Chris C Posted May 15, 2009 Share Posted May 15, 2009 looks brillant very innovative Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 15, 2009 Author Share Posted May 15, 2009 A bit out of order but here is a pic of a spring strut under construction. The Perspex end pieces have still have to be filed to shape. The finished strut only weighs 0.17 ounces (5g) but it takes 4lbs to fully compress the spring with just over 1 inch of travel. As the Hamilcar only weighs 2lbs all up it should cope with quite a heavy landing! Edited By Simon Chaddock on 15/05/2009 10:03:02 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 17, 2009 Author Share Posted May 17, 2009 Getting there! U/C completed, including a tail wheel & with all 9 servos tested one more time is was ok to complete and paint the wing centre section. Just the cockpit to do. The brown painted blotches are simply that the paint was still wet. Just a point of interest. I bought a separate 5amp BEC but first tried it with both the ESC BECS connected To my surprise it all seems to work ok. The ESC "arm" normally and all nine servos work normally with both the main motors running. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 19, 2009 Author Share Posted May 19, 2009 Nearly there! The cockpit under construction. Back to good old balsa and acetate sheet although the rear fairing is Depron planking. It will hinge to the side to give access to the battery. A personal thing, but I don't model pilots! Props fitted (9x3.8). The fine pitch should be ok as the Hamilcar will probably fly rather slowly. Compared to the camouflage the all matt black underside looks rather... er ....black. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 21, 2009 Author Share Posted May 21, 2009 Its complete! The slightly over size props - how many models have that problem? The big black flaps! As I had hoped it weighs exactly 32 ounces but I have come up against a problem, the motors produce slightly different thrust. I should have spotted this as when you turn the props by hand you can feel the magnets are a bit stronger on one then the other. The saving grace is that the more powerful motor is on the left and will thus help counter any left turn caused by engine torque, well that's what I keep telling myself. So my thoughts on this build. It is a good subject, well suited to electric power and given that it is all sheeted I doubt if I could have made it any lighter in balsa but I must say sheet Depron is not the easiest material to work on double curves. Depron is cheap enough, I used about £15 worth, but sticking so many pieces together means the glue cost is about the same! In hindsight I would have made the wing in one piece (easier and stronger) and made it removable from the fuselage as it only needs battery, elevator and rudder servo connections. In fact it is so light it will have to be a calm day flyer only and hopefully I will not discover how easily it breaks up on a heavy landing. Quote Link to comment Share on other sites More sharing options...
Chris C Posted May 21, 2009 Share Posted May 21, 2009 just woundering how good a glider (towable of course) would work with your design?? p.s i can allready imagen yours landing and disgorgeing some troops and or tanks and jeeps brillant build Edited By Chris C on 21/05/2009 20:11:12 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 21, 2009 Author Share Posted May 21, 2009 Hi Chris I am sure the Hamilcar with its big box fuselage and thick wing will glide like a brick, a sort of controlled decent - but then that is what the original was intended to-do. Actually the draggy shape should make aero towing a bit easier but on the down side it would need quite a bit of tug power. I have just test run the motors. It makes an impressive sound with the motors running in and out of sync and with over 2 lbs of thrust available the Hamilcar could go vertical! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 25, 2009 Author Share Posted May 25, 2009 Just to complete the picture I flew the Hamilcar twice yesterday (Sunday). I say flew but actually both were rather short and terminated with stability problems. With so many servos in the wing (and also right at the tail) there is quite a bit of turn inertia which the fin and rudder seem unable to control. I also suspect the CofG is a bit far back which probably makes it worse. So along with the nose repairs it will have a new slightly over scale fin and rudder and we will try again! Quote Link to comment Share on other sites More sharing options...
Former Member Posted May 25, 2009 Share Posted May 25, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 26, 2009 Author Share Posted May 26, 2009 Hi Phil I used this 3 view to get the major dimensions. To my eye none of the tail area/moments look that generous, but particularly the fin and rudder when viewed as a conventional "twin". The CofG on mine at 30% chord, I suspect 25% would be safer to start with, although I will probably have to change the U/C A frames to move the wheels forward a bit. It appears that only 2 of the 20 Hamilcars X built were ever actually ever flown, although the gliders continued to be used in training untill the early 50's. So perhaps even the full size Hamilcar X was not that good! Quote Link to comment Share on other sites More sharing options...
Former Member Posted May 26, 2009 Share Posted May 26, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 26, 2009 Author Share Posted May 26, 2009 A couple of pics to show the damage resulting from the second (and much harder) landing, about 45 degrees nose down, rolling to the right, throttle closed. RH engine nacelle torn off & the wing tip creased. The RH side of fuselage was split top to bottom in two places as marked and several seams opened up. The nose door was almost completely crushed. The original formers and side panels were salvaged but new top decking and bottom glazed area required. I suspect if i had had the nerve to put on full power rather than close it I might have avoided the ground, or maybe it would just have hit the ground faster! Soon back as good as new - its all part of the fun of design and build! Quote Link to comment Share on other sites More sharing options...
Klippy Posted May 26, 2009 Share Posted May 26, 2009 Hi Simon, looking at the 3 view, in my in-expert opinion, it will be very hard to get the CoG far enough forward. You said yourself that you felt 25% might be better. Did you try any 'chuckie' runs on low power into long grass, I've found, as a novice, it works for me to get the initial trim close to correct. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 27, 2009 Author Share Posted May 27, 2009 Hi Tony My last flight was actually intended to be a low power glide to ground. A bit too much power and not knowing how how fast it would fly I obviously over did the launch as it climbed away but flying directly away I did not notice by how much it was actually slowing down. So pilot error really. My only excuse is that with 6 servos in the light weight wings when a wing drops its inertia means it drops a lot and recovery to level is relatively slow. Due to its very light construction it will only take about 2 ounces nose ballast to bring the CofG to 25% but as it will then be in front of the main wheels I will first have to make some new U/C "A" frames to move the wheels forward a bit. Edited By Simon Chaddock on 27/05/2009 00:38:31 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 28, 2009 Author Share Posted May 28, 2009 All now back like new. This is the new slightly larger (but no heavier) fin. The old rudder is retained. Next calm day I'll try again! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 29, 2009 Author Share Posted May 29, 2009 Just before I try and fly it again I thought about to the best way to add ballast to move the GofG forward a bit to get it closer to the main spar. As I was completely rebuilding the nose door it seemed logical to incorporate the weight in it in some way so I exchanged the clear plastic nose cone (the full size had a landing light in it) for a solid one, made of lead. Not really scale, but at least it ensures the weight is as far forward as possible and can be easily removed if required. At 1.6 ounces it is about as much as can be added without modifying the U/C position as with the battery in place there is precious little load left on the tail wheel. Any take off will need a really smooth surface. If the forward CofG proves to be the answer there is just about enough room under the cockpit canopy to achieve the same effect by moving the battery compartment forward. Edited By Simon Chaddock on 29/05/2009 14:08:57 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 1, 2009 Author Share Posted June 1, 2009 Tried again today and it still has a severe stability issue. The CofG appears acceptable but it requires a huge amount of down elevator to keep the nose down so much so its either diving or climbing which not surprisingly ended in a stall, wing drop, contact with the ground and a bit more damage. I built in more or less the scale incidences and I think this is where the trouble lies. It has much more longitudinal dihedral than say my Wing Dragon (which has a similar wing section & CofG position). It will be easier to alter the tail incidence than the main plane and then wewill try again. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 4, 2009 Author Share Posted June 4, 2009 This is turning into a bit of a repair blog! Yes you guessed it, I crashed the Hamilcar again. To cure the tendency for it to keep lifting its nose, apart from the lead nose cone, I reset the tailplane incidence, moved the battery forward an inch and just to make sure I also applied rather more power. Well it all worked but rather too well. It set off like a rocket on a definite downward path, a touch of back stick and it raced skyward. Fearful of a stall as in the previous attempts, forward a bit and the nose comes down smartly. Wow was it sensitive to elevator. In hind sight I should have let it climb (altitude is safety) but having just repaired it twice I concentrated on keeping level. No stall, no wing drop i just hit the ground at a shallow angle at some speed! Not surprisingly the nose door was knocked off and suffered crushing damage. The forward part the fuselage was completely destroyed and the RH engine broke free. But apart from that the rest is fine! It will soon be fixed and I will take the opportunity to move the U/C forward abit as well. . Quote Link to comment Share on other sites More sharing options...
Chris C Posted June 4, 2009 Share Posted June 4, 2009 Thats a real shame and it was looking so good as well. Quote Link to comment Share on other sites More sharing options...
Phil Winks Posted June 6, 2009 Share Posted June 6, 2009 This really is turning into a labour of love simon but I guess thats the nature of a design & build project. looks like your enjoying it though. One suggestion I do have is the sourcing of suitble plastic caps for motor nacelles one I've discoverd that works well at both ends (makes good jet pipes too) and allready has the top cut out is from a well known male deoderant with the integral nozzel removed. see pic Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 6, 2009 Author Share Posted June 6, 2009 Thanks Phil I will keep that in mind for my next project. Repairs progressing. Fuselage almost complete with U/C mounting points moved forward 4mm and the engine nacelle rebuild in progress. Just the glazing on the underside of nose door and some painting still to do. Quote Link to comment Share on other sites More sharing options...
Phil Winks Posted June 7, 2009 Share Posted June 7, 2009 No probs Simon coming back together nicely I see Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 11, 2009 Author Share Posted June 11, 2009 Well its all back together - again. This is the third (and biggest) rebuild. The only thing left to do is to refit the U/C (not damaged as the last flight was done without it!) and fix the nose cone. I have not yet decided if it actually needs the solid lead one or whether to go back to the scale glazed version. It looks reasonable in the photo but I am not sure how many more times the basic structure can stand being fixed! Quote Link to comment Share on other sites More sharing options...
Olly P Posted June 11, 2009 Share Posted June 11, 2009 Simon, If it is overreacting to the elevator then perhaps a smaller elevator would help to stablise it, or decrease the rates on the Tx. A very good looking build, hopefully it will level out and fly right! Quote Link to comment Share on other sites More sharing options...
Gemma Jane Posted June 11, 2009 Share Posted June 11, 2009 Hi Simon, Just to say all your experiences with the Hamilcar were replicated in the BV 138 chucky I made. I went for scale tail incidence of +5 degrrees at first. It seemed impossible to find the correct CofG, it either went nose up and stalled, or went nose down into the ground. There was no stable condition. Setting the horizizontal stab to neutral or slight positive (no more than 1.5 degrees positive) immediately tamed the chucky and allowed the CofG to be set easily. It seems your onto this, so fingers crossed for the next flight. It's a great subject you chose and I so hope it will reward you in the end Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.