|Feb 23, 2008, 01:03 AM|
Joined Mar 2004
SGU 1-7 Pteradactyl 1:3 Beta
I've completed parts fit and checked finish during assembly of the major fuselage components for our 1:3 scale Pteradactyl this week (146" or 3.8 meter span). During the build I've documented the construction so I can have a complete step-by-step article with photos to post here in the next weeks after maiden. I will be covering the prototype with the old Coverite and nitrate dope and then finishing with scale colors. Wing mounting will be by scale method on mine.
Some data so far:
Horizonatal surface framed weight 5 oz. (stab and elev)
Rudder framed weight 2 oz. (later larger variant)
Fuse framed weight 40 oz. (as shown)
Expected all up weight less than 15 lbs.
For those who recieved the private messages and study plans last month and have already placed or have orders pending for the 1-7, I found two fit issues with the aft formers in the triangular truss section which have been corrected during my build and on the plans and cut files. In addition, I've determined that the simpler way to build this model is to dispense with the forked carbon tube longeron in the wing mount area and to make the top of the "seat" bulkhead more scale and offer the option to the builder to "delete" or cut off the top of the wing "joiner rib" F12 in favor of using a completely scale wing mounting lug and pin system. The current parts shipping will allow either option at the discretion of the builder and I will document this further in the complete article once posted. I've also added a 1" (25mm) protrusion at the aft end of the horizontal forward fuselage crutch that extends into the forward end of the carbon pulltruded lower longerons to strengthen this joint against shear forces where the ply part transitions to the carbon tube part. I've also added a circular yoke in the former F6 which cradles the pushrod midship for a scale-type elevator actuation method and to prevent unecessary deflection. I've also drawn parts for a simple to build scale tow release and other minor modifications to help keep it simple and easy to build.
For the wings I've opted to go with 3/32" sheeting on the ribs with the use of capstrips aft of the spar and on both upper and lower surfaces.
Note in the photos shown here that although appearing complex, the design of the fuse is built without the need for any jigs or fixtures other than a small engineers square to check the major bulkhead for veritcal orientation on the building table and a jack or step (I used and X-acto tool box) to hold up the lower aft longerons once assembled as a unit and a small spring clamp, a couple of shims and a small framing square. A line drawn on the table (I used a joint between planks) suffices for the datum line to which the forward self-jigging section and the aft tail end of the longerons is aligned.
The forward section which includes F1 through F4 bulkheads and the F11 doubler for F4 and vertical and horizontal crutches F14 and F16 is self squaring and needed only a small spring clamp and a couple of rubber bands to hold together while the cement cured.
As you can see from the final photo, the notches for 1/4" dowel forward stringers for fabric standoff are correctly sized to allow the members to snap into place. One will need to soak the last 12" (300mm) in ammonia water to allow bending into the round nose section before final installation.
To this point I've spent approximately 8 hours over as many nights and one tube of 3M DP460 adhesive for all joints in the fuse and tailplanes. No other cements have been used to date.
Tomorrow and Sunday I will cement in the aft triangulated truss members in the fuselage, bend, cut and install the stringers, begin work on the landing gear mounting formers, and build the vertical fin and send the new cut files over to Walt for cutting so I can begin on wings next week.
If anyone else would like to consider being on the list for the first cutting at the introductory price, please contact me with SGU 1-7 in the subject line by email this weekend. First run cutting order will be placed Monday and shipping will proceed right after parts arrive back. Hardware packages are already made up and kits will include wheels and tires, axle, stop collars, all carbon tube longerons, wing struts and jury strut materials, stringer stock and all complex shaped plywood parts and decals and scale instrument panel kit. Plans are two sheets and include details for construction of stabilizer brace, nose-mounted scale tow release and strut attach and hardpoints in addition to both wings, all servo mounting information and sizes, both rudder variants, and locations for seat, rudder pedals, tail skid detail and decal positions, etc.
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