Boeing B52 PSS Glider

[Terence Lynock]

Hi Tim,

do you want the plans for a B52 sloper? 78'' span, can send you the TIFF files if you want them.

 

Nah...Ill stick with this one thanks Terence.

Edited By Tim Mackey on 03/12/2011 16:42:21

[Erfolg]

I am impressed by the machine.

 

I am sure that it would cost a lot to build, without access to low cost stepper motors and interface, not withstanding the leadscrews etc.

 

All in all impressive machine (tool?) and the model build!

 

I am eager to hear more, I shall watch the thread attentively.

 

I do like the idea of the a wing cutting service, as "I could kill to birds with one stone", A day out with the better half and purchase some wings, happiness.

[Tim Mackey]

Didnt cost that much at all - job lot of stepper motors around £30 for 6

( only one of which was duff ) so four used and one is spare.

The driver interface was a tad more, but again....bargains from china to be had via ebay these days.

The lead-screws are simply threaded studding from a DIY shed, with a length of hex bar threaded to suit, that hold the cutting wire brackets

( simple brackets from the diy shop again )

The metal frame was welded up by himself, a bit of checker plate here and there.....

The clever software is simply Profili for wing sections ( pro version which allows for 4 axis ) and an another free downloadable package DEV FUS ( foam version ) for, errr, fuselages.

Finally, "Mach3" does the driving of the cutter itself.

 

The cutting is now on hold for a week or two due to holidays etc, but when we do the actual tailplane and fins, I will film the whole process - it really is most impressive to see and hear it all whirring away.

Edited By Tim Mackey on 17/12/2011 13:56:37

[Former Member]

[This posting has been removed]

[Tim Mackey]

Indeed it is Tom - at the time, the largest RC model glider ever built, and in the Guinness BOR to boot. Simon plans to bring it to the Orme again for one of next years PSS meetings.

As for me...well, I simply wouldnt have the space for one thing.

 

And a rather youthful Phil Cooke assists Simon at an aerotow back in the 1940s

[Former Member]

[This posting has been removed]

[Tim Mackey]

These days...its trailered.

[Tim Mackey]

Well it seems we had some erroneous data in our programme - the final shape ended up a bit off as it were - here on the left is the profile we ended up with, and on the right, is a quick mock up I did using my old fashioned bow and some ply templates taken off the plan.

TBH we weren't that happy with the finish on the foam anyway - recycled builders yard stuff which seemed to have a fair few hard bits in it - scattered randomly throughout, so this affected the cut - and the final finish would need a lot of sanding.

 

So.... I ve just had two more 8 x 4 panels delivered, and a quick test cut shows a much smoother finish. We just need to get the software data sorted now, and then its round two next week when Im back from Xmas visits down south.

 

My ABS engines arrived at weekend ( thanks Phil ) so Ill be doing them soon also. My plan is to trim and join as required, then fill with expanding builders foam to give some strength, before fitting to the pylons.

 

[Tim Mackey]

Ok, back on track with this project - the new 8 x 4 foam blocks were delivered, and a quick test shows them to be better than the first - no 'orrible hard bits in it. I've cut them up into manageable sized chunks, and then used the machine to square/true everything up. Its important that the block stands truly vertical with reference to the wire travel, so everything was trued up with levels, and the blocks then cut into the correct length for both the non tapered front sections, and rear tapered sections. I used a scrap offcut to do this little demo film of the cutter at work, and also to confirm that the newly drawn section was correct.

Tomorrow we plan on completing all the fuselage, and hopefully the tail feathers too.

Then I can get on in earnest with sheeting etc.

[Phil Cooke]

Great to see you making good progress on this again Tim, all the best for tomorrow's foamathon! Are you veneering inside and out?

[Phil Cooke]

BTW When I veneered some very similar sections last week on the A-10 fuz I noticed the veneer shrank a little, effectively opening up the U-section a little when it was still in two halves. I think I rushed the veneering and possibly the contact adhesive still had some drying and shrinking to do which caused it I think... Anyway one to watch.

Edited By Phil Cooke on 17/12/2011 14:15:43

[Erfolg]

Tim

 

The more i see, the more impressed i become.

 

It does seem that there is the bases for a number of articles on the

 

a) Construction of the machine

b) Software

c) Power supply, wire and set up, rates of cutting etc.

 

From my background and other ex-engineers I guess, it challenges very successfully preconceived, programmed reponces. No need for ground buttress threads with zero backlash nut assemblies, ground runners, rigid high mass frames etc.

 

It demonstrates the benefit coming to a problem asking, what is actually necessary. Above all ingenuity. All combined with a degree of the "Can do it" approach.

 

Model looks interesting to.

[Tim Mackey]

Posted by Phil Cooke on 17/12/2011 14:11:36:
Great to see you making good progress on this again Tim, all the best for tomorrow's foamathon! Are you veneering inside and out?

Nope, just 1.5mm balsa outside, then tissue/glass and PolyC.

Simon's plan does say that if you use a good ply spine ( which I am ) then inside veneer is not required.

[Tim Mackey]

Posted by Phil Cooke on 17/12/2011 14:11:44:
BTW When I veneered some very similar sections last week on the A-10 fuz I noticed the veneer shrank a little, effectively opening up the U-section a little when it was still in two halves. I think I rushed the veneering and possibly the contact adhesive still had some drying and shrinking to do which caused it I think... Anyway one to watch.

Edited By Phil Cooke on 17/12/2011 14:15:43

Thanks Phil - good tip...Ill be doing some test sections first.

I plan on soaking the balsa thoroughly, then wrapping it whilst still wet around each fus half section, securing with tape, and letting it dry thoroughly for a couple of days or so. Then, when removed I hope it retains its shape, at which point, Ill use copydex on both foam and wood. Fingers crossed.

[Tim Mackey]

Posted by Erfolg on 17/12/2011 14:22:43:

Tim

 

The more i see, the more impressed i become.

 

It does seem that there is the bases for a number of articles on the

 

a) Construction of the machine

b) Software

c) Power supply, wire and set up, rates of cutting etc.

 

From my background and other ex-engineers I guess, it challenges very successfully preconceived, programmed reponces. No need for ground buttress threads with zero backlash nut assemblies, ground runners, rigid high mass frames etc.

 

It demonstrates the benefit coming to a problem asking, what is actually necessary. Above all ingenuity. All combined with a degree of the "Can do it" approach.

 

Model looks interesting to.

 

Loads of self build "how tos" on t'internet Carl - and the prices of the equipment are reasonable too. I reckon the hardest part is learning the software. Ive been having a play around over the last few days, and as usual, actually practicing with the stuff is the answer - well it is for me anyway.

[Erfolg]

Tim

 

I suspect that you and your friend underestimate your achievement.

 

Many years ago, I headed a project to install a stepper motor system. The number of professional and technician engineers to build the system was considerable. The interface used Ladder Logic to set operational parameters so is immediately different. It did work as required, straight out of the box, but it took time and money. May be things are different now, more sources, broader knowledge.

 

I am impressed by all the achieevements, and being truthful, I am a ittle fearful in starting the project, without the crutch of a proven system. I will be trying, to fix a cost and source with particular emphasis on the control system (motors and interface). Part of the issue is identifying the current state of the art, rather the supplanted equipment or straying into cutting edge approach.

[Tim Mackey]

Oh I didnt do anything Carl....he built it all, and has pretty well got the programming sorted.

Ive just finished playing around with "devfusfoam" and think I have manged to create a whole new experimental shape - and figured out how to export the data as an ".NC" file which mach3 ( the stepper driving software ) requires

...so just off to the garage to give it a try.

[David Ashby - Moderator]

Posted by Danny Fenton on 02/12/2011 10:47:00:
Just goes to show this c of g myth is rubbish

 

As a full size pilot said to me recently while watching me fretting about with the CG on a model - "just fly it, the aeroplane will soon tell you where the CG needs to be"

 

Wow, that's a very impressive set-up Tim

 

 

[Tim Mackey]

I know....Im already up and have been playing around with it for an hour - and thats early for me these days !

Seriously tempted to make this its new home when Richie sells it on early next year.

Edited By Tim Mackey on 18/12/2011 08:03:59

[Ross Clarkson]

What a great thread Tim, loving it.

I am tuned in fully.

[Tim Mackey]

Well hopefully after today I can actually start doing something...I'm pretty well stuck until we have finished the cutting of the fus sections, and we are still having one or two issues with getting the rear section profiles just right - Im still waiting for Richie to arrive and help me out with the software

Thanks for tuning in, and as I say, hopefully things will get moving next week onwards

[Tony Bennett]

the run up to christmas week, you will get nothing done.

[Tim Mackey]

Errr, I am a bah humbug supporter, so no worries on that score.

I have NOTHING special to do, other than visit my favourite butchers for some goodies on Tuesday, after that Im in the garage full time mate.

[Stephen Grigg]

This is an interesting thread and see where the rudderless cracker model comes into the equation spooky

[Tim Mackey]

Progress has been a bit slow due to various reasons, but tonight I finally managed to get the tail feathers correct - they are actually rather a tricky shape when looked at clossely - with some acute angles and odd sweep-back etc. Further consideration needed to be given to the main spar and incidence spar positioning due to the rather small tip section once the elevators and rudder are cut free. I also had to modify the actual machine to allow the wire to traverse the acute angles involved. The wire was originally just attached with one spring at one end to allow for heat stretch etc...but this simply wouldnt allow the travel required of the horizontal carriage. I turned down a 30 mm pulley in my lathe from some bar stock, and fitted a bearing from an old brushless motor - this was then fitted to a bracket with a further bracket spaced away at the front which carries a CF nozzle - drilled with a 1mm hole to act as a guide for the wire, ensuring it stays in line with the pulley irrespective of the carriage angles.

After passing the pulley, the wire travels up to the top of the vertical carriage post, and over another pulley, and then has a heavy weight attached to maintain tension throughout.

The picture should hopefully illustrate.

So, having finally learned my way around the software, and got the machine running as required, I got the tail feathers done by the early hours.

Here they are placed on the early mocked up fuselage just to indicate the scale.

 

I made the mockup fus to see whether it would actually fit in the car in one piece - as this will save me the headache of making a two piece fus.