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‘m building up a Hatz [#493] from components welded up by Richard Lauzon. I bought this project from Tom Gastrich who had done a beautiful job building up all ribs. I now have all wings built, one aileron done, and the center section 80% done. I’m going to build a Makelan-type oversized fuel tank that I will rivet together using Proseal to seal it. I built an RV4 which has this type of tank construction. I guess it shows that I am not a welder.
I have a “0” time SMOH Lyc. 0-320, 150 h.p. for power. I’m trying to keep it light but I want climb performance on hot days and I’ll install minimum radios for Mode-C veils. I’ve used Pitts & Steen methods for drag/antidrag wires. Ailerons are per plans using piano hinge. I’m considering lengthening the gear but wonder if the benefits are worth the extra work.
Having just recently purchased a computer, I’m a newbie to the Hatz web page. What a wonderful place to go. Thanks for all your work.
If anyone has questions or wants to talk airplanes, I can be reached at hatz493@hotmail.com.
– Mark Taylor Cincinnati, OH.
On Drag/Antidrag Wires
March, 2001
In order to avoid having to purchase over $500 worth of hardware and to cut a lot of steel–my band saw liseds wood and tin foil–I chose to use the Steen Skybolt and Pitts Special method of installing drag/antidrag wires (hereafter referred to as drag wires).
Basically, that involves eliminating the rod, end clevises, and the steel straps that they attach to. The rod end clevises cost over $10 each and number 48. Add stainless rod to that and the price tag is nearly $600!
Instead, I ran the drag wires through the spars, through oak pull blocks, and finished off with a large diameter washer and a locknut. Blind nuts can be used at the front spar so that wires can be adjusted (tightened) without removing the aluminum leading edge. I used locknuts because I see no reason to readjust the drag wires until rebuild time (when the leading edge should be removed anyhow for inspection.
For compression struts, I used the Waco Taperwing method of a 1/2″ x 3/4″ wood compression strut glued to each side of the rib adjacent to the compression strut location listed on the Hatz plans (see drawings 2 and 5). Note that spacers, the same thickness as the rib gussets, have to be used between the compression strut and the rib diagonals because the compression struts lay on top of the rib gussets at both ends of the rib.
As usual, one change begats many more.
The aileron bellcrank originally mounted on the steel compression tube and deleting this tube leaves you without a place to mount the bellcrank. I used a triangular piece of 1/4″ plywood, glued on one side to the to the double compression struts and on another side to the spar reinforcement ply plate (see dwg 1).
A 1/2″ x 1/2″ douglas fir stiffener is routed out and epoxied in place on the 3rd edge of the triangle ply plate. The bellcrank is bolted on to the ply plate in the same location as is depicted in the plans, in relation to the overall wing layout. Rigidity for the mounting bolt is provided by a “tower” that is a 3/4″ high block of douglas fir. It is glued to the bottom of the ply plate (see dwg 1, 3, and 6). A 1″ x 2″ plate of 1/4″ ply is glued to the top side, opposite the “tower”. A 3/8″ hole is drilled through the tower and the ply plates. A 1/4″i.d. bushing is installed for the 1/4″ bellcrank mount bolt.
The bellcrank support ply plate is epoxied to the tops of both compression struts and to the spar reinforcement ply plates. A triangular gusset block is glued to the top and bottom of the ply plate and glued to the spar to give more glue “footing”.
Having spelled all of that out, I suppose you could just install a steel compression strut at the location of the bellcrank mount with which to mount the bellcrank, ala Hatz plans. You would just need to place large diameter washers at each end. The weight wouldn’t amount to much more, but it would sure make the bellcrank easier to mount. In fact, I’ll think I’ll try that out!
A steel tube compression strut with a drag wire mounting tang still needs to be installed at each wing root, but only 8 rod end clevices need be purchased for this instead of 48. That’s a savings or $400!
Now, in order to drill holes in the spars for the drag wires to pass through and to make sure that the hole in the front spar lines up with the hole in the rear spar without causing the drag wire to bend, I built up a simple jig to guide the drill bit for proper alignment.
A couple of pieces of 1″ x 4″ pine about 10″ long are drilled on the drill press with a 3/16″ drill bit (as per dwg 7). These are clamped on a straight 1″ x 4″ pine board that is long enough to allow alignment of one hole to the other. When I cut the stainless drag rods to proper size, I used one left over piece as a third hand by sharpening one end and inserting it into the hole in one end board.
This pointed end is inserted into a pin point dent that I pressed into the oak pull block at the location that I wanted the drag wire to exit. By the way, when manufacturing the oak pull blocks, special care should be used to get the angle of the washer bearing face to the drag wire properly measured and cut. This assures that when the wire is inserted in place and the nuts tightened down, the wire will be straight with no bend.
The method of drilling holes is to first mark the pull blocks for the spot that the wire will exit and then use a sharp punch to put a dent at that spot. Next press in the piece of sharpened rod into the hole of one end board with the sharp end pointing inward toward the other board end. While standing at the end that I plan to drill, I hold enough pull force to hold the sharpened rod in the dent of the oak pull block. I had to use a C-clamp to keep the rod from sliding out of the hole of the board end.
Chuck a 12″ long, 3/16″ drill bit into the hand drill and, while making sure that the pointed rod end is in the dent in the opposite pull block, insert the long bit into the hole of the other end of the drilling jig and drill through the bull block and spar. When finished, go around to the othere side of the wing and repeat the last task, only this time, the aligning rod is inserted into the hole just drilled.
And that’s as easy as it gets. It’s a one-man job and goes along very well. Remember to use a high drill speed and go slowly with the drill. This maked cleaner holes.
That’s the gist of my setup. I’ll be glad to answer any questions on the Hatz Forum or by phone at 513-860-0402.
P.S. Since the drag wires crisscross, the pull blocks and spars must be drilled with a gap between the wires of 3/8″ on centere. One wire is on top and the other on bottom. Don’t mistakenly drill for one wire high and the other end of the same wire low. Mark the holes for both ends of one drag wire as high and both ends for the other crossing wire as low so that they don’t meet head-on in the middle of the wing bay.