Basil Posted April 12 Share Posted April 12 (edited) Can anybody advise re above. My limited knowledge has allowed me to work out various methods but they all fall down on one aspect or the other when it actually comes to fitting them. I can't find any info on the subject of fitting airbrakes anywhere. I have looked at Chris Williams latest Foka, (Free plan) but there are no details, well not enough for me. Thanks in advance. Bas Edited April 12 by Basil Quote Link to comment Share on other sites More sharing options...
Wookman Posted April 12 Share Posted April 12 Some further explanation required please Bas. Quote Link to comment Share on other sites More sharing options...
Basil Posted April 12 Author Share Posted April 12 Well Wookman, I can work out , in theory about a lever system that works, but; there are the other things like, covering the spoiler face, that means you need access to reconnect after covering. Needing access to adjust the system so that they close properly. Both LH & RH mechanics must be identical, therefore adjustment required. Where is the ideal position of the 'Brake' on the wing surface?. I assume the surface area will be reflected by their efficiency . The T31m is my first venture into gliders our field is not that big so I think it needs brakes. A picture paints a thousand words. I can fix the servo (With adhesive )But need access to the coupling at the other end (Fix to horn) under the brake, cant seem to be able to work out the fittings required. Bas PS just had some other thoughts. I have difficulty in adding pictures;!!!!! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 12 Share Posted April 12 Spoilers and airbrakes are actually quite different so make sure you're searching for the right thing. Spoilers normally lie flat on the wing surface and were fitted to many earlier gliders. They work by spoiling that part of the wings lift but only contribute a limited amount of drag. Airbrakes are blades which come out of the wings vertically, both spoiling lift and contributing significant drag. They can be provided on the top surface only, or far more effectively, top and bottom surface with deliberate air leakage through the housing. Learning to sideslip on the approach was a very useful skill on vintage gliders! As the T31M was a conversion, essentially just sawing off the nose section to mount the engine and adding an undercarriage, I would think you can safely assume that the spoilers would be in the same place as the original glider. I've had success with using ailerons mixed to deflect upwards on several non-braked or flapped model gliders - including a 4 metre Fly-Fly Discus. Not scale of course but fairly unnoticeable except by the pickiest purist... Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted April 12 Share Posted April 12 (edited) Edited April 12 by Ron Gray Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted April 12 Share Posted April 12 Another one Quote Link to comment Share on other sites More sharing options...
Basil Posted April 12 Author Share Posted April 12 Thank you gentlemen for your input. I hope from this I can work out something that will suit this application. Once again many thanks. Bas Quote Link to comment Share on other sites More sharing options...
Basil Posted April 12 Author Share Posted April 12 4 hours ago, Ron Gray said: Another one Ron, is it possible you could tell me , better still show me how these were hinged please. Thanks. Bas Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted April 12 Share Posted April 12 Better still Bas, here are some photos of the actual model, the construction of which differs from that shown on the plans but is a lot simpler. The hinges are tape on the top surface. 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 12 Share Posted April 12 Very cunning. Quote Link to comment Share on other sites More sharing options...
Mike T Posted April 12 Share Posted April 12 Isn't it just! I'm going to knick that! 🙂 One question about the rubber band arrangements though. How effective are they in keeping the spoilers closed? From what I can see of the geometry, it seems as if they would exert very little or nor force at all to keep the spoiler closed. I think I'd have aligned the eyelets vertically, then rigged some monofil through them, attached to a horizontally tensioned band. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted April 12 Share Posted April 12 I can take no credit for the design or the build but I can attest to the fact that the rubber bands do a very good job of keeping the spoilers closed and it requires quite a bit of force to get them open! 1 Quote Link to comment Share on other sites More sharing options...
PatMc Posted April 12 Share Posted April 12 (edited) The T31M has so much built in drag that I doubt the very small spoilers would make much noticeable difference to the descent angle. IMO a better option would be to hold the throttle to a slow tick over & let the prop create the drag. Edited April 12 by PatMc 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 12 Share Posted April 12 Not for nothing was the T31 glider known as "the brick". Add a pair of large wheels and a draggy prop disc and it's not likely to be kept from getting back on the ground for very long. Just remember, if you're fitting electric power, that you won't get any braking effect from a stopped propeller. Quote Link to comment Share on other sites More sharing options...
Levanter Posted April 13 Share Posted April 13 Hello Basil On a Sonata E I built a couple of years ago I used a method very similar to Ron's however instead of using rubber bands to hold the spoilers in the closed position I used small magnets. One advantage is a positive closure that will not degrade over time. Another is that once the magnets have opened they no longer exert any force so the servo doesn't have to work so hard as it is air pressure only. I used a small servo with a standard arm but at right angles to the spoiler (not inclined) and pushing against a small piece of epoxy sheet to provide a bearing surface. Ron can achieve identical opening of the spoilers by adjusting the end point on the servos. Mine are mounted on small racks that allow a small amount of mechanical adjustment to achieve the same. Both have have the advantage that there is no direct link between the servo and the spoiler so there is no chance of stalling or buzzing the servo in the closed position. A small gap in the closed position allows the magnets / rubber bands to do their work. I didn't take photos during the build but I could do if you would like. Levanter Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted April 13 Share Posted April 13 I have a 1/5 th scale T21 with scale spoilers, they are quite effective. These have a servo on each spoiler with a simple linkage, they are top mounted and hinged with solartex (wing is covered in solartex). If you can put them on separate rx channels as it makes setting them up easier. I have an ASK11 motor glider with similar spoilers and they do make landing on our tight strip much easier. One thing to note is that I much prefer to have the spoilers on a proportional control, in my case the "throttle" stick. Years ago I had top mounted spoilers on a Chris Foss Hi Phase, these had a pull cord to pull them open and fridge magnets to keep them shut, single servo in the fus and when wings were plugged in it was a simple case of hooking the spoiler cord loops to a ball link on the servo arm, it worked very well. Quote Link to comment Share on other sites More sharing options...
PatMc Posted April 13 Share Posted April 13 10 hours ago, Martin Harris - Moderator said: Just remember, if you're fitting electric power, that you won't get any braking effect from a stopped propeller. Oh yes you will. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 13 Share Posted April 13 Ok, a tiny amount but it's negligible compared to a slow spinning disc. Quote Link to comment Share on other sites More sharing options...
PatMc Posted April 13 Share Posted April 13 Sorry, I think we've both misread the meaning in each other's posts. To be clear using a slow tick over setting with electric power allows the prop to freewheel even if the esc is set to brake when power off. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 13 Share Posted April 13 Yes - I was reinforcing your point! Hopefully this slight diversion will have clarified how EP models can benefit from a "tickover" setting for approach control, especially if they have a high wing loading and low drag - not that a T31 of any variety needs much help in this direction! Quote Link to comment Share on other sites More sharing options...
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