Delta Foxtrot
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Ok thanks Peter.
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Peter, I am well on with the job of covering the CAP and was wondering if you could point me in the direction of the decals you have on yours. I plan to make up some waterside decals and it would be good to find some files for the picture images. What fonts did you use for the fuselage lettering and registration? David
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Thanks Peter!
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Thanks for the reply Peter! I agree with your view on collets, if I use them I solder them on. If I have understood your brass tube idea, I fit the wheel inside the spat and then slide the piano wire axle through these and then insert the brass tube through the outer spat hole and solder where the tube and wire exit the spat. I guess I could tin the axle to get a more extensive soldered joint. What about the other side of the wheel, or do you mean use the brass tube on both inner and outer sides of the wheel? It does sound like a good idea, but I would like make sure I understand before cracking on with it. I am really enjoying the build and I am glad that I returned to it after having a few issues with the wing build last year.
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Peter, Fillets are done. I am just making up the wheel spats and wondered how you retain the wheels. I assume that you used collets on both sides of each wheel as the axle appears to be slid through the spat and the wheel together, so no opportunity of soldering wheel fixings.
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Thanks Peter!
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Peter, I can't see any info on the wing root fillets on the plan and I think I can see these on your photos. I like fillets, apart from the small aerodynamic benefit, they look good. What width is your fillet at the wing trailing edge? I assume that they are made in the usual way using thin ply on top of the wing and balsa to form the fillet and 1/16" ply piece behind the trailing edge?
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And not forgetting that a lot of the spitfires development was facilitated by the near doubling of the Rolls-Royce Merlins power output during WW II and the development of the Griffon. A good example of the wider team efforts that leads to successful aircraft inception and development.
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fitting line theory Posted by Peter Miller on 05/09/2015 19:00:32: Yes, read the book. The part that really amused me was when Mitchell said "I don't care what shape the wings are so long as we can get the guns in." The elliptical shape was chosen by another member of the team. If I can find the review that I did of the book fr Air Mail, I can find who that was but it was on my other laptop Edited By Peter Miller on 05/09/2015 19:01:22 The elliptical wing is down to Beverly shenstone a Canadian who worked in Germany before WW II and would have been well acquainted with the aerodynamic theory on finite wings by Ludwig Prandtl at Gottingen. It was Prandtl and his co workers that developed the lifting line theory that showed that elliptical lift distributions resulted in the minimum induced drag at low Mach Numbers. Shenstone moved to the UK to work for Supermarine before the outbreak of WW II. There is a very good paper on the RAeS website on Shenstone. Edited By Delta Foxtrot on 05/09/2015 21:36:42
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String!!! I wonder how the aircrew on the receiving end of that mod would have felt. Sounds you you had an interesting time in the RAF Peter.
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No you do not have to move the CG forward of the hinge line, but if you do you will move the forcing caused by slop in the hinging into anti-phase with the flapping motion of the main surface and stop flutter. Moving the CG forwards, but still behind the hinge line may well be enough to reduce or eliminate this. I saw a twin pioneer take off from Cranfield when I was a student there in the early 80's and was very impressed with the short take off run. So was there a flutter problem on the elevators or was this done to mitigate the risk of flutter with the engine upgrade?
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Thanks Pete! I will give them a call tomorrow
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Thanks Peter, I once did some experiments using a simple flat plate foam wing model which had ailerons constructed with horn balances. This model suffered from very violent aileron flutter due to some slop in the hinges, so bad that it was a handful to control. I made onboard video of the flutter flight and you can see the whole wing flapping violently. I then stiffened up the wing to increased the reduced frequency parameter which characterises flutter onset and this moved flutter to higher airspeeds, but it was still present and violent. The last flight in the series of experiments was to add mass balances in the form of two pound coins taped onto the mass balances. This eliminated flutter completely as expected. Moving the CG of the aileron marginally ahead of the hinge line takes the forcing caused by aileron slop out of phase with the flap mode of the wing. So this was a very practical demonstration of the benefits of mass balancing. I passed the video on to a friend who lectured at Cambridge as he thought that this would be a nice practical example. I think I will take some on video on the CAP and slowly explore the envelop to check for any signs of flutter, but based on your experience if I hinge the elevator and rudder properly I should be fine Edited By Delta Foxtrot on 31/08/2015 12:48:01
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I am currently a print subscriber and would like to add digital as well. How do I do this without cancelling my current subscription and starting a new one?
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Good to know that Peter, I assumed that you had and Gary had not. I assume that you added them to the plan after you flew the prototype as a prudent measure?
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Here is a photo showing the progress to date
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Gary, I hope that you and the CAP are still going strong. I have finally picked my CAP 20 L build again and was wondering how yours was doing. I started to look at mass balancing the elevator and rudder, but it will take quit a bit of lead in the rudder horn balance to get the balance point on the hinge line. I remembered you omitted the balance weights and I wondered if you have had any problems with flutter. It would be interested in any lessons you have learned with your CAP. Cheers Dave Edited By Delta Foxtrot on 30/08/2015 20:22:28
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I can strongly recommend the Acrowot foam e. It may not be a low wing rainer, but if you can handle the wot 4 after tuning up the rates and exploring the aerobatic capabilities of that, then the acrowot is a logical step up. It is a great little aeroplane and great value. I thought my self to fly on an easystar clone, wot 4 and then the Acrowot foamies and found this a good progression. Edited By Delta Foxtrot on 26/08/2015 21:17:59
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Thanks Peter!
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Thanks Peter. So you build sequence is something like: Make holes in elevator halves and a channel in the leading edge for the wire joiner. Slot the stab and elevator halves for hinges. shape the leading and trailing edges cover Fit hinges and joiner with stab and elevator assembly on a flat surface. This means that the block that sits on top of the tail must either be fitted afterwards or it is slotted to the rear of the fuselage to allow the tail plane to be slid in, then backfilled. I assume that the fuselage block is shaped before fitting the tailplane? I was going to use epoxy for the wire joiner, but I like the aliphatic resin suggestion as there is less change of making a mess and winding up with hard adhesive where I do not want it. I had no idea aliphatic would give a good strength joint between piano wire and balsa, but I guess it is not really under much load it is just there to prevent the joiner from sliding out. I am enjoying the build, the fuselage is looking good and it should not take too much more effort to finish, but I am only managing an hour or so in the weekday evenings. I quite like the slow paced approach to building this as it gives me a lot of time to think about the next step during the day. thanks again dave Edited By Delta Foxtrot on 26/08/2015 12:52:10 Edited By Delta Foxtrot on 26/08/2015 12:53:03
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Peter, I am just about to assemble the horizontal stab and elevator and I wondered if the elevator halves are drilled to accept the joiner through the middle of their thickness or if the joiner is just sunk into the surface on the lower surface? I have previously used CF tubes or ply to do the job, but I would like to build as plan. Regards David
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... but my glider has a folding prop, so unless you have your esc set to brake you are already getting the windmilling drag from the prop, so not much to from this. However the windmilling drag does increase rapidly with prop diameter, so a small increase could provide a useful increase, but it goes against the grain to size the prop for this. Another option is to try flaperons, but I suspect this will be of little benefit as the ailerons on the mew gull are not large.
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Another potential variable which may bleed off speed is the propeller. I find that having the propeller slowly turning over slows my electric glider down which helps to bleed off speed on calm days without a headwind to assist. Too high an rpm will obviously add to your problems. It is also beneficial to crack open the throttle a tad more when flairing out for landing to generate some elevator authority to help prevent nose overs if you are touching down with ground speed on the high side. Slow flying at altitude to get a very good feel for the slow speed behaviour of the model will help to get the approach speed as slow as possible without risking stall. Edited By Delta Foxtrot on 23/08/2015 12:44:16 Edited By Delta Foxtrot on 23/08/2015 12:46:20
