From Matronics


Zenith Aircraft Models


  CH 750
  CH 701
  CH 801

Sport Cruisers

  CH 650
  CH 601XL

601XL/650 Upgrade of December 2009

Contributors: TTP

Specs from Zenair

Zenair's drawings which define the upgrade are available at [ZU Dwgs] . Registered Zenair builders can download the photo assembly manual for the upgrade from a link on [Upgrade Page] .

Tools - Note: Ratings are from 1 (useless) to 10 (essential)

Tool Use No. Rating Cost $US URL Link
3X Rivet GunRemove solid rivets, set 5/32" solid rivets. I was not able to set 3/16\" solid rivets consistently.110~100Used tool from Ebay
Straight rivet set kit, surplusSet solid rivets11014Brown tool surplus item--this item may be sold out.
Pin punch setPrepare solid rivets for rivet gun punch11019http://browntool.com/Default.aspx?tabid=255&txtSearch=pp5&List=1&SortField=ProductNumber%2cProductNumber&ProductID=1390
Rivet Removal ToolDrill solid rivet heads1945http://browntool.com/Default.aspx?tabid=255&txtSearch=remove&List=1&SortField=ProductNumber%2cProductNumber&ProductID=154
5/32\" Hex Nut Draw Cleco - 0-1/2\" Grip RangeClamp assemblies-I think our 5/32" spring clecos will work on the center spar1751http://browntool.com/Default.aspx?tabid=255&txtSearch=KHN-5%2f32&List=1&SortField=ProductNumber%2cProductNumber&productid=1921
3/16\" Hex Nut Draw Cleco - 0-1\" Grip RangeClamp assemblies12101http://www.browntool.com/Default.aspx?tabid=255&txtSearch=khnl-3%2f16&List=1&SortField=ProductName%2cProductNumber&productid=1929
Rivet Gun Punches \"Extra Long\" - Shank Size: .401 Punch Size: 3/16 surplusPunch out solid rivets1104http://browntool.com/Default.aspx?tabid=255&CategoryID=361&List=1&SortField=ProductName%2cProductNumber&catpageindex=2&Level=a&ProductID=2638
Chucking Reamer - Size: 5/16\", Decimal: 3125Ream 5/16\" bolt holes11013http://browntool.com/Default.aspx?tabid=255&txtSearch=CR-5%2f16&List=1&SortField=ProductName%2cProductNumber&catpageindex=1&productid=959
Chucking Reamer - Size: 3/16\", Decimal: 1875 Ream 3/16\" bolt holes1810http://browntool.com/Default.aspx?tabid=255&txtSearch=CR-3%2f16&List=1&SortField=ProductName%2cProductNumber&catpageindex=1&productid=936
Chucking Reamer & Reamer Sets - Chucking Reamer - Size: 1/4\", Decimal: 2500 CR-1/4Ream 1/4\" bolt holes--didn\'t use this tool1011http://browntool.com/Default.aspx?tabid=255&CategoryID=149&List=1&SortField=ProductName%2cProductNumber&Level=a&ProductID=952
.247 x .231 HSS Piloted Chucking ReamerReam holes for AN4 bolts in spar root doubler11020http://browntool.com/Default.aspx?tabid=255&CategoryID=152&List=1&SortField=ProductName%2cProductNumber&Level=a&ProductID=1000
5 Piece Rivet Gun Punch Kit - Standard LengthPunch out 5/32\" solid rivets-bought set instead of a single punch1833http://browntool.com/Default.aspx?tabid=255&txtSearch=punch&List=1&SortField=ProductName%2cProductNumber&catpageindex=1&ProductID=84
DRILL GUIDE & BUSHING KIT Guide drilling into spar caps-used drill press instead1052http://aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=DH01-KIT
RIVET LENGTH AND SHOP HEAD GAUGE SETCheck rivet shop heads and rivet initial length1826http://aircraft-tool.com/shop/detail.aspx?PRODUCT_ID=AE1007-KIT
AT627 Bucking bar, 7.75 lbBuck 3/16\" rivets1925http://www.clearairtools.com/index.php?main_page=product_info&cPath=4&products_id=93
BUCKING BAR 1-3/4 lbs. TP-721 12-01307Too light for 3/16\" rivets1417http://www.aircraftspruce.com/menus/to/rivet_buckingbars.html
SURPLUS \"Wedge\" Bucking Bar SURP-WDGBBToo light for 3/16\" rivets147http://browntool.com/Default.aspx?tabid=255&CategoryID=361&List=1&SortField=ProductName%2cProductNumber&Level=a&ProductID=1948
3/4\" sharpened cold chisel Cut off solid and blind rivet heads110-Old chisel inherited from my father
Park TW-1 beam type torque wrenchTorque AN and NAS bolts--originally bought for prop bolts and other purposes11036http://www.performancebike.com/bikes/Product_10052_10551_1030436_-1_400036_400005_400155
Park TW-2 beam type torque wrenchTorque AN and NAS bolts--originally bought for prop bolts and other purposes11040http://www.performancebike.com/bikes/Product_10052_10551_1030438_-1_400036_400005_400155
RIVET CUTTER 12-00200Cut solid rivets to shorter lengths--this is a cheaply made tool that works. The online catalog now lists a $35 price.1813http://www.aircraftspruce.com/menus/to/rivet_3cutters.html
BELT SANDERHelps trim, and finish aluminum edges and corners. Saves time. Many other uses. Harbor Freight Item 6852 for 6" and Item 93981 for 4". The 6" will bog down with heavy cutting, don't know about the 4". The small 1/2" air belt sanders come in handy for hard to get to smoothing and trimming. Example: the 0.040" angle doublers on the rear wing spar. The outer edge can interfere with the aileron hinge. Use this to trim flush.1720 to 190http://www.harborfreight.com/catalogsearch/result/?category=&q=belt+sander
Comment by Terry Phillips

This is a dummy comment to demonstrate how one might add a comment about your own experience with the tools above, or alternative tools. Hopefully many of you will be inclined to share your hard won expertise with those of us who are following along. You need to open a Matronics Wiki account. No big deal. Then click the [edit] link at the right margin. Then just copy this example, paste it at the bottom, and edit it to convert it to your own comment. Click the "Save Page" button and your done! Try it--it's painless. Thanks.

Wing Spars

Drilling out solid 3/16" rivets

Tool list:

Rivet drilling guide tool, BAT-131, from Brown Tool

1/8" and 5/32" threaded drill bits for the BAT-131

Old, very dull, ~3/4" wide cold chisel, sharpened on one side with the bench grinder


3/16" pin punch

3X rivet gun

3/16" punch for the rivet gun


Jig to securely hold spar in place

Center punch

1. First step was to remove the rivet heads.

- Punch the center of the rivet head

- Using the rivet drilling guide tool, drill the rivet head, 1st 1/8", then 5/32" for 3/16" rivets and 3/32" and 1/8" for 5/32" rivets to a depth where the shoulder of the hole is 1/32" or 1/16" below the surface of the base metal. (I found that the drill tip likes to wander, so it worked better for me to drill the holes in 2 steps. A more skilled craftsman would likely drill in a single pass.)

- I made up a shield from 0.016 with a hole slightly larger than the rivet head to protect the spar cap and spar from the chisel See Fig. 1.


- I would place the shield with the rivet protruding through the hole, and put the chisel against the rivet,

- Then, hit the chisel lightly to just slightly flatten the edge, then hit again, but harder.

- It usually took about 3 taps with the hammer to knock off each rivet head. Both the 5/32 and 3/16 heads were easily removed.

2. Drive out the rivet shank. After much experimentation, I ended up with a procedure very close to that suggested by Zenair in their Upgrade photo guide:

- Hit the rivet with a 3/16" hand punch and a hammer until the rivet material was knocked just below the surface of the base metal. Note that this did not mean that the rivet shank was actually moved. Usually it just meant that the slightly drilled metal at the mfg head end of the rivet shank was pushed a bit into the hole. Pushing the end of the shank below the base metal surface provided a guide to keep the rivet gun punch in the hole in the next step, avoiding damage to the spar from the rivet gun punch.

- As suggested by many builders, it was very important to securely clamp the spar cap structure so that the spar cap, doubler, web, and angle could not separate when driving out the rivet. I concluded that the best procedure was to clamp the spar very tightly to the jigs with C-clamps. I set the jigs set on the table ~5 rivet pitches apart. Then I'd use a 3rd C-clamp to clamp the cap as closely to the rivet being driven as possible. That usually meant setting the 3rd C-clamp for each rivet. This required that I move the 3rd C-clamp for each rivet, but the result was that none of the rivets got hung up between separating layers of the spar cap. A typical set up is shown in Fig. 2.


- Then I used the rivet gun with the 3/16" punch to knock it out the rest of the way. It took ~3 very short bursts at max air pressure (70-75 psi with my compressor) to drive out a 3/16" rivet.

- The rivets were ejected rather violently from the spar caps. I put a wooden backstop behind the spar to prevent the extracted shanks from hitting anything.

3. Removing the 5/32" rivets took much less force. I dinged the spar cap angle a couple of time when I held the trigger for too long. With hind sight, I probably should have dropped the compressor pressure down, perhaps to 45 or 55 psi.

Center Spar

Rear Spar


Fuselage Mods

Building the Aircraft




Main Gear

Engine Installation



Earlier Models

  CH 601UL
  CH 601HD
  CH 601HDS
  CH 640
  CH 200

Flight Training


  Rotax 912 UL
  Rotax 912 ULS
  Subaru EA81
  Lycoming O-235
  Mazda 13b NA

Builder Modifications