Lucas Hofman Posted January 10, 2017 Author Share Posted January 10, 2017 True. When I was at university the Fokker the Fokker F28 was in its final design stage. Fokker had some throuble with weight creep and offered a bonus to all employees to come up with ideas to save weight. The amound was - if I remember correctly about 10 GBP per gram. The results was a couple of hundre kilograms saves. By a few hundred grams here and a few hundred grams there. Rough calculation is about 4 grams saved at the tail. Since I expect some lead will be needed in the cowl the amount of lead saved is about 20 grams. That is 24 grams saved with about 10 minutes of work. It is up to the builder if this is worth it. Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 11, 2017 Author Share Posted January 11, 2017 Weight difference is 1.4 gram. It was (for one elevator) more then 10 minutes work. I very much hope that there is weight in the cowl to save, otherwise it is quite meaningless.... (but then, as my wife says, it keeps me off the streets) Lucas Quote Link to comment Share on other sites More sharing options...
Simon Feather Posted January 11, 2017 Share Posted January 11, 2017 Going well, Lucas - I'll catch up with you eventually but need to finish my KF3 anniversary build first. I don't think I'll bother with those lightening holes! Simon Quote Link to comment Share on other sites More sharing options...
Rob Ashley Posted January 11, 2017 Share Posted January 11, 2017 Lucas, You are doing a very neat job - I am watching this with much interest. As your wife says 'If it keeps you off the streets" then cutting them out must be good. My build of a Peter Miller Grumpy Tigercub (enlarged to 72" span and retaining IC engines) has stalled in the last couple of weeks, but having read this forum I am beginning to rejuvenate my enthusiasm. Keep going Rob Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 11, 2017 Author Share Posted January 11, 2017 Thanks for the nice comments gents Looking forward to glueing the tail feathers together tonight. The weather is deplorable which makes the workshop a nice place to be! Lucas ps. found out yesterday that pull-pull wire and clamping pieces are very good to hang paintings on the wall with! Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 11, 2017 Author Share Posted January 11, 2017 The rest of the holes went quickly. This evenings results: and I bought all wood in the UK so the thickness of the tail feathers will be 1/4 inch (6.1mm). The rudder and elevators are build up from 3/32'' (2,4mm). They will become 7.2mm thick to start with, and will therefore need some sanding. Reinforcements are 2mm light ply (at last can I use it for something). Tomorrow the reinforcement on the other side. Lucas Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted January 11, 2017 Share Posted January 11, 2017 You're a much neater builder than me Lucas I thought the bottom piece on Fin was square from t.e - l.e ? John Quote Link to comment Share on other sites More sharing options...
Chris Barlow Posted January 11, 2017 Share Posted January 11, 2017 Agreed Lucas, best to save weight from the beginning and at the tail if you suspect you'll have to. My wife says if I spend too much time in the workshop I'll be out on the streets! Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 12, 2017 Author Share Posted January 12, 2017 John, it is the leading and trailing edge stock that keep the fin vertical. The bottom piece, with the grain lengthwise, does little in preventing the fin from bending when loaded sidewise. The bottom piece needs to hold the covering (keep in mind there will be no covering where it it glued between the side pieces). I had loads of 1/4'' square left after the ballerina wings, and a 1/4'' piece of scrap that fitted at the bottom. Had that piece been wider it would have been square. There is no deep thinking here Yes, I think I build quite neat. But very slow too. I estimate Peter Miller builds about 3 planes for me doing one. And then he designs them too. Mine may look a little better, but I am sure the fly the same, so I am not sure what to prefer. On the other hand, I would not enjoy not building neat, and that is the purpose of the whole activity isn't it. Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 12, 2017 Author Share Posted January 12, 2017 Chris, I majored in aerospace technology (although I never worked in that field). On any full size you will not find a rib, former or rudder horn without lightening holes wherever possible. I think the mindset sticks. Our models have usually much more power compared to full size planes, so the need to shave weight both here and there is less. I may very well be that the most honest answer to the question "Why do you save weight Lucas?" is "Because I can". So do not worry too much about it. Lucas Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted January 12, 2017 Share Posted January 12, 2017 One of my main problems is that I am always thinking of the next model while building the current one Also I admit that I am lazy and want to get the current project in the air. From time to time I do get the urge to build sometthing rather special and can produce a good model. For a few years I scratched a living making desktop models (mainly sailpanes) in lime wood to order. There I did have to achieve perfection and it was a constant strain. It also took away most of the pleasure of my own modelling. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted January 12, 2017 Share Posted January 12, 2017 Yep i follow that Lucas. Nice desktop model there Peter John Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted January 12, 2017 Share Posted January 12, 2017 Hallo Lucas, Very tidy approach as usual. But may I allow me a question, please. In your quest for tail lightness, why didn't you decide for 'build up' tailplanes as you did for your Ballerina? Possibly even with some 'laminated' LE & TE? Cheers Chris Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 13, 2017 Author Share Posted January 13, 2017 Hi Chris, I wanted to have the "ribs" showing through the covering for the elevators and rudder. In addition the radius of the corners of the elevators is very small. But as you can see in the picture below the LE of the stabilizer is laminated. Al the leftovers from the Ballerina spars find there destination here. Quite of bit of air compared to the original. I intend to put 1/4'' square where the stab leaves the fuselage (to attach the covering) and leave the center empty. Glueing LE and TE should secure the stab well enough I would think. Or do I miss anything here? Lucas Lucas Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted January 13, 2017 Share Posted January 13, 2017 Nice, Lucas. I see your point now. If I'm right, there is still the 4th stab rib missing to the right of the pic. If you leave the centre section 'open', I would add a spanwise straight doubler at your laminated LE for reinforcement between those 4th stabs and then add your two 'covering support' pieces. Just my 2 euro cent, here. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 16, 2017 Author Share Posted January 16, 2017 Only a little progress this weekend (but quite a bit of flying). The stabilizer is glued together. Next is hinging, making the elevator joiner and rounding of or bevelling all sides. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted January 16, 2017 Share Posted January 16, 2017 Tidy job there, Lucas. I see that you added a doubler to the LE & TE... and that your small 'Banggood bottles' did arrive. Cheers Chris Edited By McG 6969 on 16/01/2017 17:14:02 Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 17, 2017 Author Share Posted January 17, 2017 Yes Chris, I did. The doubled leading and trailing edge provide enough glueing area to hold the stabilizer in place. The whole stabilizer is stiffer then anything I have made before - the "ribs" could very well have been 1/8x1/4mm (6x3mm). This stab was made of the leftovers from the Ballerina. The next one will be leftovers from the skywriter, which will include 6x3mm stringers... Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 18, 2017 Author Share Posted January 18, 2017 Fitting the motor to see where the firewall will come. I will use a 3542-800kv motor on 4S. That motor is, including the propeller mount 46mm long. Including the motor mount will bring it on 49mm. If we want the backside of the propeller 4mm in front of the cowl (the 2 degrees downtrust will make it nearly touching on the bottom right side of the cowling then the firewall move about 20mm forward compared to the drawing: A pleasant side effect is that the hatch becomes 20 mm longer, which will make inserting the battery easier. And the battery moves 20 mm forward too. Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 19, 2017 Author Share Posted January 19, 2017 Marking the firewall. To get the center of the propeller in the center of the plane the motor mount need to be a little up an to the port side. 50mm (the length of motor, mount and half the propeller) x tan (2 degrees) is about 1.9mm. Rounded up to 2 and marked on the wood: Note the strip on the bottom that has to be cut off due to the firewall moving forward. No holes (except for the center) - I want all air to go under the firewall, flowing around the ESC that will be mounted under the battery plate. Thereafter up around the battery and out trough holes in the cockpit. The latter is unusual but since this plane, like the Ballerina, is mostly used on snow and ice I do not want holes in the underside of the fuse. They may scoop up snow that then melts inside. Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 22, 2017 Author Share Posted January 22, 2017 If one want a backmounted motor and the battery immediately behind the firewall the shaft needs to be shortened. Here one needs to keep in mind that and metal dust will gladly be sucked in the motor by the strong magnets there and will do no good. Probably the best method is to remove the shaft and shorten it on a lathe, keeping the bell far away. But this comes close: Put a piece of masking tape on a zip-lock bag. punch a hole in the bag 1 mm smaller as the axle. Seal the hole in the back of the bak. Put the motor inside, axle through the hole. a piece of wood for physical protection of the bag and a cutting disk on the Dremal make short match of the surplus axle. file any sharp edges Do not forget to vacuum clean the outside of the bag and your hands before opening the bag and your are done. Now the battery will not be punched by the motor shart protuding through the firewall Cheers, Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 23, 2017 Author Share Posted January 23, 2017 Big pieces feel like much progres! Cut the fuselage sides and the doublers tonight and glued them together. Hurray for 3M 777 permanent mount spray glue. Very quick and consistent glue thickness and (since it is not water base) no warping of the wood. Although chances of the latter are not big anyway when "clamped" like this: "Clamping" this way slows the drying process a lot. Not an issue with sprayglue, but when using white glue or aliphatic glue it takes much longer. Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 25, 2017 Author Share Posted January 25, 2017 Small steps. A little progress on the fuselage sides: Quote Link to comment Share on other sites More sharing options...
Chris Barlow Posted January 25, 2017 Share Posted January 25, 2017 Brilliant machines once you get used to them! That's a lot of cutting. Wouldn't fancy doing all that by hand! Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted January 26, 2017 Author Share Posted January 26, 2017 Last night I attended a club meeting where the reigning F4C (scala) champion of Norway showed his model. That was a Stearman, sort of a Skywriter but twice the size. Fuselage sides are ready now: I had to make a wing template to sand the shape in the fuselage sides accurately. Lucas Quote Link to comment Share on other sites More sharing options...
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