Simon Chaddock Posted December 15, 2013 Author Share Posted December 15, 2013 Having frightened myself with its size it seemed logical to build a 'test' nacelle to check the thrust. It all made of 2mm Depron. the top surface is shaped to match the wing profile. In this case it is built as a complete box but in the model the underside of the wing will be the top surface of the nacelle. It is 17" long (430mm) and 3.5" wide (90mm) and 1.7" (42mm) deep. First the bell mouth has to be cut off the 40mm EDF. A delicate job. Then fixed to the nacelle with a Depron dummy jet pipe alongside. The plan is to mount the elevon servo in that space. The duct has internal dimensions of 85mmx40mm which is just over 3 times the FSA! And if it all looks impossible there is a plan "B" - use 4 EDFs and never mind the expense! Being realistic 4 units with their ESCs will cost 10 times more that of the Depron required to build the airframe. Then there is always the nagging thought that I could achieve the same thrust as 4x40mm with a single 55mm at 1/4 the cost. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 19, 2013 Author Share Posted December 19, 2013 Having cut out the wing skins and along with the pieces I have already made I can make a reasonably accurate guestimate of the final weight with 2 fans and a 1800mAh 2s. It comes to 18oz. With a maximum of 8.4oz thrust this sounds like a pretty marginal thrust to weight ratio. With this in mind it would seem logical at this stage to install my second fan in the 'test' nacelle to see what thrust it delivers. I would hope it can achieve 8oz. The extra weight of the 2 fans, ESCs and a 3000mAh 2s will be about 5oz. 16 oz thrust for a 23oz flying weight sounds a better bet. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 19, 2013 Author Share Posted December 19, 2013 And just to show it actually works It does produce just a touch over 8oz thrust. Edited By Simon Chaddock on 19/12/2013 18:06:36 Quote Link to comment Share on other sites More sharing options...
Bandit Posted December 19, 2013 Share Posted December 19, 2013 Some inspiration for you from some crazys I know who want to get one flying again. They crazy in a good way Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 21, 2013 Author Share Posted December 21, 2013 So far so good but now comes the tricky bit - the wings! First each of the wing skins are 'cold formed' to approximately the right shape - leading edge droop on the first third and anhedral at the tip. The single centre rib. Concorde has a very thin 3% wing section. In 6mm Depron to provide the necessary glue area for the skin centre join. The first 7 wing 'webs' incorporating the leading edge droop. There are no spars as such. Like the fuselage the wing will rely entirely on its skin for strength. All 19 wing webs. Each web corresponds to a fuselage former. A major drawback with this type of construction is that the wing has no rigidity at all until the top skin is in place but before then 6 motor wires and a servo lead have to be run through the wing. The final challenge with this complex shape is not so much making it but getting each wing exactly the same! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 22, 2013 Author Share Posted December 22, 2013 From now on each step has to thought out carefully as any mistakes can have serious consequences. The root ribs glued on, the elevon cut out and its servo positioned. It just fits between the skins. The other cut out is for the jet pipes. I was going to build the wing as one piece and then construct the centre section of the fuselage around it. Although quite a sound method it would leave quite a bit of redundant internal structure. With so little thrust available every part has to 'earn its keep'! So I am considering a major change and build the wings and centre fuselage simultaneously on the basis that I can leave out anything that is not vital to the strength of the structure. The down side of this approach is I will need a much bigger building board and the whole thing will be horribly flexible until all the skinning is complete. Keeping both sides of the wing identical will be a nightmare but it could save as much as 10% of the airframe weight. Edited By Simon Chaddock on 22/12/2013 12:29:41 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 24, 2013 Author Share Posted December 24, 2013 The next step is to add the other wing. There are a lot of pieces. This gives some idea of the curves and twists in the wing. It is still very flexible at this stage. the final shape will only be 'set' when the top skin goes on. The complete wing will have to be carefully secured on many blocks to get the right shape. Before then the fuselage underside formers will be added & sheeted. This will allow a large part of the centre rib structure to be removed to save weight. If I was doing it again I would do it rather differently and made all the combined fuselage/wing web formers as one piece and built the whole thing all together. Quote Link to comment Share on other sites More sharing options...
Concorde Speedbird Posted December 24, 2013 Share Posted December 24, 2013 Looks pretty good to me. To get both sides correct will be fun, you'll do it well though. Great build, inspires me for my balsa one in the future. CS Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 26, 2013 Author Share Posted December 26, 2013 Only modest progress. The underside formers. The wing is blocked up and mounted on a piece of plasterboard. When the underside is fully sheeted it should then be rigid enough to hold the correct fuselage profile. Quote Link to comment Share on other sites More sharing options...
Martian Posted December 26, 2013 Share Posted December 26, 2013 it's looking superb Simon but oh dear plasterboard on the bed you are going to be in trouble Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted December 26, 2013 Share Posted December 26, 2013 It's interesting how there are no Concorde models available like a Park Zone version ready to go. I know Robbe made one years ago, but was marginal, and that was made of epp and would be interesting how this one fairs. Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted December 26, 2013 Share Posted December 26, 2013 Simon - that's a great job you are doing there! It looks really good - I wouldn't know where to start. Keep it up! Beautiful aeroplane. Terry Quote Link to comment Share on other sites More sharing options...
riverlandgirl. Posted December 27, 2013 Share Posted December 27, 2013 I really enjoy watching your building process, and am anticipating a sucessful outcome! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 27, 2013 Author Share Posted December 27, 2013 A successful outcome? Hmmmm! Just completed (you can still see the pins holding in the last plank!) the underside skinning at long last. At least it is now rigid enough to be picked up so work can now start on the upper surface and there is even more to do on that. Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted December 28, 2013 Share Posted December 28, 2013 Wow, that is really impressive Simon. Very clever how you have interpolated the cross sections, I couldn't do that but it does show what can be done with foam if you have the skills that you clearly have. You must produce a plan (a big plan!) as it is a very popular subject that is rarely modelled well. You did keep a record of the cross sections didn't you? Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 28, 2013 Author Share Posted December 28, 2013 A modest start of the top side. These webs between the wing webs correspond to the line of the fuselage skin. When complete down the full length of the wing the original centre root rib and the enclosed part of the wing skin will be cut out. Once the top wing skin and upper fuselage are skinned it will then leave the wing and fuselage as a single integrated monocoque structure but this method is a rather long way round to achieve it!. If I were to build another I would build the centre part of fuselage first (as half shells) and only add the wings once the fuselage itself was complete. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 29, 2013 Author Share Posted December 29, 2013 This is proving to be a very untidy way of building as the next step it to start removing quite a bit of what I have already built. The first stages of the root rib and wing skin being cut out. Overall it will save nearly an ounce. To be honest if I was ever to build another I would not do it this way. It would be much more efficient to build the fuselage first (as half shells) and add the wings when it was complete. I chose the 'wing first' method as I concerned at the stiffness of the very thin (3%) wing. It has proved not to be problem but then hindsight is a wonderful thing! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 31, 2013 Author Share Posted December 31, 2013 After all the recovery at last some real progress as the RH wing top skin goes on. The elevon servo is just visible under the skin. Quite a job with such a huge area to glue but it certainly seems to create a wing on adequate stiffness & strength. I am concerned at the weight of all the motor/ESC wiring so subject to CofG limitations I intend to place the 4 ESCs well back with just a single +/- heavy duty (it has to carry over 50A!) cable forward to the battery. With 4 EDF and ESC relatively close together it will probably be prudent to place the radio (an Orange 3 axis stabilised?) well forward possibly even ahead of the battery. Quote Link to comment Share on other sites More sharing options...
John Olsen 1 Posted January 1, 2014 Share Posted January 1, 2014 I don't know if you are aware of this, but ESCs can give problems if the leads to the battery are too long. I think this has been discussed here before although I can't remember what the thread was. You may need extra capacitors to supplement the ones on the ESC. Long motor leads are not a problem. John Quote Link to comment Share on other sites More sharing options...
riverlandgirl. Posted January 1, 2014 Share Posted January 1, 2014 One does tend to find the "better way" after the fact, But even so it's all looking good, and I'm betting she'll be a cracker! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 2, 2014 Author Share Posted January 2, 2014 This is still giving me sleepless nights! I am concerned at the weight of the wiring and cooling for the ESC which under test I had noted get warm pretty quickly. A neat solution to the cooling problem would be to mount the ESCs in the wing but with their heat sink flush with inside of the duct. No drag penalty and plenty of air flow. It would also save a bit of weight if the motor wires (they are remarkably thin) were soldered directly to the ESC. So another trial for the test nacelle. The flush heat sink. It seems to work ok keeping the ESC cool at full power static on the bench. In the actual plane the ESCs will be mounted in the wing underside and the duct added underneath. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 3, 2014 Author Share Posted January 3, 2014 By building a short section of the duct the EDFs and ESCs can be fully installed and tested 'on the bench'. The complete assembly can then 'inserted' into the lower wing skin. The duct has internal fairings to convert the rectangle into two circles. The duct with all 8 internal fairings in place. There are 21 separate pieces of Depron in each of these duct sections. The the lower wing skin cut out and the duct positioned. The ESC cables will be fed between the wing skins through to the fuselage. I am waiting for the final pair of EDFs and ESCs to be delivered. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 4, 2014 Author Share Posted January 4, 2014 The LH top skin added along with the elvons. Can now make a start on the main part of the fuselage. Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted January 4, 2014 Share Posted January 4, 2014 Looking Good so far , Simon Quote Link to comment Share on other sites More sharing options...
reg shaw Posted January 4, 2014 Share Posted January 4, 2014 It absolutely amazes me what you folks can do with Depron!! Beautiful work indeed. Ian. Quote Link to comment Share on other sites More sharing options...
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