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MU13 Charlesworth

Let us all watch your new project progress.
John Vella
Posts: 229
Joined: 20 Mar 2017, 22:09
Location: UK

Re: MU13 Charlesworth

Post by John Vella »

Hi Steve , thank you for the encouraging words. We are having your Australian weather here ! This certainly slows the build with more good flying weather. Here are some photos of the wing spar set up. Luckily they came out weight matched and straight. Now the fun really starts with the wing build.
Regards John.
Attachments
Level set to check symmetry.
Level set to check symmetry.
The bald patch is definitely  growing.
The bald patch is definitely growing.
The dyhedral is about 2.5 degrees.
The dyhedral is about 2.5 degrees.
John Vella
Posts: 229
Joined: 20 Mar 2017, 22:09
Location: UK

Re: MU13 Charlesworth

Post by John Vella »

The right wing construction is started with the ribs glued to the spar box rear and front. A washout taper to 6mm at tip is jigged from the start of the aileron rib. With an MU13 canopy on loan to copy the canopy frame was constructed next. The instrument panel and rear frame are 3mm ply, with the side rails constructed from 1.5mm ply and balsa composite. The riblets are 3mm ply , with 2.5 mm spruce side bars attached. The spreader tube is 4mm od brass tubing which is load bearing on keeping the wings apart. The attachment is with spring clips at the rear and a magnet under the instrument panel. 0.8 ply is used for the skirt sheeting. Just the painting and glazing is left to finish.
Attachments
Washout taper in place
Washout taper in place
Ribs attached
Ribs attached
Left root rib clamped for alignment of riblets
Left root rib clamped for alignment of riblets
Riblets and spreader tube fitted
Riblets and spreader tube fitted
Skirt sheeting done
Skirt sheeting done
Canopy frame complete
Canopy frame complete
John Vella
Posts: 229
Joined: 20 Mar 2017, 22:09
Location: UK

Re: MU13 Charlesworth

Post by John Vella »

Right wing construction basic structure was done, with the trailing edge made from balsa ply balsa composite. Abit of regiging of ribs was required to get a good alignment of the washout . The rear joiner brass box was boxed in with 1.5mm ply. The aileron servo was installed on a removable hatch, along with the spoiler servo. The false leading edge of 1.5 mm balsa was glued. The drag spars of 5mm ×3mm spruce were fitted.The facings are 1.5 mm ply.A departure from the original design was the replacement of the 0.4 mm ply facings between the ailerons and rear wing box with 1.5mm balsa sheet. So the 5mm sq spruce spars had to be positioned further apart to accommodate the balsa facings.The facings top and bottom would still be retained for the continuity of the 0.4 mm ply wing skinning. The wing tips are constructed with laminations of balsa sandwiching 0.8 mm ply. So at this stage the t.e and tip need final profiling and then the ailerons cut out and facings fitted.
Attachments
Rear joiner 1.5mm ply boxing.
Rear joiner 1.5mm ply boxing.
Aileron servo installed.
Aileron servo installed.
False leading edge glued up.
False leading edge glued up.
5mm×3mm spruce drag spars
5mm×3mm spruce drag spars
1.5mm ply facing fitted.
1.5mm ply facing fitted.
Spoiler servo installed.
Spoiler servo installed.
5mm sq spruce  for aileron box.
5mm sq spruce for aileron box.
Tips in balsa ply lamination.
Tips in balsa ply lamination.
T.e to be trimmed and ailerons to be cut out.
T.e to be trimmed and ailerons to be cut out.
Tip ready for trimming.
Tip ready for trimming.
User avatar
RobbieB
Posts: 547
Joined: 07 Mar 2015, 22:22
Location: North West

Re: MU13 Charlesworth

Post by RobbieB »

John, been watching your build with interest.

Not wishing to be a killjoy here, you might want to consider changing those straight servo extension leads for twisted triples. They might just be fine but twisted will obviate any cross talk between cores and the subsequent servo problems.
Barry_Cole

Re: MU13 Charlesworth

Post by Barry_Cole »

John Vella
Posts: 229
Joined: 20 Mar 2017, 22:09
Location: UK

Re: MU13 Charlesworth

Post by John Vella »

Thanks for the advice. I will replace with twisted triwire. No point taking a chance. Regards John.
John Vella
Posts: 229
Joined: 20 Mar 2017, 22:09
Location: UK

Re: MU13 Charlesworth

Post by John Vella »

Next the making of the aileron. It is faced with 1.5mm medium balsa from 48 inch stock. The control horn is glass fibre mounted in a box of 1.5mm ply between the ribs. The aileron is fitted and top hinged on 5 "Robart" metal pinned hinges. The wing tip and tip aileron profiles were further blended. The 0.4mm ply facings were added top and bottom, and the 0.4mm cap strips which blend into TE gussets. This scale feature adds considerable strength to a fragile point of the wing. The balsa facings were worked to give a small gap at the top and V section underneath with room for the fitting of an aerodynamic seal. The spoiler box frame is built from 2.6mm sq spruce strip and 4mm section balsa rib doublers. The "letter box" 0.4mm ply surround is glued on. The leading edge will but upto the wing D box 0.4 ply sheeting. The Next job will be the ply root facing rib to fit and blend in with the fuselage. Some more reprofiling of the ribs then the fun of wing skinning begins. I will be using J G' s method (See Ghost Squadron excellent video). Regards John.
Attachments
Aileron fitted and hinged
Aileron fitted and hinged
Wing tip blended
Wing tip blended
Wing root awaits facing ply rib
Wing root awaits facing ply rib
0.4mm ply facings and cap strips fitted
0.4mm ply facings and cap strips fitted
View of aileron with small top gap.
View of aileron with small top gap.
Tip profiled
Tip profiled
Spoiler box frame
Spoiler box frame
Letterbox surround fitted
Letterbox surround fitted
The LE will but upto the wing D box 0.4mm  sheeting.
The LE will but upto the wing D box 0.4mm sheeting.
User avatar
Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: MU13 Charlesworth

Post by Peter Balcombe »

Chris,
I understand that twisted wires are principally used to reduce Mutual interference from external radiated noise sources.
The idea is that the twisting ensures that all wires pick up the same amount of interference, rather than some being partially shielded from noise coming from any given direction.
The presence of similar noise on all wires means that the differential signal between the wires (which is usually what the device at the end of the wires is interested in) is largely unaffected by the interference picked up.
This type of wiring was often backed in particularly noisy environments with differential signal receivers which were able to virtually totally ignore any interference common to both signal & ground lines.

Note that twisted wires (for Mutual Interference reduction) & ferrite rings (for Conducted interference reduction) were common in 35MHz days when the long aileron etc. servo runs approached 1/4 wavelength, but this is no longer the case with 2.4GHz equipment as the wavelength is 1000 times shorter.
Modern equipment also tends to have for better out-of-band filtering performance.
Peter
John Vella
Posts: 229
Joined: 20 Mar 2017, 22:09
Location: UK

Re: MU13 Charlesworth

Post by John Vella »

Hi Gents what you say makes perfect sense to me. Thanks and on the subject of interference I would be much more concerned about mobile phones on the flight line. I gather they have to be very close to the transmitter to have any affect, however I keep mine in the model park when flying and not on my person. Regards John.
John Vella
Posts: 229
Joined: 20 Mar 2017, 22:09
Location: UK

Re: MU13 Charlesworth

Post by John Vella »

Here we go with some more progress over the last few weeks. The top sheeting of 0.4mm ply was glued on with 6mm balsa rib doublers at joints. All reprofiling of ribs etc were with slivers of balsa soaked in cyano for a durable sandable finish. PVA glue was used on skinning with the hot iron method. Around the tips Aliphatic (yellow) glue was used for feather sanding to profiles. Aliphatic glue was used on most of the structure including the rib caps. The Delux Materials Resin does have a fast grab time if used in 25 deg temperature of my model room. The photo of the root end of the Aileron shows the structure of the balsa facing on 5mm sq spruce boxed by 0.4 mm ply top and bottom. 0.4 mm ply cap strips flair into the TE of balsa 0.8mm ply balsa sandwich. 6mm thick ply blocks were glued to the root ribs to take screw hooks for rubber band wing retainers.The bottom sheeting was then added with rib caps and capping of the cutouts and covers for the spoiler and Aileron servos. The top skin is joined at rib 28 to accommodate the compound curve at the tip. The gentler curve underneath allows a continuous skin to the tip. So next year the balsa leading edge and root rib capping will complete the starboard wing. A HAPPY NEW YEAR to you all.
Attachments
Balsa cap fillet on top drag spar
Balsa cap fillet on top drag spar
Top 0.4 mm skinning  to  balsa rib doubler.
Top 0.4 mm skinning to balsa rib doubler.
Top skinning on
Top skinning on
Aileron Root view.
Aileron Root view.
Rear attachment  block.
Rear attachment block.
Front block and 2.6mm  spruce support strips.
Front block and 2.6mm spruce support strips.
Lower skins and capping completed.
Lower skins and capping completed.
Top skin tip view.
Top skin tip view.
Bottom skin  tip view.
Bottom skin tip view.
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