Tips & Tricks
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Below are some great tips and tricks that I have compiled while building the 601HDS. If you have any ideas that would help a fellow builder, please e-mail me at and I will be glad to add it.



bulletI'm currently working on the project after work and on weekends. On particularly hard days at work it is often impossible for me to concentrate. I'm caught in desperately wanting to work on the project, but not wanting to screw things up. I've learned that it is best to put the project off until my mind is 100% into doing it right.
One of the ways I catch myself doing the wrong thing is whenever I start mentally saying, "it probably won't matter- what's a little ?" or something similiar. Then I know it's time to quit. In the end, that kind of workmanship is not the plane that I want to trust my life to.
bulletI work at my regular job full time, but do "something" every day on the zodiac. When I have difficulty understanding a part of the construction, I allow myself to sleep on it, and somehow it becomes clear the next day. Don't forget to get moral support as well as technical from other builders in the area. Go for it!
bulletWhere do I get Rivets if I don't want to purchase from ZAC (article taken for Matronics List)
If your intention is to follow the plans... and I > think it is reasonable to do so, you need the
countersunk (flat) rivet head.   The part nos are: 01604-00412 for the A4 rivet, 01606-00514 for the A5 rivet.
Avdel Textron takes orders on the phone with credit > cards.  The phone number is 800-268-9947.  Their web site address is  Don't be surprised if you don't find these part nos.
in  their catalog... these are the UK rivets.  The US rivets have the following part nos.  1682-0412 and 1682-0514.  C. Heinz recommends the UK rivets


bulletUse a block(s) of wood or similar material clamped to your table to help mark the centerlines on your ribs and various other items. This is especially helpful when you have to mark centerlines on multiple ribs, etc. Just get the proper distance from table to top of the top of your clamped wood. This needs to be the correct distance to your rib centerline and use the wood to mark your line.
bulletTake a ruler (metal based seems to work best) and pre-drill your rivet pitch actually into the ruler. You can then clamp the ruler to your work and use the ruler as a drill guide and end up with really nice and straight rivet lines. Especially in areas where you need to do 10 or more rivets and you have a straight line for reference. To see a picture of me using the ruler template on the wings just click, Ruler Template Picture. (BTW, you may notice in the picture that some of rib rivet lines are not straight. These unfortunately were done by Zenith. If you take your time and make a good template, the end results are fantastically straight rivet lines.)



bulletInstallation of the Elevator Trim Piano Hinge - Rivet the elevator trim's piano hinge to the elevator before riveting the elevator's top skin. Once the top skin has been riveted there isn't enough clearance for the A4 rivets. Two local builders (myself included) waited until after riveting the top skin which required us to prop up the hinge just enough to provide clearance for the rivet and try to "pull the rivet" at the same time.


bulletMake L angles out of wood to properly align the ribs to the spars. If you use 2 pieces of 1x3x10 wood butted together to make a 90 degree angle this will not only help keep all angles perpendicular as necessary, but also stiffen the structure while building. Make sure you have enough clamps on hand. I needed approx. 10. There is a picture of this in the photo album stabilizer section (photo album).
bulletUse my pre-made drilling template for the rear spar attachment. A great time saver. In Adobe Acrobat Format - Rear Spar Attachment Drilling Guide.
bulletUse spacers for the two outer ribs that are beyond the doublers. This will make installing the stabilizer skin easier and require less trimming. This is because the spars bow inwards at the edges (both rear and front) since the outer ribs on each side are effectively shorter than the inner ribs (inner ribs are installed over the doubler which adds approx. 2mm, outer ribs are attached directly to the spars). Since the skin is cut perfectly, it makes it hard to line up the edge of the skin to back of the bowing spar.
bulletStrap the skin properly to ensure you don't damage the delicate stabilizer skeleton. When strapping the skin to drill the top side I didn't understand why ZAC called for running the straps underneath your work bench. If you don't you easily bend the rear spar when tightening the straps. Also, be careful not to over tighten the straps. Very tempting and will tend to warp the stabilizer skeleton and create a ghost image of the end ribs on the stabilizer skin.

Outer Wing Sections

bulletLeading Edge Fuel Tanks - Drilling for the Filler Neck & Drain Holes:

Found that putting some lipstick on the drain hole is a great way to mark the hole position. Just keep in mind that as the top skin compresses the cork, the hole may move slightly. Came up with a neat idea for the filler hole. Took a 2 1/2" hole saw, laid it on a piece of 12" x 12" construction paper. Marked the outline of the 2 1/2" hole. Cut out with an exacta knife. Laid paper on the fuel tank (install in wing without the nose skin on). Punch holes in paper that matched up with rivet holes. Clecoed paper. Made sure hole was centered around filler neck. Un-clecoed the paper and moved it to the nose skin. Clecoed used the same matching holes on the nose skin. Drilled out filler neck hole. Only done this on the first wing, but it came out great. Hope to have some pictures on the second wing. Digital camera is in the shop for repair.

bulletRear O/B Splice Plate - Use my pre-made drilling template. In ADF format - Rear O/B Splice Plate Drilling Guide
bulletTech Support E-Mail Q&A: In reference to the Leading Edge Fuel Tanks - Replacement Rib 7A touches (interferes) with the buck rivets on the main spar. What should be done? (Cover them, drill them out, drill a  hole in the NR7A, etc.)
Response from ZAC: You are right, the rib should not interfere with the solid rivets, the following are two approaches to attaching the Nose Rib 7A at station 410mm:

1) The solid rivet underneath the rib flange 7A can be drilled out and replaced with a solid rivet through the rib flange  or with an AN3 bolt through the rib flange and the Spar extrusion.

2) Leave the solid rivet in the Spar and make a cutout in the rib flange to clear the head of the solid rivet.   Reinforce the side of NR 7A with a length of L angle (same width as the Rib and Spar) riveted into the rib web and into the spar with  seven A5. The L angle goes on the outboard side of the Rib with .040 angle on the inboard side of the Rib.
bulletTech Support E-mail Q&A: In the Speed Wing Plans for the 601HDS it shows the Rear O/B Splice Plate
with the 20 degree cut on the bottom and the 33 degree cut on the top. In the draft PDF Speed Wing Instructions it says and shows the reverse (20 on top, 33 on bottom). Which is correct?
Response from ZAC: Placing the 20 degrees  on the top will mean better clearance on the bottom for
the aileron push rod.  However both will work, it would just appear better to do less filling!
bulletTech Support E-mail Q&A: Are the fuel caps vented?  Response from ZAC:  The cap is vented underneath the side flanges, the two little   hole in the middle of the cap are interconnected with the side
flanges: blow through the middle holes to check they are free!
bulletTech Support E-mail Q&A: Should I seal all of the threaded fixtures with a TFE type paste (with
Teflon) compound to prevent leaking?  If so can you recommend a brand?  Or is a standard plumbing pipe thread compound OK?  Response from ZAC:   Use extreme caution when using Teflon tape:  keep the edge of the tape back from the end of the fitting to  show at least 2 threads on the fitting - do not start the tape flush with the end of the fitting: the NPT thread will allow the tape to come loose and restrict the fuel flow.
bulletTech Support E-mail Q&A: The gascolator has four threaded openings.   I can only figure out what 3 are
for.  Can you give me directions on how the fuel flows into the gascolator. My guess is that two of the openings are for fuel coming into the gascolator from the wing tanks.   One opening is for the for the 1/8" drain and the fourth is for the outgoing fuel line to the header tank.  Is this correct?  Response from ZAC:   The gascolator for the wing locker tanks connects the left and the right tanks at the gascolator with one outlet to the header tank. The fourth hole is the drain at the bottom.
bulletTech Support E-mail Q&A:  You have provided an area to mount a fuel gauge sender unit on the side of the L/E tank.  Can you recommend a specific unit that you know will work with the tanks? Response from ZAC: The tapped holes have an SAE 3 bolt patter common to most automotive float type of fuel sender units. An alternative fuel sender is an inductor bendable probe as available  by Skysport at 1-800-AIR-STUFF 
bulletWing Baggage Lockers:  Be careful when trimming the hinges. This must be done after reversing the hinge. When the hinge is reversed it moves over one "slot" which offsets the hinge if trimmed before reversing.
bulletTech Support E-mail Q&A:  What are the grounding cable attachment points for the LE HDS Fuel Tanks? 
Response from ZAC:  The tanks is supplied with welded tab, this is specifically installed as a mounting plate for the grounding cable.
bulletTech Support E-mail Q&A:  What is the best way to secure the grounding cable (rivet, screw, AN bolt, etc.)?
Response from ZAC: This will depend somewhat on what type of electrical fitting is installed  at the end of the grounding wire: if the right size hole cannot be found then a bolt would be preferred.
bulletTech Support E-mail Q&A:  What gauge wire should be used for the grounding cable?
Response from ZAC: Grounding wire was  not supplied in the kit.  This does not have to be a very large gauge wire, #10 should be more than adequate!

Center Wing Section


One builder's results of industrial plating his struts, etc. ...
<< I located a plating company that I think is a first class operation, operated by some really nice folks, and charges what I think is very reasonable.  I tell you what, I really got an education about plating. Some of you already have hard-chromed your struts, etc, but for the rest of you I'll pass along some information that might come in handy.  True Industrial Hard Chrome is not like "bumper chrome".  If you turn in a part that is polished like a mirror, then you will get a part back that looks like a mirror.  What ever your struts look like when you turn them in.. they will not look better than that when you get them back, but will be plated with this stuff that is harder than you would ever believe, no rusting problems to worry about, and extends the strut life. I was told by someone else that the hard-chromed areas will not wear your strut bearings out as fast as unplated steel on aluminum contact.  I turned my stuts in after I had polished them up with emery cloth.  I also decided to plate my control stick assembly and the two steps that stick out behind the wings.  After a discussion with Rich at Chrome Wright Inc., he convinced me to use a combination of hard chrome and nickel plating.  He showed me that contrary to nickel plating that virtually plates every nook an cranny, inside threaded holes and so forth, that hard chrome won't plate very good into recessed corners and holes (like where the mounting plates are welded on the strut tubes). I wound up polishing the control stick with emery cloth, and getting it plated in nickel.  Looks Dynamite! He then glass beaded the step tubes (which produces a really nice looking micro texture), and plated them in nickel, and that looks great too. The main gear struts are plated with hard chrome and because of what was pointed out to me before we even began plating, I will spray the lower mounting plate with a blending metallic paint.  The nose gear strut was hard chromed in the bearing areas, glass beaded and nickel plated in the areas of the cross members, bolts, and the lower strut tube and mounting plate.   Because he used nickel on the lower portion of the nose gear strut, it looks terrific and the plate won't have to be painted.  If you don't find someone in your area to do this for you, consider these folks.  I asked him for some prices and information to pass along to you guys on the net and I received the following.   **Prepare the parts to look like you expect them to look when they are done. The industrial hard chrome will not build up and smooth things out.  Be sure to remove ALL the "mill scale" (that's the black coating that's on the stick and step tubing).  The pricing is as follows: The two main gear struts are
$90. a pair.  Nose gear strut is $55.  Steps are $45. for the pair, and the stick is also $45.  The person to contact is "Rich" at Chrome Wright, Inc. 97 East Oldham Parkway,   Lee's Summit, Mo. 64081  Phone number is (816) 525-5417.

Remember, the good experience I had with these folks is like getting a great meal at a restaurant and then passing the recommendation along.... Don't assume that by just sending something in, that you will be just as pleased. You need to talk to him thoroughly, and make your own decision and arrangements.  All I can say is that I like what I got, and think Rich is a really first class guy to do business with.  Hope this information will come in handy and be of a benefit to some of you.   "Soft Landing"..  Fred   >>


Adding Bearing Material for Gear Slides, Lower Bearing, and Upper Gear Plate.
A lot builders, myself included, have put UHM(PWE/W), Delrin, or Nylon on the gear slides, lower bearing, and upper gear plates. Some builders have reported no appreciable wear after over 150 hours of flight. While those using only grease have found considerable wear after the 150+ hours. I went ahead with UHM material because it doesn't expand and contract as much as Nylon. Didn't go with Delrin just because I wasn't familiar enough to know the pros and cons. If you decide you'd like to go with UHM, it can be purchased from Cadillac Plastics @ (800) 274-1000 or (480) 275-6295. Would suggest ordering 12"x12" sheets of 1/4" and 1/2" and use as needed.






bulletCalculating TAS using a known ground distance by Michael Cooper:

You need two legs, reciprocal to each other.

Plot the distance and course between the two VORs you want to use, then fly that course and it's reciprocal. Do not correct for wind; head/tail or x-winds will cancel out on the inbound and outbound legs. Time the legs, then average them. You now have a known distance on the ground with the time to fly it.

To do this, fly the course between the two VORs but ABEAM the VORs, i.e. a few miles to the left or right parallel to the antennas and set your OBS for the radial 90 degrees from your course. For example, say the course between the VORs is 180 degrees. Fly 180 a couple of miles west of the VOR, with 270 selected in the OBS. When your needle centers on the OBS, start
the time. Now set up for the next VOR using the same radial. Maintain 180, and when the needle centers, stop the time.

This way, you avoid the ambiguity directly above the antenna.

Also, when you do the TAS thing with the VORs you need to fly both courses at the same altitude for accurate results, so it's
necessary to coordinate with the FAA as you'll be busting the hemispheric cruising altitudes.

From Don Honabach: Buy a GPS and be poorer, but HAPPY!

Firewall Engine

Maximizing Cruise Speed

The following two articles were taken from the Zenith Internet Newsgroup.

bulletHow to get the most performance from your airplane:

1. To get a good comparison with the manufacturer's published figures it's necessary to know at what power setting THEY were published at. Most production aircraft publish max. continuous cruise numbers for 75% power, as that is the engine's max cont. cruise limit. I assume it's the same for the 601/Rotax combination??

2. In order to get this setting on a new prop/engine installation I assume one has the manufacturer's charts etc. available to convert rpm vs. altitude & temp. into % power. The maximum cruise speed occurs at the altitude where 75% power is achieved with the throttle wide open. This usually happens around 7 to 8,000 feet (+/-) for a normally aspirated engine (i.e. no turbocharger).

3. The accuracy of the tachometer readings are important here. The tach. in the factory demo I flew was not easy to read in detail (i.e. only one hand on the scale), so flying at full throttle at the altitude which will limit power to 75% seems like a good way to also 'calibrate' the tach readings.

4. All of the above is also affected by the propeller pitch setting, as mentioned by Bernie. A judicious choice of prop angle is required to balance cruise speed with take-off & climb performance. If you're flying from mostly 'real' airports, then why not sacrifice a few more feet of take-off roll to get a higher cruise speed. By comparison, the takeoff roll for a Cherokee 140 at gross wt. at sea level is 700 ft., increasing to 1,000 feet at 4,000 ASL (i.e. Calgary).

5. Once you've got a good idea that your engine output is close to 75%, then the next step is to do some runs along a known track (or use a GPS?) and calculate the TAS. Especially with a newly installed system I wouldn't trust the IAS much until it's verified (see George Pinneao's experience finding a good location for the static ports, etc.)
So I guess the GPS is really the best method to establish a true ground speed. To work from there to a TAS, it seems to me you'd have to run at least a triangular course (or maybe four legs n/s & e/w to simplify the math?). I'd have to sit down and work this out a bit as I haven't done it yet and my math needs refreshing. Anyone out there have a good formula for the least number of legs needed to derive the TAS from a known Ground speed and track only?
If you can fly on a day when you KNOW that the wind is essentially calm at altitude, (btw, the wind at the ground is NOT a good indicator of this), or get an ACCURATE read out from another aircraft with an airspeed indicator that is PROVEN to be accurate, then it makes the job easier.

6. All this to say that you want to REALLY know if your aircraft is REALLY that much slower than the published figures.

7. If it is then some of the things to 'clean up'(with only 80 hp. every little bit counts!!) - rigging: is it put together properly :-) - wings both at the same angle? (notice any consistent trim tendencies?) - weight and balance? properly in the envelope? (closer to the rear of the envelope is better for cruise speed, but probably not significant in such a small aircraft...?) - are the controls carefully adjusted to the proper settings - both ailerons properly 'faired' with the stick centered, etc. (see previous comments, from George Pinnaeo? regarding aileron settings) - Wheel pants? (spats?) ... Bernie, I think, has a good handle on how much difference they actually make to the speed. - Radiator and oil cooler placement. I'm sure they can have significant impact.- canopy sealed well? I know ventilation is a consideration under that big dome, but ANY leakage will drag down the speed. - likewise the engine needed here to have sufficient airflow for cooling, but not more than necessary. - all over the aircraft, check where air leakages might occur. (control/fuselage joints, etc.) (that's the beauty of the flexi-hinge aileron; absolutely NO air leakage) - did you install the fairing at the back of the fuselage where it meets with the bottom of the vertical stabilizer? - install some kind of grommets/fairings where control cables exit the fuselage (be careful about anything that might cause a jam!!)

8. I once heard Jim Bede at Oshkosh address the issue of drag and I was surprised how much emphasis he put on small air leakages. (say what you want about the success of his aircraft from a manufacturing point of view - his designs are always very efficient in terms of speed vs. thrust!)- antennae installations can also add a couple of knots drag! Again, with a small engine, small things really can add up. - did you remember to replace all those clecos with rivets - they really add a lot of drag - JOKING, JOKING....

bulletYour aileron's position can make a difference in your cruise speed.

An interesting observation is that a friend flew with me and observed that my ailerons "were up" meaning above the nominal trim-line, as he saw it. So, willing to learn from reversable adjustments, I extended both the aileron push-rods somewhat to bring both ailerons down to what he believed to be the appropriate trim-line. I then flew the plane and felt no difference in smooth control, etc.
However, this adjustment resulted in a loss of about 3-5 mph in cruise!! So I reversed the adjustment, bringing the ailerons back to their original "up" position; this restored the speed.
Moral: slightly "up" ailerons is faster than "down" ailerons.

The following was a response to the above message:

It is well known that reflexing ailerons and flaps does increase cruise and maximum airspeeds, however, you are also increasing your stall speed by fixing these control surfaces up a few degrees above neutral. You will find that your stall speeds will be similarly reduced (to a point) by fixing them down relative to neutral. This phenomenon is most useful if you can adjust your flap/aileron settings "on the fly" (sorry) for cruise and landing/takeoff operations. I guess I would say if you want higher cruise at the expense of higher stall speeds that is great. But be advised that if you have your control surfaces positions fixed "up" relative to neutral, you are most likely giving up some of your low end performance!



Letter to Matco and Matco's Response

I received 3 Matco wheels and 2 MC-5 Master Cylinders with my Zodiac 601HDS Kit from Zenith Aircraft Co.

Can you tell me what wheel(s) of yours they use? I've looked at your web page and can't find an exact match.

I'm also trying to determine what would be the best material to use for brake lines. Do you have any suggestions?

What is the min. recommended pressure rating for the brake line?

Are there any definite hoses / brake lines that shouldn't be use?

Do you have any instructions (for dummies) on how to fill up the break system properly or a book to reference for the basics. I have no previous experience and this is a bit overwhelming without any background knowledge.

MATCO Response:

Dear Mr. Honabach:

Because the wheels we manufacture for Zenith are custom to their application, we do not have them on our web site at this time.

We recommend that you use a rigid nylon tubing for your brake lines.  This helps to prevent the expansion you get with softer poly tubing while still having the advantages of a one inch bending radius a bursting strength of 1700 PSI and clear tube for bleeding.

We recommend a minimum working pressure for your tubing of 450 PSI.  This is the absolute minimum recommended for the Zodiac 601HDS.

I would recommend against using the polyflow tubing as I believe it has an operating range of 175 PSI and tends to expand under pressure.  Many customers have used this tubing over the years with great success however.  If you think you want to go this route, you should conduct a pressure test to determine how much pressure you are exerting.  Be aware that the MC-5 master cylinder with a 2 1/2 to 1 mechanical advantage and a pilot exerting only 150 pounds of force will generate 815 PSI.

This system bleeds very easily from the bottom up with a simple oil can.  If you would like specific information on bleeding methods, please take a moment to send me your fax number and I can fax this information to you.

FiberGlass Primer


E-mails from Matronics News List about the West system

Gougeon Brothers, Bay Cities MI, makes and wholesales what I, and many thousands, call "WEST".  It's a system of epoxy resins, hardeners and fillers that let you do a bunch of things from building cedar strip canoes to whole aircraft.  You can get all the technical insights you could possibly want from some of Martin Holman's books but the Gougeon brothers sell their own technical hardcover book on Boat Building. It makes an interesting read: from boats to 100' windmill blades of Wood Epoxy Saturation Technique -WEST.

Pinneo's Rule # 48: friends don't let friends use polyester/glass.  Use EPOXY.

Pinneo's Rule # 3: Epoxies bond to each other and to polyester. This can be very important in the air or on the water.

WEST epoxy/glass is simple, which is why it's used to repair beached sailboats and 100' long windmill blades for the DOE. You don't have to vacuum bag it, but that will give you more strength and less weight.  Hand layup is all I used to make 2 sets of wheel fairings, gearbox fairings, aileron pushrod fairings, the canopy fairing, the spinner and about 4 different sequential cowl mods.  (I've got to do another one of those to get a sleeker, more attractive shape.)

Look up WEST Resins or Gougeon Brothers on the Net; they've a technical manual online that's all you really need before you buy a pump-kit and make a fairing.  It's a little messy but you can handle that.  It's much less toxic than polyester, smells better, will really, REALLY bond to things and is easy to sand and paint.

If you can visualize the fairing you want, you can make it in WEST.  You can use glass, carbon, Kevlar cloth in your composite.  You can go nuts and use honeycomb or balsacore.  You can glass-in studs or nutplates; you can get almost any shape conceivable.

You can learn to use it by using it; there are a lot of WEST-a-holics out there!



Hello.  It seems like it would be a good idea to install parts
like fiberglass wing tips, the fiberglass light fairing on the
rudder, etc., with some sort of anchor nuts so they could be
removed later for maintenance if necessary.  What kind of anchor
nuts are folks using, and how are they attached?  Are smaller
rivets commonly used?  Are they epoxy'd in place in the wingtips?

Thanks for any help.

601HD Trike


To create a captive threaded self-locking fastener on a sheet metal part, use ACS #AN366F-832; this is an 8 x 32 elastic nut plate. $4.20 list each (ouch.)I drill out the two mounting holes to accept A4 rivets.

To create a captive threaded self-locking fastener in a spinner skirt, wheel fairing, cowl, etc., use an EZ-Point nut, ACS # 04-06370 @ $1.60 ea, and just epoxy/glass it to the other fiberglass or epoxy part. You can use ACS #0406330 which is a threaded stud @ $1.60 ea.



West System can be found on the Web @