Spar Kit

For more detailed descriptions and larger images, use the Spar Kit Construction menu item just below the Spar Kit menu item that brought you to this page.

The Spar Kit Arrived on May 10, 2014.  The weight on the shipping slip said 185#, but my son and I could barely lift it, so be prepared with some strong friends.  So, I unpacked the crate and began taking my inventory of parts.  There are parts in the crate that are not for the spar and I am sure they came with the shipment to save on future shipping costs.  I found it difficult to get to all the parts labels because they were bolted together with hardware store bolts.  I made the mistake of thinking this was just for shipping purposes.  Not so.  Do not remove those bolts at this time.  It took me two days and the help of Tony and Bob, to get them back together in the right order.  I did learn a lot during that process.  The left spar and right spar are not constructed the same.  The right spar will fit in front of the left spar when installed in the plane.  Therefore the stiffeners for the left spar are on the aft side and those for the right spar are on the front side.  Here are a couple of quick picks of those spars, with full details to come later.  You may also notice that the Cave has been converted from Winter to Summer and the benches have taken on another configuration for the construction of the spars and wings.

SparKit_04 SparKit_01 SparKit_03So, now the spars are all back together and ready for “up-drilling”.


Drilling for the rivets is pretty simple, because you are not encumbered by having to get a “tight fit”.  The builders manual informs you that the rivets will fill the hole, given that you drill a 3/16 for a 3/16 rivet.  Your problem comes in when you have to drill for a “tight fit” for a bolt or screw, when you don’t know the diameter and discover that you cannot count on the diameter of all the AN3 bolts and screws being the same.  You are instructed to test, and test you must.  Even then, I was not fortunate enough to get all of them to be a “tight fit”, because after “up-drilling” and re-assembling the spars, the bolts and rivets did not fit at all, for some of them, so I had to either re-drill or ream.  An AN3 bolt has a tolerance of .186 to .189 and I am not sure what the AN3 machine screw has, but do know that it may not be the same as your AN3 bolt.

Here is a picture of my tests and the WolfCraft Drill Guide that I used for drilling and reaming.

SparKit_06 SparKit_05

Here showing that using a #12 bit, I can slip the AN3 bolt in the hole with finger pressure.  That is NOT a “tight fit’.


These are the only areas that I found that needed to be cleaned up from the factory machining.  I used the vixen file first then smoothed out the marks created by the file with this sanding wheel.

I like to deburr with the Burr Away, so got a 3/16″ from The Yard.

SparKit_08 SparKit_09SparKit_10

After deburring, I used the Scotch Brite wheel on my drill to remove the little bit that is always left over.  This also makes the finish look real nice.



The only countersink that I could find for the flush fasteners is a #10.  With the rivet holes being 3/16″, the #10 won’t countersink bit will not fit, so not wanting to drill thru all the material with a #10 bit, I waited til I took the spar apart for deburring and then drilled only the top layer with the #10.  I have always had a problem getting the microstop adjusted just right.  It seems that it is right, then after a few uses, the rivet does not fit flush.  (I test every one).  At one point near the end of the process, I noticed that the aluminum was getting hot.  This made me think that the heat could be the reason for the change.  So I got a cup of cold water with ice in it and soaked the microstop in the ice cold water after each use.  This appeared to solve the problem, but I was at the end, so cannot be sure.  Give it a try if you are having the same problem.





Tony has a very good illustration on his Picasa site showing the process of determining if you have the proper countersink created to make your rivet flush.  If it is a little high, you can always shave it with a rivet shaver bit, but if it is low, what do to.  Dan suggested taping a #8 washer over the end of the rivet before squeezing.  I tried it and it works very well.  I think I had 6 that were low and after squeezing, they all appear to be properly seated.  The image of that result will be posted near the end of this page when I post the results of the rivet squeezing.


I decided to insert the bushings before all the screws, bolts, and rivets had been secured.  Once that was done, there would be no recourse in the event that the bushing holes were even slightly out of alignment.

What you see here is BoeLube, the best lubricant that I have ever used for these kinds of operations.  A wrench and a long ratcheting torque wrench used as a breaker bar.  I bought bolts from Lowes, but was not satisfied with the results of that and using the socket, so went to Fastenal and got all the bolts, washers, and nuts to do the job.


To be sure that the large washer would not hinder the pulling of the bushing, I marked the outline and then secured 3 of the washers with hot glue.  I then used a 7/16 washer over the remaining hole to pull the bushing thru.  I lubricated this with Boelube before starting the process.  This is the last one that I need to do, and I finally got it right.  I hope you are able to get good results from the start.  I did find that no matter how good I do it, I get some fine metal filing pulled thru, but I am sure that is not a problem, but rather just a consequence of using such a crude method for getting this task accomplished.  The hot glue is easily removed with Lacquer thinner.

SparKit_17 SparKit_16

The spars are ready for riveting and the squeezer is on order.

Squeezer arrived on Wednesday evening July 2, 2014.  Rivet squeezing was completed July 5, 2014 and squeezer returned to SPA on July 7, 2014.  Below are some images and posting about the squeezing process.  For more detailed descriptions and larger images, use the Spar Kit Construction menu item just below the Spar Kit menu item that brought you to this page.

The first spar riveted.  Note the hardware bolts with the dotted circle around them.  These were used to make sure that they did not get riveted and to secure a “tight stack”.  On the thin end of the spar, I also replaced every other rivet hole with an AN-3 bolt to keep the stack tight and further into the thick end, I put AN-3 bolts as needed.

SparKitComplete_7052014_03 SparKitComplete_7052014_02





On this spar, I knew that I had several rivets that were below flush, so, I checked them out using a straight edge and pushing the rivet up against it to see if there was movement, and marked each one that moved.

SparKitComplete_7052014_04 SparKitComplete_7052014_05





On each of the ones that I marked, I hot glued a #8 washer, thinking that I needed visibility for riveting, not thinking that it would have been easier to use clear tape.


This turned out very good and the rivets are seated as they should be.


One man operation.  Very easy, but a bit slow, when compared to a two man operation.


Two man is way more faster…  We were setting a rivet about every 15 seconds.  The entire job of riveting both spars was completed in about 5 hours.  We ran a section of about 18 inches on one side, then reversed the squeezer and plates, turned the spar over and ran a section of about 36 inches and repeated the process.  This is my brother Dave.  You may have seen him before when we were dimpling rivets.  We work very well together, then go to McAllisters for lunch.


All finished and I wanted to see how it would look as it will be installed in the Panther.

For more detailed descriptions and larger images, use the Spar Kit Construction menu item just below the Spar Kit menu item that brought you to this page.

  • Posts in the Spar Kit Category
    There are no posts for this category