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Re: MU13 Charlesworth

Posted: 07 Mar 2018, 08:54
by John Vella
Andy thanks for the photo. I really like your Horton flying wing as well. Regards John.

Re: MU13 Charlesworth

Posted: 11 Mar 2018, 18:42
by John Vella
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.

Re: MU13 Charlesworth

Posted: 20 Mar 2018, 17:10
by John Vella
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.

Re: MU13 Charlesworth

Posted: 20 Mar 2018, 23:18
by John Vella
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.
Rear view of incidence flat plate brass box.
Rear view of incidence flat plate brass box.

Re: MU13 Charlesworth

Posted: 02 Apr 2018, 15:23
by John Vella
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.

Re: MU13 Charlesworth

Posted: 27 Apr 2018, 15:17
by John Vella
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.

Re: MU13 Charlesworth

Posted: 14 May 2018, 16:28
by John Vella
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 !

Re: MU13 Charlesworth

Posted: 11 Jun 2018, 12:12
by John Vella
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.

Re: MU13 Charlesworth

Posted: 21 Jul 2018, 19:01
by John Vella
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.

Re: MU13 Charlesworth

Posted: 25 Jul 2018, 05:58
by SteveArchibald
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