Colin Leighfield Posted April 20, 2014 Share Posted April 20, 2014 All that's true Simon, I'd never try and compare it with the Valkyrie, but it would make a fantastic and interesting looking model. I think the conclusive "killer" problem with the 188 was the inability to carry sufficient fuel to achieve any reasonable flight duration, essential to get to altitude and sustain maximum power for long enough to accelerate all the way through to very high Mach numbers. Anyway, it has been modelled, but I don't think the 730 has. Apart from the wing shape, the 730 is a canard and looks totally different. There is a model of the 730 at Cosford. Looking at drawings is one thing, but in three dimensions it looks interesting, to say the least. Your XB70 captures the real thing amazingly in the air, I think your expertise with Depron would make the 730 a similarly interesting possibility. I'll continue to ponder! Quote Link to comment Share on other sites More sharing options...
Stuphedd Posted April 21, 2014 Share Posted April 21, 2014 Cheers Simon , Thanks for that I have tried every calculation in the book and they all give a different answer , I have made a "little " glider in an attempt to zero in on the cg . It came out at 48% so yours at 50 gives me confidence thanks Pete Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 1, 2014 Author Share Posted May 1, 2014 Due to the replacement servos being delivered from China rather than the UK I decided to make use of the current calm weather and fly the Valkyrie again to confirm my diagnosis of its control issues. It flies fine with plenty of power but tends to pull to the right which is odd because the motor torque should make it bank left. This means the roll authority is at best weak and at slow speed almost non existent. This is made worse by the fact it will continue to fly at the most ridiculous AOA indeed under power is develops into a stable position. I do wonder if this is the result of the 3 axis radio Cutting the power is the only way to make the nose to drop. The first time I did this it went into a normal but steep recovery. The second time it fell into a tail slide and flopped over onto its back and needed a lot of height to recover. It really does need all the tail surfaces to act as ailerons. The next question is whether the canard should fixed with an elevator, all moving or 'compound' with both. So far I have not been able to get the Tx to switch the stability function off. Quote Link to comment Share on other sites More sharing options...
Chris Anthony Posted May 2, 2014 Share Posted May 2, 2014 Hi Simon, The flight video looked good, well done. Can you say any more about the 3-axis gyro in your RX? How exactly does it add stability to the aircraft, does it modify servo output somehow? I have not come across them before. Chris Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 2, 2014 Author Share Posted May 2, 2014 Chris Its one of these. **LINK** The gyros 'influence' the servo motion to limit any sudden change in attitude unless commanded by the Tx.. The Orange 3-axis Rx has the gyros built in to the radio. Very simple to use but there are some drawbacks like you cant use any of the aileron, elevator or rudder mixing functions on the transmitter. You have to use those built into the Rx. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 12, 2014 Author Share Posted May 12, 2014 With the new servo available a start can be made to revise the control system First the canard. I decide to keep it simple and just use elevators on a fixed fore plane but it needs a big hole to be cut out of the fuselage to fit them! Whilst there is plenty of room to fit a servo close by to maintain the CofG the servo will have to go back as far as possible so a light weight snake will have to be used. The canard elevators joined by a glass fibre torque tube with a central horn. They will be tape top hinged so each elevator leading edge is angled back 45 degrees to give plenty of 'down' movement. The four servo for the elevator and ailerons removed. Not that easy as they were glued in. The one piece elevators (maybe elevons) will each be driven by a servo more or less in the existing inboard position. Progress is slow as each step has to be carefully thought out (think twice, cut once!) as structurally I can't afford to cut too many new holes in the rather highly stress skin! Quote Link to comment Share on other sites More sharing options...
Erfolg Posted May 13, 2014 Share Posted May 13, 2014 I know it is a bit late now, but, but, could you not have left elevator servos in place. I would have been tempted to either have "Y" leaded the two servos together or to have been able to switch the elevator servos on the mainplane in with the foreplane as a back up if the foreplane elevator proved troublesome. I guess there will be another complication, in that you will be moving the CG foreward? I would guess the CG is now for a Delta. I was also wondering how much the foreplanes were a trimming feature, to remove the reflex from the main wing, rather than a true lifting surface. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 13, 2014 Author Share Posted May 13, 2014 Erfolg I did think long and hard about doing this change and one option was to retain the existing servos but the problem was the way they were wired up (all soldered joints!) as an inboard elevator pair and an outboard aileron pair. I was going to have to remove the servos to get at the wires. I also was not very happy with the control surface's deep and narrow shape as it did not really suite a tape top hinge. It was not unknown for the adjacent surfaces to clash. I have retained the two servo wires running up the fuselage to the radio. With the new servos in place these wires will simply connect the L& R ailerons. The new servo and big (but unpainted) LH aileron. The XB70 is a low aspect ratio delta which gives adequate natural longitudinal stability without any reflex, indeed it still had positive (but reduced) stability when the fixed canard was added. For the initial flight I may actually fix the canard elevator and just use the tail surfaces as elevons. As long as the CofG is unchanged it should fly in that configuration. By adjusting the relevant servo travel I can then slowly transfer elevator authority to the canard. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 17, 2014 Author Share Posted May 17, 2014 The many holes cut in the fuselage to give access to install the canard elevator snake & servo, a new radio and connect up the aileron servos. With the snake and its servo tested the fuselage skin can be made good. All the fuselage holes made good once the full system had been tested. Initially I intend to use the ailerons as elevons working in conjunction with the canard elevators. If the canards prove adequate it will then be just a TX programming job to revert the elevons back to be simple ailerons. Testing the new control system. The Orange 3 axis radio has been replaced by a very small 'Lemon' 6 channel. Now just need to find out if the Valkyrie is controllable with an 'active' canard. Edited By Simon Chaddock on 17/05/2014 00:07:17 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 19, 2014 Author Share Posted May 19, 2014 The Valkyrie flying with an active canard. The elevons remain connected but are set to 50% on the elevator dual rate switch to get an idea of how much the canard contributes. The canard remains at 100% I kept fairly high in case it ran into stability issues. With the dual rate 'on'' the pitch authority was significantly reduced, almost by as much as you might expect when using the elevons alone, suggesting the canard elevator does not contribute that much. This was confirmed by a second flight with the dual rate set to 20% where pitch control became very limited so for the moment the combined elevon and canard has to remain. It is possible that by moving the CofG further back the pitch sensitivity will be increased to a point where the canard alone might be sufficient but it is a strategy not without a degree of risk! Quote Link to comment Share on other sites More sharing options...
Erfolg Posted May 19, 2014 Share Posted May 19, 2014 Simon It could well be that the foreplane is just there to assist with trimming, and reducing the reflex required on the delta part. Many years ago, there was a USA pilot, working for a charter company out of Ringway, who was a member of our club. It seems that he flew in the USAF a B58 (Hustler) which he mentioned at some time that it would fly in a fugoid/dolphin at speed. It could be this aspect they were trying to avoid with the XB 70. The model looks really good. Just to mention my own delta has virtually no reflex (45 degree sweep from memory). Just as significantly, I found by accident, the range of CG is massive, just needing more reflex when the CG moves forward 55mm on a 36" span (or thereabouts). This has occurred as the Lipo demolished the impact bolster inside. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 21, 2014 Author Share Posted May 21, 2014 Having proved to my satisfaction that the canard is not powerful enough to give adequate pitch control on it own I took the opportunity is fine weather today to test the capabilities of the Valkyrie at bit. An edited video of it doing some simple aerobatics. Not that easy to see as I kept high as I no idea of what might happen! It actually performs quite well although the roll is painfully slow. With a bit of practise i shold be able to do the aerobatics quite a bit lower and closer to the camera. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 21, 2014 Share Posted May 21, 2014 It looks great Simon, the light weight must be very advantageous in achieving such good handling at low speeds. You have really captured the presence of the full size. Amazing. Quote Link to comment Share on other sites More sharing options...
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