Trevor Rushton Posted September 11, 2014 Share Posted September 11, 2014 Nick, I built one of these about 4 years ago; it was my first model for a very long time. Powered by an OS Alpha 56 and with a 12x6 master airscrew it's performance was not great; I felt that it was underpowered and infact loss of power was it's undoing as it flopped back down after a poor take off. however, whilst I don't have its Auw I do think that I built it heavy. I used glass on the solid surfaces and made a hash of it, I also used far too much silver paint. The accident caused a nasty crack around the fuselage which I have now repaired; I stripped everything off back to balsa and recovered using glass and poly c on the solid sheet and polyester solarfilm on the wings and rail. This time I used the red/grey/white scheme which looks really good. I put a Saito 72 up front but I am afraid I have not flown it yet so don't know how successful the improvements will be. What I can say is that with the OS once airborne she flew really well, especially with the flaps deployed on landing. I am certainly up for having another go having learnt such a lot on building and finishing since then trevor Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 11, 2014 Share Posted September 11, 2014 I'm rather surprised by a couple of points. ZK - did you really get yours flying at 2.5 Kg? That's only 5 1/2 lbs in old money which seems remarkably light - even if gravity's the other way up where you live! Unless the 56 Alpha and/or Master Paintstirrer prop is a giant step back in power from the older 52 Trevor, it sounds possible that your model may have ended up massively heavy as mine (and another example which I've flown with an SC 52FS) both had more than adequate power. In fact the model was designed for 4 strokes between 40 to 70 size and Brian Borland told me that the prototype flew well on a tired old 40 FS. Could you weigh yours? Adding more weight from a bigger engine could even make it a bit more of a handful if you're unlucky. Quote Link to comment Share on other sites More sharing options...
Trevor Rushton Posted September 11, 2014 Share Posted September 11, 2014 Martin, I weighed mine tonight; 1.3 kg for the wings and an embarrassing 2.465kg for the fuselage, a total of 8.3 lbs in old money! Perhaps I have the answer to the power problem!. I did feel that I'd built it a bit heavy Trevor Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 11, 2014 Share Posted September 11, 2014 That's only 5 ounces more than mine - and I've carried a small video camera on board which would have weighed more than 5 ounces with no noticeable detriment to the handling. Did you build the recommended wash-out into the wings? Co-incidentally, I re-maidened the SC 52FS engined model (dates back to 2003 as does mine) for another new owner this afternoon and weighed it at 7.7 lbs with fuel - this one only has a single lightweight pilot (mine are an Action Man and one of Sindy's girlfriends - both Douglas Baderised) and is without an onboard glow. Edited By Martin Harris on 11/09/2014 23:32:29 Quote Link to comment Share on other sites More sharing options...
Nick J Posted September 12, 2014 Share Posted September 12, 2014 if thats the case, maybe a chipmunk weighing 8lbs or more may not fly that good with the 0s fs48 , oh well, i wish the instructions had of stated what the flying weight was roughly before i went off and bought the fs48. Quote Link to comment Share on other sites More sharing options...
Trevor Rushton Posted September 12, 2014 Share Posted September 12, 2014 Martin, I think it may have been heavier before my mods since the glass treatment was my first attempt and did not go very well; I have since stripped all of the old material off ( used paint stripper). I had put loads of pva rivets on hitch looked great, but I have now changed these to the Mick Reeves type and slightly fewer of them. Well worth the effort though. Yes, the wing was per plan with washout and the ( optional) flaps. the first take off run was at Old Warden and was impossibly long, but we found that the engine was not developing full power; once that was sorted take off was acceptable but you still needed to watch the speed. Due to my ineptitude and inexperience she would have a tendency to have a kick to the left just after taking off, but I am sure that was me. Once up everything was fine but I probably only flew it about 10 times before the crash. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 12, 2014 Share Posted September 12, 2014 Nick, Let's hope things go better when it's re-done. If it comes in below 8 1/2 lbs I don't see that you should find any problem with a correctly running 48. The friend's one that I flew yesterday was just as benign as mine and on the second flight I adopted my normal practice of using half throttle for the take off run in order to get a nice scale run from grass which hasn't been cut for a couple of weeks. During the handling checks, I couldn't get a wing drop clean but at full flap it did want to drop a wing. Were you using flap for your take offs? If so, how much movement did you set? I use the full size settings of 15 degrees for take off and 30 degrees maximum for landing which are quite small (but effective) settings compared with many other aircraft. Quote Link to comment Share on other sites More sharing options...
ZK BAP Posted September 13, 2014 Author Share Posted September 13, 2014 Martin, i managed to get my mates scales and weighed mine again. I was not too far out as it came in at 2.69kg with no cowling or fuel Fuel tank is 600ml dubro so a full tank will bring it up a bit. Using a foam tail wheel also helps in keeping the tail weight down. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 13, 2014 Share Posted September 13, 2014 The cowling weighs three fifths of not a lot so that is an amazing result! I'm not the lightest of builders but the other one was built by someone more sparing with the glue - and he even substituted some of the wing sheeting for lighter wood, as I recall. Quote Link to comment Share on other sites More sharing options...
Martin Whybrow Posted October 5, 2014 Share Posted October 5, 2014 Any update on the kits yet? Quote Link to comment Share on other sites More sharing options...
Stevo Posted October 5, 2014 Share Posted October 5, 2014 Ah.. the Whybird's getting impatient... as wecall are !!! Quote Link to comment Share on other sites More sharing options...
Nick J Posted October 5, 2014 Share Posted October 5, 2014 did you sign up for a kit? Quote Link to comment Share on other sites More sharing options...
Stevo Posted October 5, 2014 Share Posted October 5, 2014 Well I did... Quote Link to comment Share on other sites More sharing options...
ZK BAP Posted October 6, 2014 Author Share Posted October 6, 2014 As far as we understand the kits are somewhere between China and UK. The importer is trying to get a more precise delivery date, but sounds not too far away. Just to 'chip in' I have also managed to wangle a kit out of Airsail so i can build another one. this time i have a 91fs to put in. i dont know when i will start the kit as i already have two others on the build. Took my one out for the first time in four weeks due to moving house, but after many attempts to start the 61fs was left returning home. Once home i pulled the cowling off to find a simple fuel filter was blocked causing no fuel to get to the carb. My own doing as i should of pre run it the day before after sitting for so long. never the less, i have a few weeks up my sleeve now so will be heading back to the field as the weather improves. On another note, my mates chippy that he is building in my hangar is at the stage where he has now sheeted the wing with the washout in etc and will hopefully be starting the fuse next week. will try and get some more pics. His build blog was published in our national magazine last month model flying nz. Sorry for being sparse as i have been unpacking boxes and fighting with tv aerials etc due to the move. Will keep you posted. Cheers ZK BAP Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 13, 2014 Share Posted October 13, 2014 Not sure if you guys have spotted this over on a Dutch site? Nice Airsail build blog Having now got into the Dennis Brynat build more. I think the Airsail one looks more accurate, and a much easier build, ah well. Cheers Danny Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 14, 2014 Share Posted October 14, 2014 Hello all Can anyone tell me what the incidence should be on the wing and t/plane please. Not having any luck with google. John Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 14, 2014 Share Posted October 14, 2014 I just built mine off the plan and it seems fine...or are you looking for details of the full size? Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 14, 2014 Share Posted October 14, 2014 I am using D. Bryant plan Martin, I took it for granted they would be the same. John Quote Link to comment Share on other sites More sharing options...
ZK BAP Posted October 27, 2014 Author Share Posted October 27, 2014 Hi John. Wing incidence on a chippie should be 2 deg. The Airsail plan is quiet accurate and shows a positive incidence. All chippies I build have the 2 deg and fly superb. Im not sure what the other plans out there show, but I would still be inclined to put the 2 deg in, just to be safe. regards ZK BAP Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 27, 2014 Share Posted October 27, 2014 Cheers ZK I think my plan will be right, it just has little info and I like to know. John Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 28, 2014 Share Posted October 28, 2014 I haven't looked at my wing plan yet to see if there is any wash-out. The Spitfire has 2 degrees at the root but the wing then twists progressively to minus 1/2 degree at the tip, giving a mean incidence of 1 1/4 degrees and wash-out of 2 1/2. It's why the wing on the full-size behaves so well in the turn and doesn't tip-stall. I think there might be benefits to span-wise air flow as well. Perhaps the Chipmunk doesn't need it. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 28, 2014 Share Posted October 28, 2014 The Airsail Chipmunk does have washout. You jig up the rear spar with some scrap balsa while sheeting the D box. TBH I can't recall whether it's detailed on the plan (which I haven't got immediately to hand) but it certainly emphasises it in the build instructions (which I have). Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 28, 2014 Share Posted October 28, 2014 Interesting, I'll have a look at my DB plan when I get home. I don't recall a reference to wash-out in the books on the full-size I've got but again I'll look when I get back. It certainly makes sense on a tapered wing like this. Quote Link to comment Share on other sites More sharing options...
ZK BAP Posted October 28, 2014 Author Share Posted October 28, 2014 Yes Martin and Colin are right. Washout is built into the wing to stop tip stalling. This is done by placing the wing panel on the building board flat along the main spar and a 6.5mm packer is put under the rear tip spar and a 2.5mm packer placed under the root rear spar. This should not be forgotten when building the wing as it greatly improves the slow flying characteristics and prevents the nasty tip stall that can sneak up on you on a slow approach. Also because the wing is similar to a spitty, ( hence ' poor mans spitfire ' ) the aircraft is quite aerobatic, but because the pointy tips have been replaced with blunt ends it is much more predictable whereas the spitfire was designed to be thrown around in dog fights. The chippie was designed as a trainer. I have seen many spitfire models destroyed on landing due to a too slow approach resulting in a tip stall only meters above ground level which is almost impossible to rectify at that height resulting in matchwood. The trick is to get both wings exactly the same with washout or the aircraft will constantly want to pull one direction. This must be done during the building of the wing and not simply 'twisted' using the covering to hold its position. If done that way you end up with twisted wings from root to tip and no washout as to say. I can slow my one down on landing so much so that a three pointer is very easy to achieve safely at nothing more so than a fast walking pace. Bear in mind to keep the weight down too. This will ensure a never ending glide when power is pulled back. The flaps are also very effective and I recommend everyone build flaps into their chippie. You will kick yourself in the future if you choose to not put flaps on. luckily the kits we have sent now come with laser cut parts for the flap addition, making building the wing much more enjoyable. Regards ZK BAP MFNZ 11300 Quote Link to comment Share on other sites More sharing options...
ZK BAP Posted October 31, 2014 Author Share Posted October 31, 2014 The kits have landed! Albeit at the wrong port some 250 miles away from the importer! Never less the importer is now in negotiations with the shipping agent to arrange delivery. So hopefully very soon he will have his hands on them. Will keep you updated as info comes through to me. Thank you for all your patience on this epic journey across the globe. Regards ZK BAP MFNZ 11300 Quote Link to comment Share on other sites More sharing options...
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