ben goodfellow 1 Posted August 11, 2014 Share Posted August 11, 2014 ive just been trying a bl25 motor in and it looks to be about right at about 550 watt 700+max. 4cell lipo on a tray with plenty of scope for cof g. i have went the way of a hatch on the bottom behind the cowl i internd to make my proper lipo tray tomorrow so ill try to get a pic or two on then for you.. fly low Quote Link to comment Share on other sites More sharing options...
ben goodfellow 1 Posted August 11, 2014 Share Posted August 11, 2014 ive just been trying a bl25 motor in and it looks to be about right at about 550 watt 700+max. 4cell lipo on a tray with plenty of scope for cof g. i have went the way of a hatch on the bottom behind the cowl i internd to make my proper lipo tray tomorrow so ill try to get a pic or two on then for you.. fly low Quote Link to comment Share on other sites More sharing options...
ben goodfellow 1 Posted August 12, 2014 Share Posted August 12, 2014 Quote Link to comment Share on other sites More sharing options...
Gary Vinten 1 Posted August 13, 2014 Author Share Posted August 13, 2014 Hi Ben Looks good are you going to have to remove the wing to charge the lipo Have you constructed the wing yet Quote Link to comment Share on other sites More sharing options...
Matt Johnstone Posted November 30, 2014 Share Posted November 30, 2014 Hi, I've just started building this Cap 21 from the same plan and I'm struggling to figure out what undercarriage I need to get for the model (sorry fairly new to the hobby) I'm also struggling to find the canopy I looked on vortex but I can't seen to find it is there another supplier I can contact? I've really enjoyed reading this thread and it was the reason I chose to build this plane. Quote Link to comment Share on other sites More sharing options...
Jimbo565 Posted November 30, 2014 Share Posted November 30, 2014 Matt I got my canopy from Steve Davis at Vortex,I feel sure if you sent him an email asking for Peter's cap 21 canopy he will sort you out. I cant get his web site up, looks like its been Hi jacked by Goldstar. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted November 30, 2014 Share Posted November 30, 2014 Phone Steve after 6 pm on 01162207080 and ask for the Cap 21 canopy. They are the same canopy. Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted August 30, 2015 Share Posted August 30, 2015 Gary, I hope that you and the CAP are still going strong. I have finally picked my CAP 20 L build again and was wondering how yours was doing. I started to look at mass balancing the elevator and rudder, but it will take quit a bit of lead in the rudder horn balance to get the balance point on the hinge line. I remembered you omitted the balance weights and I wondered if you have had any problems with flutter. It would be interested in any lessons you have learned with your CAP. Cheers Dave Edited By Delta Foxtrot on 30/08/2015 20:22:28 Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted August 30, 2015 Share Posted August 30, 2015 Here is a photo showing the progress to date Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted August 30, 2015 Share Posted August 30, 2015 I had no trouble with flutter even though I didn't fit the mass balances. Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted August 30, 2015 Share Posted August 30, 2015 Good to know that Peter, I assumed that you had and Gary had not. I assume that you added them to the plan after you flew the prototype as a prudent measure? Quote Link to comment Share on other sites More sharing options...
Gary Vinten 1 Posted August 30, 2015 Author Share Posted August 30, 2015 Hi deltaI did not use any lead and things are all ok no flutter Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted August 31, 2015 Share Posted August 31, 2015 I fitted them to the CAP 21 but left them off the CAP 20L. In the past I had flutter on a tailplane due to a sloppy snake with too much exposed inner. Just to see what would happen I added mass balances instead of a proper cure and they worked. In that case I added arm attached to the elevator extending forward with lumps oflead on them Quote Link to comment Share on other sites More sharing options...
Braddock, VC Posted August 31, 2015 Share Posted August 31, 2015 Posted by Peter Miller on 30/08/2015 21:59:35: I had no trouble with flutter even though I didn't fit the mass balances. You're obviously not applying adequate power whilst diving . Every time I've heard flutter it makes me think it's the aeronautical version of a raspberry . Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted August 31, 2015 Share Posted August 31, 2015 Thanks Peter, I once did some experiments using a simple flat plate foam wing model which had ailerons constructed with horn balances. This model suffered from very violent aileron flutter due to some slop in the hinges, so bad that it was a handful to control. I made onboard video of the flutter flight and you can see the whole wing flapping violently. I then stiffened up the wing to increased the reduced frequency parameter which characterises flutter onset and this moved flutter to higher airspeeds, but it was still present and violent. The last flight in the series of experiments was to add mass balances in the form of two pound coins taped onto the mass balances. This eliminated flutter completely as expected. Moving the CG of the aileron marginally ahead of the hinge line takes the forcing caused by aileron slop out of phase with the flap mode of the wing. So this was a very practical demonstration of the benefits of mass balancing. I passed the video on to a friend who lectured at Cambridge as he thought that this would be a nice practical example. I think I will take some on video on the CAP and slowly explore the envelop to check for any signs of flutter, but based on your experience if I hinge the elevator and rudder properly I should be fine Edited By Delta Foxtrot on 31/08/2015 12:48:01 Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted August 31, 2015 Share Posted August 31, 2015 I don't think you have to move the CG forward of txhe hinge line, justmove itclose to txhe hinge line. I remember that part of a big mod program on Twin Pins in Aden involved trying to squeeze long strips of lead into the elevator leading edges. and get the skins back on. I am not sure where the CG was moved to as I was involved in fitting hatches in the nacelles to take the new fire extinguisher bottles. THis was needed because they were fitting more powerful engines. and there was no room for the fire extinguishers in the cowl with the engines In passing, we got modification kits fromScottish Aviation. The big problem was that the nacelles were not jig built and the frames (formers) could vary as much as two inches apart on nacelles on the same aircraft. No one of my most loved aircraft Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted August 31, 2015 Share Posted August 31, 2015 No you do not have to move the CG forward of the hinge line, but if you do you will move the forcing caused by slop in the hinging into anti-phase with the flapping motion of the main surface and stop flutter. Moving the CG forwards, but still behind the hinge line may well be enough to reduce or eliminate this. I saw a twin pioneer take off from Cranfield when I was a student there in the early 80's and was very impressed with the short take off run. So was there a flutter problem on the elevators or was this done to mitigate the risk of flutter with the engine upgrade? Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted August 31, 2015 Share Posted August 31, 2015 I have seen a Twin PIn vleterally hoving over the flag pole in a bit of a breeze. I suspect that the mod was done in case it flew fast enough to generate flutter. Most of the time they didn't tell us why, just said get on with it. The Twin pin had a diabolical system with ahugh hydraulic jack in the centre section that operated all the flaps and slats via cables. and chains. This was nicknamed the Bicycle. When we had to change all the cables after some were found to be fraying the system created total havoc because they didn't have the spares and some cretin of an engineering officer decided to replace them all with string until the proper cabes arrived. Proper proceedure was to replace each cable in turn with the correct spare. Talk about a cats cradle! I did go on air test in one. Trouble was that I had a sinus proble at the time and the pain was bad. My fault. I did try and go on anther air test but one engine ran away on take of twice and the pilot decided not to go until it was fixed. I declined the invitation to the next time. As I said, not my favourite aircraft. Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted August 31, 2015 Share Posted August 31, 2015 String!!! I wonder how the aircrew on the receiving end of that mod would have felt. Sounds you you had an interesting time in the RAF Peter. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted September 1, 2015 Share Posted September 1, 2015 I don't know about the aircrew. I do know that when the string was being repalced it was a total shambles . Yes, I had an interesting time over 12 years. Still on Twin Pins. FI still remember a caption competition in the Aden Flight Safety magazine. Picture of a Twi Pin lying on its back in the desert. The winning cation was. "There I was, upside down, with nothing on the clock taking a star shot with the bomb sight...." Edited By Peter Miller on 01/09/2015 08:02:16 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.