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Old Feb 16, 2012, 03:31 PM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Nacelle metal brackets installed & styrene parts fitted to each other:

Fitting the lower vacuum form bottom was not easy. The framing needed more adjusting to the correct depth than I foresaw.
Re-thinking the inter structure now for the final version
I added x2 plates underneath the sheeting and brackets for a better mounting pad for the bolts.
All the brackets are 050 aluminum and tapered at the front and rear. The clearance between the vacuum plastic and the center AC ply is critical.
Ends are tapered for the correct angle to the N- struts
I am re-considering making new flaring, now that I know better now to make them.
Vacuum forming the front cowl next and checking it to the top and bottom nacelle parts.
Allen
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Old Feb 16, 2012, 10:22 PM
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sarkantyu's Avatar
United States, MI, Lake Orion
Joined Feb 2004
293 Posts
Found some great footage of the SM 55 with lots of details. Enjoy.Joe
Trasvolata Atlantica Italo Balbo documentario part 2 (12 min 41 sec)
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Old Feb 17, 2012, 07:17 AM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Thanks Joe for your posting of this video!
What a fantastic find, great details, on questions, I have always had.
Rene emailed me more details that he found, on the engine nacelle.
Information like this is a big help in understanding the SM55X.
Thanks again to all,
Allen
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Old Feb 20, 2012, 06:09 AM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Detail changes:

With the canopy now revised it can be split at the V-strut junction, front & rear cockpit.
Metal aluminum brackets will be made to fit underneath the engine nacelle, exited right and left of the inboard strut flaring. Metal brackets will also be used at the wing center top underneath the removable canopy front and rear.
The rear V-struts are located rear of the cockpit canopy and the rear of the canopy on the top wing center section.
The struts will be 2/56 threaded rods with airfoil aluminum tubing over them for appearance.
The ends will be adjustable threaded brass tubes, flattened on one end, for the bolt attachment points.
I used two layers of 1/64 AC ply soaked in water and ammonia for several hours, to help make the bends in the radius ends. Epoxy lite was used again, to re-shape the radius ends and sides.
Once this step is completed the booms can be built next and attached to the rear hull tops.
Allen
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Old Feb 20, 2012, 11:18 AM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Cowl & nacelle flaring:

The cowl is checked to the nacelle top & bottom. I see two different configurations for the front cowl size.
One is a larger diameter on the bottom, and one is the same outside diameter, matching the nacelle diameter.
The cowl on the left shows what happens when vacuum forming a mold without air holes to allow a flat draw down on the part.
Both are shown here.
The top three flaring segments are, vacuum formed separately, and glued to the top cowl lining up with the nacelle.
The new strut flaring are finished and now being checked again for there fit.
Chamfering them is necessary,inboard for a good fit to the wing top and nacelle
More later.
Allen
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Old Feb 21, 2012, 03:54 PM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Bracket details & wiring:

Figuring out the V-strut brackets has taken some time to resolve.
The locating holes have been tapped for 2/56 bolts, eliminating the need to hand hold the nuts to secure the bracket.
The bracket lenght might still need to be modified, to the V-struts, once checked to the wing and nacelle for strut end attacment locations?
The vacuum form bottom part is still removable if changes need to made to the brackets?
All the attachment points will use this method to simplify the assembly.
The wires through the N- strut worked for once, the first time.
I hope to complete the attachment points to the nacelle next. with the new flaring attached. Priming the bottom nacelle helped show the details.
Allen
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Old Feb 22, 2012, 07:48 AM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
V-strut details:

The challenge, to design the metal struts to be made with simple hand tools, and not machined.
Here is one solution. Parts are shown, to build the struts in the photos posted.
2/56 threaded rod on one end, 1/8" OD x.029" wall brass tube, 1/8 x3/4 brass tubes, and 5/52x3/4 brass tubes.
The 1/8 x .029 tube can be threaded for the 2/56 threaded rods. This will allow turning the flattened end, 90 degrees to the airfoil tubes.
This will also allow the length to be adjusted, to fine tune the struts.
With N-strut flaring now attached to the nacelle only, you can how close the V-strut clearance is. Not allot of room for mistakes.
The throttle wires from the controllers will be installed in the V-struts, aluminum struts.
The N-struts at the wing center section can not be installed until the wings are covered.
Finishing the three remaining V-struts is next!
Allen
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Old Feb 22, 2012, 03:15 PM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
V-struts finished:

Much time has been spent of this important part, of the SM55X. I did not make these V-struts on scale model, the first prototype!
The 1/12 scale using more power and torque, makes the struts functional. They should really help stabilize the engine nacelle.
The 1/2" airfoil tubes can be added once the wing is covered. Removing the strut ends at the wing makes it easy to add or remove the outer struts and install the wire extensions. The inter strut rods can remain attached to the strut ends at the nacelle bottom. Threading them at the top also makes them removable from the bolted strut ends.
Allen
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Old Feb 27, 2012, 06:34 AM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Checking the part assemblies to each other:

Laying out the hull center line, wing, rudders and stab, is critical to the bracket locations. This is the final check to make sure it will work, as the plans show.
The 3/4 aluminum tubes needs to be cut at the right angle, bottom tube to the top tube. The booms will be bolted together at the rear and at the vertical front strut location.
The top tube needs to be slotted to accept the rudder tab that aligns it to the booms.
Once the booms are assembled, detailing them can be done!
Allen
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Old Feb 28, 2012, 11:07 AM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Boom details & attachment points, hull top, wing center:

The rear strut boom brackets should have been installed earlier. It would have been much easier during the keel assembly.
Once the new stab is built, the boom assembly, tail group, can be test fit to the wing.
It will be nice to finally see the project start to look like an aircraft instead of misc. parts!
I am considering bolting the hulls to the lower wing center section rather than gluing them in place?
Allen
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Old Feb 28, 2012, 06:39 PM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Thinking ahead now for the tail group controls:

Before building now the 2nd stab with the new control slots and bell crank, best to check the old parts for the new design concept.
The plan is to guild the cable along side the inter boom using 2/56 Rigging couplers as cable guides. Pulleys could be an alterative, but require more material and work.
I have used the couplers many times before on the Sikorsky S-38 & S-39 models with the same cable system. I know it works for a pull, pull set up!
Allen
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Old Feb 29, 2012, 07:02 AM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Rudder & stab control layout detail at the center crutch:

Building the new stab now, with the control slot cut in place, and rudder slot reinforced.
Not sure this will work, but worth the effort to try it out.
All the parts are hand cut for the concept build, shown here.
Back up plan would be, drive the rudders with seperate servos, turning the horn 90 degrees to the control rod. I have used this method before and it works.
We will see?
Allen
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Old Feb 29, 2012, 02:39 PM
classicaero
oxford,MI
Joined Jul 2004
891 Posts
Re-thinking the control linkage set up:

Joe Rubinstein was kind enough to stop over and review my design on the control linkage.
Joe is posting the Loening build on RC Groups.
He can up with a better design and I am going to change what you see here.
It is a simpler design and incorporates the center rudder in the set up.
Taking a break from that and bolting the assembly, hull wing, boom, and tail group together.
Allen
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