46" Spacewalker

[Henri Squier]

Hello everyone,

This is in fact a side project while building up a TN Spitfire.

A broke my own design Spit mainly because, flying until now exclusively park flyers, I didn't manage to land a heavy loaded plane.

Thus, this one will be my training horse ...

So, picked up a 3 view and "sketckuped" it.

Classic shape :

--> no worry about its flying ability.

--> Should not take long to built (anyway it's winter).

"46' TN Spitfire trainer" :

--> so 46' wing span,

--> Eppler 197 instead of my usual beloved naca 2415,

--> target weight 1,0 Kg in order to reach +/- 45-50 gr/dm2.

Not over powered (ProtroniK 2610/1200 - 250 W with 10-4) :

--> Because flying heavy planes is the problem (and I have to admit also because I already have this engine).

Solid landing gear :

--> because landing is also the problem !

Skechup allows me to plans that I can print and re print if necessary.

[john stones 1 - Moderator]

Nice choice Henri, a very forgiving and nice to fly aeroplane

John

[Henri Squier]

Classic old school building (I suddenly realize that you feel old when you say that).

2mm medium hard balsa.

Nothing very new isn't it ? Hope not to bore some one in fact.

But balsa is magic.

I confess having once a "Depron period".

But you always come back to balsa.

Because balsa is the best.

[Henri Squier]

But don't misunderstand me ...

I love balsa but ...

even if sometimes I wonder ...

... I won't marry with it.

Some times you feel your efforts are not fairly rewarded.

[Henri Squier]

Oh ! thank you John Stones 1, thank you for your support.

[Former Member]

[This posting has been removed]

[Henri Squier]

Thanks for comment Percy (but do you include crash as a landing ?),

A part of the problem is "my" runway . It's a country road between two fields that once was paved and which is now only flat on a small portion (2,5 m x 25-30 m). Perfect for 200-450 gr parkflyers but far too small up to my pilot skills for a heavier plane.

Have to learn precision landing ... or change flying field ... (or change hobby (female point of view).

I had a couple hours free ...

I must tell this is not my favorite part.

Here some pics of the dry fit.

Everything went perfect (except one or two angles to trim). This became quite constant since using Sketchup for plans.

Good evening to all, henri.

[Andy Shailer]

Looking good henri, nice model and nice building

Andy

[john stones 1 - Moderator]

That is coming together nicely Henri

Your build looks to be nice and light, I don't think this one will be heavy

John

[cymaz]

Nice build Henri, don't forget, take offs are optional and landings are mandatory.

It's easier not to fly in marginal weather than attempt a landing in one.

[kc]

note that it should be " not '

( you would be able to get inside at 46 ft span! )

It's no problem here but don't order balsa using ' instead of " or the size of vehicle needed to deliver it will surprise you!

[Former Member]

[This posting has been removed]

[Chris Bott - Moderator]

Posted by Henri Squier on 06/01/2015 21:18:45:

Shame on me, Shame on me !!!

I try to ask for modification, sorry, I'm not used with non metrical system, I was really unwitting.

Sorted Henri

[kc]

Actually metric measurements might be quite acceptable. Most younger people only think in metric, while older people are able to use either feet and inches or milliimetres & metres. Most of us older people hate centimetres and prefer just millimetres.

However convention seems to be that wingspan is in inches and wing loading is in ounces per square foot. Kilograms are OK to us but gms/dm2 probably seems very unusual to most aeromodellers in Britain!

I couldn't see any provision for wing dowels or wing bolts so is it to be rubber bands or a one piece model?

 

 

Edited By kc on 07/01/2015 11:56:53

[Henri Squier]

Thank you kc for "resizing" !

Your eyes are sharp ! you're totally correct there are few things I have shamefully put on the side and will have to decide some day :

- I will in all likelihood bolt wing, I'm waiting finishing the wing in order to drill the holes.

- How will I fix the LIPO ?? and how will I fed them in the plane ? I think it will be an opening at the lower part of the cowl, have to decide.

- I hesitated, I hesitated, I hesitated and finally decided it won't be a scale under carriage but a simple piano wire bolted just in front of the leading edge of the wing (initial program was to quickly do a trainer...).

Thing are going dead slowly ... here are latest pictures (must admit only weakly exciting) ...

Fuselage has been glued

When I see some master pieces I feel a little shame with my small Spacewalker.

When I see in some posts a the working table with holes and square to build square the fuselage I feel like prehistoric :

Cables were fitted in

and some planking

and finally some more work on the wings :

thanks again, henri.

[Tim Hooper]

Henri,

You have nothing to apolgise for; that's a nice, tidy, well thought build - congratualtions!

I see you're using SketchUp as a CAD programme. I'm thinking of throwing my crayons away in the near future and switching to CAD too, and SketchUp seems a good (cheap) way to start. Have you any previous CAD experience?

tim

[Henri Squier]

Hi Tim, thanks, No, none to answer you question.

I managed Sketchup quite (very) fast although I admit I was initially a little afraid. I give you the tutorial that helped me a lot at the beginning, up to me very good (on top of that it's RC oriented).

**LINK**

I've been sea sick at the beginning but now it's Ok.

I used Sketchup because it was free and really easy (ah! be able to print, print and reprint .... what a joy !), but will perhaps change in the future for a CAD "laser cut" friendly. But i'm still using pen & paper.

henri

 

Edited By Henri Squier on 14/01/2015 23:22:44

[Charles Smitheman]

Hello Henri,

That Sketchup program looks good, thanks for the link, perhaps I too can throw away my pencil!

I too am working on my Spacewalker, a Sig 1/4 scale one which I am rebuilding after a bad landing :} Well a bad crash actually!

Keep up the good work.

Charles

[kc]

I find it saves a lot of time & frustration by planning the locations of all the equipment well before construction starts. All the holes for dowels, slots for Lipo velcro straps, wires etc can then be drilled easily when the parts are flat on the bench. Much more difficult to drill holes accurately when fuselage is partly assembled.

I think you will find that a drill won't quite align squarely with your former which takes the dowel ( or dowels) making it a bit difficult to drill accurately. In that case I suggest a smaller drill bit to start with and then use a tapered round file or a prop reamer to enlarge to perfect size and location.

The wing will need reinforcement around the wing bolt area if wing bolts are used. If rubber bands are used the fuselage will need a strong area to take the wing band dowels which go across the fuselage and should go through the ply doubler if possible. I think you will find it difficult to make the model to 1 kilo total weight and it may well end up over 1.5 kilos so all the wing retaining parts should be strong enough to allow for a model of 1.5 to 2 kilos. Check out similar models made by expert builders like Peter Miller. His 48 inch span model usually come out around 2 kilos. For example see his free plan in the latest RCME. The design he uses for wing retention is adequate. A lesser ( weaker) design would probably result in structural failure.

You could also consider a wire undercarriage mounted in the same way Peter Miller has done in recent models. That is a torque rod principle which uses ply plates with slots in mounted vertically in the fuselage. Very forgiving u/c for grass runways as they bend back a little as the torque rod part rotates then recovers. It means installing the ply plates at about the time the fuselage is assembled ( i.e. now )

[Tim Hooper]

Thank you, Henri!

I'll bookmark your link, and explore it further later.

tim

[Henri Squier]

Your welcome Tim !

Hi kc, thank you for your interest.

It's funny how life is ... just before discovering your post I intended to tell how painful it is to come back on work that has not been previously though or poorly anticipated.

As you suggest thinking how things will fit together became with time (and age ?) a growing part of the job.

But at a time I just have to leave all calculation and puzzle with balsa ...

Initially I thought screwing in the piano wire of undercarriage but was seduced by your slot idea :

It will be the slot system :

It's meant to be removable, will see...

Thanks to all, henri.

[kc]

Your idea is used on a few small models but is not a torque rod u/c. Torque rod is better. A torque rod u/c as used on many David Boddington designs and most of the modern Peter Miller designs consists of 2 u/c legs ( one right , one left) which go across the fuselage and then up into ply plates which are glued onto fuselage ( along the fus, not across! ) It's the bit that goes across the fuselage which twists and is the torque rod. Note that it's easier to angle the slots to rake the u/c and make the wire flat in one plane rather than bend the wire into 3 dimensions. Study a few plans to see how this very common u/c is made.

[kc]

A photo of the torque rod u/c on one of my models - a Peter Miller design called Swamp Rat - which shows the 2 parallel u/c wires -

 

The 8 SWG piano wire rods go up vertically - each goes up on the OPPOSITE side to it's wheel -  into the ply glued along the fuselage.  So there is a section of wire across the fuselage which can twist.  The movement as the u/c hits the ground forces the wheels back which then converts to a twisting motion of the wire across the fuselage which gives springing.  Similar principle is used on for the suspension of original VW 'Beetle' and many other cars instead of coil or leaf springs.

Edited By kc on 17/01/2015 12:28:35

Edited By kc on 17/01/2015 12:31:02

[Keith Evans 3]

Wherever possible on my own or other models I build from plans I opt for the torque under carriage system . I've never had an undercarriage failure .They can bend and distort but easy to correct ,unlike the solid dural type bolted into a ply plate ,which if you don't use nylon bolts will rip half the fuselage away .

I first came across this system a number of years ago when building a Super Tauri .

[kc]

If you used the u/c in your picture then the wire would have to be secured firmly to the ply. Peter Miller used this shape of u/c on some small models but he used multiple wires to 'sew' the u/c to the former and then soldered the wires. This meant the u/c was not removeable and had to be inserted at an early stage, it would then be in the way when covering. Some people use that shape of u/c but bent at right angles so the 'loop' goes along the fuselage ( horizontal not vertical) and is secured by u/c clamps onto a ply plate under the model

I prefer designs like Swamp Rat which have a torque rod u/c installed after covering. Easier to cover and the u/c soaks up the landing shocks well. Note that instead of trying to drill up into a 6mm ply block it's easier to saw a slot in a 3mm ply and laminate another 3mm piece ontop.

These two photos show typical  blocks for torque rod u/c, in one you can see the slot  uncovered in the 3mm ply. in the other the slot is covered by some 3mm ply.  The slot was sawn slightly undersize and after assembly a drill was used to enlarge to exact size of the piano wire.

 

Note that the fuselage sides have a 1/32 ply doubler and that the u/c block is glued to the ply , not just onto balsa.  Also the ply u/c blocks locate against the former strengthening both and also creating a recess to help  'jig' the fuselage when assembling.    Provision has been made for the servo bearer mounting.  All worked out at the design stage!

Edited By kc on 17/01/2015 13:27:19