martin collins 1 Posted September 28, 2018 Share Posted September 28, 2018 Hi all, just bought this Magister, looks like a Bryant one at 68" wingspan, the engine bay arrangement with the beech bearers etc is a givaway. Wings however are foam not built up, i guess someone had them cut to save time (not weight!) This is going to be an electric conversion using a 5 cell A123 pack, looking for a suitable motor at the moment, have used Prop drives before at this size but i will see what`s around or may pick up a good used motor if something is out there. Will probably be repainted in the yellow scheme of Peter Holloway`s one that was at Old Warden as i had a flight in that a number of years ago, even took the stick for a few minuets. Will have to make up a set of trousers and spats for it, any offerings on the best way to produce and secure to the wire undercarriage legs? ...............Martin Edited By martin collins 1 on 28/09/2018 13:06:57 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted September 28, 2018 Share Posted September 28, 2018 Great project Martin, I'm very fond of the Maggie, in my avatar is a Magister.A quick question, why the A123 battery? Surely a lipo would give you better endurance and overall performance? BEB Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted September 28, 2018 Author Share Posted September 28, 2018 The A123 packs i have are 5 cells and i have 4 of them which i made for a 10ft B17 i used to fly, one pack per motor, they are 3300 mah, i compared them in an 75" fighter i used to fly the comparison pack was a 4000mah 4s lipo. I got as much endurance and performance from both packs as i could drain the A123 pack virtually to nothing without the risk of ruining the pack or puffing the cells. I have had these packs for probably 8 years now and they still charge up exactly as they did when new and i can leave them on a shelf for over a year without touching them and still they perform once charged. I cannot fault these cells and they will fast charge without problems as i used to do to get the B17 in the air as quickly as possible for a second sortie! The shape of the packs makes them ideal to fit in where the old glow fuel tank used to sit. I wouldn`t swap them for lipos although i do fly other planes with those..........Martin Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted September 28, 2018 Share Posted September 28, 2018 Sounds like a Propdrive v2 5050 580 might fit the bill there. That long cowl should do nicely to hold a pack of 123s, possibly even 2P depending on how it balances. Where do you get your 123s from? I still have one pack that I made up e-bay cells that I used for a glow starter for the last few years. I must find a use for it as I use 6S Lipo for preference so far. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted September 28, 2018 Share Posted September 28, 2018 In my limited (though far from zero) experience of glow to electric conversion fitting batteries in the area set aside for a liquid fuel tank doesn't always work so well. I've usually found that the weight needs to be further forward to avoid (or at least limit) the amount of lead ballast needed to get the CoG right. From the photograph it looks as though there's some scope to push the batteries further forward. 68" is quite a substantial model. Any idea what the all up weight is likely to be? My Mew Gull weighs just short of 10lbs (4.6 kg) and flies well on 6S LiPos with an EMaxGT4030/06 supplying 1.2kw power. I've used smaller EMaxGT motors in both my DB 58"ws Tiger and Gypsy Moths very successfully on 4S LiPos. I bought them all from Totem Hobbies. Looks to be an attractive model and rewarding conversion. I have the same problem with spats on the Mew Gull, which are very characteristic of the full-size. Initially I fixed them to the wing on a sort of plinth. I flew it without them initially and, because of nose-over issues I bent the torsion bar piano wire legs forward to cure it. Now the spats don't fit! I had intended to keep them as far forward as possible to give room for the legs to spring back and I think that might work if I reset the mounts. I have HK oleos on the wire legs. Geoff Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted September 28, 2018 Share Posted September 28, 2018 There are lots of pictures on Google images of the full size being operated trouserless. Just bare legs. Those would be a much easier proposition to base yours on. Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted September 28, 2018 Author Share Posted September 28, 2018 Here is a picture of my Bryant Gull six, this balances perfectly with no lead with the 5s A123 pack where the tank used to go so i am hoping for the same on the Magister, the motor in the Gull is a Propdrive 50/50 500. Was thinking of maybe trying a Tornado Thumper 4260/06 500kv motor on the 5s A123 pack, any thoughts on that motor? Not sure on the weight yet but i hope to be quite a bit under 10lbs (hope i don`t eat my words!) .............Martin Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted September 28, 2018 Author Share Posted September 28, 2018 Trousers and spats are going on the model, i have a few ideas, probably thick balsa sheets laminated and carved/sanded to a scale looking shape, made up to 2 halves with a ply core with saddle clamps round the leg with a couple of small screws to keep the two halves together. I am going to change the servos for some newer Futaba ones and sort the motor mount/battery position this weekend and get it ready to test fly as is before i make the spats and refurb it, hopefully be in the air next week, watch this space!.................Martin Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted September 28, 2018 Share Posted September 28, 2018 My experience of several glow-to-electric conversions is similar to that mentioned above, namely that the battery needs to go as far forward as possible -- usually further forward that the fuel tank bay. I usually achieve this by cutting a large rectangular hole in the original firewall, then constructing a battery box which extends through this hole and has a solid ply front end to mount the motor on, rather than by using long stand-offs as shown in the Gull Six picture above. A couple of my models -- a 57" w/s Liberty Sport at 5lb 15oz and a 58" w/s Tiger Moth at 6lb 2oz both use 6S A123 packs with AXI 4120 motors and 14" or 15" props. I use 5S A123 with an AXI 2826/12 motor and 12" prop in my 60" 5lb 15oz Magnatilla but get much better duration in that one with 4S 3300mAh LiPo. I love the A123s for the properties that have been mentioned above. Mine were harvested from DeWalt battery packs over 11 years ago, and are still going strong. But they're 2300mAh capacity, not 3300. Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted October 1, 2018 Author Share Posted October 1, 2018 Ok, having to modify the cell count, did a motor test of the Prop drive in the Gull six on 5s A123 and it is only pulling 38 A and 530 W on the 14x8 prop, weight on that model is 8.9Lbs, the Magister will probably come in similar, less scale detail but a foam wing. I am looking for 100W per Lb so will go with 6s as some on here have suggested, the figures on the Hobbyking site for this motor suggest i will get that no problem. Also going to go with lipos on this now due to the battery bay area being restricted by the two hardwood bearers, the best solution for the space would be two 3s packs in series, they will slot right between the bearers, one 6s may be an issue with length if i access the pack from the top of the model as i would prefer and i will have to take half the bearer width out. Any thoughts on using two packs in series? Motor mount is now fitted, went with a solid block in the end and just bolt the motor straight through that, will post pics shortly. Thanks for the advice so far...............Martin Quote Link to comment Share on other sites More sharing options...
Geoff S Posted October 1, 2018 Share Posted October 1, 2018 I don't see any problem with 2 3S LiPo batteries in series (both would need to be the same capacity - 4AH?). You might also consider 2 smaller 6S pack in parallel depending on the space available. 6S is nominally 23v so to achieve your 100 watts/lb then max current would be around 40/45 amps, so not excessive. However I doubt you will need to use maximum power for very long. With modern, more efficient and lighter power systems 80 watts/lb still gives a spritely, scale performance. Geoff Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted October 1, 2018 Share Posted October 1, 2018 How come this model is for sale on Ebay for £500 at the moment, with a MDS engine? £500 is a bit steep...! Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted October 1, 2018 Author Share Posted October 1, 2018 Ha, Ha, i noticed that too, i bought the plane via another site and expected the ebay listing to be cancelled, price on there was originally £150 (i didn`t pay that!). I think the seller is not au fait with how to cancel the listing so he has shoved it up so high that no one will bid I was offered the engine but politely declined.............. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted October 1, 2018 Share Posted October 1, 2018 That explains it... Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted November 7, 2018 Author Share Posted November 7, 2018 Progress has been made, motor and battery fitted, this was the only pale the 6s could go, i took some of the wood out of the beach bearers and it is a nice snug fit. A number of other issues have been sorted and it is now ready to be maidend. Once flown and trimmed i will turn my attention to the cowling which is made from ply parts which are a very poor fit and cracked, they will do for a few flights but will be replaced either with new wooden ones and ally tape or from ally sheet bent to shape. Have gone with a balance point 1/3 of the way back from the leading edge as i don`t have a copy of the plan.................Martin Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted January 6, 2019 Author Share Posted January 6, 2019 The Magister has now flown, test flight went well today, final set up was the 50-50 Propdrive 580kv on a 13x7 Turnigy wood prop with a 3300 6s flight pack. Nice flying model with bags of power. Just waiting on a new f/g front cowl piece from Sarik and i have the cowl sides to make from some thin ply. Will post some pictures once that is done. Quote Link to comment Share on other sites More sharing options...
Ray Wood 4 Posted January 7, 2019 Share Posted January 7, 2019 Hi Martin, The C of G on the drawing is 3 1/4" back from the leading edge, hope that helps, On my list to build, I've only had the drawing 35 years 😃 Regards Ray Quote Link to comment Share on other sites More sharing options...
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