john carpenter Posted March 3, 2009 Share Posted March 3, 2009 Andy Please get in touch. My computer has been down (busted and now rebuilt) and I need to advise on your fuselage build urgently John Carpenter Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 3, 2009 Author Share Posted March 3, 2009 Oh Oh....................... Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted March 4, 2009 Share Posted March 4, 2009 Good job its dark because we are all in it with you Andy ,cant wait for the next installment Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 4, 2009 Author Share Posted March 4, 2009 Well good news. John has spotted a potentially serious mistake, but fortunately an easy one to fix. The fuselage has a 1/32 ply sheet section on each side, as can be seen. Also, as I have been detailing, I have added a 1/4" square strip around the perimeter to add strength and rigidity. Unfortunately this was wrong- it should have been a solid 1/4" thick sheet the whole size of the ply. I can understand how I made the error looking back at the plans, but the term doubler would probably have steered someone more experienced to realise the sheet was required. Anyway, as John keeps reminding me- it's only wood! And fortunately today I was able to sneak off early and drive to Blackburn to pick up some 1/4" sheet- so it shouldn't hold me up too much. I don't plan to remove the strip I have added, but to use the sheet to fill the gaps. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted March 5, 2009 Share Posted March 5, 2009 Thats a relief Andy we were all of a tither Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 5, 2009 Author Share Posted March 5, 2009 Well John has written again and told me my infil plan isn't going to be strong enough, so I will have to strip off the side formers and perimeter. Makes the job a bit longer, bu nothing really serious as I now have enough wood to do the job. I am interested though, in why John thinks it will be too weak. Perhaps one of you that knows about these things could explain. I can see the whole lamination adds a lot of strength, but to simplify the picture, lets assume the ply sheet is a simple rectangle- maybe 12"*4". If I attach a 1/4 sheet length ways along this ply sheet I will add a lot of rigidity, but the grain of the balsa will mean there is a lot of that strength length ways- ie the 12" sides will not bend. But I would have thought the 4" sides would be more flexible because they run across the grain- so there might be some flex that way. I would have thought a strip running vertically across in the middle of the 12" strips would have added some rigidity in this direction, without compromising much of the lateral strength. Obviously I am wrong, but I'm not sure why- the only thing I can think of is the vertical formers act to give the strength in this direction. Must be that! Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 5, 2009 Author Share Posted March 5, 2009 Oh, and just to keep people up to speed, last week I was getting a bit fed up with thinking for an hour before glueing a single piece in place! I decided I needed something that would show quick results and rapid progress, so I got out the mirror image wing sheet and have done a load of the second wing- no photos- it's identical to the first one..........well it's a mirror image, but you know what I mean! It's funny, but I clamped the 2 wings together- just for a look- and that gull wing is a very menacing shape. Quote Link to comment Share on other sites More sharing options...
Ken Lighten Posted March 5, 2009 Share Posted March 5, 2009 Andy, The simplest thing I can suggest in relation to the ply/balsa lamination is to make yourself 2 test pieces, one as per your existing structure and one as per John's plan. Try bending them and see for yourself which is strongest - I know where I'd put my money!! Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 5, 2009 Author Share Posted March 5, 2009 Ha Ha, There is no need- I trust him far more than my ideas- the question for me is why. I just like to understand these things. Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 8, 2009 Author Share Posted March 8, 2009 Well more rubbish weather, but work has meant just a single day of building this weekend. I decided to bite the bullet and get this pesky fuselage built properly. This consisted of stripping off all the 1/4" square "edging" I had put around the ply sheet. Then I needed to cut the ply formers to allow the new 1/4" balsa sheet to pass through, as I had cut it to just pass the ply sheet through. Stripping the edging wasn't too bad. To cut the ply I almost tried to take the formers off, and almost bought new ply and thought about rebuilding the front fuselage completely. In the end I patiently cut slots through the formers with my dremel clone and its saw blade. This was the first time I had tried that, but it worked pretty well. Unfortunately some of the shaped side formers needed removing. So although it was pretty time consuming it went ok. Then it was simply a case of cutting a new panel to match the ply sheet, and gluing it in place. Once it was dry, turn it over and same again on the other side! Now I am regluing the side formers back into place, and I am back to where I was a week ago (except my fuselage won't collapse I suppose!) Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 15, 2009 Author Share Posted March 15, 2009 Almost a week since my last update, and building has slowed due to work commitments. The fuselage is back to it's previous state. One thing I realised is that I had dislodged a number of sections on the formers where I had held them whilst either dislodging the old stuff I was removing or fitting the new sheets. I had to carefully check every part of every one and glue a number back secure. I have also got the second wing to the same stage as the first. This will now become awkwards to proceed with as I am missing a number of parts- oleos being the main one as I wait for Mick Reeves to make up some 1/4 scale ones. Then I need to really start making my mind up about servos and mounting them! Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 15, 2009 Author Share Posted March 15, 2009 Well, some proper progress! I built a tail! This would have been very quick and easy, except for the fact that the horizontal stabiliser and elevators are erm....built in. The other problem is trying to build square- there doesn't seem to be a single horizontal line in the plane to act as a reference- well unless I have built it really wrong! The problem with the stab is making sure it would go in after the tail was built up. I initially planned to put it in place then build over it. Obviously it needs to be horizontal, and I figured that using a spirit level across fuselage had too much scope for error, as the fuselage is quite slim. I decided to wait until later to add it, probably when the wings can be added to give me a better idea of the plane being straight. Instead I left the space for the horizontal stab clear, and built the tail up. It was easy once I decided to glue the ribs onto the post before I fitted the post to the back of the plane. Once I had done that everything fitted together quite nicely. Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 15, 2009 Author Share Posted March 15, 2009 Having built the tail I got an irresistable urge to play, so I clamped the wings together, and sat the fuselage on top- guess what- it actually looks like there's a stuka in there somewhere! Quote Link to comment Share on other sites More sharing options...
Chris C Posted March 16, 2009 Share Posted March 16, 2009 you can really see the out line of the finished product, have you found a siren yet?? Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 16, 2009 Author Share Posted March 16, 2009 Not yet, but I need to start making a decision. There are 3 problems that need to be balanced. 1) Cost. I can get a ready built system for about £200 all in. There are some question marks about how effective they are for the single LOUD noise I want, rather than a continual engine for example. 2) Weight. I am really talking about speaker weight here- a powerful speaker uses heavy magnets. 3) Authenticity. It needs to sound like the real thing, otherwise it's not worth doing. I can extend my procrastination by working on the dive brakes first, but I think siren needs to be considered soon. Quote Link to comment Share on other sites More sharing options...
Kelly Posted March 16, 2009 Share Posted March 16, 2009 What a fine model great thread, one of my fave WW2 aircraft . Nice build Andy Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 18, 2009 Author Share Posted March 18, 2009 Well I have had a very interesting, and head scratching couple of days. I have decided it's time to think about all the electronics in the wings. I need a lot with 4 flaps, 2 ailerons and 2 dive brakes. Oh, and a landing light! I have decided to start on the dive brakes. The ones shown on the plan are static, and for a good reason- they are apparantly completely ineffective on the model. Only an idiot would make the plane heavier, more complicated and more expensive just to have "working" dive brakes that no one can see and don't actually work! And that's exactly what I plan to do! So, how do you build working dive brakes- because my stuka will have them! I had an email off a guy with a Ziroli stuka who has made working brakes on his. He had sketched out some of the supports and hinging that he used. It's a good job, because I was struggling to find a clear picture. Anyway, I decided the best thing to do would be to build a dummy dive brake and run a dummy instalation. This would make sure everything works as it should. So I cut out some ply shapes and drilled them. I also cut a dive brake out and some little ply "lugs" that I cyanoed onto the divebrake to attach it. It looked pretty good for a first attempt: The hinge is made from some pushrod. It runs the whole length of the dive brake, but it's a dummy, and it's easier to do it like that. You can just see the wooden lug that also has the rod passing through it. The brake is upside down there, and the scrap sheet is the underside of the wing. The hinging was easy enough, and using one long hinge is a good idea for making sure everything aligns before glueing. The rod can then be removed and new short ones added. Even better, it moves nicely and freely: The only problem is by the time the divebrake hits the bottom of the wing (it's upside down remember) it's not vertical. The fixings I made are too small! So it was back to the cutting board! Edited By andy watson on 18/03/2009 15:23:18 Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 18, 2009 Author Share Posted March 18, 2009 So a resizing of the fixings later, and the brake is working perfectly. Note, the actual dive brake broke during one of many insertions/removals of the push rod. I widened the drilled holes and patched up the brake! Just in case anyone was wondering! Now the brake snaps to a close vertical, just above the wings lower surface. So a sucessful days messing around! The actual brake fixings are going to be made of a thick plastic called proskin sold by Mick Reeves. The thin stuff is used for skinning models, but the thicker sheets can be used for horns etc. I might make the brake itself out of it, but I haven't really had a good look at it yet to see what it's like. Tonight- how the heck will I get it to connect to a servo! Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 18, 2009 Author Share Posted March 18, 2009 OK, how the heck to connect it to a servo! Well I decided the best thing to do was make a replica of the wing section that it's going to be mounted on. To do this I cut 2 new ribs as far back as the spars. I then added some spars between them and the false leading edge. One wing also calls for a balsa block behind the LE at this point (for a landing light to be mounted), and I figured that would make my life hard, so I included it, (no point designing a system that would work without the block if it wouldn't work with it, but the reverse is fine). Finally I "sheeted" it with my scrap sheet that I mounted the dive brake on yesterday. It is a thing of beauty............ The idea is simple enough. If I can hook a servo up to the brake and make it work here, it will slot straight into the real thing. Finally it looked like this: That photo is upside down! The brake hangs below the wing. The 2 central brake mounts are slill loose- they will go either side of my fixing mechanism. Early trials looked promising, but got held up fairly quickly. I simply trimmed and glued a horn to the dive brake. I then ran a pushrod up into the wing. I didn't hook up a servo (but with careful trimming one will fit), but just pushed and pulled to see the brakes action. The movement to about 45 degrees was excellent- exactly as planned. After that point though, the relative moments start to bend the dive brake in preference to pulling it vertical. Putting the central mounts in worked to support it to a degree, but once the bending got worse at about 60 degrees they then locked onto the brake, stopping further movement. Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 18, 2009 Author Share Posted March 18, 2009 A bit of fiddling, and fettling, and I might have been a bit hard on my system. I think the horn was catching on the clevis, and restricting the movement. One thing is for certain, I need something more reliable as a hinge than 2 bits of bent pushrod- much of the evening has been spent looking for them on the floor! Dive brakes up Dive dive dive Thats about the best angle I have managed so far, but I think some adaption of the lugs connected to the brake might improve things if combined with a change in the hinge position. If anyone has any ideas please let me know! Oh, the plan is to connect the other end of the pushrod to the servo with a right angle bend and a swing in keeper. There remains the possibility of a bell crank system- that would let me lose a servo too. I am not worried about slop- these things don't do anything noticeable remember! Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 20, 2009 Author Share Posted March 20, 2009 Well, after a reasonably sucessful start, I decided to try refine the design slightly. To do this I replaced the lugs on the divebrakes with longer ones. I then drilled another hole in the mount. This one was further back, which would give the pushrod a better angle to work with the hinge. This should reduce the tendency to pull the dive brake and bend it rather than rotate it. Because the lugs are longer, this meant the brakes were hanging too low when in the normal flying position. I drilled a couple of other holes in the mount to try lift the brake closer to the wing. I discovered the hinge point needs to be below the centre of the dive brake in the vertical position. If it is higher then the dive brake cannot reach vertical. If it is too low, then there is too big a gap between the brake and the wing. I found a position in the middle brought the brake as close to the wing as possible, but still allowed the brake to move to the vertical. With the hinging working well, I turned my attention to the servo. This was actually very straightforwards- once I had cut the screw mounts off the servo it fit neatly into the gap between the leading edge block and spar. A custom designed servo holder was called for: Now I needed to test it. I have a very old 4 channel 35MHz system I have stuck in a 2 channel glider, so I removed the canopy of the glider and plugged my dive brake into a spare channel. Initial tests look very promising- it seemed to be working perfectly (albeit a lot of messing around with end points and the like will be needed). Unfortunately the tx was almost out of power, so I left it on charge and will try more rigorous testing tonight. Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 30, 2009 Author Share Posted March 30, 2009 Well the good news is the dive brake test was 100% successful. These will be installed into the wings and set via a Y lead into a single channel on the receiver which will be operated by an on/off switch. The original plan was to also hook the siren up to the same switch, as the brakes should only be used when the siren is also on, but as the servos will run off 6V and the siren will be probably running off 9 then I guess that will give me an issue! Anyway, a bit of fettling has been done in the mean time. I got a commercial elevator joiner with the horn already attached. his will be deeply buried in the back of the fuselage, so I really didn't want any chance of failure. Rather than cobble one together myself I spent a quid and bought one! Apart from the integral horn the method was the standard. Not the best bit of drilling I ever did- or my drill wasn't sharp enough for the balsa and tore it! Bit of filler might be needed! One of the really nice things about the stuka that I didn't appreciate at first are some of the details. They add a lot of fiddly complexity to the build, but at the same time add a lot of points of interest. One of these is the use of counterweights around the tail. I guess the Germans were trying to avoid filling the nose with lead! The tailplane has unusual tips. These are fixed to the stabiliser and the elevator and sort of rotate through each other like a joint, although they are not actually connected to each other. Another nice little detail that won't be visible in the air The "fish" looking ones attach to the stabiliser, the triangular ones attach to the elevator. Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted March 31, 2009 Share Posted March 31, 2009 PHooey Andy this is impressive stuff Quote Link to comment Share on other sites More sharing options...
Fred Keegan Posted March 31, 2009 Share Posted March 31, 2009 Hi Andy, following your build, VERY GOOD. When I have to drill small holes in balsa I use brass tube sharp at one end it gives a nice clean hole. Fred Quote Link to comment Share on other sites More sharing options...
andy watson Posted March 31, 2009 Author Share Posted March 31, 2009 I might try that next time Fred. It was pretty thin stuff, so it was a pain to get it square- especially as it tapered down to the TE, so no real possibility to try jig it and keep it all straight! Should be collecting the engine tomorrow, which will allow me to progress with the front of the fuselage. Quote Link to comment Share on other sites More sharing options...
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