share Posted January 16, 2012 Beautiful weekend and a successful maiden. A little scary at first, but I've since settled down to some smooth flying and landing, including all the loops, rolls, cuban 8s etc. Loads of fun! Here is a Youtube video of the maiden. One happy Comet flyer ! Edited By Nick Chudley on 16/01/2012 14:18:32 Quote Link to comment Share on other sites More sharing options...
Nick Chudley Posted January 16, 2012 Share Posted January 16, 2012 Well, that didn't work! Let's try the photo.. Edited By Nick Chudley on 16/01/2012 14:16:26 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 16, 2012 Share Posted January 16, 2012 Looks gorgeous Nick - have a look here, and follow the tutorial EXACTLY, as we all want to see the video! Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted January 16, 2012 Share Posted January 16, 2012 Well done Nick the flights sound great. Can't wait to see the video. If you are really struggling, try sending me a PM and paste the link in there. Then I'll see if I can get it to show here. CheersChris Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted January 16, 2012 Share Posted January 16, 2012 Nick I think I've found your video. I hope you don't mind me posting it? Looks like it went very well, especially as it sounds quite windy. Were you really as close to the hedge at the end as it looks? That looks an "interesting" direction to have to approach from! Quote Link to comment Share on other sites More sharing options...
Alan Randall Posted January 16, 2012 Share Posted January 16, 2012 Interesting to read that Chris is trying handed motors because thats exactly what De-Havilland did on the Hornet/Sea Hornet which was, I suppose, the ultimate development of the DH twin theme.The Hornet / Sea Hornet had two Merlins designed to rotate in the opposite directions to cancel out swing on takeoff. Particularly useful for a carrier plane. like the Sea Hornet Alan Quote Link to comment Share on other sites More sharing options...
Nick Chudley Posted January 16, 2012 Share Posted January 16, 2012 Thanks guys! Yes it was quite windy for a maiden, 9mph. I think the take-off suffered from too much up-elevator too soon. I've since trimmed in a bit of down elevator and an even smaller bit of right aileron, which coupled with being ready for it means I've had no more narrow squeaks like that. The landing seemed to be going very well when she suddenly dropped onto the runway, not responding at all to my efforts to make her flair. Ivan (the designer of the plans) saw the video and suggested the problem might have been wind-shear. I don't have any other explanation and I haven't experienced that problem again. I haven't yet experienced the dreaded tip stall. In fact I think that bad take-off in the video shows a pretty good resilience against tip stalling. I have tried some high-up straight stalls without any scares but I haven't had the nerve to try a real spin. The problem with opposite handed props is getting hold of nice spinners. Those aluminium ones I've got came from Giantcod.co.uk - highly recommended. They even came with molded clear plastic packaging that was ideal for the landing light lens. Looks as if the fine weather's coming to an end. Here's an in-flight photo : Edited By Nick Chudley on 16/01/2012 22:44:08 Quote Link to comment Share on other sites More sharing options...
Graham Keegan 2 Posted February 19, 2012 Share Posted February 19, 2012 Hi all Possibly not the correct place to post but here goes!. Does anybody have any dimensions for the ASM Comet oleo legs? i have a Black horse Mosquito that i have been trying to find something more scale than the single spindly wire suplied. It is however only 63" so think the ASM oleos may be too big. Thanks Graham Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted February 19, 2012 Share Posted February 19, 2012 Hi Graham I have a set of the ASM legs and can measure anything you like. Just a little busy at the moment but I'll sort something out today or tomorrow unless someone else can help quicker. Is there anything in particular that you need to know? Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted February 19, 2012 Share Posted February 19, 2012 Ok took a couple of photos, do these help? Sorry about the quality. Quote Link to comment Share on other sites More sharing options...
Graham Keegan 2 Posted February 19, 2012 Share Posted February 19, 2012 Wow what a quick response. Thanks Chris that is exactly what i was looking for. not sure 100% if they will fit because the kit i,s 'in stock' shall we say, in the loft. They certainly look in the right ballpark. Also look a nice bit of kit for the £20 they are listed at. Once again thanks for your effort Chris. Graham Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 19, 2012 Share Posted February 19, 2012 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted February 19, 2012 Share Posted February 19, 2012 I think Chris is reliving his tip stall Eric and of course depends on how much height you have when the drama unfolds.We have a club member who often crashes on a dead stick because he always insists on turning,Better a longer walk and an undamaged model than 50 yards to the wreckage Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted February 19, 2012 Share Posted February 19, 2012 Thanks Stephen yes, straight ahead is best if you don't have lot's of height. If straight on would end up 1.5 miles away then straight on would just be silly!. Hence the "if possible" in my sentence. The DH88, unless it's very lighly loaded, is very prone to a tip stall. Treating it like flying a glider seems to me to be asking for trouble. However with a lot of height, keeping the speed up and turning gently would of course be in order. Quote Link to comment Share on other sites More sharing options...
Andy Gates Posted February 24, 2012 Share Posted February 24, 2012 I am one of Nicks mates building the IP Comet. It is not that which I want to comment on. What I want to comment on is the issues regarding deadstick landings. Time and time again I see or read of pilots of RC planes having issues with flying planes with a dead engine and crashing or struggling to mantain control. I guess I do not understand the issues here because my start to RC flying was on 100" thermal gliders with no spoilers, where you only had one chance at landing. This required carefully planned and controlled downwind legs as well as turns, speed and height all controlled. Surely this is no different to our normal "with power" landings, so a quick question, does anyone practice deadstick landings on a regular basis? Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted February 24, 2012 Share Posted February 24, 2012 hello andy--the only know i can think of practicing d/stick landings is with the engine at low tick over....also i would have thought that the wing loading on some power models would be a lot greater..than some gliders......and some power models are pretty unstable(ie rearward c of g) .. to carry out some aerobatics .... 'i've seen a few end up as dead sticks' ..... ken anderson dead stick dept... Edited By ken anderson. on 24/02/2012 18:38:24 Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted February 24, 2012 Share Posted February 24, 2012 Hi Andy I guess everyone is different when it comes to practicing deadsticks. Most IC models are no issue at all to land deadstick. Problems start to creep in with things like higher wing loadings. Take warbirds for example, unless lightly loaded these are usually landed with flaps down and a little power on. When we go deadstick, the speed has to be kept up to keep from stalling and this means putting the nose down. This is fine as long as you have height and time to plan turns to put the model in the right place for a decent approach. But problems arise when the deadstick happens in the wrong place at the wrong height... The DH88 is even worse. The pointy wings are prone to tip stalling, so any misjudgement of speed, especially in a turn and this wings can be suddenly vertical and the model nose down. Again recoverable with enough height, but not if it happens in the wrong place. My biggest fear with mine though is one motor failing while the other keeps going. This almost instantly flicks the model into a spretty severe spin. You have to be very quick thinking to chop the power on the other engine and recover and land. Keeps us on our toes though! Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted February 24, 2012 Share Posted February 24, 2012 the fullsize that dead sticked into the hudson river in America was a goodin.... ken anderson ne..1. dead stick dept. Quote Link to comment Share on other sites More sharing options...
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