Anton Webers Posted May 10, 2020 Share Posted May 10, 2020 The tail part of the fuselage where the sides are just balsa you mean? Yes, I was wondering about the stability of the sides. I was also considering to cover the top part with a thin balsa sheet covering the ribs. Makes it look smother. I need to buy good foil anyway and hope it won't deform that much then. Quote Link to comment Share on other sites More sharing options...
Jeffrey Cottrell 2 Posted May 11, 2020 Share Posted May 11, 2020 Hi Shaun, just a quick question. One of the main issues I have with my T30 build is the wing spars. These are laser cut from very soft material and only 4mm square. Also supplied in two parts, intended to be butt jointed. In my opinion these would not survive the stresses in normal flight, let alone the odd 'hard' landing. DW are telling me that this is an old kit (2017) and they have improved since. Just wonder what your opinion was of the spar material supplied in your kit. Cheers Jeff Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted May 11, 2020 Author Share Posted May 11, 2020 Posted by Jeffrey Cottrell 2 on 11/05/2020 14:29:19: Hi Shaun, just a quick question. One of the main issues I have with my T30 build is the wing spars. These are laser cut from very soft material and only 4mm square. Also supplied in two parts, intended to be butt jointed. In my opinion these would not survive the stresses in normal flight, let alone the odd 'hard' landing. DW are telling me that this is an old kit (2017) and they have improved since. Just wonder what your opinion was of the spar material supplied in your kit. Cheers Jeff Hi Jeff The spars in the Space Walker were supplied in lengths sufficient for half of the full wing span so only needed to be joined in the centre. Also they were made of Paulownia wood, I think, and were quite firm. However I did take the precaution of adding webs between the upper and lower spars all the way to the wing tips as the wings were somewhat flexible in torsion prior to adding the leading edge sheeting. Quote Link to comment Share on other sites More sharing options...
Jeffrey Cottrell 2 Posted May 11, 2020 Share Posted May 11, 2020 Hi Shaun, thanks for the quick reply. So, no mid wing joins in yours. Never run into Paulownia before, but it sounds stronger than balsa. So, DW are correct in saying they are improving their kits. Oddly enough, they did supply spar webs in mine, but these were plywood. So, soft balsa spars and ply webs. Sounds the wrong way round to me. Cheers Jeff Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted May 11, 2020 Author Share Posted May 11, 2020 Posted by Jeffrey Cottrell 2 on 11/05/2020 15:25:32: Hi Shaun, thanks for the quick reply. So, no mid wing joins in yours. Never run into Paulownia before, but it sounds stronger than balsa. So, DW are correct in saying they are improving their kits. Oddly enough, they did supply spar webs in mine, but these were plywood. So, soft balsa spars and ply webs. Sounds the wrong way round to me. Cheers Jeff Hi Jeff I just found the scrap that surrounded the spars and they are medium/hard grade balsa, not Paulownia. The original design has top and bottom spars joined with ply webs in the first three bays. I decided to add balsa webs to the tips as the wing could flex quite a bit. Admittedly this was before the leading edge sheeting was added which would have helped rigidity a lot. The wing as I built it seems very strong but the proof of the pudding etc. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted May 14, 2020 Author Share Posted May 14, 2020 Not sure how well this is going to fly, the pilot's not looking where he is going! Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted May 14, 2020 Author Share Posted May 14, 2020 Covered the fuselage with the red film supplied with the kit. The cowl was lightly sanded to provide a key and then given two coats of white plastic primer followed by two coats of Audi Misano Red car paint, its quite a good match for the film colour. Quote Link to comment Share on other sites More sharing options...
Rob Fairweather 1 Posted May 14, 2020 Share Posted May 14, 2020 Nice one Shaun. My Astro junior is awaiting covering . . . Building an SE5a first. Quote Link to comment Share on other sites More sharing options...
Anton Webers Posted May 15, 2020 Share Posted May 15, 2020 Yes, very nice. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted May 21, 2020 Author Share Posted May 21, 2020 Almost done now, taiplane and fin attached and tail wheel fitted. The tail wheel didn't go on exactly as per instructions but just needed a bit of bending to get it to follow the contour of the rudder. The COG is 70mm from the leading edge according to the plan so I decided to assemble everything and check where the battery needed to be placed to get the balance correct. the picture shows the approximate position, a bit further back then expected! Total weight including 2.2Ah battery is 1100g, motor pulls 17A on a 10x5 prop with a 3S battery so it may be possible to drop the battery size a bit and still get reasonable flight times. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 2, 2020 Author Share Posted September 2, 2020 It's been a while but the Space Walker had its maiden flight a couple of weeks ago in the hands of the club instructor. Flew it with a 1400 3S and the COG as shown on plan, 70mm from the leading edge. The instructor's comments were "It's a bit twitchy!", especially on the ailerons, however it had enough power and trimmed out OK for level flight. The landing however was "interesting". on the final approach cutting the throttle resulted in the model pitching rapidly nose down, it took three attempts to get it down for a safe but somewhat speedy landing. I have looked at a couple of other versions of this model by other manufacturers and the COG on those seems further forward. I have reduced the aileron throw and will move the COG forward by 10mm for the next attempt, fingers crossed! Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 4, 2020 Author Share Posted September 4, 2020 Have just put the Spacewalker's dimensions into cgCalc and the recommended COG comes out at 45 to 55mm, somewhat ahead of the plan's 70mm. This might explain the twitch behaviour. Its time for a larger battery and some weight in the nose I think! Quote Link to comment Share on other sites More sharing options...
Anton Webers Posted September 5, 2020 Share Posted September 5, 2020 I am not sure I can follow you. The CG is where the center of gravity is by weight. So the point where you can balance the plane on one finger, or on a line perpendicular to the axis and horizontal. So calculating it will most likely end you up with the wrong value if you have no clue on what the weight distribution is. The important point is to shift the CG to the location around the CP (center of pressure). Only then the stability is the best. So the CG is better measured than calculated. Either the construction plan is giving you advise on where the CG should be, bad on their knowledge of the CP location, or if that is also off like some other things in the plan, then typically the CP is somewhere around a certain location of the wing cord. This video explains it pretty nicely. Video Boris Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 5, 2020 Author Share Posted September 5, 2020 Posted by Anton Webers on 05/09/2020 06:16:38: I am not sure I can follow you. The CG is where the center of gravity is by weight. So the point where you can balance the plane on one finger, or on a line perpendicular to the axis and horizontal. So calculating it will most likely end you up with the wrong value if you have no clue on what the weight distribution is. The important point is to shift the CG to the location around the CP (center of pressure). Only then the stability is the best. So the CG is better measured than calculated. Either the construction plan is giving you advise on where the CG should be, bad on their knowledge of the CP location, or if that is also off like some other things in the plan, then typically the CP is somewhere around a certain location of the wing cord. This video explains it pretty nicely. Video Boris Hi Anton Take a look at the cgCalc web site, it explains it far better than I can. **LINK** Shaun Edited By Shaun Walsh on 05/09/2020 08:25:27 Quote Link to comment Share on other sites More sharing options...
Anton Webers Posted September 5, 2020 Share Posted September 5, 2020 OK, yes. That makes more sense. I haven't checked for the tool before and thought it's one where you type in some weight elements of your components or so. But considering wing dimensions and the tail is a more accurate way than what I wondered you did Thanks for sharing, Anton Quote Link to comment Share on other sites More sharing options...
trevor wood 2 Posted September 5, 2020 Share Posted September 5, 2020 Shaun, the new CG location will place it at the “standard” 25% position that’s always a good starting point for flat bottom, Clarke Y type of aerofoils. I’ve a warm feeling that your next flight will produce far less knee trembling. See you at BCC on Monday? Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 5, 2020 Author Share Posted September 5, 2020 Posted by trevor wood 2 on 05/09/2020 14:15:40: Shaun, the new CG location will place it at the “standard” 25% position that’s always a good starting point for flat bottom, Clarke Y type of aerofoils. I’ve a warm feeling that your next flight will produce far less knee trembling. See you at BCC on Monday? Yes I'll be at BCC on Monday, weather permitting. Did you use cgCalc to work out the COG for your Gnatsum? Will you be flying it on Monday with a stronger nose leg hopefully? Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 14, 2020 Author Share Posted September 14, 2020 Flown today with a 3000mAh battery and 30g of weight on the motor mount. It flew much better with the COG at 50mm from the LE. Pottered around for 6 minutes and still 80% of the battery left. Quote Link to comment Share on other sites More sharing options...
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