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Old Aug 06, 2014, 02:47 PM
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BBCC6 - "55 Special" by John Stroud (Diesel FF to Electric RC Conversion)

I am continuing this build in the 6th Balsa Builders' Conversion contest (BBCC6), located HERE.

I started this entry in BBCC5, thread is HERE.
I have edited Post #1 to incorporate all of the ideas I've adopted in the initial discussion.
I will be building a version of John Stroud's "55 Special," a 41-inch, low-wing, sport plane originally designed as a free flight model using the PAW 55BR Diesel Engine.

I will be making the following changes:
  • Enlarging the plane to 50-inches, to preserve some wing loading, i.e. providing some wing area that can carry the battery.
  • Widening the fuselage slightly to improve the "scale" looks.
  • Adding ailerons, elevator and rudder.
  • Fully sheeting the wing.
  • Changing the airfoil to a 110% thick Clark Y.
  • Adjusting some of the dimensions, rounding to the nearest fraction inch.
  • Lengthening the nose slightly, to help it contain a battery.
  • Converting the plane to 4-channel radio control.
  • Converting the diesel powerplant to electric power.
  • Making the wing removable.
  • Installing large wheels and UC suitable to grass field operations.

I found the plan on the outstanding Outerzone website, HERE.



I plan to make my model look like an early, low-wing fighter aircraft; and, for fun, plan to mark the aircraft in the livery of the Royal Air Force of Babar's Kingdom... the Royal Babarian Air Force. With hope I will be able to find or make an appropriate elephantine pilot.

I plan to use a two color "Spitfire-like" camouflage, using the emerald green of HM's suit and grey of his skin on top, and the pale yellow of the pennant on the underside.

When finished, I may draw up a finalized CAD version of the plans.
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Last edited by davidterrell80; Feb 01, 2015 at 08:06 PM. Reason: rolling over to BBCC6
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Old Aug 06, 2014, 02:47 PM
davidterrell80 is offline
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UM-to-60-inch fixed wing
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Reserved for proof of flight
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Old Aug 06, 2014, 08:15 PM
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Nice choice - a neat little sportster. You might want to increase the rudder size, though... ; )
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Old Aug 06, 2014, 09:53 PM
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Modifications wish list

Oh, yes... it is a freeflight set up for dethermalizer.

Changes I expect to make, include:

Horizontal and Vertical Stabilizers: Changing the structure to include rudder and elevator. Eliminating the lifting airfoil on the horizontal stab. I'm considering whether to make the stabs symmetrical airfoils rather than flat.

Wings: Adding ailerons. Strengthening the spars out to the landing gear attach points with spar webs or sheeting. Using light glass fabric on the dihedral joint.

Fuselage: Consider weight reduction measures such as adding cutouts to the sheet balsa fuselage structure abaft the wings. Change the cantilever motor mount to a electric mounting. Add a hatch to the upper fuselage to access electronics and battery connection. Add a tail wheel or a metal skid. Enhance the UC, making the struts more realistic than a piece of bare wire. An appropriate pilot figure. Add exhaust stacks like those for an in-line engine.

Markings: I'm thinking an upper Spitfire-like two-color camouflage using the emerald green of HM's suit and the gray of his skin. Using the white and red of his shirt and neckcloth as trim colors. The lower surfaces being the uniform darker yellow of the pennant, giving the plane a pseudo-coordination aircraft look. A blue-yellow-red fin flash. Roundels based on the red flag. A fuselage band based on the light yellow pennant bearing the cypher. The simple "Block B" pennant, shown small, up by the cockpit; perhaps surmounted by the crown.

I'm also thinking about a photo op... putting the plane on the pavement outside and surrounding it with human figures scaled to the elephant pilot, thus making the "elephant-sized" single-seat fighter seem the size of a B-17.

This can be fun... the kids in the surrounding apartments will love it.
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Old Aug 06, 2014, 11:21 PM
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Sounds like fun. I didn't notice the lifting stab - I'd be inclined to just make it flat. Interesting that the fuse only has two longerons at the bottom corners
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Old Aug 07, 2014, 12:34 AM
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The structure made sense to me, after I thought about it.

Normally, the Freeflight plane never experiences the high g-forces of a terminal speed pullout. It cruises around, calm and happy. Therefore the wing doesn't need much sheeting or spar webs.

As this plane was designed for a diesel engine, there are none of the compression and torsion forces placed on a rubber-powered ship as when there are 5,000 turns stored in 48 strands of 1/8 inch rubber trying to relieve themselves. So a massive truss is not required.

Stroud did put a 1/32 ply doubler in the fuselage sides, forward of the wing. I think he did this to provide a measure of crashworthyness. In a nose-down gliding landing, the nose will stop first, and the wings will want to keep going. The ply doublers keeps the forward fuselage from buckling in compression as the wing mass strives to keep moving forward. In a wheels-first landing into grass, the wheels would cause a moment pivoting the nose down onto the ground. The doubler would keep the nose from breaking off.

The only time the aft fuselage and surfaces would get unusual forces is in a cartwheeling accident. I will just have to avoid cartwheeling. I'm going to keep the freeflight dihedral.
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Old Aug 07, 2014, 12:59 PM
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Great choice ! Subscribed

Guess I'll have to get Tin Tin as my pilot
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Old Aug 16, 2014, 05:19 AM
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55 Special

DT,

I'm thinking about building this same bird, but in foam.........flat wing, lots of aileron, no landing gear......I know, I know, I've been taken by the dark side.....
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Old Aug 16, 2014, 07:42 AM
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I thought the same thing. I just have not mastered the hot wire cutting. I'd have to cut the skins as one piece and wrap them around a LE dowel and a couple of spars. And, before I did this one, I'd have to finish that Cartoon DH Comet I started last year. The partially completed fselage lookd down on me with accusing eyes.

I do like a little dihedral, though. I flattened the wing of the Blackburn Skua I built in BBCC 1 and it turned into a plane needing constant close attention attention. Given my tendency towards attention deficit, that was not a good thing; a passing SQUIRREL and "Oh!" the excitement and humanity of it all.
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Old Aug 16, 2014, 05:17 PM
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Quote:
Originally Posted by davidterrell80 View Post
I thought the same thing. I just have not mastered the hot wire cutting. I'd have to cut the skins as one piece and wrap them around a LE dowel and a couple of spars.
I've been cutting solid core wings......even tapered ones.......and I've learned that when cutting 12" wide wing sections, it's better (at least for me) to have the wire stationary...so I clamp it to the layout table........easier to control the feed rate...

Oh look ....a squirrel !
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Old Aug 21, 2014, 06:58 PM
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Plans:

I'm going to do a built up wing, per the plan, except using some TE stock instead of the 1/16 sheet and doubling R7 and R10 for aileron. Then, I'm going to add some foam blocks in the aft end of the 3 bays nearest the tip to add a aileron separation line; putting two strips of 1/16 in the wing parallel to the TE to act as hingeline material. I'l put two 5g servos out in the wings.

I'm not going to install the gear and I'm going to move the plywood dihedral/UC brace back to the spar LE.

I'm also going to use foam pieces for shear webbing and, am considering to fill the innards of the stabilizers with foam sheet. If people don't like it, they can vote for someone else's plane

The aft turtledeck will be two pieces of 1/32 fitted over the bulkheads and glue laminated.
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Old Aug 22, 2014, 03:44 PM
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More thoughts:

I'm planning to try and improve my fine building skills with this one; particularly in the wing. Until now, my planes always look hacked up and thrown together... like homemade college dorm furniture.

I'm going to try to make a pretty job out of the ailerons and the wing center section. I've been considering the dihedral bracing today, wanting to do more than butt-glue two ribs together.

I've also given thought to making the entire rounded section of the upper fuselage a single, removable hatch. I'd cut all the bulkheads into two pieces and tape them back together for the construction and covering process. I would add a gunwale inside along the top of the flat sides, and a couple of thwarts to keep the sections firm. Then, after the fuselage is essentially complete, I would slice the top off, remove the tape, and install the innards and hatch attachment fittings.

Doing this, I still want the wing removable but I want to think about mounting the wing to the fuselage with something other than rubber bands.
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Old Aug 27, 2014, 04:30 AM
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Wing strength

Quote:
Originally Posted by davidterrell80 View Post
Plans:

I'm going to do a built up wing, per the plan, except using some TE stock instead of the 1/16 sheet and doubling R7 and R10 for aileron. Then, I'm going to add some foam blocks in the aft end of the 3 bays nearest the tip to add a aileron separation line; putting two strips of 1/16 in the wing parallel to the TE to act as hingeline material. I'l put two 5g servos out in the wings.

I'm not going to install the gear and I'm going to move the plywood dihedral/UC brace back to the spar LE.

I'm also going to use foam pieces for shear webbing and, am considering to fill the innards of the stabilizers with foam sheet. If people don't like it, they can vote for someone else's plane

The aft turtledeck will be two pieces of 1/32 fitted over the bulkheads and glue laminated.
I folded the wings on the foam version of the 55 special yesterday.....pilot and builder error.....spar joint just wasn't up to the task for emergency recovery......and I suspected that when I built her.....Wing II will be much stronger.
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Old Aug 29, 2014, 11:43 PM
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I'd build the lifting stab as shown. It may help maintain "level" flight , rather than a "pitching nose up" when going to full power . Also, it will help with inverted flight. My little Brigidier has a lifting stab and flies much nicer than the Dallaire Sportster which has a flat stab.
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Old Aug 30, 2014, 04:58 AM
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Landing gear

Quote:
Originally Posted by davidterrell80 View Post
Plans:

I'm not going to install the gear and I'm going to move the plywood dihedral/UC brace back to the spar LE.
David,

You might want to reconsider installing the landing gear.....there's not much to hold onto when she has a smooth belly, and hand launching her can be, well, exciting .....at least it was for the version I built.....Of course, my 48 Special has a much faster wing and little or no dihedral, and my pitching arm ain't what it used to be ! LOL......Version 2.1 has a wire UC that's fuse mounted.
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