Martyn K Posted September 9, 2013 Author Share Posted September 9, 2013 Hi Alex Get it framed (if it is not already), I would have loved to have met the man. BW Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 9, 2013 Author Share Posted September 9, 2013 Tonight's offering. I have managed to get in the shed for a couple of hours tonight to start work on the tailplane mounting. Getting the +0.75deg incidence was easier than expected. I simply measured up from the datum on the plan and replicated the same measurements on the model. Fortunately, I had to take material away.. about 3mm at the LE and 2mm at the TE. Careful sanding to maintain the profile and as I got nearer to the correct fit I also checked that the tailplane was seated laterally at the correct angle. The fuselage is clamped in the bench vice with the upper decking checked for horizontal using a spirit level. The bench is also level! Lots of glue to hold the tailplane down and a pair of clamps making sure that the tail is pushed firmly down into the seat. Using BEB's 3 pin triangulation technique (see the Tiffie thread) - but using string to ensure that both tail tips are the same distance from the firewall centreline. The tailplane is also adjusted so that each pin is an equal distance above the bench (in this case exactly 50mm) Firewall C/L.... Underside view - with the glue being pushed out... Finally a lower view showing the carved and sanded fin outline... Now being left to dry for at least 12 hours (I sometimes get an hour in the shed before I go to work...) More to come. Next will be the fin subframe and sheeting.. Martyn Edited By Martyn K on 09/09/2013 21:21:54 Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 12, 2013 Author Share Posted September 12, 2013 A bit more progress. It's amazing how much work was involved cutting and fitting the four pieces of balsa that comprised the subframe for the fin (one piece is hidden). The difficulty was measuring the double taper (upwards and rearwards and getting all the pieces lined up so the outer sheeting would fit correctly. When dry the fin sheeting was carefully cut and glued/clamped. It was very reassuring to see that the piece I cut for the left side fitted the right side perfectly Again - left to dry for a few hours... I was really quite pleased with this after it had all been sanded to shape. Probably the neatest bit of building I have ever done. Finally for tonight, I have started to think about where the throttle servo will go. You can see from this shot that the fuel tank does not readily allow an easy path through for the throttle push rod so I am thinking of mounting the MG-90 servo roughly where it is being held. However, it may be too close to the exhaust outlet. Any suggestions? I am happy to box the servo in and heat shield it with foil, there is sufficient space to do this but the temperature in this area may be too high.. Your thoughts or suggestions would be welcome. I don't like bowden cable very much, but I could possibly route a golden rod through and mount the servo above the wing. More to come.. Martyn Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted September 13, 2013 Share Posted September 13, 2013 Martyn, is the photo deceptive or is there room to run a snake between the tank and fuselage side? I'd definitely avoid bowden cable around the engine bay as it always seem to wick in fuel which thickens up nicely to jam the cable. How would the servo function that close to a header pipe? I don't think I'd want to find out for myself but feel free to let us know how long it survives Must get back on the Mustfire build, I seem to have lost enthusiasm when it comes to building the wing. Nothing whatsoever to do with the 6" of detritus that needs clearing to gain visibility of the bench, honest. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 13, 2013 Author Share Posted September 13, 2013 Hi Bob I have had a sleep on this overnight and decided that this was a bad idea as well.. The slight problem is that although there is space to get a rod through, it needed a couple of bends to get from the correct angle for the throttle arm to bring it back into the 'servo area' above the wing. However, I have managed to get a red golden rod through this morning and the movement is quite smooth. I will also be able to use a proper sized servo as well. How Hanno managed to get 3 servo links through; throttle, mixture and VP prop control, completely defeats me, the fuselage looks huge, but its actually quite narrow. If I had gone for a wider fuel tank, I wouldn't have stood a chance. Thanks and take care M Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 13, 2013 Author Share Posted September 13, 2013 Posted by Bob Cotsford on 13/09/2013 09:18:57: Must get back on the Mustfire build, I seem to have lost enthusiasm when it comes to building the wing. Nothing whatsoever to do with the 6" of detritus that needs clearing to gain visibility of the bench, honest. My fourth most useful power tool (Dremel, Pillar Drill and Bandsaw are 1-2-3 in no particular order) is an old vacuum cleaner (an aquavac) that lives under the bench. It is marvellous for getting rid of dust, shavings , lost nuts and bolts and rarely, the wing off an indoor model.. Start building, the enthusiasm will flow back again. Martyn Quote Link to comment Share on other sites More sharing options...
Steve Dunning Posted September 13, 2013 Share Posted September 13, 2013 Good work Martyn. Nice to see the Webra in a model. To add my thoughts, throttle servo is a little close to the header to give reliable operation. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 16, 2013 Author Share Posted September 16, 2013 Thanks Steve. It's coming along - certainly not the quickest build that I have ever done, but I am making every effort to make it accurate. Which brings me to the latest update. I have been working on the lower front fuselage. This involves mainly getting the retracts and fuel tank plumbed in. The u/c plate marked up and drilled. Note the half moon at the front to provide enough space to get the tuned pipe swan neck through. I can only assume that Hanno built his in permanently, I can't afford to be so extravagant The retract in place. The front leg pivot is about 10mm further back than that on the plan - Hanno used MK retracts, mine are HK.. I have since added the lower fuel tank floor, internal and external cheeks and started carving and sanding to shape. Photo to follow... While waiting for the glue to dry I started work on the plug for the upper deck, This will form the first stage mould, a female will be taken from this and the final deck will be moulded from that. The mould is carved from four blocks of dried flower arranging foam glued to a 3/8 balsa floor. Then planed - using a razor plane - to shape. It planes very easily although it is very soft - it will crush with the slightest provacation, The dust produced is awful - you will need a mask. It needs further sanding around the font end, It will then be covered in G/F cloth and varnished/smoothed to make the plug. This will be a new experience for me, I have never made anything like this before. More to come.. Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 17, 2013 Author Share Posted September 17, 2013 The missing photos from last night. A general shot into the front wheel bay. The floor has been added and the lower cheeks have been carved and roughly sanded. I can't do any more until I fit (buy) the undercarriage legs and then fit the remainder of the block to keep the airflow as clean as possible. From this shot, it can be seen that the front former is set too low. This shows the front end with the 1/16" ply dummy bulkhead in place. Dispite being cut from the plan, its about 10mm too low. I have worked out that there is a draughting error in the plan. The former shown (and copied) - although it has the correct hole location for the exhaust and mount is actually the front section displaced up to and including the GF upper cowl. This is not where this former (F1) is shown on the plan The reality is that there is an air gap (to allow colling air to flow through) aboove the fuselage but inside the top cowling. The compunded result of this error is that my fuselage is too narrow at the top and stoo wide at the bottom. Nothing irrecoverable though. More to come Martyn More to come. Edited By Martyn K on 17/09/2013 14:57:08 Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 17, 2013 Author Share Posted September 17, 2013 I need to think about UC legs. The actuators I have have got 5mm stub legs. HK sell some oleos and wheels (with brakes!) for these retracts but they weigh in at 240g (about 8oz in old money). Is that rather heavy? **LINK** Any suggestions on getting some 8g legs fastened to these legs? Does anyone make/sell couplers? Martyn Edited By Martyn K on 17/09/2013 15:29:55 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted September 17, 2013 Share Posted September 17, 2013 Not far off, but on the Blue Angel I used a Lado retract for the nosewheel which came with a 6mm stub. I sleeved the wire leg up to 6mm with brass tube and simply replaced the stub with the fattened leg. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 17, 2013 Author Share Posted September 17, 2013 Thanks Bob That looks simple enough - I thought about doing something similar but was concerned that the tube would not be stronge enough Martyn Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 17, 2013 Share Posted September 17, 2013 Martin; I've been impressed with Oleo's from HK. I notice that the ilisted units - a selection available at different lengths come with. 5mm pin. Weight obviously varies with length, but a pair of these weighs 80g, and to be honest I don't think you will get a pair of wire legs with a spring much lighter than that. There are also nose wheels available. The problem at present seems to be stock levels but they do seem to come back into stock from time to time. Great build by the way. I'll be watching your mould making with interest. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 17, 2013 Author Share Posted September 17, 2013 Thanks Graham I need a trike set - which was the link that I used - and as a bonus it's in stock. I'll weight up a length of 8G piano wire and some wheels and compare. I am really keen to keep the weight down. Martyn Quote Link to comment Share on other sites More sharing options...
GrahamC Posted September 17, 2013 Share Posted September 17, 2013 You can buy a single cranked nose leg to go with those.... But then stock issues again.... I suspect that quite a bit of the weight in the ones you linked to is in the hubs which include brakes. They might be heavy but it would be a very cool feature! Wind up to full power and then release the brakes.... Not quite in the spirit of Classic pattern maybe! Quote Link to comment Share on other sites More sharing options...
Bill Michie Posted September 22, 2013 Share Posted September 22, 2013 Hi Martyn, just caught up with your thread again.............. I take it your Webra is the .80, as it's pumped with red head & carb cover; if so it'll turn large pitch props really well! Bill Webra fan.................. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 22, 2013 Author Share Posted September 22, 2013 Hi Bill Nope, its the .60.. It came with a 12x10 prop = much larger pitch than I am used to.. BW Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 22, 2013 Author Share Posted September 22, 2013 Some more progress - lots of sanding and not much else... Some help needed - please see below.. Started work on the front cowl. Basically, its 2 pieces of lite ply backbone and all the parts glued to it have been partly split in case i need to split the plug into 2 pieces Adding reinforcement to try and keep it all square. In the meantime, the shroud plug has been subject to more sanding.. Sanding this outside because the dust is awful.. I have also added more reinforcement and extensions front and rear. I'll make it too big and cut it back.. A trip to B&Q (to buy fence posts) and I spotted this - I think its the pink version of blue foam that is used in foam wing cores. If so, it's a nice manageablesize, 60mm thick, about 600mm wide and just over 1m long. Cost about £7.00 per sheet. I am using this for the foam fill for the cowl plug. This is all the info I have to show me what the front end should look like. In addition to the plan, but there is no detailed section information. About as much use as a chocolate fireguard. Before I started carving then sanding And after about 3 hours work. There are a few dings to fill, but it's 99% done. HELP - A couple of questions. How do I seal the foam and finish it? I need to get from this granular surface to a high gloss mirror surface. Any suggestions please. Can I make a single mould from this cowl plug (without splitting it)? If I split it, I will add flanges to each half so that I can cut back, but if it can be made in one piece that would be Magic.. The air intake has quite a narrow lip on the lower edge. I appreciate that I may need to make this wider, but what is the narrowest that I can get away with? I need to get release agaent, gel coat and cloth into the mould . What weight cloth should I be buying for the cowl and the shroud. The shroud is very lightly loaded, the cowl gets the heat, fuel and heavy handling etc so I guess this will need to be much heavier cloth. This week, I'll be buying the materials to make the mould and also the finished item (hopefully). Thanks Martyn Quote Link to comment Share on other sites More sharing options...
Braddock, VC Posted September 22, 2013 Share Posted September 22, 2013 To answer Q1, cover the plug in profilm then polish that and put mould release gunge on it prior to making your mould. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 22, 2013 Author Share Posted September 22, 2013 Thanks Braddock. I think that would work well for the shroud,however, the cowl has a lot of very intricate curves and I don't think I would get to cover properly.. I was actually thinking od covering it in glass cloth and then 6 or more coats of varnish and sanding down inbetween each coat, then poliching then release agent etc.. I'll see what other suggestions I get. Martyn Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted September 23, 2013 Share Posted September 23, 2013 Martyn, if you go that route then why not use epoxy with the glass rather than varnish and just melt out the foam to leave you with your cowl? Hi-build primer, sand and paint - job done. You would want at least a couple of laminations of 1 or 2oz cloth to give it any strength. Some ARTFs seem to use a single lamination of something like 2oz but they can be a bit fragile. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 23, 2013 Author Share Posted September 23, 2013 Hi Bob An interesting thought - something I hadn't really considered. I could still put release agent on the plug/mould and just pull it when the top has hardened. It would be easy enough to do this and if I am not happy with the result then I can still revert to plan B (providing I can keep the plug in one piece. Thanks Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 24, 2013 Author Share Posted September 24, 2013 I have had a contribution from Danny Fenton in the form of a PM. Copied here for posterity: ========================== On 24/09/2013 14:11:44 Danny Fenton wrote: Hi Martyn, the finish I get on the blue foam is really nice and i do it with those foam packed sanding pads that you can get from Halfors. I tend to take the newness off by using them on balsa or ply first, then they sort of buff the foam. However the foam is not strong enough to use as is and needs a layer of glass cloth (25gsm skinning cloth) applied with EPOXY resin. Once cured brush on another coat of resin and once that is cured you can sand it with normal abrasives and apply filler/primer etc to get it super smooth for making a mould. If you are making a one-off, skip the mould, just skin with perhaps a couple of coats of skinning cloth, and when hard dissolve out the foam with thinners you are left with a hard shell. Hope this helps? Cheers Danny ========================= ... Thanks Danny! Edited By Martyn K on 24/09/2013 14:27:37 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted September 24, 2013 Share Posted September 24, 2013 Hi Martyn, no problem at all, sorry I didn't see your plea for help, your thread slipped past my radar. I think I have just said what others had already really. The one thing I will say about blue foam (never tried the pink) I find it has to be one piece, (if multiple pieces are joined keep the glue from the finished surface) this is because the stuff sands so easily anything that isn't foam will alter the ease of sanding. I would not have used ply to give you the shapes, just simply used the foam alone. Magic is looking er.... magic Cheers Danny Quote Link to comment Share on other sites More sharing options...
Martyn K Posted September 24, 2013 Author Share Posted September 24, 2013 Hi Danny Thanks for that. The reason I used a ply subframe on the cowl was in case I had to split it to make 2 paired moulds. I am hoping that I can do it in one piece... It has sanded OK, it just needs final sealing and finishing before I worry about the mould. Many thanks Martyn Quote Link to comment Share on other sites More sharing options...
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