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How to Build an OT R/C-Model
Updated 17-May-2010

Building Tips and Tricks 1 of 4

by Tandy Walker

Layout and SAM Site Integration and Editing by Web Master Ned Nevels

(material provided by builder Tandy Walker)

 

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I have started building another Class A Lanzo Bomber for SAM R/C Assist Class A LER Ignition competition. Picture 1 This shows the lay up of the left stab tip. The spline is made up of a lamination of three 1/16" X 1/4" balsa strips. They were soaked in hot water for two hours and then Tite Bond alaphatic glue was spread between the strips, which was then formed around a cardboard form as shown in the picture. Picture 2 This shows the right stab tip after it was removed from the form. Picture 3 This shows the lay up of the left wing tip. This spline is made up of a lamination of four 1/16" X 3/8" balsa strips.

After completing the Class A Bomber stabilizer and elevator, I hinged the two together. I noticed the built up rear spar of the stabilizer, which holds the the forward portion of the hinges, could flex for and aft rather easily. Therefore, I added some 1/16" X 3/32" diagonal members to form an inplane truss between the mid spar and aft spar as shown in the picture below. Notice that a strip of aluminum angle is clamped to the stab rear spar in four places to keep the structure straight while gluing in the diagonal truss members. The rear spar is now stiff as a board! Later I will send some close up pictures of the laminated tip integrated into the stab and elevator structures.

Tandy's Use of Cardboard as template material for his laminations is both effective and cheap.(shown above right) It is readily available and easy to shape.

Tandy Walker ,of Arlington Texas, is a A retired Engineer from Vought Aircraft and a long-time SAM member and, quite obviously, a talented and meticulous Model Builder. Tandy is shown above at the 1998 SAM Champs with his full-sized Chet Lanzo Bomber. Tandy generally documents his model building projects with a digital camera during the various construction phases. He recently finished a Class A Lanzo Bomber in which he has been sharing his efforts with several of us by way of digital photos attached to e-mails almost on a weekly basis for the past eight months. Tandy's e-mails have been so informative and instructive that I decided to take the collection of his e-mail material and develop a "how to" article for the SAM web site. The intent of this article is to provide less experienced modelers with techniques and insights on building a competitive OT/R/C model that Tandy has developed during his modeling career of over 60 years.

I have attached two pictures below showing the completed fuselage planking on the Class A Bomber. Picture 1 This shows the top of the diamond shaped fuselage. The planking is inlaid between the structure frame members. Diagonals were added aft of the planking. The pylon structure attaches to center top longeron. The eyelet on the forward right is opening for the high tension lead. Picture 2 This shows the bottom of the diamond shaped fuselage with the right side to the top of the picture. You can see the three hatches I use for equipment installation and access...

 

Tandy and wife Sue Walker of Arlington Texas with Tandy's A LER Bomber, powered by the Shilen Old Timer .19

The first picture below shows the 1/16" stab mounting platform now glued on to the fuselage longerons. The top longeron had to be removed in this area in order to mount the stab platform. Notice the two plywood inserts integrated into the platform where the nylon mounting screw holes are.

The second picture is a bottom view of the stab mounting using the four nylon screws and nylon washers. I use nylon screws because they are lighter and because they do not vibrate loose like metal screws. Notice the spruce doublers used to reinforce the insides of the two longerons that the stab platform is bonded to. These doubles are used to compensate for having to cut the top longeron. Also notice the 3/16" triangular strips bonded to the longerons, which are used to provide the interface between the longerons and the stab platform.

Before I started the wing construction, I decided to check the alignment of wing saddle with the stab platform. I screwed the stab onto the stab platform and jigged up the fuselage so that the wing saddle was level. Bless my soul, the stab was in fact misaligned! @#%$&

So I have been busily going about developing a stab shim to tilt the stab and align it with the wing saddle. For reference, the first picture below shows the stab mounting platform glued onto the fuselage structure. I selected a piece of medium 1/32" balsa sheet, cut it into three pieces, and bonded it together cross grain. I mixed up some 45 minute epoxy and squeegeed it out into a thin layer over the stab mounting platform. The 1/32" balsa sheet I had made up was placed onto the the epoxy and moved around to smooth out and press out the excess epoxy. Some spruce strips were placed longitudinally on the top of the 1/32" balsa sheet near the edges and a row of cloths pins was used on each side to clamp the sheet to the platform and this was put up to dry overnight.

Next, the four mounting holes were drilled through the 1/32" balsa sheet and the sheet overhang was trimmed back to the platform edges. This is shown in the second picture below. Now for the tricky part. Since the stab was tilted right tip down, I placed a strip of masking tape along the right edge of the sheet to preserve 1/32" thickness. Using the fine side of one of these nail file made for sculpturing artificial nails, I began the long process of carefully sanding and working down the left side of the 1/32" balsa sheet, using the masking tape along the right edge as a sanding guide to preserve 1/32" thickness on the right side. Effectively, I was shaping a wedge across the entire stab mounting platform.

Once I got this stab shim worked down, I screwed the stab onto the stab platform, jigged up the fuselage, and checked the alignment. After some three iterations, I finally had the stab shim shaped to bring the stab into alignment. The last iteration was done with the masking tape removed so entire shim could be sanded as a unit. The final shim result can be seen in the last picture below.

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