SDF
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Everything posted by SDF
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I don't think those PAW prices are correct. The Jan 2016 list price for the PAW 09 DS (non-r/c) is £62+VAT and for the r/c version its £75+VAT.
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I've bought it from here in the past.
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Lets not perpetuate this nonsense. Danny is completely correct and Mal is wholly wrong. It is the leadout position wrt the CofG that matters the belcrank within reason can go anywhere. It is, however, usual to try to place the belcrank such that the rake of the lines is tangential to the arc of the lines in flight. This avoids a bend in the leadouts where they exit the wing.
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Erflog, (Looks like you spotted the error whilst I was typing) I think there is and error in your calculation. You appear to have multiplied the mass by the speed then squared the result making your estimate of the force a factor of ten too big. 40 lb = 18.1kg 30mph = 13.4m/s 120ft = 36.6m 18.1*(13.4^2) / 36.6 = 88.8N or just over 9kg or at 40mph just over 16kg But I think 40 mph might be too low a speed for such a machine to fly so it would probably still need to be tethered to the preverbial immovable object. Edited By SDF on 24/06/2013 21:53:12
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I like sewn hinges, cheap to make and very low friction.
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We had a demo at the club I used to belong to of how to glass a wing but can't remember who it was by now. Use laminating epoxy as already advised. Thin this as required using pure methanol. Lay the glass cloth over the wing. Don't try to use a brush. Pour the epoxy sparingly onto the cloth/wing and then use a camel hair paint roller cut down to about 2" wide to spread the epoxy. Gives really good results with just the right amount of epoxy to properly wet the cloth without excessive weight gain. Pop the roller in a jam jar of acetone before the epoxy sets and it can be reused.
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Available for purchase from this very site
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I think I may have a copy. What I'm not sure of is where it is. I'll have a rummage and see if I can find it.
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Are you trying to tell me you can't fly both the popular modes?
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I could never really see the point of buddy leads. What is the problem with passing the TX between tutor and trainee? Thats how I learnt to fly. Keep it simple.
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Soldering piano wire for UC legs
SDF replied to Eifion Herbert's topic in Model Engineering and Accessories
You could solder it with the butane torch but it would be very difficult to ensure the wire is not over heated and its temper lost. The wire won't go brittle it will go soft. Personally I would spend a little more on an electric iron they are not really that expensive. -
You do realise Diamond is a form of carbon and will burn quite nicely. I would suggest keeping them away from the torch unless you want to buy some more. A (probably) cheaper alternative is a bit of brass tube sharpened at the end with knife.
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I googled Waco SRE and came up with a 3-view, a Peter Rake plan from Traplet, a Walt Mooney plan, a Sterling 33" plan, a Sterling 13" plan and an Earl Stahl 21" plan. I also found a lot of google images photos but the link to that won't work on here. Edited By SDF on 06/04/2013 19:32:10 Edited By SDF on 06/04/2013 19:32:35 Edited By SDF on 06/04/2013 19:33:18 Edited By SDF on 06/04/2013 19:34:34
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"Building & Flying Indoor Model Airplanes" by Ron Williams - the best aeromodelling book ever published IMHO. "Model Aircraft Aerodynamics" by Martin Simons - great book on the fundamentals of how model aircraft fly.
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Halford's Petrol Resistant Lacquer
SDF replied to Martyn K's topic in Building from Traditional Kits and Plans
There has been a thread running on the other forum I frequent about fuel proofer. It would appear that Tufcote is no longer available from Ripmax but this was just relabeled Rustins Plastic Coating. Try searching for it on e-bay. The floor type is said to cure faster than the furiture type which may or may not be what you want. -
My free flight KK Pirate had a PAW 55 BR in it - plenty of power. Are you making the Tomboy free flight, radio or radio assist?
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A model shop that stocks Model Technics fuel should be able to get diesel fuel for you.
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You might like to try here for Dave Stapleton Engineering, thats certainly the address were I used to buy my FAI rubber from.
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Just to put the cat among the pidgens I'd like to suggest a control-line mass build. And don't try to tell me this is an RC forum its ModelFlying.co.uk.
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BEB, I see what you mean but the dynamic imbalance is likely to be very small as blade thickness is small compared to the diameter so the scope for misalignment of the pricipal axis is, I would have thought, quite limited. This would probably also show up as a static imbalance with the prop vertical, but I don't suppose may people check the balance of their prop in that orientation. Erflog, I suspect the vibration would damp out pretty fast without any stimulus but can't be sure. Might be an interesting exercise to try and computer model it, not done any of that for a while. The kineic energy of the blades may be different but I think that only becomes relevant when you try to change it. Same effect as the angular acceleration I described. Could your post arrival vibration problem be due to a partial failure in the internal model structure making it more flexible than intended. I have a control-line twin (same configuration as a F82) with two diesels and on the ground there is a beat frequency oscillation when both motors are running that makes the two fuselages forward of the wing visibly flex from side to side quite alarmingly but there is no problem in the air. Funny old stuff vibration.
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Erfolg, Interesting paper on balancing rotors. Not really sure what your getting at with the parallel axis theorem though. It just says if you rotate a body about its centre of mass the moment of inertia is a minimum about a given axis. Our staically balanced prop is being rotated about its centre of mass. Say our staically balanced prop has the mass distributed so there is a lump of mass M at radius -2R and a lump of mass 2M at R with respect to the hub centre, i.e. one lump in each blade. Clearly not an even distribution. The centripetal acceleration at any radius (r) is given by -r*w*w (w should be omega, can't do greek i.e. the angular velocity). The acceleration is linear along the blade in the rotating axis set so the net force (F=ma) at the shaft is 2R*w*w*M - R*w*w*2M = 0. No out of balance. So the radial distribution of mass doesn't matter a jot at fixed RPM and single bladed props and bob weights work fine. Under angular acceleration (changing RPM) there is an out of balance as the moment of inertia of each of our two lumps of mass is proportional to the square of their respective radii from the hub. There is a net force perpendicular to the axis along the blades as a result of the uneven torques required to achieve the same angular acceleration. Don't know how significant this effect might be but I suspect small on a normal prop. There could also be a coupled moment perpendicular to the axis of rotation if the masses are not evenly distributed throught the thickness of the blade (principal axis misalignment). The same effect as the car wheel dynamic balance already mentioned. As the blade thickness is small compared to the diameter the misalingment is likely to be very small and I wouldn't expect this to be a significant effect. I shall look forward to reading the article to seeing what it actually says.
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I haven't seen the article either but it sounds like snake oil - show me the maths. Edited By SDF on 19/09/2012 23:16:18
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Watching with interest. A STOL is on my to do list but probably the MK1.
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Balsa can tend to go a bit brittle with age. Build it using new timber then sell the original kit on e-bay which should easily recover the cost of the new wood.
