Pete B Posted February 17, 2012 Share Posted February 17, 2012 They're heading there right now! Pete Quote Link to comment Share on other sites More sharing options...
Pete B Posted February 17, 2012 Share Posted February 17, 2012 OK, first the excuses - grey day, no colour anywhere, black and silver aircraft, ISO800 to give me a chance - but a bit of fettling has produced these. First two are climbing away from take-off: Despite the lack of colour, I think they are rather atmospheric in a monotone sort of way......... Little did we realise but on this pass it was heading towards the scene of the accident........ Next time I photograph the Tiggie, it'll be Spring with blue skies, a verdant countryside and gentle zephyrs! Pete Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted February 17, 2012 Share Posted February 17, 2012 It sure does look lovely Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted February 17, 2012 Share Posted February 17, 2012 I have tried to use the quote button, not sure it worked? Anyway in answer to your question, and sorry I missed it Chris, I don't think it is the prop stalling as I have had something similar on innitial spin and not using WOT either. I have put it down to a combination of the Turnigy motor, and the ESC. In the worst case it will not innitially spin up at all and just oscillates as though only two fields are active. I have to disconnect the ESC from the cells and re-initialise. Its embarrasing more than anything, but still takes less time than to fire up a recalcitrent diesel. Cheers Danny Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted February 17, 2012 Author Share Posted February 17, 2012 Thanks guys and thanks Pete for the pics - does look the biz doesn't it. I think that what has been said makes sense and maybe we'll never know for sure but will have a good look at the electrickery when I take it apart. I will probably have an initial examination over the next few days but the actual rebuild will be best left for a while! Terry Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted February 17, 2012 Share Posted February 17, 2012 I'm not so sure, but you may be right. I think the squeal in the air could possibly be the rotating field continuing at a pace while the prop, shaft and magnets have suddenly slowed right down due to the stall. Much like David described in his article when he mentioned an engine going deadstick. Where's BEB when you need him? Not that it matters, it's just an effect we need to be aware of with some electric setups. A slower opening of the throttle seems to prevent the squeal. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted February 17, 2012 Share Posted February 17, 2012 Mmmm, interesting. Well of course its impossible to know - doubly so not being there! - but it must be said all the conditions were in place to stall the prop. Airspeed low (going downwind), sudden increase in prop speed - so low Va and high Vr, the perfect conditions for a stalling a prop. Prop stalling is very rarely fatal for the model - you get a big increase in prop drag and a loss of thrust - but most models can fly through it, eventually building enough airspeed to unstall the prop, with some "funny noises" as the only symtom! But of course if you're "low and slow" as here there is little scope for flying your way out of the problem. The biggest danger with an IC engine is that the sudden increase in load (from the increased drag) stalls the engine. With an electric motor like this that won't happen of course. The problem is - not flying much electric to be honest I'm entirely sure what an electric motor would do! My guess is it would give a massive current spike and issue some protesting noises - much like this one seems to have! I think this could have been a prop stall - as I say the conditions were right and the symptoms sound right - but there is absolutely no way of knowing and Danny could equally be right that its just a feature of this motor/ESC combination when you open the throttle smartly. One question - sorry if this is given earlier in the thread - what was the prop size? If the pitch was higher than average then that would add further weight to the prop stalling theory. BEB Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted February 18, 2012 Author Share Posted February 18, 2012 The morning after......... Well at least the sun is shining today! Thanks again for the support and views they are much appreciated. What we do know is that the a/c lost thrust one way or another. I think the prop stall is compatible with what seemed to be happening but I will have a good look at the all the bits later. The prop was securely attached when we came to remove it before testing the motor in situ. The prop size is 13 x 8, motor E-Max 4020/08 with 60Amp ESC on 3600 5S - draws 33 Amps max Terry Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted February 18, 2012 Share Posted February 18, 2012 13X8 is a very "middle of the road" prop - dia/pitch ratio 1.625, more or less spot on the nominal 1.6. That neither weakens nor adds weight to the prop stall theory. A 13x8 prop could stall of course but its not as if it was a 13x10 in which case I think I might have been "pointing the finger" with more vigour! Pity whatever the cause of course =- but at least she looks well repairable Terry. BEB PS Just edited this, I typed: dia-colon-pitch to denote ratio, and got this: diaitch - obviously "colon p" means a smilie! Edited By Biggles' Elder Brother - Moderator on 18/02/2012 09:08:37 Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted February 18, 2012 Author Share Posted February 18, 2012 Posted by Biggles' Elder Brother - Moderator on 18/02/2012 09:05:42: 13X8 is a very "middle of the road" prop - dia/pitch ratio 1.625, more or less spot on the nominal 1.6. That neither weakens nor adds weight to the prop stall theory. A 13x8 prop could stall of course but its not as if it was a 13x10 in which case I think I might have been "pointing the finger" with more vigour! Pity whatever the cause of course =- but at least she looks well repairable Terry. BEB PS Just edited this, I typed: dia-colon-pitch to denote ratio, and got this: diaitch - obviously "colon p" means a smilie! Edited By Biggles' Elder Brother - Moderator on 18/02/2012 09:08:37 Thanks BEB - I thought my set up was 'MOR' - I did the calcs and bounced them off my local advisor (Pete B) and it gave me 93 Watts which is more than enough for this one. In fact take off yesterday was less than half throttle! Tiggie will definitely be repaired but I'll let a bit of time pass so I carry out the repair without the current hurt feeling and with proper preparation! Terry Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted March 21, 2012 Author Share Posted March 21, 2012 Well - here we are in March and it's now Spring and in Spring a old bloke's fancy turns to his bent Tiger Moth! Before I start I will mention the great service I've had from Eddie at DB Sport and Scale in sorting out new cabane cut pieces and pre formed supporting wire for them. This will help me cut the time down a bit. Eddie had to identify the correct files on the computer and separate then out to cut the parts. All done 'with pleasure' and promptly sent to me in France and all for a tenner! Thanks Eddie! Still haven't found anything wrong with the motor but it hasn't been tested under load so that's yet to come. It runs fine without any load but who knows what's going on inside! We''ll find out later on this month I hope! The rebuild started by dismantling the airframe. As I can get the Tiger in my C15 van fully mounted I hadn't been expecting to take it apart this soon. A bit of cutting of split pins took place to de-rig the wings and my lovely false rigging was sacrificed! Painful! The upper wing was checked again and found to be completely sound. No damage to the fuz or tail surfaces. Cowl - looks worse inside but repairable - I did buy a spare when I ordered the kit from DB - How's that for self confidence! The cabane structure was not easy to remove but I've managed quite a nice job - the Dremel came in very handy. I had to take all the cabane apart because it is constructed with a wire armature which is sewn (yes I can sew but I don't take in alterations!) into the top plate. All nicely cleaned up ready for rebuilding. The lower wing was a different story. I carefully removed the solartex from all the wing and also removed the ailerons. This wing was more badly damaged on the port side than I had thought. The aeroplane had obvious hit the ground port tip front edge first and that impact had pushed the leading edge inwards which had dislodged all the riblets and broken some of the ribs on that side. Some damage was also found to the struts fixing points. The energy had ended up in the centre section and broken all of the structure forward of the main spars. The starboard wing had a small amount of damage close to the centre section with a sprung leading edge and some loose riblets. A good challenge! Luckily in my store cupboard and stuck with masking tape to the side were 2 ribs left over from the build and these were used as templates for cutting out new parts to replace those damaged. By the end of the day I had rebuilt and reinforced most of the centre section. Before finishing I cleaned the leading edge joints of the port wing and selected a nice piece of hard balsa sheet of the right thickness and cut a new square leading edge to be fitted and shaped next time. It's not going to be a quick job but now I've started I feel a lot better and looking forward to have the old girl back in the air so that Pete B can keep his promise to get at least one photo in a blue sky! Terry Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted March 22, 2012 Author Share Posted March 22, 2012 Raining and windy today - lovely! Getting on with the rebuild. First of all the new l/e was fitted to the damaged port wing: Then I found that the 'old' riblets that had collapsed in the impact were going to be too short after 'cleaning' up. So............that meant nearly 20 new ones had to be cut and fitted. Didn't actually take too long either - I quite enjoyed it. Some other minor damage to joints on this wing was also repaired before starting on the new cabane structure by sanding the cut pieces to profile and epoxying together over copies of that part of the plan. The cabane structure is reinforced by two identical U shaped pieces of piano wire. In order for these wires to be attached to the wooden cabane side frames the builder is advised to cover what will become the vertical parts of the wire frame with 1/1/2 turns of masking tape and then epoxying or PVA glueing to the wood. At least this time it doesn't seem so bizarre and I am not so disbelieving especially as I now know hard they were to remove!! It works! Firstly the width of masking tape is estimated and then positioned with one of the long edges rubbed down. Then the rest of the tape is carefully wound around the length of piano wire The the rest of the tapes are done so we have four 'legs' prepared. Then I redrilled the holes in the top plate of the cabane structure for the 'sewing' mentioned yesterday. The holes had been closed by the remaining thread and epoxy residue from the first build. Quite pleased with what got done today - apologies to Courier fans - will be more on that soon! Terry Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted March 22, 2012 Share Posted March 22, 2012 It's looking good Terry, are you at the point yet where you can see that it can all be done? That's my favourite repair milestone. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 22, 2012 Share Posted March 22, 2012 well done Terry, the hardest part is starting, its going back together really well Cheers Danny Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted March 23, 2012 Author Share Posted March 23, 2012 Posted by Chris Bott - Moderator on 22/03/2012 21:25:19: It's looking good Terry, are you at the point yet where you can see that it can all be done? That's my favourite repair milestone. Well not quite there yet but it feels good to be on the way! Danny - It is hard to start but it's the way they look at you every time you walk past them that makes you feel so guilty! Thanks guys. Onwards and upwards! Terry Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted March 23, 2012 Author Share Posted March 23, 2012 A good day today although it was very sunny (but a bit windy as soon as I thought I might go flying this pm - typical!) This morning I decided it was warm enough to do the cowl repairs outside. I do have the parts for a new cowl but I decided it was bad practice to just put the new one together. Better to repair the old one and still have a spare! So got the resin, newspaper, gloves, scissors, mixing tray and stirrer. All I needed was the glass reinforced ribbon. An hour later and a good sort out of my workshop I found it where it shouldn't have been - someone must have moved it. So, a bit delayed, I repaired the damaged interior of the cowl with tape, resin and a bit of finger poking!. That done I then did the first filling on the exterior! Then a quick rub down and the first primer coat applied. Then the second filling! Then a second spray of primer - still not perfect but from where I started - definitely getting there! This is the best side! I also used a triangular file to re-define the panel lines before spraying. The cowl is now 'resting' overnight but won't be sprayed gloss black tomorrow because I'm off out all day!! Terry then begged a darning needle off SWMBO so he could sit and sew the piano wire cabane frame onto the cabane top panel - we know how to live here! If you think the stitches are a little uneven the explanation is that I was multi-tasking at the time - see the photo after this one. Putting the cabane structure together requires a bit of thinking. As I had already done this in the initial build I am a little wiser now! Firstly two pieces of scrap strip were clamped to inverted top panel specifically to help position the four corner uprights and ensure the top of the upright sits flush with the top surface of the panel. Next the wood and piano wire have to be permanently fixed together. Forget clamps! The rounded surface of the wire just allows clamps to slide off and it will drive you crackers. It is easy if you simply ensure the wires and wood sit well together then apply epoxy to the appropriate face of the uprights and then hold the wires in place under slight tension by using good old masking tape! Job done! "Here's one I made earlier" as they say on Blue Peter We're getting there! Terry Edited By Terry Walters on 23/03/2012 19:51:15 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 23, 2012 Share Posted March 23, 2012 Don't make that cowl too good Terry, never look authentic if it isn't a bit wavy Cheers Danny Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted March 29, 2012 Author Share Posted March 29, 2012 Well too much good outside working weather has seen great progress with stripping,sanding and repainting woodwork but not much on the Tiger! But there has been some progress! After the cabane structure was put together the bottom fairing was cut and sanded to shape before the visible surface was then covered with a corrugated card (not cardboard) which SWMBO uses for her Scrapbooking - perfect for simulating the corrugations of the fuel tank! See previous pre crash photos. This will be sealed and then painted with silver Solarlac. Athough there was no substantial damage to the fuz I took the opportunity to improve the battery access and housing. Those who read the pre-maiden part of this blog will recall I had to change the power system at the end of the build. I had taken the measurements of the new larger Lipo on order at that time as gospel and created the access to suit - when it arrived of course it was larger than the spec! So now's the time to get it right so as to avoid that embarrassing fiddling and cursing to get the battery in place and to get it out again! Firstly I extended the battery tray so that the battery can lie flat. I also ground away at an angle some of the ply floor to improve the access. During this work I noticed that the top brace between F1 and F2 was broken so It was removed and replaced with a sturdier piece of ply. The repaired bottom wing was trial fitted to the fuz - it fits!! Hooray! The new 'extension of the battery box was closed with a substantial forward end plate which has top cross piece to hold the battery flat. This end plate was shaped at the bottom edges/sides so as not to foul the cowl. Still need to work out how the Lipo will be restrained at the rearward end! Something will turn up! A new cowl retaining screw block was needed to sit astride the top brace. Finally, as the Lipo box cab be seen thro' the front of the cowl it was painted black! We are getting there! Can't wait to fly the Tiger again! Terry Quote Link to comment Share on other sites More sharing options...
Pete B Posted March 30, 2012 Share Posted March 30, 2012 That's some excellent progress you're making there, Terry - told you it would buff out! Must get on with my Beaver when I get back............. Pete Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted April 18, 2012 Author Share Posted April 18, 2012 Hi all, sorry about the gap in this thread but this was due to me being off line for courtesy of France Telecom for 10 days! Finally got back on line yesterday afternoon so I feel whole again! The Tiger is ready for re-maiden now so rather than go over the past two weeks in details a resume is probably best. The original motor which failed on me was found to have thrown a magnet. Simple as that. When under load the offending magnet was evident. A second identical motor was then fitted. This motor was an unused Emax 4020 which was purchased at the same time as the first - that was about two years ago. All excited I called SWMBO outside to witness the taxi trials on the terrace. Slow running was fine and the Tiger performed perfectly. So I decided to try WOT and guess what? Yes it threw a magnet - Arrrrgh!!! Attempts by me to refit the magnets and make at least one decent motor out of two failed!! Doh! So a new motor was ordered. As I had created the mounting specifically for the Emax 4020 I was really limited to try another and so one was ordered and duly arrived. To be fair the new motor seemed better made and ran much more smoothly than either of the previous two and at least I have a guarantee of sorts. So far so good. So feeling more positive I got on with the finishing touches. Firstly hand cutting another set of 185mm reg letters for the underside of the lower wing! Relaxtion therapy it is not! Can you see what it is yet? The black Solartrim is a bit reflective but if you look hard enough you can see how I have economised on the the trim and used some of the straight cuts between different letters. Mean or what? Next I popped the Tiger onto the bench to touch up a few knocks and scratches with black enamel. Then I added the walkways and 'no step' notation. So apart from the bottom lettering it looks ok doesn't it? The final touch - the registration lettering was put onto the bottom surface - those parts of the letters on the ailerons are the original! That's it - back to the scary bits chaps! Keep you posted re-maiden but this time it will be a blue sky and the weather here is terrible at the moment and we are back with heavy rain, strong winds and log fires! Terry Edited By Terry Walters on 18/04/2012 20:02:29 Edited By Katy Purvis on 31/05/2012 14:45:48 Quote Link to comment Share on other sites More sharing options...
Pete B Posted April 18, 2012 Share Posted April 18, 2012 Well, I saw it 'in the flesh' today, as it were, and I can vouch for the fact that, IMHO, it's looking better than ever for the re-fettling. Very nice job on the cowl, Terry! Just need this very English weather to pass through now and get some necessary blue sky for the in-flight piccies............ Pete Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted May 30, 2012 Author Share Posted May 30, 2012 Hi all!! Yes it has happened - it's finally back in the air! After Chris Bott had manfully put his painstakingly rebuilt beautiful DH Comet into the air recently how could I procrastinate any longer. Yesterday the forecast promised very light winds but by the time SWMBO and me had had a 'special' lunch, packed the van and got to the strip the thermic effect was already generating 10+kph winds with some meaty gusts now and again - oh and I nearly forgot the wind was ranging between 70 and 110 degrees x/wind. So did we fly? What would you have done? I had a trial flight with my Phoenix Rainbow first which went well and the wind pretended to settle down so we went for it. Short video below - enjoy!! I did! The quality is better if you watch on YouTube - here on the forum it looks a bit like someone's old Super 8 movie (No - not that sort!) What you don't see are the other 5 take-offs and landings! The take-offs were all successful but only one of the landings didn't end up on the nose!! Already filled and painted the cowl (again). Our strip has a loose surface supplied by Permagrit!! What I would give for a nice short grass strip!!!!! Needs the rigging of the top wing looking at as it's not quite true at the moment and there is a noticeable tendency towards a 'heavy' right wing. So not there yet but very pleased to have her back in the air. Looking forward to lots more flights but next time I will wait for that 'perfect day'? (Or will he?) Terry Edited By Terry Walters on 30/05/2012 19:06:48 Edited By Terry Walters on 30/05/2012 19:13:01 Quote Link to comment Share on other sites More sharing options...
Pete B Posted May 30, 2012 Share Posted May 30, 2012 Nice one, Terry! I see you seem to have adopted my 'poseur extraordinaire' style of flying - those nice slow passes.......... I'll forgive you the nose-over - the gravel-trap on that side of the strip would stop a runaway train! 'Short grass strip'. Is that a hint? If so, come on down............it's freshly-mown! Pete Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted May 31, 2012 Author Share Posted May 31, 2012 Thanks Pete - will ring you for a booking but first we have to have a day out (tomorrow or Sat?) at the club strip so we can get some pics of your CG Cub and my TM in formation?? The nose over was a disappointment but an unresistable effect of a) a biplane b) a wethercocking into the x/wind, a ineffective tail skid and an inexperienced biplane pilot. I rest my case! Cheers Terry Quote Link to comment Share on other sites More sharing options...
Peter Wood Posted June 9, 2012 Share Posted June 9, 2012 I am completeing a DB and sport, bought from a former metoer pilot who learned on Tigers, who is now unable to fly, but need to install the electric motor. The plans were cut to suit the building board, but makes it dificult to see complete picture. Can anyone sell me a copy of plan, or let me copy it Peter (Milton Keynes) Quote Link to comment Share on other sites More sharing options...
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