1923 B3 'Charlotte II' in 1:3 Scale

[ARUP]

The fin is done! The fuselage was needed to get it properly sized. Considering thicknesses added for sheeting of the fuselage, the vertical fin post was clamped to the vertical on the fuselage. The horizontal member of the fin was 'gusseted' to the fin post. After glue dried this was removed from fuselage then finished on the plan. All the cross members will get pinned to the outer perimeter using toothpicks and the gusset will get cut away. here is the fin on the fuselage. The mounting points will get fabricated next.

[ARUP]

Snap rolls! I just hope this thing flies!

Oooops! Can't build fin until fuselage is more complete. So that's what I did! Some diagonal shear struts were added inside. Cockpit opening created. The fore struts were tied to the airfoil shaped portion by adding some 'layers' to the joint were strut inserts into airfoiled wing mount. Balsa added to nose then sanded fair. The rear of fuselage was 'fleshed out' in readiness for the fin. I need the length across top of fuse and fin post height to make the fin fit properly.





Happy Easter, everyone!

[lenb]

Michael,
You WAY deserve that avatar. Your financial support as well as content has inspired many and continues to make this site interesting. \

It's good you are making the struts functional, since the snap rolls we plan on doing may test the structure. ( one and done )
Nice work pal

len

[ARUP]

I'd like to thanks you guys for giving the 'Founding Member' badge of honor to my avatar. I don't think I deserve that but I certainly don't mind contributing in different ways to this wonderful site. I certainly enjoy it here... very, very much! All of you are the GREATEST!

The struts are done! The second pic shows how the balsa cladding hides the CF tubes and also shows the airfoil of the strut. Don't know how accurate the strut construction is but sometimes ya just gotta do what seems logical.



The fin build is next. Stay tuned!

[ARUP]

Struttin' their stuff! The paint dried so the fittings were trimmed to size and roughened with a Dremel cutoff wheel. The thicker longer one in the bottom of the first pic is the strut carry-through to be mounted in fuselage. Pictures of this are shown. The spruce struts were drilled to accept the metal fittings. The fore spruce strut member is drilled both ends. The aft spruce strut member is only drilled at the wing attach end. The fuselage end of this aft spruce member will be tapered to fit onto the fore strut member. First one strut then the other was fabricated because the building board is too small to do both at the same time. Both inverted, the wing was attached to the fuselage then the washout was jigged into the wing. The root end is zero while the strut end is 7.5 degrees at the strut attach end. The spruce was cut to length and the fittings were test fitted into the strut ends after drilling the proper depth. I had to check the fuse against the wing for dihedral of 2.5 degrees, too. Ya don't want more dihedral on one side than the other! The struts, metal fittings and plywood gusset plates were all slow-cure epoxied together. Once the epoxy cured the struts were removed. They look like long 'A' shapes. The drawing shows there to be 'ribs' on the struts. Also, the black CF tubes may show through the covering so 1/16" balsa cladding will help hide this. The CF tubes were epoxied to the mid section of the struts, not because the struts aren't strong enough for flight loads, but because I worry they might collapse under landing loads. Anyway... the struts are almost done!

[ARUP]

A tutorial to 'solder music wire and stuff' was put in the how to section of the forum. Feel free to add your tips and tricks!

The 'V' (or 'A' Frame) struts for the Charlotte are substantial. They are ~56" long and are ~9" wide where they attach to the wing. Nobody knows what was used for the struts on the full scale version except that 'they were reinforced with plywood'. They look pretty thin and possibly have an airfoil. Photos of the Charlotte in flight show the struts bowing significantly! I am using 1/2" x 1/4" spruce for the main members. Balsa will be used to 'flesh them out'. The spruce members got grooved on the 1/4" side to receive a 24" CF tube epoxied 'on center'. This will stiffen them up substantially. Don't want the struts to buckle on a less than perfect arrival! Before the struts can be assembled some fittings had to be made. Music wire was used. Their ends were heated cherry red then hammered flat and wide enough for a 4-40 bolt to pass. The picture shows them hammered but not drilled and cleaned. The strut ends are 1/8" music wire. The fuselage 'carry through' is 3/32" music wire with the ends drilled and tapped to fit 4-40 bolts. Hopefully there will be clearance enough that the struts will stay attached to the wings and only the 4-40 bolt at the carry through be unscrewed to remove the wings. The wire fittings were painted and, tomorrow, they'll be fitted to the struts ends.







The struts will be partially built 'in situ' in order to get the basic 'A' frame. Once epoxy cures they will get pulled off and 'fleshed out' with an airfoil, sanding of LE and TE and etc. Good night!

[ARUP]

Thanks, fellas! The secret is using eye of newt, chicken lips and frog hair combined with adequate incantations from Wagner's 'Ring Cycle'! Seriously though, when I get home I'll show needed tools and technique.

[Stew2]

What's impressive to me is he as able to successfully solder tabs to music wire!!! How the heck do you do that? Do you anneal the wire first? What's the secret man??

[lenb]

That's pretty darn impressive.

[ARUP]

Thanks, Blake! You absolutely nailed it in your post #76 above. A leather apron wouldn't be a bad idea, either!

The tabs were soldered onto the hoops, the hoops were painted and 4-40 brass inserts were let into the hoop skid mount plates on the wing. Here they are trial fitted. The 'struts' are getting fabricated. Note the washout in the wing. The same jigs will be used for the other wing when its struts get started.The cables were run. Once a few metal fittings are made so the struts can be attached to structure everything comes apart so the wings can get fabric! I'm excited!





Thanks for looking!

[blake]

Michael

Well done!
That springback is crazy with music wire.....

Blake

[ARUP]

Look out... snake!



Mandrels or forms were made from plywood. They were screwed to the work surface and a lone wood screw was located near the form but not on it. One end of the wire abutted the screw while the wire was wrapped around the form. The forms were grooved to help keep the wire from wandering. Music wire has tremendous 'springback'! Look how small the ply forms are and I still had to 'massage' the hoops by hand (leather gloves worn for this work). Five hoops made in total before getting the two needed. The first was a disaster when I sleeved some aluminum tubing over the wire in order to make it appear a little thicker. The tubing flexed so many times during the forming process that it split. Another hoop was ruined when trying to bend the ends while clamped in a vise. The end broke at the bend. Another broke even with the heat from a torch while bending. It finally 'played out' bending them 'in the air' over a torch flame. Not the most accurate method but heck... the hoops are formed. Now the mounting tabs will need to get Stay-Brite soldered in place at the bends. My hands were cramping after all of this. It took four hours then I had to mow grass!!!

[ARUP]

This isn't Four Corners, USA! Photographic (and three view) evidence shows the adjacent control surfaces have sharp corners at the TE. Only their outer corners are rounded. I fixed those by sawing the rounded corners and scarfing some balsa in place. It got sanded fair and all is good with the world, now!

1/4" marine ply was attached to the structure so that the 'hoop' skids can eventually get attached. I'll drill for 4-40 brass threaded inserts once the hoops are fabricated.

[ARUP]

Art, the 'hoop' skids are semi-circular so they will get a bracket at their ends to fasten onto marine ply pads attached flush to the wings' under surfaces.

Blake and Jeremy, thanks for the great ideas. The music wire will be pretty stout so leather gloves are a great idea. If things don't go my way then plan 'B' will be to 'telescope' some soft K&S aluminum tubing over a smaller diameter music wire. This will give the diameter needed, be slightly lighter and easier to work(?) I'm gonna fasten the skids to their respective plates using some slightly compromised nylon bolts. I want the bolts to break so the structure doesn't get damaged. If I partially saw the bolts at their heads then any 'pear shaped' landing that makes the skid lay over will pop the bolt heads and leave enough threaded portion of bolt to be easily removed. That's the theory, anyway!

[Swiss1]

I do the same thing but for one small step. Drill a hole in the PVC pipe, bend a short length of the wire to 90 degrees to be captured by the tube and wrap, let go and check for length as you go.