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Martin's Skywriter, aliitle late but....

A scratch built Skywriter incorporating the corrections, mods suggested by others

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Martin Dance 114/02/2017 20:50:12
129 forum posts
33 photos

tail weight.jpgHi,

I enjoyed building the Ballerina last year. As a notoriously slow builder I found following others progress made me build quicker! Slow? well 31/2 years to build Peter Millers RF4 is slow!

I am by nature a scratch builder, start with a heap of materials, drawings sharp scalpel blades etc and I'm off...slowly! I've been building models since I was 12 and now HMG pays my wages!

I thought I would start with the tail group because it is easy and I'm considering closed loop linkage for the rudder so having the tail group to hand should help with the positioning with the holes for the closed loop wires. Nicked the laminated LE idea using 6 lams of 1/16th balsa around a MDF former.tailplane laminating.jpg

john stones 114/02/2017 21:14:06
avatar
8369 forum posts
1330 photos

Hi Martin, welcome aboard, good weight on your tail plane and your formers n fuzz cut out already yes

John

Martin Dance 115/02/2017 22:03:08
129 forum posts
33 photos

Today's efforts were aimed to get the top wing looking ummmm more wing like!

most ribs in place, top wing.jpg

The first photo shows most ribs in position, but importantly there holding the rear spar in place whilst the glue sets. The next photo shows the wing at close of play. With all the top wing ribs in place and the top spar glued in place. The LE and TE are for tomorrow.

ribs and top spar.jpg

Martin Dance 115/02/2017 22:03:09
129 forum posts
33 photos

Today's efforts were aimed to get the top wing looking ummmm more wing like!

most ribs in place, top wing.jpg

The first photo shows most ribs in position, but importantly there holding the rear spar in place whilst the glue sets. The next photo shows the wing at close of play. With all the top wing ribs in place and the top spar glued in place. The LE and TE are for tomorrow.

ribs and top spar.jpg

Tim Ballinger16/02/2017 10:09:22
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155 forum posts
73 photos

Doesn't look like slow building to me Martin, quite the opposite.

Laminated tips seem to be catching on .

Tim

Lucas Hofman17/02/2017 13:41:36
465 forum posts
231 photos

You are going fast Martin. And your stabilizer looks very good too. How do you plan to make he pull-pull rudder horn?

Lucas

Martin Dance 117/02/2017 21:00:40
129 forum posts
33 photos

Hi @ Tim and Lucas, my rapid progress is an illusion! I like building wings so I tend to make rapid progress. So at the moment progress is Hare like. When I start the fuselage I will slow to a tortoises pace and then covering will be carried out at a snails pace, finally installation and linkages U/C etc will be done at a Sloth's pace! The rudder horn for the closed loop system will be made from 1mm epoxy/glass sheet, as indeed will the horns linking the upper and lower ailerons. I have used ply for horns on slower models but I'm not convinced they're adequate in this application. The gluing area will be roughened before applying epoxy. One of the reasons for doing the tail group first was to make the positioning of the rudder servo easier and the position of the holes in the fuselage for the control wires easier to determine. This in turn will impact on the elevator servo position and the choice of elevator linkage all moments for endless Sloth speed work! One point I should have made in an earlier post is my decision to use 3mm threaded inserts to retain the bolts holding the upper wing to the cabane. I found some online a year or so back but I failed to bookmark the site, but here is a photo.

3mm threaded insert.jpg

Finally tonight a photo of the upper wing this evening now requires the tips and the ailerons shaped.

topwing sheeting capstips and aileron material.jpg

john stones 117/02/2017 21:11:33
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8369 forum posts
1330 photos

Nice wing yes

Lucas Hofman18/02/2017 11:25:33
465 forum posts
231 photos

This is stimulating Martin! The weather is foggy and -4 degrees here so top sheeting will be applied this afternoon.

The inserts look nice, do you skrew them in the ply under the sheeting?

Regard, lucas

Martin Dance 118/02/2017 11:40:51
129 forum posts
33 photos

Hi Lucas, yes,they have sort of a thread more of a fine spiral ridge than a thread. What I did was to run a nut onto an M3 machine screw then screw the machine screw into the insert and then screw it into the plywood piece as on the plan. I used 4mm birch ply on my wing. The core diameter of the insert allows a 4.5mm hole to be drilled leaving just enough material for the thread on the insert to bite on.

Tim Ballinger18/02/2017 18:04:44
avatar
155 forum posts
73 photos

Is it a left hand thread ?

Martin Dance 118/02/2017 19:11:56
129 forum posts
33 photos

Tim, No its a right hand thread, but calling it a thread is overstating it, it is more a spiral ridge than a fully formed thread, a little epoxy or cyano will ensure they won't easily come out.

Tim Ballinger19/02/2017 08:38:12
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155 forum posts
73 photos

Remembered where you got them yet ?

Tim

Denis Watkins19/02/2017 08:43:26
1874 forum posts
94 photos

Threaded inserts

http://www.modelfixings.co.uk/threaded_inserts.htm

Tim Ballinger19/02/2017 13:34:04
avatar
155 forum posts
73 photos

Thanks Dennis, a proper fixings emporium!

Tim

Martin Dance 122/02/2017 13:28:57
129 forum posts
33 photos

A little more progress, but first I have failed to remember/ find the source of the 3mm inserts. looked at my ebay history, nothing, looked at my Paypal history but it only goes back to the start of 2016. I'm pretty certain I bought them in 2015. Modelfixings only go down to 4mm inserts. A recent search on Google finds plenty of 3mm inserts but not the same as I bought originally, annoying because I could do with some more.

Any way next photo shows top wing with the nearly complete tips in place and the ailerons tacked in place and roughly shaped.

top wing tips and ailerons.jpg

By the way Lucas how did you form your tips? I toyed with laminating but decided against it. I seem to have a bit of an issue at the trailing edge/aileron interface trying to ensure there is enough material to produce a flat surface to line up with the aileron.

lower wing underway.jpg

Another week, another wing! the start of the lower wing. One thing I should have spotted is that the innermost LR2 rib needs to be cut in order to fit the dihedral brace. a little surgery needed here. Any one spotted how much dihedral this wing has before I start drawing all over my plan. Finally the last two photos remind me to have a tidy up!

Tim Ballinger22/02/2017 17:20:01
avatar
155 forum posts
73 photos

With regard to the inserts I also noted they did not seem to make a 3mm. Also noted Lyndsy used 4mm on the original. Might just stick with the T nuts.

Tim

Martin Dance 126/02/2017 22:35:04
129 forum posts
33 photos

More progress on the lower wings, the first photo shows the leading edge sheeting in place, the second shows the pitot head in place, I'm tending to build telemetry into new builds. Air speed is useful but it does need a talking Tx, the first model I installed an ASI was quite small and cruised around at about 70mph or so I didn't have a talking TX then and you cannot look down at the screen with a small model at speed smiley

lower wing trailing edge sheet.jpg

pitot tube installed.jpg

One small error I have noticed whilst building the wings concerns the lower spar spacing on the wing rib drawings does not line up with the wing drawing. My ribs placed the rear spar about 1/16" forward of the position on the drawing. No big deal. One explanation could be movement in the paper. I'm working from photo copies of the original plan and there is a tiny difference between the right way round wing drawing and the mirror image copy.

Finally the main construction of the lower wing finished with the glue setting on the last piece of sheeting and the cap strips.

final sheeting and cap srips lower wing.jpg

By the way I found a source of M3 threaded inserts whilst looking for something else and they look better than the ones I bought originally. The supplier is Nexus model supplies.

john stones 126/02/2017 22:40:26
avatar
8369 forum posts
1330 photos

Mine never matched either Martin, air speed indicator eh, you a boy racer then smiley

John

Martin Dance 127/02/2017 08:55:03
129 forum posts
33 photos

No John, the ASI dates from when I bought my DX8 which has telemetry. I bought at the time a range of sensors as much out of curiosity as anything else. I have a 40g G force sensor which has never experienced anything above 3g! well it is in an Anzani Longster, free plan four years or so ago. Altimeter is useful in that it shows that 400' is not an unreasonable altitude limit for most types of models, not thermal gliders of course. All of these sensors you can read from the screen whilst flying or set up a warning, the Longster had a warning set at 2G! However you can't read the ASI whilst flying anything remotely quick, you need a friend to read out your airspeed. So the introduction of voice alerts makes telemetry much more practical. One guy I fly with has an ASI fitted because he has a habit of trying to fly the approach too slowly so its an aid to keeping the approach speed above the stall speed, no boy racing going on here, on the other hand!!!!

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