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Recommended Model B upgrades by Bill Nesting


Model B Upgrades

Since the subject comes up often, I thought it might be a good idea to list all of the needed and recommended Model B upgrades in one place.  I will put my input in and if anybody wants to make additions let me know and I will revise the data.  If you disagree with anything I recommend, feel free to make comments.

If you are competent with your hands, have the proper tools and the patience to take your time and do the job right, your Model B can be rebuilt to equal or exceed the current factory planes.  One of the best things you can do to help insure that you do the job right, is to spend many, many hours reading the posts on this group.  After reading a few hundred posts, you will begin to know what each member of the group brings to the group and almost all of the members do have good advice to offer.  Many have years of experience in building, maintaining and flying Weedhoppers and some have a lot of just plain common sense.

If you are in a big hurry, or just don't have the time or the skills to do the job right, don't do it.  If you just want to slap in a new boom tube and go flying, don't do it.  (Remember, all structures are only as strong as their weakest link.)  Your life is too valuable to just throw away.

The absolute minimum tools required:

        Drill Press

        Center-it (or other jig for getting drilled holes in the center of tubes)
        Small Torque Wrench
        Tape measure
        Level or Angle Finder
        Micrometer or caliper (for checking tube wall thickness)
        Miscellaneous hand tools
If you need to replace any bent tubes, you need a bending tool (or take the tube to your local muffler shop).  Note: Filling a tube (taped at both ends) with uncooked rice or wet sand, helps tremendously to keep the tube from collapsing when bending.

You will also need Loctite and safety wire.

Do not fly without:

Aluminum wing tangs – Replace with stainless steel (304 preferred)

1” compression strut – Replace with 1-1/2” (.065 preferred)
Check all tubes for worn or elongated holes – Replace as required
Check all bolts and pins – Replace any worn or non-AN parts
Test all sails – Replace as required
Check all tubing wall thickness – Minimum wall thickness as below:
1” tubing (particularly all struts and braces) – .065”
1-1/2” tubing – .058 (.065 preferred and mandatory for thrust drag spar if over 30 HP)
Check CG (center of gravity) – Modify as required
Check dihedral and washout – Modify as required

Strongly recommended:

Replace 1-1/2” boom tube with 2-1/2” dia x .125” wall or 2” x .125 wall square 6061T6 or 6063T351.  (2” x .125” square is adequate, less expensive and easier to find and use.) 


Move the rear fuselage braces to the connection point at the bottom of the rudder. (See the Model C drawings in the “Files” section.)

Replace horizontal stabilizer support cables with tube supports (45 degree), from the bottom of the rudder connection point to the horizontal stabilizer. (See the Model C drawings in the “Files” section.)
Replace the trailing edge braces with rear fuselage braces.  (See the Model C drawings in the “Files” section.)
Rework the main axle connections to eliminate the tube-to-tube connections.  (See “Bill’s Drawings”, “Main Axle Connections” in the “Files” section, for a possible design.)
Use plastic saddles at all tube to fuselage connections.  (Available at most ultralight supply houses for under $1 each.)
If using a larger engine, consider moving your wing forward (and using a longer boom tube), to avoid having to modify the wing sails.

Nice additions:

Replace all wood stiffeners with UHMW plastic.

Use UHMW tape or spacers at all wear (hinge or rubbing) points.
Use UHMW rod fillers in all tube ends.  (See message #11258.)
 The above recommendations (at least until modified by others recommendations) are mine, do not necessarily include all necessary repairs or modifications and their use is solely at the discretion of the user.  These modifications will not assure that your aircraft is airworthy, but I believe it will get you close.  These modifications seem like a lot of work and expense, but aluminum tubing and a few bolts do not add up very quickly and it will probably take you more time to decide what and how to do your mods, than to actually do them.  A few hundred dollars spent now, may save you many dollars in medical expense or your loved ones funeral costs.

Remember, do it right or don't do it!

Bill Nesting

Redding, CA