Geoff Gardiner Posted May 24, 2014 Share Posted May 24, 2014 Cambrian Spitfire Mk IX - 55 inch Wingspan This will be my second ‘proper’ build, having cut my teeth on an Avicraft Mini Panic. I am building this to gain experience and hoping that I end up with something at least airworthy! I will be converting this to an electric setup and fitting e-flite retracts. I also fancy having a go at a glass/resin finish and maybe a bit of airbrushing (keeping an eye on weight}. I will mention that, to date, I am quite a slow builder (I tend to do an awful lot of thinking). So …… onward and upward. After much deliberation I am diving in with fitting the retracts. I made a template of the suggested mounting plate that was drawn on the plan and used this to set out the position of the retracts on each wing. I made the decision to make a ply box with bearers to fix into a recess cut into the wing – I think this will be much stronger and easier to set the correct angles I then set about with the Dremel type tool to fashion the wheel well. Add some bearers and glue some extra ply to the mounting plates. More later.... Edited By Geoff Gardiner on 24/05/2014 19:27:21 Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted May 24, 2014 Author Share Posted May 24, 2014 OK.. here's a bit more. Glue on the leading edges and rear spars using Gorilla glue Then glue on the wing tips. I had to add a bit of scrap balsa as the wing tip was not quite thick enough when centered. Laid out the wing just to get an idea of the shape. Then attack it with the David plane and create a bit of mess. Bend the wire aileron cranks taking care to get the angle right and glue on the inboard trailing edges. More later... Quote Link to comment Share on other sites More sharing options...
Concorde Speedbird Posted May 24, 2014 Share Posted May 24, 2014 My one is awful looking at this. CS Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 25, 2014 Share Posted May 25, 2014 Nice work that Geoff. I like the way you have fitted the retracts. Always tricky with a Spit! Watching with interest. Even in rough the profile of that wing looks gorgeous doesn't it! BEB PS And that's not true CSB - I think yours was looking great last time we saw it. How about updating us? Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted May 25, 2014 Share Posted May 25, 2014 nice work sir. foam core wings do speed up a build dont they. Quote Link to comment Share on other sites More sharing options...
Brett Jones Posted May 25, 2014 Share Posted May 25, 2014 lovely building, just noticed does the servo for the aileron servo go on the bottom or top of the wing? as you have the control horn on the bottom of the wing? Edited By Brett Jones on 25/05/2014 10:38:25 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 25, 2014 Share Posted May 25, 2014 Well spotted Brett! Yes that definitely looks a bit odd It would usually be the other way - pointing to the inside (upper face) of the wing. BEB Quote Link to comment Share on other sites More sharing options...
Ted Posted May 25, 2014 Share Posted May 25, 2014 I think perhaps port aileron is pinned on stbd wing? Hopefully anyway. ted Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted May 25, 2014 Author Share Posted May 25, 2014 Oh darn.............. it was going so well! Thanks everyone for your comments. Yours looks great CS - is it finished yet? I intend this as a warts and all build log, as I'm learning as I go, and here's my first wart!. Looks like I have no choice other than cut off the trailing edges off and put them on the correct way around, unless anyone has a cunning plan. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 25, 2014 Share Posted May 25, 2014 Sorry Geoff - no cunning plan that I can think of! I think you will just have to very carefully cut off the trailing edge, swop the control arms around and then reattach it. Don't be too down - we all make mistakes - its part of the game! BEB Quote Link to comment Share on other sites More sharing options...
Concorde Speedbird Posted May 25, 2014 Share Posted May 25, 2014 Mine is not, been busy with exams and some other planes so only done some bits and pieces. I'll update it soon. That's an easy mistake to make, looks like you will simply have to cut the trailing edge off and swap them around. I look forwards to the next update. CS Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted May 25, 2014 Author Share Posted May 25, 2014 OK.... back on track (I hope). I had put the wrong trailing edge on the wrong wing half. I decided the easiest thing would be to cut the rear spar in half and swap everything around as a unit. Sanded the edges flat and glued back on correct wing half. Bit of filler and a final sand and I think it should be good to go. One thought. The design is for a single servo for the ailerons but I am thinking it may be better to use two, thus giving the option for programming flaperons. What are you doing CS. More later... Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted May 25, 2014 Share Posted May 25, 2014 Nice get out Geoff, I like it John Quote Link to comment Share on other sites More sharing options...
Concorde Speedbird Posted May 25, 2014 Share Posted May 25, 2014 I'm using a single servo for lightness. I don't think flaperons are a good idea, I think they can induce tip stalling which is bad! It should slow up alright on it's own with the wheels down but I don't yet have experience of flying this sort of model. Good neat repair work there. CS Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 25, 2014 Share Posted May 25, 2014 Yes, nice escape Geoff. No harm done - no one but us will ever know I agree with CSB - I wouldn't use flaperons on a Spitfire. They have a tendency towards tip stalling at the best of times - some aileron droop would effectively increase the AoA of the wing tips - which would only aggrevate that tendency - it would be like having wash-in! Definitely not good when you are in the late stages of an approach and looking to flair (and so increase the AoA) anyway as you could find yourself with a model that had a real likeness for severely dropping a wing just at the wrong moment! Warbirds like to be landed quite quickly - flown in all the way then just back right off the throttle at the last instant. BEB Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted May 26, 2014 Author Share Posted May 26, 2014 Good Info - thanks. I will avoid flaperons. A few more pictures to bring things up to date: Glue in the retract mountings using Gorilla glue (the foaming variety). Test fit retract units. This is my first experience with retract units and I have found that, due to the angle that you have to mount the unit, the wheel well has to be much bigger than the wheel in order to stop it jamming on the edge. Is this usual or do I need to put a bend in the leg? The video below, which I made before I switched the trailing edges, hopefully gives you an idea of what I mean. The wheel just about clears the edge but I am concerned that if the leg gets slightly bent during use it will bind. More later... Quote Link to comment Share on other sites More sharing options...
Concorde Speedbird Posted May 26, 2014 Share Posted May 26, 2014 Looks lovely. What size wheels are you using? I think they are smaller than my ones, I used the scale sized ones which did mean a large wheel well. Keep going! CS Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 26, 2014 Share Posted May 26, 2014 Yes its quite normal to have to allow yourself a little "wiggle room". Also you may have to play with the depth of the cut-out a little as you will probably have to rotate the wheel slightly so that the tracking is right when the gear is down. If you want to find out a bit more about the joys and delights of retract geometry you can have a look at my efforts (with input from Danny Fenton and others) on my Typhoon build thread here. The discussion starts around there and spreads over the next couple of pages. Lots of useful stuff and some good links. There is a video a couple of pages later that shows that I did actually eventually get it right - somehow! BEB Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted May 27, 2014 Author Share Posted May 27, 2014 Looks lovely. What size wheels are you using? I think they are smaller than my ones, I used the scale sized ones which did mean a large wheel well. Keep going! CS I am using 70mm diameter wheels which I think are roughly about scale. Quote Link to comment Share on other sites More sharing options...
Electriflier Posted May 27, 2014 Share Posted May 27, 2014 Geoff, I agree wholeheartedly with BEB. Having just built a Spit', encountered exactly what you describe in your posting, the tendency to catch the edge of the wheel well, the slightly angled wheel once stowed etc. Similarly to BEB, I too eventually got it right although I found getting it right took up quite a lot of time and patience. Your installation looks really neat and precise by the way. You're correct though in thinking that a less than perfect landing may have a tendency to bend the legs slightly and you might find yourself easing them one way or another once you start flying. This is not just a trait of the Spitty though, all retracts can be troublesome in one way or another. Getting the wheel spats to align and lay flat and stay aligned is also quite testing but looking at your level of building proficiency I'd say you'll more than cope. Lovely build to follow..... keep up the good work sir Regards Roy Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted May 29, 2014 Author Share Posted May 29, 2014 OK, so I am thinking about what motor and battery combo I am going to use before I start building the fuselage - in case I need to make any modifications. I would like to use kit that I already have, to try and keep costs down. Namely: Lipo Battery - 5S 4000mah Motor - I have two to choose from, both Overlander Thumpers. These are the Specs 1. Tornado C4250, 600kv, 720 watt max, 3-7 Lipo, 45A ESC, Prop from 10x5 2. V2 T5045/10, 720kv, 1250 watt, 3-7 Lipo, 80A ESC, Prop from 13inch The suggested average weight for this Spitfire is 5.5lbs. Do you think either of these combos would be suitable? I am thinking the 2nd option but I do get a bit confused with all the numbers. Any advice gratefully received. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 29, 2014 Share Posted May 29, 2014 Hi Geoff, Its a bit hard to give a clear view here - as I haven't used these motors and Overlanders website is a bit sparse on important details! In particular the maximum current the motor can cope with. They tell us what ESC to use - but not the actual max motor current! But lets assume the second motor can cope with 70A - the ESC current minus 15% or so. With a 4s that would give you a max possible power of nominally 1kW - which is far more than you need for a warbird weighing 5.5lbs - you should be looking for a max power of around 750-800W. So that all looks good - because you could probably prop-down to that level no problem. The First motor let's assume a max motor current of 40A - so on 4s that's a max nominal power of about 600W. Now, without doubt that will fly a Spitfire of 5.5lbs - but with not a lot left over! And the system would have to be prop'ed spot on to deliver the max current. On balance I'd go with motor two as its a bit more flexible on prop choice and has a bit more "in hand". But of course as always the Wattmeter is the only really accurate way of knowing. BEB Quote Link to comment Share on other sites More sharing options...
steve tandy Posted June 1, 2014 Share Posted June 1, 2014 Hi Geoff just to let you know nice build Steve Cambrian Model Co Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted June 7, 2014 Author Share Posted June 7, 2014 So… I have set out the motor, 100A ESC and battery on the plan to see how things fit. The battery is a bit of I tight fit length ways – I may have to move the servos slightly. Also need to decide which way up the battery should go. I will need to cut away some of F3 to get the battery through. Thanks, BEB, for your wise words regarding motor choice. I will go with the option 2 - Overlander Thumper V2 T5045/10, 720kv, 1250 watt. However, the batteries I have are 5s – so I think this gives the following: W = V x I (18.5 x 70) which gives us 1295W RPM = V x KV (18.5 x 720) which gives us 13320rpm If I want to achieve around 800W, I will need to select a prop that draws around 43W (I = W/V) and hope it doesn't look too small for the scale of the aircraft. Does that sound about right or do you think I will need to use 4s batteries? More later... Quote Link to comment Share on other sites More sharing options...
Ian101 Posted June 8, 2014 Share Posted June 8, 2014 Hi Geoff. I hope you don't mind me sticking my nose in, but it might be worth moving the battery forwards as far as possible. On my Spitfire, the batteries are almost touching the back of the motor and I still had to add a little nose weight. It is also depron, so the tail will be probably be lighter than yours. Enjoying watching this build. Ian Quote Link to comment Share on other sites More sharing options...
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