EarlyBird Posted January 4 Author Share Posted January 4 I was taught old school, even though it was only seven years ago, and use washers to adjust the thrust lines. As a beginner the idea of using mixes was well beyond me, at the time. It does seem to me that built in thrust lines is just another starting point for using mixes and presumably if the designer is correct no mixes will be required, but if they are I can make adjustments using the Tx. Steve Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 7 Author Share Posted January 7 (edited) The pursuit of perfection has got in the way of production here is my latest gadget for cutting and sanding joints. It works well if my latest joint is to be any kind of measure. The top joint is with and the bottom one is without the use of the gadget, proof of the pudding? Steve Edited January 7 by EarlyBird 1 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 7 Author Share Posted January 7 With the last joint glued and clamped that is the second side built on top of the first, not quite identical but good enough. I now need to make a decision regarding the tail, it's definitely going to be a steerable tail wheel and possibly both servos beneath the tailplane. Steve 1 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 7 Author Share Posted January 7 Both servos will fit beneath the tailplane. Just. Each servo weights 56 grams which should counter balance the added weight of the petrol engine, maybe too much though. Steve 1 Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted January 7 Share Posted January 7 Personally, unless you think you'll need the weight at the tail, I'd keep them forward, use pull pull for rudder, and a carbon pushrod or a snake for elevator. Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted January 7 Share Posted January 7 So 100 grams x the moment arm is quite a lot of weight to compensate for a few extra ounces of engine..... looks like little structure left to support them as well Quote Link to comment Share on other sites More sharing options...
kc Posted January 7 Share Posted January 7 EarlyBird, those joints look immaculate. If you want to make a deluxe version of the sanding jig there is one here based on the old RCME design. Note that it has a 'safe edge' on the sanding block to avoid wearing away the baseplate edge. ( Permagrit sheet is available for this ) 1 Quote Link to comment Share on other sites More sharing options...
John Rickett 102 Posted January 7 Share Posted January 7 Steve, as Grumpy Gnome has said, unless there is a compelling reason you want to put the servos in the tail, you'd be much better off with them at the front. The Mighty Barnstormer does not have a particularly long nose so its unlikely the cg will be too far forward with everything as near the front as you can achieve, and an aeroplane with a forward cg will almost certainly fly better than one with a rearward cg, or extra weight to compensate. Those who want the most power and precision at the control surface will accept the trade-off but a Barnstormer is not in that league. As suggested, a closed loop (pull pull) arrangement for the rudder and tailwheel, and a snake to the elevator would be ideal for the model. Its your build of course and you're free to do whatever you want, but you may regret it later... 1 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 7 Author Share Posted January 7 That raised a smile John, remember this? These were originally in the tale of my giant stick and as advised, possibly by you, I moved them from the tail and installed in the fuselage exactly as you are now advising me and with the giant stick I was able to remove one pound of lead from under the engine. Although I like making mistakes because that's the way I learn it looks like I've already learned this lesson.🤣 Yes one of these servos in the tail would equate to something like 250 grams of weight at the front and obviously for two five hundred grams putting it this way makes it look a totally ridiculous idea. Back to the drawing board for me I think. Thanks everyone for your advice and you've probably just saved one model, well done. Steve Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 8 Author Share Posted January 8 Oh dear me after some thought I remember that I made exactly the same mistake with the Ohmen in that following suggestion that the model would be nose heavy I put the servos in the rear and reduced the length of the nose and that turned out to be a big mistake which I was about to repeat. Both sides have now met each other for the first trial fit. So that I can mark up the positions of the slots for the firewall. I can then cut them out prior to gluing them on, it's easier that way. Steve 1 Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted January 9 Share Posted January 9 Good reasons to put servos near the tail: a. Reduce slop b. Correct/prevent nose heaviness c. Avoid complex control surface geometry. Bad reasons for putting servos near the tail: a. Fashion b. Bad advice. 🙂 Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 9 Share Posted January 9 Best reason to not put servos in the tail is that the tail-moment is typically 2.5 to 3.0 times the nose-moment... so if the model comes out tail-heavy as a result of that decision, then that's a lot of unnecessary lead to be added to the front end. Quote Link to comment Share on other sites More sharing options...
Nigel Sharp Posted January 9 Share Posted January 9 Plus inertia to overcome/damp out... Weight at extream ends is not good. To feel the effect try putting heavy items at the front of a supermarket trolley (farthest from the handle) and try going round the aisle corners. You'll soon realise how hard it is to stop the motion. 1 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 10 Author Share Posted January 10 Thanks guys but weight is not something I had a problem with, until now and Christmas doesn't help with all the fattening treats. A new firewall has been made to suit the new location, the slots have all been cut in the ply doublers which have now been glued in place. Before I assemble the two sides I need to work out anything that will be easier to glue in place at this stage. I am thinking of servo tray and tank tray. Also I could make the undercarriage mounting plates. As with many designs there is a section of the fuselage that is parallel and I like to make any components that will hold the relevant formers at right angles, just makes life easier when trying to keep the right angles during the gluing process. Steve 2 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 11 Author Share Posted January 11 The undercarriage mounting plates was the obvious choice. This and the former were glued in place making sure that the former were kept vertical. Once dried the second former was glued and the second side was added. I use a right angle at the tail to make sure that the two sides were in line if not I made adjustments so that they were in line. I must apologise for not taking more pictures of the process but I got carried away by a burst of enthusiasm. Steve 1 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 14 Author Share Posted January 14 With the two sides joined it is now time for the fuselage jig. All of the cross members have been made and test fitted. As usual setting up the jig took longer than the rest of the process. Next is glue time again. Steve 2 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 15 Author Share Posted January 15 With the tail all glued up it's time to turn the model in the jig and test fit the firewall. It all looks okay so far. Steve 1 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 16 Author Share Posted January 16 Spoke too soon because on offering up the engine it looks like there is three and a half degrees of right offset. I was aiming for 2 degrees or two and a half degrees at the most. The firewall is not yet glued so I will shim it to reduce the offset. Steve Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 16 Author Share Posted January 16 With 1/16 shim With 3/32 shim The 3/32 has my vote. Conveniently I can measure the offset at 2 degrees. Steve Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 16 Author Share Posted January 16 Looks good with the engine in place. Steve 2 Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 17 Author Share Posted January 17 With the engine mount bolted in next is the fuel tank positioning. A bit of thinking time is required, unfortunately. Steve Quote Link to comment Share on other sites More sharing options...
Jonathan M Posted January 18 Share Posted January 18 At first glance I thought you'd written "a bit of drinking time is required..." which wouldn't bode well in the morning! 😅 What tank type are you using? Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 18 Author Share Posted January 18 Hi Jonathan, It will be a standard eight ounce tank with a petrol conversion. This is what I am using at the moment but I do have a 10 ounce tank however the way I fly the smaller tank will last for one hour flying time. I am quite happy to execute a couple of circuits and a successful landing and my day will be done. Steve Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted January 25 Author Share Posted January 25 As I thought thinking time of course has caused problems. This was going to be the donor plane. Having looked at the issues with this plane I decided to fix this up. I will use some of the parts, particularly the undercarriage, from the mighty barn stormer. Steve 1 Quote Link to comment Share on other sites More sharing options...
David perry 1 Posted January 25 Share Posted January 25 On 05/02/2024 at 11:08, Nick Cripps said: That's how I see it too, Steve. Odd that it has a lifting section tailplane, they are normally only seen on free-flight models. I guess Boddo's intention was that it would be flown that way, with just the occasional intervention by the pilot. Make sure you check the controls before flying, unlike Boddo... Strangely that’s exactly what my son said about the tail section of my latest vintage model. Dad, he says, tailplanes should produce downward lift surely. The ignorance of youth. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.