Scale Soaring UK

I am well into the build now, thanks to the time saved with Cliff's laser cut short kit. The jig is window sill planking as a base. Being very solid it was turned round on the building table to work on each side when doing the "stick" work. The fuselage is out of the jig and nearly done. Sorry about the orientation as I am not building it inverted.

Very tidy, I had a 2nd hand one (it's now 3rd hand with a friend!), flew lovely.

Thanks for the encouragement Andy and Frank. I am sure the effort will be worth it . Here are some more photos with it out of the jig.
Regards John.

Now side skins and top nose complete. The gap between keel and sides filled as shown with 0.4 ply skin to follow to protect against arrivals on "outfield" landings. Very little weight for alot of work. I did similar on K8 and it's worth it.

Fuselage skins finished, and floor between F1 and F2 glassed to reinforce the ballast compartment. A disc type nose release was fitted to the balsa nose block before bonding the block to F1. Weight of basic fuselage is just under 24 ozs.

looking good john. may temp me to do some balsa bashing myself ???????? ROO

roo Hawkins wrote: ↑05 Mar 2018, 14:31 looking good john. may temp me to do some balsa bashing myself ???????? ROO

Roo, your far to young to go balsa bashing. It takes a whole different mindset

Hey Geoff steady on I think at 71 I am just getting into my stride as far as balsa bashing goes. It is most enjoyable when it is freezing outside to balsa bash in a really warm model room. It is also sound proof so I can't be disturbed by the "boss".

John Vella wrote: ↑05 Mar 2018, 18:02 Hey Geoff steady on I think at 71 I am just getting into my stride as far as balsa bashing goes. It is most enjoyable when it is freezing outside to balsa bash in a really warm model room. It is also sound proof so I can't be disturbed by the "boss".

Hi John, I know what you mean, I'm also 71........The comment was meant for Roo....

Andy A wrote: ↑05 Mar 2018, 20:40 Looking Good Any ideas on colour and finnish yet?

Andy at the rate I build the decision of the colour scheme is some way off. What scheme is your MU13 ? Have you any photos ? Regards John.

Andy thanks for the photo. I really like your Horton flying wing as well. Regards John.

Fuselage build nearly done. One tricky bit was the repositioning of the diagonal uprights to accommodate the curve of the side stringers between F6 and F7. The side stringers were 4 by 6mm pine from Wicks some 5ft long. The spreaders were 6 by 3mm hard wood slotted into the diagonals. All joints have 0.4mm ply fillet reinforcements. Wing centre box work and sheeting to follow next to complete the fuselage.

Here is the wing centre box work on the MU13. Ply doublers used on the flat plate joining boxes. The main joiner is 15mm by 2mm steel, and the wing incidence joiner being 10mm by 1mm steel. I have fitted a ply cross brace at the back of F5 to reinforce the corner joint and act as a base for the front of the 5mm top balsa sheeting. The centre sheeting will be covered by 0.4 ply skin to blend in with the wing skin covering when the wings are built. It is a slow but enjoyable build so far.

As Cliff says the canopy is built up from sheet material and a metal frame. The 4th photo should be the rear view of the incidence flat plate box and ply doublers.

After a break the build continues with the Empennage , another clever light weight Charlesworth design. The ribs on the tail needed a bit of work. The ply doubler is capped by 1.5mm sq spruce and the same is used to support the rear shroud. The lightening cutouts were filled with 1.5mm soft balsa to support the ribs and seal the tailplane against the elements, the weight being negligible. Now it's ready for 0.4mm ply sheeting and LE capping.

The next job was the elevator hinges. They were cut and laminated from pieces of 1.5mm Epoxy board. The pins are 2mm steel and a key step made to locate the hinge in position in the slot on the tail spar. The pins are glued in a slot in the rear of the elevator spar. The elevator was fitted on hinges on the tailplane for final profiling. The rudder was built next in a traditional balsa ply balsa sandwich. The ply was laminated from 2 pieces of 0.8mm ply. The rudder spar from 13mm×20mm medium hard balsa.the ribs from 2mm medium hard balsa. The construction was a fiddle but the weight was very light at 1.5 oz complete awaiting its pintle hinging.

The Fin construction was next. All ribs were reprofiled then the 2mm hard balsa false LE glued to form the frame with the base box and joining tongue fitted. The tongue was stiffened with glass over the 3mm ply. The joining pin is 3mm brass locating through a ply box glued into the rear 3mm balsa sheeting. The rear fin joiner is a 2mm steel rod locating into brass tubing bonded to the fin spar and the rear fuselage bulkhead respectively.
The Pintle hinge system is made with 10g brass on the bottom and 20g brass on the top. A 20mm long steel pin on the bottom and a 10mm pin at the top locate into brass tubes fitted in the rudder post. All facings are reinforced with 3mm ply capping.
On rigging the rudder more profiling was required. So off came the 0.4mm ply gussets and then reglued when the fit was right.
For a little extra work one ends up with a light structure which deriggs easily which is good for transportation as this vintage large wing area has rather large tail surfaces !

Back to the build after holidays and other distractions. The tailplane and elevators were fabricated in The usual Charlesworth light weight design. The stiffness of a pretty light structure of the tailplane is given by the 0.4 mm ply D box skins. Hopefully the pin hinges are fit and forget. The elevator spar is reinforced by 0.8 mm doublers at the hinge points. The area of the tailplane is huge by modern standards and a total weight of 5 ozs is impressive. I am going along with the detachable tail surfaces as they could be vulnerable to transit damage. Also storage can be a problem with these vintage gliders.Yes I am running out of fuselage hanging space. Heyho wings next job.

The spars are constructed from Baltic Pine 4mm section from 2.4 m length, hard balsa webs from 1.5mm 48 inch by 4 inch stock. This gives a spar with no scarfs and only one scarf on the webs. The spars were matched for straight grain and shaped to taper and the ends were steam bent to follow tip curve profiles. The 15mm brass box is supported in 4 ply cross pieces, 2 are 3mm and The middle 2 are 1.5mm ply. Every 30 cms there are 2mm hard balsa braces to support the side webs. The set of the spars is 3 degrees dyhedral which is set with the spar in place on the glider before the second side web is bonded. The spar box was held on the building board with weights while the resin set and luckily has come out straight. If you like building and take your time Charlesworth designs produce a very satisfying model. If it flies as well as my K8 the effort will be worthwhile.
Regards John.

Hi John,

I am new here and just poking around to get the lay of the land so to speak. Great build and the MU is one on my future build lists. Fabulous work.

Kind Regards
Steve

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.

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.

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.

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.

I use this:-

https://www.componentshop.co.uk/3-way-h ... 2-awg.html

It works for me.

BC

Thanks for the advice. I will replace with twisted triwire. No point taking a chance. Regards John.

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.

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

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.

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.

Cliff, happy New Year. At this point I would like to add my thanks to you for all your hard work . I am struggling with an MU13 scheme . With my K8s you are spoilt for choice. Any suggestions for a MU13D scheme are welcome. Regards John.

The next little job is fitting and shaping the leading edge. It is from 4ft long 6mm medium hard balsa. Aliphatic resin was used and pinned in place . The profiling started with the trusty David Plane then sanding with the butting sheet ply protected with insulating tape. The Gottingen 540 profile is pretty blunt and crude by modern day standards, but does the job and is scale. (Scale Police take note). Next the wing tips were profiled with the 0.4 mm ply blending into the balsa. The final constructional job was the root rib facings made from 1.6 birch ply, and made in 2 sections to account for the bend at the canopy cut out. On offering up the wing on its joiners the fit looked pretty good. The starboard wing including servos comes out at 38 ozs. On most of my gliders the wings weigh about half the gross weight of the complete model. So it looks like a target weight of around 10lbs might be achievable.

This an update on the slow build of the MU13 wings. The problem I am finding is the time taken in reprofiling the wing ribs. The humps and bumps occur on the top rib surface only on the plans which the Laser Cutting follows exactly. The strange thing was the fuselage and empenage were very accurate, and went together a treat. I like a challenge but the time taken to reprofile the ribs is testing my patience. What would we do without the trusty Straight Edge and a good set of Glasses? Hopefully the MU13 will fly in the Spring of this Year.

John, the straight edge is mandatory but the glasses must be filled with a good malt whiskey.
Brian.

Brian a glass of Glenmorangie would not go amiss after this build.

Here we go again ,with the forecast showing Spring returning soon and flying weather, is an update on the left wing build. I decided to construct the rear structure to the spar first and build the front ribs afterwards on the second wing. The false leading edge is 2 mm medium hard balsa .The front root rib was partially cut through for the cockpit angle ,and jigged on the fuselage rib to get exact alignment before fitting on the wing and glued. The trailing edge and tips were the balsa 0.8 mm ply balsa laminate. All ribs were reprofiled in situ.

With flying weather arriving the build is progressing slowly. The fitting of the 5mm × 3mm spruce drag spars are next. Then the 1.5mm ply inter rib webbing. On this wing there is continuous webbing between rib 2 and 3 with a slot for the rear brass box. The brass box is loose fitted ,.then the left wing is mounted and jigged with the fuselage and right wing. The brass box is glued in position with 30 minute epoxy. Care was taken with wing root alignment to allow for spacing when the ply facing rib is fitted. The next job is the 1.5mm ply boxing the rear incident box. Then the skinning of the left wing will commence.

Here we are Bank Holiday and a heat wave ! Model room temperatures are still reasonable so on with the build. The left wing build was done as per the right with the last job being the root facing rib out of 0.8mm ply. The wings were rigged to check any high spots on the wing root. The time consuming job was the profiling of the hard balsa leading edge. The next job is covering in Oratex. The colour scheme German circa 1938. Regards to all the builders out there, John.

Is this an Kit or is the Plan avible to buy? Im looking for an new projekt.

Ben, welcome to the Forum. I see you express interest in a K8 as well as the MU13. I fly the 3.75m Charlesworth K8 and have flown a MU13. They both fly very well. They both require alot of building to make them scale. You could build from the Charlesworth plans or from,the "short kit" by Lasercutsailplanes. Regards John.

Thank you for the link. I know that there is a lot of work. I dont want to built full scale. It will be my first old lady.

At last the finishing begins. The fuselage top is skinned in .4 mm ply to blend in with the wings. The cockpit and canopy are painted in flat sky grey acrylic. The rudder push pull system is installed via an indirect 180 deg bellcrank drive. Elevator control is via a carbon push rod to a brass elevator control horn. Access is through a slot in the rear balsa floor. The tailplane is mounted on a balsa seat with steel front pins and a 4M nylon bolt into a captive nut. The fin is attached with a ply tongue located in a ply box and at the rear post a 1mm steel pin mounted in brass tubing.
The diagonal upright into former 7 is supported by a balsa fillet which helps blending the covering at the angle change in that area. The transition under the fuselage wing seat aft from the 0.8mm ply at former 6 is a thin balsa fillet. The covering is in Oratex which works well on compound curves.
The final rigging check is done with wings and fuselage in the garden. The covered empenage are rigged and checked for alignment. The fuselage is covered in four sections with all overlaps going downwards. The radio and servos are fitted and checked. The three servos in the fuselage are Hitec 645mgs.

Thanks Cliff, as you say not to far away to completion. A slow build hopefully gives time to get it right. None of these so called "professional " builds for me. Regards John.

Hi John, looks like the MU is coming along nicely

So after a few issues the covering of the airframe is complete . I had a problem requiring the reskinning of the top rear
Inboard ply skins of both wings. However with some heat the skins peeled back more or less intact. Covering in ORATEX was very straight forward with plenty of shrinkage around the compound curves. BALSALOC was only required on certain edges. The flying control set up was next. The ailerons set with 2 to 1 differential, 10mm down to 20mm up at root T.E. The elevators 25mm up and 20mm down. The carbon push rod is very stiff and so is unsupported from servo under the wing to the elevator horn. The rudder has a lot of movement, about 25 deg each way on a push pull cable system. A spring steel skid completes the back end. I guess that the main wheel being infront of the C of G unlike the K8 will mean the skid will get a hammering. The air brakes were the next job. ScalePolice please note that only the top operating DFS brakes are functioning as the bottom moving back paddles would be vulnerable to out landing on heather etc. The letter box openings are lined with 3mm sq spruce. The arms and side hinge frames are from 2.5mm glass fibre board. The hinge sides are joined by 3mm ply and 2mm steel pins used.the assemblies are fitted and glued to the skins upto the 3mm spruce strips between the letter box and the rear spar. The slots in the skins accommodate about 70 deg movement.the brakes are made from 6mm hard balsa sheet covered by 0.4mm ply skins. 3mm ply reinforcement mounts are inserted for the plastic horn mountings. The airframe needs a rig check when the weather allows. Regards John.

Thanks Cliff, yes an NSFK colour scheme circa 1943 . I Hope to have it as a Munich area glider with the "Flying Man" on the nose. Regards John.

Hi, due to a short illness and bereavement in the family the modelling has come to a tempory halt. Here are the last set of pics taken of the build. The pilot is a Pete's pilot on loan from my Charlesworth K8. Regards John.