BOWMAN KITS - Dave Banham's Miles Magister 1 E-Convertion & Restoration

[Roy Thompson]

Instead of hogging Martin's Magister resurrection thread. I thought it's time to start my own thread.

 

This is my build log of my current restoration and electric conversion I started a couple of months ago. The model is the largest of the few scale models that Bowman produced, at 85 inches and 10 1/4lbs, designed by Dave Banham in 1997. These scale kits were intended to be easy to build with a budget price tag, that allowed the modeller to add as little or as much to the model in the way of detail, as they liked.

A few months back, not one but two Bowman Kits Miles Magister appeared on eBay. First was a complete airframe, nicely built, but old and needing a lot of TLC. The main issue, as you will see from the pictures, was the condition of the veneer on the foam wings, which had badly split and delaminated. Then out of the blue came the second one, an incomplete kit part built. Two things attracted me, the fibreglass cowl and spats and the wings were there and untouched. Well, it occurred to me that hopefully there would be enough parts between the two, to turn out one very nice electric powered example.

I did chuckle when the seller messaged me saying, the kit was her late fathers (ex proprietor of the model shop in Hemel Hempstead), and that they had thought they had cleared his stash. That was until their mum passed, and they started clearing her house, only to find a large second stash, that she was sure her mother had no idea about!

It was at this point I thought maybe I should mention my next purchase to my own dear lady

The up shot of all this was I had two trips up and down the M3 and M25 around London to go collect my new toys. One thing I hadn't fully taken into account was just how long a one piece wing 85 inches is, until I was trying to fit it in the back of my estate car! Anyhow, with a bit of trial and error, we got there.

The plan I had in my head for this model was, first work out a plan of attack for the wing veneers & or replace it with the one from the other kit. Unfortunately, the CTR section of that wing has also suffered bad delamination after being removed from its outer cores for many years. Then there was the electric conversion, and to that end I was thinking along the lines of a 6S power system to replace the 91/120 four stroke. The intent initially was to use the new cowl to save on patching up the old one. I'll expand on this later.

I was hoping to retain as much of the patina of the original model, as it was obvious that who ever built it originally was an accomplished modeller. Unfortunately, the more I inspected the model, the more little issues I found. Rather than ending up with a patch work of repairs, I came to the conclusion that a total refurb was going to be the way.

 

I'll catch up with the progress I've made over the intervening moths in the next few posts, but this will do for now.

 

[Roy Thompson]

Following on from the first post, doing my research about this model I came up is this Website, Ivy and Martin's Web Page with a review of the kit back in the day.
It's a good read with some interesting notes and reassuring about the flying quality of the model.

Miles Magister Bowman Models kit review.pdf

[Roy Thompson]

Continuing on with the theme of research; the magister is not one of those aeroplanes that I knew a lot about before starting on this project. To try and put that right, I have scoured the internet for information, photos and have put my hand in pocket to purchase the detail photo CD from traplet. Before starting on any project I do like to get as much info as I can, and internet searches are fine, but no substitute for getting up close with your own eyes. This meant only one thing, a trip to shuttleworth collection was in order, as they have two examples. They also have engineers who can answer question on the finer points.

 

There were two questions I had from looking at photos. One, there is an instrument on the instrument panel that looks a bit like a U-Tube manometer, a glass tube with pink fluid in it. As a retired avionics eng, I should know these sorts of things, but as they say every day is a school day, and you don’t come across them in airliner world. If I had looked and thought about the other instrument on the panel a bit longer, I could have worked it out.  Looking at the panel, front and centre is the turn and slip gauge, well that gives you roll and yaw status, leaving only pitch to find. It’s easy when someone tells you it’s a pitch indicator! Apparently some moths have them as well. Second up, why are Venturi tubes all in different places? Answer because they are, and you won’t be wrong wherever you put them. That’s my kind of answer, and I have to admit from my days as an instructor you never try to answer why question.

 

Anyhow, with all this wealth of information, we were good to get cracking.

[Roy Thompson]

Inspection and assessment;

Having collected both models, the first order of the day was to go through them and inspect them to see what I had and what was going to need fixing. Starting with the finished model, the wing's obvious defect was that veneer, but also there were serval other items that needed addressing. Both windscreens discoloured and damaged, wing mounting and lose fixed nuts and a radio switch plate, add to this there were areas where the paper covering was cracked or damaged. Luckily there was not too much oil damage to the wood, the worse bit being the top deck above the tank bay. The builder had treated most of the likely areas around motor and fuel take to a coat of epoxy, which has saved this model from being full of oil soaked wood.  

The cowling at first glance looked like it beyond help, but over the time I had it I’ve managed to clean it up and have been experimenting with repairs, but for now that on a back burner. The other little thing I noticed is the cockpit instrument panel, it’s nice enough but it’s from a moth not a Maggie.  

 

As for the second kit, the fuselage needs a lot of work to complete. The balsa planking and top deck has suffered from its years of storage, and will need replacing, and to be honest would benefit from be done in rolled ply like the other model. There are no tail parts, they have been lost over time, but I do have a section of the plan of the tail. As to what’s happened to the rest of the instruction and plan is anybody’s guess. None of the kit wood is left either but most of the hardware is still there surprisingly, including wheels, tank, fitting and of course untouched cowl and spats.

 

The wings which first attracted me may still be of used one day. The two outer panels are still in their foam outers and are and good condition, but as I said before the centre section veneer has come unstuck after being out of its outer cores for many years. However, this is still salvageable if I want to put in the time.

 

The thing about the wings is their size, and today a one piece wing 2.16M in length is a bit of a pain to store and transport. Far better would be a two or three part wing, for now I will live with the wing as is, but I’m tempted to build a new 3 part wing using the second kit's parts later.

Edited August 11, 2023 by Roy Thompson

[Roy Thompson]

The elephant in the room is the wing veneer, how to tackle it was the first issue to deal with. Repair or replace the obeche veneer with new were the two options. I’d been looking around for obeche, but the largest I could find was only 4" wide sheets. There is an alternative however, Poplar, and you can buy this in large sheets. Not a veneer I'd heard of before so asked around and apparently, poplar is of a similar density to obeche and also slightly stronger but, is softer and more porous, so it will most likely soak up more paint/glue.

In the end, I started experimenting with a repair scheme, and touch wood it seems to be working OK, and it goes like this.

1/ Open up the crack. 2/ Wick in glue. 3/ Clean up. 4/ Pull the split together with tape. 5/ Lay packing on top to add pressure to the split area. 6/ Use what's at hand to apply weight. 7/ Leave it a day to go off.

To finish I've sanded it back to the veneer then glassed over the wing. It’s time-consuming, but seems to be working even on the larger ones just need to make sure you get all the voids are filled with glue.  

[john stones 1 - Moderator]

Job on your hands there Roy, hope all goes well.

[Roy Thompson]

There was an area on the wing leading edge that had some cracking around what look like a lump of car body filler. To be on the safe side, with some persuasion this was taken off, to revile what it's hiding. To be honest, the damage was not too bad, just a crushed balsa leading edge. It didn’t take long to splice in new wood.

 

Putting the wing to one side, I made a start on the fuselage, by removing the old windscreens, they both need replacing with new. The other kit still has the plastic sheet for them; unfortunately it’s starting to turn yellow also. As I can't get hold of a fresh copy of the plans, it not too hard to use these old ones as patents.

 

One of the Small areas that needed attention, on the fuselage, is I assume a latter badly done radio switch - charging connection fitment. Whatever it was, it's gone now. Another small area that needed attention is an old repair on the anti-spin fairings, a gentle sanding and recovering was all that was needed.

 

On the subject of sanding, I had an Idea about retaining as much of the original patina as possible, as I liked seeing the hand painted insignia. Well, that idea went out the window, the more I looked, the more unrealistic it became. So no turning back, I took the sander to the tissue covering. It's surprisingly tough to sand.

 

The last little bit for now that makes me think, that this model was originally made by a very good scale modeller, are the stitched fabric hinges on all the control surfaces, so I was hoping to retain them all. However, the rudder hinge fabric has started to pull away, giving slop in the rudder movement, also, the rudder covering would benefit from redoing. So after a lot of shall, I, won't I, I've taken a knife to it and it's off!

Edited August 11, 2023 by Roy Thompson

[Roy Thompson]

The Electric Conversion. 

From the outset, this was always going to be a conversion from glow to electric power. As standard, this model would have had a 61 two-stroke or 120 Four stroke, giving around 2 bhp of power for a weight of around 1Kg in a model of 4.5 to 5 Kg.  So this gives me a starting point for the conversion.

First thing to consider was where the battery going to go, and how are we going to access it. Then how many cells 4, 5 or 6 or even 8!, and finally what motor.

 

Starting with where to fit the battery, well the oblivious place is in the tank bay of course. Next is how to get at it, well my first bad thought was from under an opening engine cowl side panel. The reason being that, I could chop out the cutup side of the cowl and replace it with a new aluminium panel. This doesn’t take in to account the new cowl (or the other new I have on new cowls for this model) I have available, or the fuse structure.  Anyway the sensible way to access the battery is from the top of course no grovelling on the ground, no trying to flip a large model over etc.. Just lift off the top part of the cowling, easy.

 

As it happens, the top deck of the tank bay was one area where there was oil damage and I wanted to remove it to inspect the tank bay properly. Separating the thin ply deck was easily done, plus one 1/8 balsa side part that was also in need of replacing.  These were both used as templates for the new parts. Having a good look in the fuel tank bay, I can’t see any contamination, just lots of epoxy painted on all sides.  Here after this makes fitting a battery box and ESC fitting a lot easier. Cutting the whole top of the cowl off and making it removable should be reasonably straightforward (I say that Now!) and in keeping with the removable cowling on the full-size.

 

To give room to adjust the CG and to make sure I can get as much useful mass as far forward as I can, the battery tray will pass through the firewall into the engine bay. I think the biggest issues is going to be getting the CG far enough forward, the large lump of lead that came with the firewall suggest this was an issue in its glow days as well.

 

The motor I’ve chosen is 5065-07 435KV out runner with a suggested power rating of 1750 Watts, well that’s 2.3bhp so hopefully that should be enough for what we need using a 6S pack and a 16 or 17 inch prop. The mounting for the motor is using plate on studs, picking up on the original T-Nut for the engine mount. It’s a little snug, but once setup, I shouldn’t have to touch it again.  

Edited August 14, 2023 by Roy Thompson

[Roy Thompson]

Continuing with the conversion, I’ve been giving the balance some thought. Assuming that this model had a 120 4 stroke originally at 1Kg plus another 620g of lead, I need to be around 1.6 to 1.7Kg hanging off the firewall. So let’s assume the battery will be around 6 to 700g the motor is 375g, and with the lead added as well, I’m hoping that this put me at around the 1.6Kg mark and not too far away from a reasonable starting point for the CG. Time will tell.

 

 

Over the last couple of weeks I’ve been busy with the sanders and loads of sheets of sand paper, resulting in covering everything in the workshop with a thick layer of dust! This despite the vacuum cleaner being on the go the hole time. Glad that's dune and dusted 🤣

I was wondering how many nasties I would find, but touch wood, no more than I already knew about. The main one was the dent in the left hand leading edge. With all the paint out of the way, I could see just how much the damage was. All that was needed in the end was to splice a new 3” long piece of wood in to the leading edge.

 

The fuselage and wing have now been covered in light weight  glass cloth and EZE-Kote. Before covering the wing, I've taken the time to fit servo drawstrings and tidy up the servo lead opening with new foam and thin ply. At least when the wing is off, it's going to look a lot nicer than it did. Now we are back into the process of painting on coats of EZE-Kote , primmer filler and then sanding back before repeating.  This is the point where I have to stop myself thinking why don’t I just buy BNF’s
 

Edited August 17, 2023 by Roy Thompson

[Roy Thompson]

Progress is happening and despite the fact I've been working on it for a few hours every day, it seems dreadfully slow progress. This hasn't been help be the strong winds every time I want to spray a coat of primer or paint.

This week, however, I called a stop to rubbing down on the wing and finished it in a coat of grey primer all over. Only to remember that the yellow underside will need white primer. First job this week, trip to the car spares shop for white primer. On the subject of the yellow, I've been in two mind about matt or gloss. The pre /post ww2 all yellow A/C are gloss yellow, and the camo was only added for the war years with little regard for any standard layout. So I think I'm going with gloss on the underside.

One small embellishment to the wing, I've added wing joiner capping strips, made from card. One way to recycle the cornflakes box. I will use card to simulate the cockpit & storage box doors, as when you look at them, none are flush with the skin. The same idea will be used for the refuelling panels on the wings as well at some point.

The rudder has been refurbished. The covering, which wasn't done as nice as it could have been, was removed and replaced with new Solertex from an old roll I've had for years, originally brought to cover parts of the MB5. The fabric hinge is now replaced with 3 pin hinges, and it's been given a coat of matt yellow for now.

Hopefully by the end of this week we will start to add some colour to the rest of her.
 

[Geoff S]

It's looking very good.  From my own experience it's ideal to get the battery as far forward as possible in a glow/electric conversion because modern brushless motors/LiPos are so much lighter than the glow engines they're replacing (and very much lighter than brushed/NiCad set ups).  You've obviously made an effort with the forward extending battery box. Will the cowl shape allow a bit more?

 

It looks a satisfying project.  I loved the 'second model stash' story.  I'm fortunate to have a very tolerant wife, though she is encouraging me to get rid of some pedal cycles as well as some long unflown models.

[Roy Thompson]

1 hour ago, Geoff S said:

You've obviously made an effort with the forward extending battery box. Will the cowl shape allow a bit more?

 

 

No not really it all gets very snug from that point in. There will be the large lump of lead to go back on the front of the battery box as well. If I’ve done my calculations correctly I’m hoping not to be too far off, time will tell.

 

We all need a bit of tolerance in our lives. I let her have control of the TV remote, she lets me play with my toy planes!

[Roy Thompson]

Been very busy with the cornflakes box today. Storage box boor, cockpit doors and front  instruments panel access panel all made from card, very pleased with the overall effect. 

[Roy Thompson]

Not a lot to report this week in the few hrs I've had, just priming, rubbing down followed by more primer and a little paint here and there. Hopefully by the end of the week we should have something worth showing.

[Roy Thompson]

We have some visible progress this week. I've made an effort this week to spend at least a couple of hours each day, just to get it to the point where I can start fitting out the rest of the gear on the inside.

After having some issues with the primer just down one side where I was using a white primer over a coat of high build primer sanded back, the white crinkled. I don't know why it should do it just on the one side, as the other side went on OK. Anyhow, that resulted in more rubbing down on the that side and an over light coat of the high build before the yellow top coat, without the white. Strange.

Next up, an evening spent masking all the yellow and the top of the fin where the insignia will go. The following day I managed to spray most of the dark earth areas ready for the dark green, I've had to wait until the wind drops to allow me to do this outside in the garden, I don't like spray-painting in my workshop even with extractor fans and a face masks, plus the dust from the overspray get everywhere.

The other issue with painting inside is I can't assemble this model in the workshop, I just don't have the room. Which has meant that the dark green had to wait until Sunday afternoon, when we got home from the Popham model air show.

As soon as I was happy with the camo, I couldn't wait to get the masking off and see what see looked like. It's like the butterfly emerging from its chrysalis.
Well, it's not perfect, but for my needs it's will do.

[RottenRow]

That looks very nice Roy.

 

Are you using aerosols or a small spray gun?

 

Brian.

[Roy Thompson]

Humbol aerosols for the top, Halford's car paint for the yellow. I do have an airbrush setup I could have used but, but aerosols was quick and easy.

[Roy Thompson]

Yesterday I refitted the rudder using pin hinges, installed and adjusted the closed loop system. Undercarriage saddle clamps cleaned and painted, before reinstalling the gear. Motor ESC and radio installed, and tail fin insignia painted. Painted 3D printed latches for the stowage. Cut out two new windscreens.

It’s starting to fill like it’s moving on a lot quicker, still lots to do but not anywhere as much as there was.

The only down side is where I used frog tape for masking it has marked the yellow paint finish, so I will need to give it a going over with cutting paste before too long. This could be the first and last time I try frog tape.

[Roy Thompson]

Pictures of yesterday’s progress. We are almost at the point where I can stick a battery in it and bring it to life for the first time in who know how many years, or decades for that matter.

[Outrunner]

Looks really good Roy, should be flying soon!

 

What battery are you going to use?

[Alan Hilton]

Cracking job it looked like a black bag job at the start .My dad used to fix them during the war .He was rather rude about the main spar which he had to re glue often .

 

[Roy Thompson]

Thanks.

 

I’m going to use a 6S 5000mAh pack, and if my calculations are correct it should give me a bit more horsepower than a 120 4S. Must admit I’m looking forward to powering it up to see what the performance is like. 

[Roy Thompson]

5 minutes ago, Alan Hilton said:

Cracking job it looked like a black bag job at the start .My dad used to fix them during the war .He was rather rude about the main spar which he had to re glue often .

 

That’s the problem with giving perfectly serviceable aircraft to pilots, and worse still student pilots. 

[Roy Thompson]

Well we didn’t make it to the E Fly-In event with the Magister, besides it not being ready I don’t think I could have fitted it in the car with all the other models I wanted to take.

The Great British weather did its best to put the mockers on the day, after the hottest day of the year on Saturday But nonetheless we had fun. 

 

 

[Roy Thompson]

Things are moving on this week.

Monday I decided to tackle making the battery bay cover. The cowling from this model you may remember was very beaten up, and that I had spent some time making repairs, I also have an untouched, cowl from the other kit. Hopefully the reason for patching up the cowl will now become clear.

As you may know, Martin has also picked up a second hand Bowman Magister to home his old Kalt 22cc petrol engine. Martin's example, I must admit, was in far better condition than mine but lacking a cowling. Martin reached out to me about finding/making a replacement cowl, and as I had already thought it would be a good idea to make a mould from my untouched example before I began cutting it apart, I offered it to martin to use as a plug. By good luck, Martin has contacts with a company who specialise in composites, and their quote to make up a handful of copies turned out to be very reasonable.

My plan therefore is to use one of these new cowl to replace my old original cowl eventually, but first I'm going to use the old one to work out how to make the battery bay hatch. Once I'm happy with it, I will then start cutting the new one using the knowledge gained. With luck, I will be collecting the new ones from Martin at the BMFA Model Building Show at the end of the mouth.

Getting back to Monday, I spent the day measuring and marking out the cowl panel lines for the top panel, before attacking it with the dremel and cutting disc. The idea is plywood tabs along the sides will locate the top part, and magnets fore and aft will hold it in place. I have thought about having other fixing or latches, but this seems the simplest and less visible way of fixing, and so far so good.

Wednesday we had a pleasant couple of hours in the garden assembling and checking the model for CG, radio and control movements, my garage workshop being too small to fit the model assembled.

The good news from this was the model wasn't nearly as tail heavy as I was expecting, allowing the removal of a lot of the lead (340g worth) I had fitted, the total weight being dead on 13lbs. With all the setting up out of the way, now we were ready to take her up the field at last.

This afternoon, with my new 6s 5200mAh pack charged for the first time, loaded her up in the car and headed out for the flying field. All went fine, the range check was good, the motor run-up showed a total power of 1578 Watts spinning a 18x8 wooden prop. In a 13lb model I think this is more than enough.

There came a point where there was nothing else to do but take her out on the strip and give her a go. I've been told that these models fly like a big old trainer, and I can now agree with that. The first flight was kept short, just over 2 minutes, and I only flew circuits (sorry no video). She was air bourn, very quickly with little over haft throttle, in fact I never used fall throttle during the flight. As for trim, only a couple of clicks were needed, she does fly very well and my best guesstimate control throws are about right.

The only issue I had was a radio signal low warning from my transmitter. I don't know what is coursing, as I can't find anything obvious. There is no sign of any signal loss in flight the telemetry doesn't drop out, and on the ground I can get up to 50 steps before losing signal on the range test. For some reason, my Jumper TX doesn't like this Orange receiver, although it works OK with my old spektrume radio's. I will swap it out tomorrow.

Now we know it fly wells, I can concentrate on finishing up all the details, but that's for another day.