Simon Chaddock Posted February 8, 2020 Author Share Posted February 8, 2020 The next important bit is mounting the 30 A ESC with its heat sink flush with fuselage skin just ahead of the left intake so it should have significant airflow over its surface. I did the same thing with my Concorde although there I removed the shrink wrap to improve the heat transfer. I may have to do the same on this. The ESC has 2 mm bullet connectors so is, by my standards, fairly easy to remove just in case. As the wing is a one piece structure stressed skin structure it can be adequately retained by four M4 nylon bolts close to the leading and trailing edges. They use 3D printed fittings. A removable wing was chosen for ease of storage and transport as there is nothing under the wing that requires access. Of course there is a slight weight penalty compared to simply gluing the wing on but it is only a few grams. With the ESC in place a 'nose on the scales' test showed a thrust of 11.75 oz (333 g). I am happy with that as the slightly shorter prototype duct only gave 1/4 of an oz more and its inlets were in 'free air' rather being alongside the cockpit wall in the plane. So far so good. Quote Link to comment Share on other sites More sharing options...
Dad_flyer Posted February 8, 2020 Share Posted February 8, 2020 This is an amazing build. Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted February 9, 2020 Share Posted February 9, 2020 Posted by Dad_flyer on 08/02/2020 18:37:24: This is an amazing build. Yes i second that. Nice Simon. Steve. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 9, 2020 Author Share Posted February 9, 2020 Thanks for the kind words but at the moment I fear the pictures rather mask the actual quality. The one piece top and bottom skins on the flying surfaces are good enough but the planked fuselage does not give the same quality of finish. With the fuselage completed above the wing the basic construction is complete. Before any painting the fuselage including the EDF and ESC weighs just under 8 oz (225 g). The wing is 2.5 oz (71 g). The 1500 mAh 3 s is 3.85 oz (109 g). I am hoping for close to 15 oz when painted and ready to go. Quote Link to comment Share on other sites More sharing options...
Trevor Crook Posted February 9, 2020 Share Posted February 9, 2020 That's light for its size! Should be a good "proof of concept" machine so don't beat yourself up too much about the finish. You'll never see it when it's cruising around the sky on a calm summer's day. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 11, 2020 Author Share Posted February 11, 2020 I decided I really didn't like the finish of the planked fuselage so it comes down to the age old "paint, sand, fill, sand, repeat" process. In this case the first 'paint' acts as a filler/sealer which hardens the surface and make meaningful but still very light sanding even possible. It will add a bit of weight but fortunately its only the fuselage that needs any treatment. It seems to require 3 'cycles' to get a reasonable surface. The sanding is slow but at least it removes about 50% of the previous layer. It is Scola 'scarlet red' artists water based acrylic so its easy to wash out the brush but like any emulsion it is very water proof when dry.. Almost a 'gel' it has an vast amount of colour in it but is best applied 'as is' and well brushed in. Adding even a small amount of water tends to make it turn into 'droplets' on the Depron surface. We shall see. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 15, 2020 Author Share Posted February 15, 2020 After much painting and sanding along with a light coat of white on the flying surfaces the Gnat is complete. A Lemon stab rx (borrowed from my Ballerina) is fitted on the cockpit floor. The intention is that this rx will be 'temporary' just for the initial testing until a safe CofG is found. With a 1500 3s in the nose it has ended up slightly heavier than I wanted at just over 15 oz (425 g) but it should still manage happily enough with its 11.5 oz of available thrust. As storm Dennis is about to hit and the field is already very soggy it could be a while before the true effects of using true scale inlets and exhaust can be tested. Edited By Simon Chaddock on 15/02/2020 10:16:37 Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted February 15, 2020 Share Posted February 15, 2020 ... really impressive as usual, Simon. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 7, 2020 Author Share Posted March 7, 2020 The good weather than allowed me to maiden the B57D gave me opportunity to do the same for the Gnat. Two maidens on the same day. The Gnat first flight did not go too well. Almost no right hand roll control so after just a couple of seconds, power off and it flew gently into a tree. A crease in the fuselage at the cockpit resulting from when it hit the branch.. And a 'ding' in the leading edge of the LH wing from a branch. After carefully pushing the wing damage back into place, refitted the cockpit and knowing it would need lots of RH stick I launched again. Apart from needing full right aileron trim and a touch of RH stick it flew well enough. As expected it flies pretty slowly and has plenty of thrust. I even switch off the gyro but the flight characteristics felt a bit odd to say the least. After 3 minutes with the gyro back on a nice and gentle into wind glide landing. This picture clearly shows what was wrong. It is remarkable it managed to fly at all, particularly as it has small scale ailerons. Depron easily distorts above about 25 degrees C so by careful hand manipulation in a hot air stream from a hot air gun the twist can be removed and more importantly it also removes any residual stresses so it should remain that way. Repairs to the fuselage and its ready to go.. Just need the weather although the weather forecast suggest it could be some time before the gales and rain subside! Edited By Simon Chaddock on 07/03/2020 18:52:31 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 23, 2020 Author Share Posted March 23, 2020 The Gnat has had a rather chequed career so far and all of it my fault. First attempt result. Still turned right, too much wind so it went in fast at a shallow angle..Although the nose is completely destroyed the crumpling absorbed the energy so the rest of the air frame is undamaged. To make matters worse I had forgotten to switch on the gyro which would probably have saved it. A completely rebuilt nose. A week later complete and ready to go again. Second attempt. Nearly this time except it 'sank' after the launch still banking right touched a wing tip and cartwheeled. This time the impact snapped off the nose although there was quite a bit of crushing damage at the break. I had forgotten to switch on the gyro again! Once is forgetful, twice is a seriously distracted mind. 3 days later. After a bit of cutting and gluing to remove the wing warp it actually flew today and with the gyro on. Still a bit of a right turn tendency but within trim limits. Nothing special just 5 minutes of gentle flying as with all the rebuilds it really was another maiden. Unfortunately given Boris's latest edicts I am not sure when it will be able to fly again to find out more about how it flies but at least it has. Edited By Simon Chaddock on 23/03/2020 23:14:29 Quote Link to comment Share on other sites More sharing options...
Dad_flyer Posted March 24, 2020 Share Posted March 24, 2020 That is perseverance, and a lot of planking. Well done for success at the end. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 24, 2020 Share Posted March 24, 2020 Your builds and flight reports are always among the most interesting things on the forum for me. I think that the hours that you must put in on the way aren’t always apparent, you don’t plan and construct projects like these in five minutes. Quote Link to comment Share on other sites More sharing options...
Steve Jones 2 Posted March 24, 2020 Share Posted March 24, 2020 Build a TN Gnat... flys straight off the building board without problems and saves all the rebuilds .. impressive patience steve Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 24, 2020 Author Share Posted March 24, 2020 Steve Of course I could build a TN Gnat but it would likely need a cheat hole to work well and not needing one yet keeping scale inlets and exhaust was my target for this building. Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted March 24, 2020 Share Posted March 24, 2020 Posted by Colin Leighfield on 24/03/2020 19:16:15: Your builds and flight reports are always among the most interesting things on the forum for me. I think that the hours that you must put in on the way aren’t always apparent, you don’t plan and construct projects like these in five minutes. I second that. Steve. Quote Link to comment Share on other sites More sharing options...
Yorkman Posted March 29, 2020 Share Posted March 29, 2020 I think you need a pre-takeoff checklist Simon-just read your sea vixen build thread where you also launched with gyro off....or just have the gyro permanently switched on! I'd like to know how you manage to get a decent finish with Depron and Uhu Por. I've built a couple of Mosquitos with fuselage construction similar to yours though fewer planks and thicker depron- and as you have said, the depron sands but the glue doesn't...so I could never get the joints to disappear... Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 1, 2020 Author Share Posted June 1, 2020 Having at last got it sorted and the lock down reduced the Gnat flies and with the Gyro on! An edited video as the breeze and sun directions made low flying for the camera rather awkward. The launch does show the benefit of a gyro in fact if you don't do something about it it will just fly away! It also managed its first loop. As you can tell from the sound track it can cruise on much reduced power. I shall have to find out for how long. It also glides pretty well as demonstrated by the 'long walk' resulting from an enforced high approach. Quote Link to comment Share on other sites More sharing options...
Former Member Posted June 1, 2020 Share Posted June 1, 2020 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.