Martyn K Posted November 14, 2016 Author Share Posted November 14, 2016 Thanks kc Yes a very good point.I always really considered the middle clamp to stop the leg from sliding sideways but of course there will be a toque load on it as well. I'll double check on the materials list, I have since thought about a couple of other items needed. 1/16 sheet is the biggie tough Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted November 16, 2016 Author Share Posted November 16, 2016 The two fuselages got their first public airing at the pub last night (club meet - honest) and no horror stories were identified. So cracking on with the wing. Apologies for the lack of progress reports etc, but I did set myself a rather challenging deadline... The webs between the front spars have been fitted - grain vertical an then sanded back flush with the top of the spar. I put the webs behind the spar as I believe that it adds greater stiffness. Once the spars and LE were in place it was time to add the TE sections. The upper side added first and also encloses/covers the ailerons. This helps keep everything nice and flat. I will separate the ailerons after the lower sheeting has been added/completed. Cut the sheet slightly too wide and almost cover the rear spar. Need to leave about 2mm at the edge to provide a base for the cap strips. Fit both halved, using begs to secure the sheet to the ribs and the rear spar When dry, trim back the TE sheet to the chord width, not the end of the ribs and carefully sand a very slight chamfer - not to a point though or it will warp when the glue is applied. You can see the chamfer in this shot. Note that the bottom sheet does not cover the aileron - yet The ply dihedral brace is added. Only links the centre 2 bays but will get additional reinforcement when I fit the u/c bearers which run across the centre section The upper LE sheeting added with lots of pegs and pins to hold it in place. The upper centre sheeting has also been added. That's it for tonight. Tomorrow its the undercarriage and wing bolt plates and the first dry fit of the wing to the fuselage. That is when I will really find out whether the CAD is accurate... Sorry its all a bit terse but I need to spend more time building and less time typing. More to come Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted November 18, 2016 Author Share Posted November 18, 2016 The KF4 has been put aside until the wing ribs arrive from Dylan So getting on with the KF3. I know the undercarriage layout I am suggesting will upset some. I cant claim its my idea though, I stole it from Mick Reeves who used it on the new Gangster. It never failed on my model, although I have made a few changes The hardwood block that doubles as a wing brace and torque block for the undercarriage - 12x6 mm beech inlaid into the centre rib and out just past the next rib on each side (W2). To accommodate the dihedral, the slot in the centre is about 1mm deeper than at the next rib. This is glued to the ply dihedral brace The 3mm ply undercarriage mounting plates inlaid into W2,3 and 4 and glued to the webs behind the spar. 25x12x6 hardwood blocks glued under the plate and butted to the rib. These carry the wood screws that hold the saddle clamps. Sorry for the messy glue. I only spotted it after the photo was taken The plate is also reinforced with 6mm triangle strip to the web The undercarriage legs are bent and clamped as shown. This wont break and I actually think that it is stronger than a conventional hardwood block. There is more surface area to carry the impact load and the torsion load is transmitted to the torque block linked to the dihedral brace. . . So - now I have a fuselage, a wing and an undercarriage - so time for a dry fit Weight at this point is 1.31kg . that is with engine, fuel tank and 1 servo in the tail at the moment. Looking like its heading for an AUW of 1.7kg - less than 4lbs.. It will be very Kwik Time to get on with ailerons. The ailerons are top hinged with a slot in the lower side. The push rod actuation point should (ideally) be in line with the hinge. This means that conventional horns would be difficult to fit. Two hand crafted horns from glassfibre sheet created with slots to fit into the upper and lower aileron spars, Dry fit tested then glued into place using epoxy The exact location depends on the servo arm that will be used. Because of the actuation distance from the push rod linkage to the hinge, a long servo arm will be needed. Adjust the width then pack into place with balsa each side and allow to dry. Back on the fuselage, the rear servos (standard size) have been fitted into the fuselage. I was intending to use Midi sized servos but the CG was looking like it was a little too forward and I had these Spekky servos spare. I dont like them sitting too proud so a 3mm ply securing plate was fabricated and glued around the full sized slot cut into the fuselage side. Its a very tight fit but both elevator and rudder servos have been test fitted and removed while the glue dries They fit...One on top of the other on opposite sides Horrible woodwork that will be cleaned up when the glue dries. More to come Martyn Edited By Martyn K on 18/11/2016 21:50:56 Quote Link to comment Share on other sites More sharing options...
IanN Posted November 18, 2016 Share Posted November 18, 2016 Quote Link to comment Share on other sites More sharing options...
kc Posted November 19, 2016 Share Posted November 19, 2016 The tiny defects Martyn mentions look like dents. Those tiny dents could probably be fixed without any time or effort by the old trick of putting a tiny drip of water into the recess and just letting it swell the balsa. It's magic! Far better than filler! ( I expect Martyn knows this trick but there will be others watching this who perhaps do not ) Quote Link to comment Share on other sites More sharing options...
Martyn K Posted November 19, 2016 Author Share Posted November 19, 2016 Cheers kc Yes - I use the water trick, its a great way of removing dings - especially those caused by putting a newly sheeted wing down on something hard on the bard while you sand down the other side. It only takes a little water and best applied with a brush rather than spray - you don't want the wood to warp The problem I had with the cut outs was the refusal of anew scalpel to cut through the balsa cleanly... a little bit of hacking was required. It will be invisible when the servo is fitted but that is not the point... Nothing done today, I have been out for the day Christmas shopping Martyn Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted November 23, 2016 Share Posted November 23, 2016 Martyn, hopefully you are shopped out now and back at the building board(s). I don't fancy the MB Skywriter myself but a Kwik Fli 40 - Electric, is another matter. I have an Axi 2826/12 and several 4s LiPos which would be suitable I think. So yes, I would like to build one when you have the finalised plan ready. If you were able to email the PDF plan as an attachment that would be fantastic, I can get it economically printed locally. Following the rest of your builds with interest and good luck with the maidens. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted November 23, 2016 Author Share Posted November 23, 2016 That's great - thanks Piers. Plans are very nearly ready to release. I was going to do two variants of plane. A set that is organised for optimised tile printing and another standard set plus DXF files for those who want to use their favourite laser cutter. The first laser cut set of parts for the E version of the 4-40 should be with me tomorrow or Friday, I'll build the wing and if all OK I'll publish the plans Best wishes Martyn Quote Link to comment Share on other sites More sharing options...
IanN Posted November 23, 2016 Share Posted November 23, 2016 Yes, I'm also definitely in for one of these. An E if I already have the components to hand, otherwise it'll be i.c. Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted November 23, 2016 Share Posted November 23, 2016 Martyn, any thoughts about the aileron hinging. Would (on this size) it be possible to create a hinge using the film used to cover the wings? A 2.5m glider I have uses tape hinges for both flaps and ailerons (using clear cellotape). This has hold for 3 years now and that plane often flies faster then my F3A planes. Lucas. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted November 26, 2016 Author Share Posted November 26, 2016 Apologies for the delay. I have been away for 2 days and additionally, 2 nights total lack of sleep have taken their toll. Lucas - yes - top hinging is not a problem, You would just need to adjust the rake of the aileron slightly but that could easily be accommodated. I would use a heavy film rather than sellotape if using an ic model though.. I would hinge from both sides though. Hinge and seal the top, fold it over so the aileron is lying flat on the wing then hinge the lower edge. A bit of progress on the KF40-3. Still waiting for the KF4-40 parts though Aileron(s) has now been separated. You can see the web supporting the aileron horn here Balsa hinge blocks glued into place. These are from two pieces of 3mm balsa but not glued in the centre where the Mylar hinge will be fitted The whole lot is then carefully sanded to get the correct rake - top 4.5mm as well The rear edge of the wing is sheeted with 1.5mm balsa in the aileron well and blocks added for the hinges on the wing side. Again - not glued along the upper edge where the hinge will be fitted The aileron section looks like this (before it gets a final sanding polish). The hinge line is along the lower edge of the upper spar. While the glue was drying, the beams for the aileron servos have been added. The slot is offset slightly because I got it wrong and didn't allow a big enough gap to get the servo cable out.. While that glue was drying, the elevators were cut out, sanded and joined using 14swg piano wire - not dowel as I have drawn on the plan.. Another correction.. And while that was drying, I finished the cowl. Note the hardwood blocks top and bottom that locate on the nylon mount and support the self tap screws. Probably the best fitting cowl I have ever made.. And the 1/32 ply reinforcement where the silencer is located..A worthwhile addition. The bearers for the engine throttle servo added. I'll be using a MG90S but modified to sit in rubber grommets, easily done, simply drill the retaining holes to M4 The model has been covered and trimmed and it weighs this much less the flight battery and receiver. 3,77lbs in old money so the sub 4lb target will be achieved And it looks like this and and This is 1967. The BMFA didn't exist and aeromodellers were engineers Elevator and Rudder Servos inlaid into the fuselage Carbon Fibre push rods and a little camera shake..(sorry) Underneath has my now standard contrast/invasion stripes and Quote Link to comment Share on other sites More sharing options...
IanN Posted November 30, 2016 Share Posted November 30, 2016 Posted by IanN on 23/11/2016 09:11:48: Yes, I'm also definitely in for one of these. An E if I already have the components to hand, otherwise it'll be i.c. I've decided that I rather fancy a go at the Kwik Fli 40 IV Having hunted through the various draws full of bits it seems I already have a suitable electric powertrain aswell as a few Irvines looking fro a good home, so I'm spoiled for choice Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 1, 2016 Author Share Posted December 1, 2016 Thanks Ian - that's great. The KF4-40 Electric parts arrived on Tuesday and I needed to carry out a sanity check. This is what the 'kit' looks like. There were a couple of drafting errors, the long battery tray was 1mm too wide at F2 and F3 - easily fixed on the drawing, the lower ESC hatch was 2mm too long - again - easily fixed. One stupid error was that I had 4 of W8 and no W6 - so that has been fixed as well. I had to cut 2 W6 this morning. One problem I do have is that I assumed that 3mm ply would be - well - 3mm thick. It clearly varies as this ply was only 2.75mm wide. So the interlocking front section is a bit sloppy. I am not sure what to do about that at the moment. I have checked other 3mm ply that I have and there does seem to be a slight variation in thickness. Last night I tile printed the plan out - 6 sheets of A4 for 1/2 wing - and joined it up. Another slight error which I am not sure where it came from is that the main spar on the plan seems slightly displaced. It may be a parallax error but I am not losing sleep over it. So, this morning, I hacked through the ice to get to the shed and started building the wing. Main spar pinned down. Note the doublers. The slots in the ribs are 6mm square, I am using 1/4" square so the slots need opening very slightly.. The 300mm rules gently weigh the ribs down so they sit flat on the building tabs. Again - note the offset to the end of the doublers. All fitting nicely.. More to come Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 13, 2016 Author Share Posted December 13, 2016 A bit more progress: W1 is split to allow the doubler to be fitted. It is better to do this before you glue it into place Set the dihedral before the brace is glued. I use clamps to gently hold it together while the glue sets. Use the build tabs in the wing half that is lifted to make sure you don't build a twist into the wing. Prop a suitably sized piece of wood to set the correct dihedral angle. While the glue was drying I fabricated a couple of aileron horns from Glassfibre sheet. I did consider trying to fit shop bought horns by angling them forward but it looked messy and compromised the structure too much. The shape isn't critical - a large glue area is a good idea though With the horn glued into place (with slow setting epoxy) against the end rib of the aileron, the lower aileron sheet was added. I was asked it the ailerons can be top hinged. The answer is basically yes - but instead of fitting the 1/16" balsa aileron cap sheet on top of the ribs, it will need to be inlaid like this. Its a bit tricky but not too difficult. The 1/16" balsa cap on the TE of the wing for the ailerons is still fitted on top of the ribs. This is what the (blurred) cross section looks like at the end of the aileron. You can see there is not a lot of the top spar left after sanding to fit. The 3mm ply wing bolt support plate added. Another oversight on the plan - I forgot to include slots for the plate All these minor errors will be corrected. Undercarriage mounting plates added - after the webs have been fitted. A moment of panic when I couldn't find one of them. Eventually traced to the dustbin... You can see the balsa infill above the hardwood brace between the the plates The rear half of the W1 and the 1/16" ply dihedral brace added as well The short hardwood block (4 off required) for the saddle clamp screws and triangle section between the plate and the web Another thing I had overlooked was the missing half rib 4W7C that holds the aileron servo blocks. This is a replica of the main 4W7 rib and will need to be trimmed to fit depending on the width of the aileron servos that you choose to fit. This part is now included in the wing rib cut files. With it all assembled and sat on its undercarriage legs it looks like this and some seasonal decoration Underneath - you can see the lower vented hatch in this shot. Quite pleased with that. Running about 3 weeks late but it was a bit of a silly challenge to take on in hindsight. Next job is fit the aileron servos, get an estimate for the loaded CG, fit the R/E servos in the rear or in the fus and cover it Nearly done. More to come Martyn Edited By Martyn K on 13/12/2016 14:10:19 Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 13, 2016 Share Posted December 13, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 13, 2016 Author Share Posted December 13, 2016 Thanks Percy. When completed, I will have 4 different KF variants to choose from and I am still thinking about building a 115% version of the IV for an OS120FS. Something about this design I just love - I think its the Fin shape, but the whole model just looks so right. Martyn Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 13, 2016 Share Posted December 13, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 13, 2016 Author Share Posted December 13, 2016 There are 2 versions described in this blog. A Kwik Fli III (as used by Phil Kraft to win the 1967 W/C) with parallel chord wing and the Kwik Fli IV (used by Larry Leonard to win the 1969 US Nationals) with tapered wing. That was the last of the KF line.. Both have been scaled by about 0.9 (just slightly less in fact) to accomodate a 40 sized IC or electric equivalent There are IC and electric versions of both - so a total of 4 options to choose from. Its like trying to choose a dessert in a good quality restaurant.. Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 13, 2016 Share Posted December 13, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 13, 2016 Author Share Posted December 13, 2016 I built the Flea Fli about 4 years ago. Its a great little flier - I never really got it trimmed - used cheap servos and regretted it afterwards It still flies well but a little too twitchy to be described as a precision aerobatic aeroplane Martyn Quote Link to comment Share on other sites More sharing options...
Simon Feather Posted December 13, 2016 Share Posted December 13, 2016 I've just started building a 100% scale KF3, to accommodate an OS61: build blog to follow in due course. Martyn, like you I too have used wire to join the elevators rather than dowel as shown on the original plans, this seems a somewhat safer solution. Simon Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 13, 2016 Author Share Posted December 13, 2016 That will be great Simon - looking forward to seeing it in due course. Keep it as light as you dare.. AUW target should be 6lbs. Are you building a sheet box fuselage or open rear frame as per the original plan? Martyn Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 13, 2016 Share Posted December 13, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Simon Feather Posted December 13, 2016 Share Posted December 13, 2016 open rear frame is the plan as per original! But I'll make some other concessions, such as using wing bolts not rubber bands to hold the wings on. Original has solid fin, I may do built up instead to save a little weight in sensitive place. Just about to start on the rib templates to create my rack of ribs. Quote Link to comment Share on other sites More sharing options...
Peter Burgess Posted December 13, 2016 Share Posted December 13, 2016 I certainly would be interested in a 115% KF 4 Any I dea what wing span that works out at? Quote Link to comment Share on other sites More sharing options...
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