Bowman Miles Magister resurrection thread.

[Roy Thompson]

That looks impressive Martin.

 

Excluding gliders, the largest powered model I’ve flown in terms of wingspan is the TN Dak at 72”, in terms of wight then it had to be my old Dan Parson’s MB5 when it she had twin brushed motors and 20 nicads at 13.5 lbs on a 55” wing, the gravity was strong in this model back in the day before Lipo’s and brushless motors.

If anything the larger the models the nicer they tend to fly and less prone to being bounced around if the wind is a bit choppy.  

 

Edited August 3, 2023 by Roy Thompson

[martin collins 1]

Love the Dakota Roy, biggest span i owned was a 10ft plan built B17, i bought it with 4 .52 4 strokes in it but converted it to Electric, flew like a big trainer.

[martin collins 1]

Test flew the Magister late this afternoon, flight went great, nice flying model unfortunately the landing left a bit to be desired. The old Kalt, didn`t miss a beat but a combination of no wind, a floating on Maggie and me paying too much attention to pulling the throttle trim down rather than flying the plane on to the deck meant i ended up with too little airspeed and still a a bit of air under the wings, this is a consequence of only flying electric for the last fifteen years and not having to worry about trying to shut the throttle on a trim. If the spats hadn`t been on it i might have got away with it but they were built onto the wing complete with filler so nothing could flex, result they punched into the wing as the gear tried to flex back 🤬. Suggestions on the best way to repair appreciated, i guess cut out the compressed stuff, presumably you put new foam in if so where can i buy it? Once epoxied in re sheet with some thin balsa? Not sure what the model is covered in but will worry about that once it is structurally sound again, the good news is the U/C blocks have not been compromised the damage is all from the spats.

[Roy Thompson]

Congrats on the first flight, and shame about the landing. We’ve all done it, flew my other MB5 of the 3rd time yesterday did two practice approaches/ touch & goes; spot on, then banged it in hard on the landing and broke the retract mounting plate. 🙄

 

looking at the pictures, I would replace the foam with a block cut from any old polystyrene packaging, glued in with PVA. Cut back the veneer a little larger and replace with 1/32 ply. You could buy new veneer from balsa hut but for the amount and plus I think ply would stand up better from the loads the spats may put on it.

 

Option two fill the void with light weight filler and cover in 1/32 ply.

 

Looking at the finish, I would say that just like mine was, it’s covered with dope and tissue. A tried  and tested method of the day. 

 

This goes to show that Ivy & Martin had a point about the spats in their review, how many years ago it was.

 

[jeff2wings]

I think something like this would be better suited to a model of this size rather than a bit of piano wire, if these are any good to you p.m me 

 

[aidan mcatamney]

On 30/07/2023 at 11:19, martin collins 1 said:

Yes did see it and wondered, a bit big for a Bryant one unless it was built from blown up plans. Mine is making progress, tank and battery going in today, servos will have to be rear mounted and a small amount of lead to balance with the Kalt 22cc up front.

Nice looking plane. 

[aidan mcatamney]

On 03/08/2023 at 11:15, martin collins 1 said:

Love the Dakota Roy, biggest span i owned was a 10ft plan built B17, i bought it with 4 .52 4 strokes in it but converted it to Electric, flew like a big trainer.

Fantastic looking aircraft.  

[Eric Robson]

1 hour ago, Roy Thompson said:

Congrats on the first flight, and shame about the landing. We’ve all done it, flew my other MB5 of the 3rd time yesterday did two practice approaches/ touch & goes; spot on, then banged it in hard on the landing and broke the retract mounting plate. 🙄

 

looking at the pictures, I would replace the foam with a block cut from any old polystyrene packaging, glued in with PVA. Cut back the veneer a little larger and replace with 1/32 ply. You could buy new veneer from balsa hut but for the amount and plus I think ply would stand up better from the loads the spats may put on it.

 

Option two fill the void with light weight filler and cover in 1/32 ply.

 

Looking at the finish, I would say that just like mine was, it’s covered with dope and tissue. A tried  and tested method of the day. 

 

This goes to show that Ivy & Martin had a point about the spats in their review, how many years ago it was.

 

Do not use pva to glue foam into foam it doesn't go off, I once glued undercarriage blocks in to a foam wing and when it had its first flight the undercarriage  pulled out and the glue was as wet as when used a few weeks ago. PVA is air drying, since then I have always used epoxy. 

[Roy Thompson]

11 minutes ago, Eric Robson said:

Do not use pva to glue foam into foam it doesn't go off, I once glued undercarriage blocks in to a foam wing and when it had its first flight the undercarriage  pulled out and the glue was as wet as when used a few weeks ago. PVA is air drying, since then I have always used epoxy. 

Small area, not structural, don't flood with pva, should be OK. If glueing undercarriage blocks in, then epoxy every time.

[Piers Bowlan]

14 hours ago, martin collins 1 said:

Test flew the Magister late this afternoon, flight went great, nice flying model unfortunately the landing left a bit to be desired. The old Kalt, didn`t miss a beat but a combination of no wind, a floating on Maggie and me paying too much attention to pulling the throttle trim down rather than flying the plane on to the deck meant i ended up with too little airspeed and still a a bit of air under the wings, this is a consequence of only flying electric for the last fifteen years and not having to worry about trying to shut the throttle on a trim. If the spats hadn`t been on it i might have got away with it but they were built onto the wing complete with filler so nothing could flex, result they punched into the wing as the gear tried to flex back 🤬. Suggestions on the best way to repair appreciated, i guess cut out the compressed stuff, presumably you put new foam in if so where can i buy it? Once epoxied in re sheet with some thin balsa? Not sure what the model is covered in but will worry about that once it is structurally sound again, the good news is the U/C blocks have not been compromised the damage is all from the spats.

The torsion-bar type undercarriage is incompatible with the spats being glued to the bottom of the wing!
Personally just fill the hole (balsa & lightweight filler, it’s non structural) then leave a gap between the top of the spat and the wing so that the leg can bend backwards somewhat in the event of a ‘ firm arrival’. Not scale but it would survive a firm landing. The full sized had oleo struts which compressed on landing and the spats had ‘trousers’ which could slide up and down with the oleo leg.

Edited August 5, 2023 by Piers Bowlan
Took closer look at photos!

[Piers Bowlan]

It’s a great looking model Martin, I hope you have her fixed up and flying again soon.

[martin collins 1]

11 minutes ago, Piers Bowlan said:

It’s a great looking model Martin, I hope you have her fixed up and flying again soon.

Thanks Piers, got a fly in to go to next Friday and plan on taking the Maggie so repairs are under way!

[RottenRow]

Mine doesn’t have the spats (The RAF removed them in service for easier maintenance) but I disliked the ‘twangy’ piano wire legs.

 

Stiffening them up on a completed model is quite difficult, but I made some improvement by shortening the torsion bar length to about 60% of its original length.

 

It was then necessary to fit some ply inserts into the wings to take the 90 degree bent ends of the torque rods in their new positions. This was achieved  by cutting cylindrical holes from the top surface of the wings right down to the top of the existing hardwood U/C mount and epoxying in place two cylinders made up of discs of 1/4” ply. These were drilled to accept the ends of the torque rods.

 

The reduced lengths of the torque rods, and their longer bent ends (almost the whole wing thickness) has certainly stiffened up the U/C.

 

Note that the positions of the inserts were such that they are hidden by the wing seat fairings when the wing is in place.

 

Hopefully the photos help with explaining this.

 

On the Magister I’m currently building from the Hangar One plan the U/C comprises Robart struts mounted into pairs of substantial ply plates, this couldn’t really be replicated for the Bowmans foam wing version.

 

 

Brian.

[Roy Thompson]

Thank you Brian, I was wondering what these were!

[martin collins 1]

Gone with balsa block as the repair medium, epoxied in with the 30 min stuff, will sand to shape and tissue/dope before painting. Is cellulose dope ok on foam, shouldn`t get near it because of the balsa but just so i know..........

[jeff2wings]

Don't get cellulose near foam it'll melt,just use thinned down PVA to attach the tissue, btw what size is the wire? 

[Roy Thompson]

As we're on the topic of landing gear. Mine doesn't have the spats, and who ever made it did a very reasonable job on the struts. Although they have lost thr drag links. 

Just wondering if the forks were home made or brought.

[Roy Thompson]

Quick note as to how my one is coming on. The fuselage and bottom of the wing have been covered in glass cloth and EZE-Kote, just the top to do.

Before covering the wing, I've taken the time to fit drawstrings to the wing 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.

Other jobs, 3D printed two booster cushions for the pilots. Added ply doubler and refitted the wing mounting T-nuts, this was only 1/8 ply and didn't hold the nuts well (picture 3 as they were originally). Wile I was at it also cleaned up the wing fairings.

 

My club has its Electric Fly-In on September 10th, I've hoping to probably not finish it, but to at least get it flying by then. Well, that's the plan if I don't cripple myself any more doing the gardening, and can walk that is!

[Roy Thompson]

Hi Martin, rather than high jacking your thread, I've started another build thread.

 

[martin collins 1]

Repairs to wing completed, paint will go on today, i took the opportunity to repair a split in the veneer sheet which was just behind the spat damaged area at the same time. I have also cut the spat tops away at 45' from behind the wire legs to allow them to move without damage to the wing. 

[martin collins 1]

The Maggie has been in the air again today, i'm at a RAFMAA fly in at Shipdham. It flies great, undercarriage rrpair/ mods worked well but i would say the u/c wire needs to be of a thicker gauge, it is very springy as fitted currently. 

[Roy Thompson]

Looks good sitting in the sunshine.

[martin collins 1]

On 05/08/2023 at 13:38, RottenRow said:

Stiffening them up on a completed model is quite difficult, but I made some improvement by shortening the torsion bar length to about 60% of its original length.

 

It was then necessary to fit some ply inserts into the wings to take the 90 degree bent ends of the torque rods in their new positions. This was achieved  by cutting cylindrical holes from the top surface of the wings right down to the top of the existing hardwood U/C mount and epoxying in place two cylinders made up of discs of 1/4” ply. These were drilled to accept the ends of the torque rods.

 

The reduced lengths of the torque rods, and their longer bent ends (almost the whole wing thickness) has certainly stiffened up the U/C.

I think i will look at replicating this on mine, the legs as on the model are going to be a constant headache which spoils the enjoyment i am currently getting with this model. Could you pm me with more details on your process, was the wing foam removed with a circular cutter in a drill and was that same cutter used to cut your ply discs? Looking forward to flying it again but i feel even a slight bounce on the current set up is going to spring the modified spats back into the wing before the gear returns to where it should be as it has happened already on quite a reasonable touchdown.

[RottenRow]

Hi Martin,

 

I have a set of these hole cutters. They are cheap off of eBay, come in sets of ten or twelve, and are supposedly diamond coated. I don't think they would last long on any hard material but they work well for cutting out lightening holes in balsa and ply. They do not have a centre drill so tend to wander off course if you use a hand drill, so are best used in a pillar drill when possible.

 

 

I used a 28mm one to cut out 12 discs from 1/4" ply. I then marked the centre of one of the discs and drilled it with a clearance hole for some long screws I had. This must be smaller than the diameter of the piano wire of the undercarriage. I used this disc as a template to drill the rest.

 

The discs were then glued together into two stacks of six, with the long screws holding them tightly together whilst the glue set. Once set they were sanded smooth.

 

I marked suitable positions for the new torque rod ends onto the hardwood U/C bearer. Mine were 90mm from the centre line. Further out would make the U/C stiffer but the blocks would be visible on the top of the wing; at 90mm they are covered up by the wing fairings. Holes were then drilled through the groove in the bearer at these positions, right through the wing, making sure that the drill was perpendicular to the undersurface of the wing at that point.

 

The big holes in the wings were cut using the next cutter size down from that used to cut the discs (25mm). The diamond coating on these cutters is quite thick so they cut oversize on the outside and undersize on the inside. The holes were cut from the top surface, centred on the two holes previously made. I think I cut the veneer away first using a sharp knife, then used the cutter by hand to cut through the foam until the cutter reached the top of hardwood bearer in the wing. After digging the foam out I carefully trimmed the holes using sandpaper wrapped around a piece of tubing until the stacks of disks were a snug fit. They were then epoxied into place, making sure that the holes in the discs lined up with the ones in the bearer.

 

When set, the holes were opened up to suit the U/C piano wire, making them a tight fit. The tops of the ply discs that protruded from the wing surface were reduced down with a Permagrit file and they were then sealed with a coat of epoxy.

 

The bent ends of the original U/C legs were cut off and re-bent at 90 degrees in such a position that the undercarriage legs remained in the same place as previously. The bends were made long enough to almost protrude through the tops of the ply discs. The legs were then reinstalled.

 

The above doesn't completely stop the bending of the legs but reduces it significantly. If it is still a problem then new legs will be needed, made from a larger gauge wire.

 

I hope that all makes sense...

 

Brian.

 

[martin collins 1]

I have a set of those cutters Brian, thanks for the detailed explanation, will give it a go.