Simon Chaddock Posted March 8, 2015 Author Share Posted March 8, 2015 The battery box provides support for the next two formers leaving just a small nose piece to create the full fuselage but without a skin. A test showed it gave a bit over 4 oz thrust so hopefully even with the wing root inlets in place it will still have 4 oz. The 950mA 2s looks rather 'lost' in the battery big box. Indeed four could fit quite easily so hopefully there is plenty of scope for CofG adjustment! Wings are next. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 9, 2015 Author Share Posted March 9, 2015 A bit of research confirmed the Venom (like the Vampire) used a true symmetrical section. The incomplete guide to wing sections (here) says it used an EC1040 section which was developed by the RAE just after the war to operate in the transonic region but there is very little information about it. A bit more digging and I found a paper published in 1951 concerning transonic wind tunnel tests and the author very kindly included the coordinates which showed it was a 10% section with its maximum thickness at 42% chord. I also found out the Vampire section was reduced to 7% by the tip (the Vampire was 14% to 9%). Using a free graph plotting facility I was able to generate the sections for the outer panel root (10%) and tip (7%). I would have to admit that at a micro scale the final detail of wing section makes precious little difference to its aerodynamic performance but I do get some satisfaction in 'getting it right'. The outer wing panels are a spar less and rib less construction so are ridiculously simple. Top and bottom wing skins and 3 shear webs cut to exactly the right size so when the skins are drawn together it forms a perfect symmetrical section of the correct profile - well pretty nearly. The shear webs glued to the 2mm Depron lower skin and the trailing edge sanded down. The complete outer wing panel with a 6mm Depron leading edge. Using UHU POR as a contact adhesive ensures the skins stay stuck down but you do have to get them exactly in position first time! The 'rib less' section. Just 6 pieces of Depron and weighs only 0.32 oz (9g)! The aileron will be cut out and the servo inserted and lie flush with the lower skin. The rib less construction makes it easy to feed the servo lead down through the wing. Of course the inner wing panel with the inlet duct inside it will be rather more complicated to make! Edited By Simon Chaddock on 09/03/2015 17:21:39 Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 9, 2015 Share Posted March 9, 2015 That looks like a true laminar flow section Simon, seems as if you've got it spot on. Chris Golds told me that when he was flying Venoms in Germany they weren't fast enough to catch anything and were out of control at Mach 0.84. That's a lower limiting Mach No. than a Spitfire, which I think was 12% thick at the root and 6% at the tip. It seems to confirm that "laminar flow' advantages were illusory and that wing thickness was more important. Supermarine made a connected mistake when they assumed that using a laminar flow section on the Spiteful/Seafang/Attacker would allow them to use a slightly thicker section and finished up with a wing with a limiting Mach No. pretty much the same as the Venom and lower than the Spitfire wing it was designed to replace.I bet you R.J.Mitchell wouldn't have made that mistake. Having said that, I think the Venom is a really interesting and attractive plane, it's what inspired me to convert my Pushy-Cat into the "Super Venom" which I subsequently wrecked! That's what comes of me trying to create my imagined idea of what a really sorted out Venom perhaps could have been. I think your interpretation looks more promising than mine did. Edited By Colin Leighfield on 09/03/2015 17:39:26 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 11, 2015 Author Share Posted March 11, 2015 It appears from the 1951 report that the critical Mach number for the RAE1040 section was a humble 0.785 although the rise in drag and flow separation was modest up to 0.84 suggesting control would be maintained. As you point out this does rather highlight the impressive 0.89 critical Mach of the Spitfire wing! In some respects you could understand the thinking behind the use of laminar flow sections in that they did exhibit significantly lower drag at high cruising speeds, an important feature for the thirsty early jets. It is just that this advantage did not carry through into the transonic region! After some thought the only way to build the wing roots was to start from the inside and work out so first the inlet ducts fixed to the fuselage. Quite tricky to ensure the duct smoothly blends with the fuselage duct. The actual inlets as scale size. The wing root structure is then built up over the ducts. The first skin added. Both wing roots complete. As with the Vampire all the parts of the airframe are needed, along with their servo leads, before any of it can be glued together so the booms and tail are next. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 11, 2015 Share Posted March 11, 2015 I'd call that ingenious Simon, an intelligent design. Good one. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 12, 2015 Author Share Posted March 12, 2015 Thank you Colin The wing roots came out rather better than I feared. The simple tailplane. top and bottom 2mm Depron with a 2mm Depron shear web at 36% chord. It weighs 7.2g complete. The elevator servo lead runs inside the tailplane to pass down the boom The elevator servo has small fairings on the top side. It is flush with the lower surface. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 14, 2015 Author Share Posted March 14, 2015 As the tail boom is the scale length, unlike the over long ones on the Vampire. they can be built up in just Depron. 2mm sides with 6mm top and bottom to allow the scale shape to be sanded. A completed boom. It weighs 0.1 oz (3.1g) The fins will be single sheets of 2mm Depron. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 15, 2015 Author Share Posted March 15, 2015 The booms and tail complete with the elevator servo wire running inside the boom. The ESC is mounted above the duct with its 'bare' heat sink flush with the duct inner surface for cooling. To save weight the motor and battery wires are soldered direct to the ESC. The 6ch Lemon radio is below. There will be a hatch to allow binding. As I have no more model memories on my DX6i the Venom servos have been set up to work in the same sense as the Vampire so it can be bound to the same model slot - named "Venpire"? Edited By Simon Chaddock on 15/03/2015 17:26:53 Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 15, 2015 Share Posted March 15, 2015 If you have them both bound in to the same channel, perhaps you will be able to fly them in formation Simon? Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted March 15, 2015 Share Posted March 15, 2015 Posted by Colin Leighfield on 15/03/2015 18:01:34: If you have them both bound in to the same channel, perhaps you will be able to fly them in formation Simon? Now wouldn't that be entertaining . Steve Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted March 16, 2015 Share Posted March 16, 2015 Posted by Stephen Jones on 15/03/2015 23:52:28: Posted by Colin Leighfield on 15/03/2015 18:01:34: If you have them both bound in to the same channel, perhaps you will be able to fly them in formation Simon? Now wouldn't that be entertaining . Steve But short lived I would suspect! As always a blooming work of (minature) art ........ Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 16, 2015 Author Share Posted March 16, 2015 At last the bits can be put together. Not so easy when the servo wires have to be fed through the wing root before joint can be glued. The fuselage can no be skinned (planked!) In this condition (servos, ESC & radio it weighs 3.8 oz (108g). Hopefully just under 6 oz when finally complete. Quote Link to comment Share on other sites More sharing options...
onetenor Posted March 17, 2015 Share Posted March 17, 2015 Flyimg soon I trust Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 19, 2015 Author Share Posted March 19, 2015 A start of the fuselage planking. Tedious as each plank has to shaped to fit. Whilst doing it I keep thinking this process is more trouble than it is worth but the human brain quickly forgets the boring bits so its the same thing each time! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 21, 2015 Author Share Posted March 21, 2015 The fuselage planking complete and the Depron nose block added - its hollow. First stage of filling and sanding under way, The cockpit 'hatch' is under construction. I will have to start thinking about a colour scheme. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 21, 2015 Share Posted March 21, 2015 The Venom is a pretty aeroplane and once again, you've captured it. I would imagine that it's very likely the Sipa Minijet was inspired by the Vampire/Venom. I bet Stephen likes this one. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 22, 2015 Author Share Posted March 22, 2015 Started the painting. Decided on a simple purple and white scheme for no reason other than I have alot of purple left over from the Q400 and the white will only need a very light coat. It actually looks more purple that that in the flesh. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 22, 2015 Share Posted March 22, 2015 That certainly looks the part Simon. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 22, 2015 Author Share Posted March 22, 2015 Actually I had in mind to to use something like the private Hunter "Miss Demeanour" until I saw how complicated it was. **LINK** So I thought it would do something rather simpler - "Miss Directed" maybe! Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 22, 2015 Share Posted March 22, 2015 I saw what you mean. Perhaps Miss Aubergine might do it. It looks quite striking anyway. I bet it will fly a treat. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 24, 2015 Author Share Posted March 24, 2015 Now virtually complete. Just a light spray of clear acrylic to give a bit of shine to the wings. With a 950mAh 2s it weighs 5.75 oz (163 g) giving a wing loading of 4.3 oz/sqft. Next bit of calm weather and 'give it a try' Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted March 24, 2015 Share Posted March 24, 2015 Looks great..... but at 163g do you have access to some special under the counter Depron thats helium filled? Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted March 24, 2015 Share Posted March 24, 2015 Looks great . Good Luck with the maiden Simon , Steve Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 25, 2015 Author Share Posted March 25, 2015 Calm but chilly today. The maiden As always with these tiny planes it has been edited to show just the bits where there is something to see. It flies but not particularly well although it is not short of thrust, indeed I had to throttle well back to get it under control. It needs both more nose weight and the tailplane negative incidence reducing. The battery can go forward but requires it box to be extended into the nose. The tailplane will have to be cut free from the boom. The mounts sanded down and then all stuck back on but all the while taking care no to damage the elevator servo wire! Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted March 25, 2015 Share Posted March 25, 2015 Well, it survived Simon and looks good. Makes those modifications and it will be a good'un, no doubt about it! Quote Link to comment Share on other sites More sharing options...
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