Teardrop Aluminum Strut Material

I found a source for teardrop aluminum strut material. It is:

David Gordon
AED Motorsport Products 5373 West 86th Street Indianapolis, Indiana 46268 USA Phone: 317-334-0569 / US Toll-free 888-413-0233 Fax: 317-879-9397

email: dave@aedmotorsport.com

or web site: www.aedmotorsports.com

They offer teardrop tubing made fro 1.5" x 0.058" wall 6061-T6 per the Skyote plans. They custom make this to order so they only deal in 12' lengths. The best deal is to order three 12' lengths which will make struts for two airplanes with one strut to spare.

Drilling First Main Spar

Tom and I drilled the first spar last Friday the 14th. We proceeded with extra care as it was the first spar to be drilled using the laser cut spar drill/assembly jig. We drilled all of the holes for the ribs and fittings in about 50 minutes. We did not drill any holes in the tapered section of the tip.

Everything worked as planned. We will drill an aft spar next. We plan to complete the rib/fitting/spar assembly for one wing before drilling the remaining spars. Better safe than sorry.

Excellent Fuselage Construction Book

As a neophyte fuselage builder, I have found the book "Construction of Tubular Steel Fuselages" by David Russo to be very helpful. Much of the information in this book directly transfers to the building of a VR3 fuselage. The book can be found here: http://www.actechbooks.com/construction_tubular_steel.htm

VR3 Final Report

I am happy to report that the final version of the VR3 Skyote fuselage tube kit has been assembled and checked. I received the replacement longeron and firewall tubes last week but just got around to assembling them yesterday. These tubes have a different arrangement for the joint between the longerons and the firewall tubes. The new joint arrangement provides the same type of interface with the landing gear and flying wire fittings as called for on the plans. The original joint design from VR3 was not wrong, just different.
The new joint design provides the same "perch" for the fittings, but eliminates the need for plugging the end of the longeron tube by mitering it to the vertical firewall tube. Since a picture is worth a thousand words, just take a look at the latest posting in the VR3 photo album. Others may take issue, but I am satisfied that the new joint is structurally equivalent to Pete's design while being easier and more accurate to build.
I am very happy with the VR3 kit. I have had a couple of experienced tube fuse builders look at it and they said that it would not be possible for them to duplicate the accuracy and fit quality using the traditional manual profiling methods.
The VR3 kit is about the same cost as Pete Bartoe's rib kit. In my opinion, the VR3 is at least, if not more of a time saver, than the rib kit. I think I could eventually hammer out the ribs if I had to. I'm not sure that I would ever get the fuse hand fitted to a point that would make me happy.
In my book, there are only two valid reasons not to go with the VR3 kit:
(1) You WANT to fit the tubes yourself.
(2) You can't justify the $$.
If you are not burdened by either of the above "problems" then VR3 is the way to go.
In conclusion, I have no connection with VR3, financial or otherwise.

Aluminum Spacers

I just received the first aluminum wing fitting spacers.

I got them from http://www.aluminum-spacers.com/ . In a quantity of 500 they were only $0.17 each. These are 1/2"dia. x 5/16"bore x 3/8" long. I wil make the shorter spacers by cutting down some of these.

The spacers are a perfect fit with the 5/16" 4130 tubing which will be used to make the bushings that fit inside.

The actual company name is Daven Screw Machine Co.. They are a small family run business and were very easy to deal with. If you don't see what you need on the web site, give them a call as some standard sizes are not listed as was the case for the above spacers.

Spar Drill/Assembly Jigs

I got the spar drill/assembly jigs from the laser cutter yesterday. They will allow all of the holes to be drilled in all five spar components as an assembly. No layout of individual holes will be required. Maybe I will have time to give them a trial run over the weekend. There are approxomately 134 holes in each spar assembly. Multiply that by eight spars and that's a lot of holes!

The spar jigs were laser cut while the wing fittings were cut by waterjet yet the holes match perfectly.

I built a flat table using MDF. It has a spline to hold spar flat. All of the hole locations for ribs and fittings are in the jig. No layout necessary!

Radius Bender

A while back I sketched up a precision radius bender. I based it on some Thompson Linear Ball Bushings which were surplus from some project long past.

My friend and fellow RV builder, Les Kanna, finished building the radius bender today. I decided to bend a few fittings and I am happy to say it works great!

The bender features a micrometer adjustable stop which precisely sets the bend centerline under the radius bar. The distance from the bend center to the edge of the part is given by the CAD program. I am using a 20 ton hydraulic press from Harbor Freight.

It produces a nice smooth bend of the correct radius. The bender is currently set up for a 0.125" bend radius

Fittings Cut by Waterjet

I received the first batch of wing fittings about two weeks ago.

The quality is excellent.

VR3 Kit Assembly Completed

I was able to complete the test assembly of Skyote VR3 kit #001 yesterday (Nov. 21). The tubes all assembled as advertised with no visible gaps. VR3 will be replacing the longeron tubes and the firewall perimeter tubes so that the longeron/firewall joint will better conform to Bartoe's drawing. The change in the joint arrangement will allow the fittings for landing gear struts and flying wires to interface with the longeron tubes as originally intended.

The VR3 Kit is an incredible time saver. I'm not sure that I would ever be able to fit the tubes in the traditional manner. I know that I could never match the quality of the work!

New style Assembly Jig

I decided to redesign the assembly jig for better accuracy and better access to the tubes. The new jig is an internal structure as opposed to the external structure of the previous jig. The stability and accuracy is much better as well as better access to the tubes. Each tubular crossmember is supported by a pedestal which locates it in the correct dimension in all dimensions. The longerons are added next followed by the diagonals. The VR3 tubes don't actually need this much jigging for welding, but my intent here is two-fold. I want to confirm that the tubes conform to Bartoe's drawings as well as confirm that the fit each other properly.

Fuselage Progress

I was able to put in about 7 hours during the past week. The progress is apparent in the photos. The fit of the tubes is excellent. There is really no "fitting" to do at all. All of my time is spent building the assembly jig to hold the tubes in the correct position. Absolutely no grinding or cutting tubes required.

I am not satisfied with the stability of the jig. The tall 2x4 posts are relatively easy to deflect at the top end. If I add gusset bracing it will obstruct access to the tubes.

Trial Fitting Fuselage Tubes

I decided to purchase a CNC profiled tubing kit from VR3 in Canada. Since this was to be the first Skyote kit produced by VR3 there was some design time involved. I placed the order on 9/09/07 and received the complete kit around 10/27/07. Subsequent kits should have a shorter delivery time. As purchaser of Skyote Kit #001 it falls to me to perform the initial check-out of the tubes to confirm that they all fit well and conform to Mr. Bartoe's drawings. The tubes will need to be assembled in 3-D without welding as some of them may need to be modified. This means that the assembly jig will likely be a little more elaborate than what will be required to assemble and weld subsequent tube kits.

The Fuselage Assembly Table was completed on the afternoon of Nov. 2 so we took a shot at assembling a few tubes starting at the firewall. The tubes all fit perfectly. Unfortunately the design of the joint between the firewall tubes and the longerons does not agree with the Skyote Drawings. As supplied, the longeron tubes butt into the firewall tubes which are mitered to each other. The Skyote drawings call for the longerons to extend through and be flush with the forward surface of the firewall tubes. This allows the firewall tubes to butt into the longerons. I spoke to Don VanRaay of VR3 about this discrepancy and he readily agreed to supply replacement tubes per the drawings. We agreed to wait until all of the remaining tubes have been fitted before replacing the tubes in question so that all of the tubes can be corrected at once.

The Drawings

Many people find the Skyote Drawings to be difficult to interpret. I would guess that Dwg.# 100200 causes the most difficulty due to the high density of information packed into it. In my opinion, this particular drawing is a designer's layout drawing and not really a builder's drawing. It contains many dimensions which are not pertinent to fabrication but are there as part of the design process. An example is the dimensions which locate the center of the bolt holes in the lugs which fasten the drag and anti-drag wires to the spars. These were required to calculate the dimensions of the drag and anti-drag wires. Otherwise they are not relevant to the builder.

The 7.2 degree sweep of the wings creates the opportunity for confusion in several areas. The rib locations along the spars (Dwg. # 100202) are given two different dimensions for each location. The larger number is the "Station" dimension and is measured from the longitudinal centerline of the airplane and perpendicular to that centerline. The smaller number is the actual measurement from the onboard or "zero" end of the spar and is measured along the axis of the swept-back spar. This is not readily apparent in first reading the drawing.

The swept wings also contribute to the possibility of small errors in the fittings which attach the interplane struts to the vertical surfaces of the spars. The dimensions on the drawings are correct for the center plane of the pair of fittings. The fittings don't actually reside in the center plane but are separated by 0.080". This separation causes the inboard fitting to move "forward" and the outboard fitting to move "rearward" resulting in a mismatch of about 0.030". This falls in "small stuff" catagory, but since everything is calculated to three decimal places, it seems a shame to ignore it.

I have found a few small errors so far.

Constructing Fuselage Jig/Welding Table

Almost completed the fuselage jig/welding table today.

I doubled up on the middle set of legs so that the table can be cut in half making two tables when the fuse is finished. Of course, it can always be screwed back together for that next project!

As you can see from the final photo, I added a lower level using MDF. It makes a great place to store tools and materials.

VR3 Fuselage Tube Kit

The VR3 profiled tube kit for the fuselage arrived today. The kit includes 124 profiled tubes plus a bag of scrap ends for welding practice. It came in a carton about 8"x8"x48" and a tube about 6"x60". Total weight is 42#. The kit includes every tube included in Skyote Dwg. #100400 EXCEPT the streamline tubes which anchor the flying wires and the upper end of the landing gear strut, and the two round tubes which brace the streamline tubes to the fuse.

The kit also includes 1/4 scale CAD drawings, both 3-view and perspective of the assembled fuselage with every tube listed and numbered. Also each tube is labeled with its number and spec.

Introduction

This blog is a build record of Skyote #88. All my building experience is limited to Van's RV's so I have no experience with building tube & fabric or "plans building". I have much to learn so take everything I write with a grain of salt and reasonable skepticisim.

I do not intend to follow a "traditional" path for the construction of #88. I intend to employ low level technology and $ to reduce the construction time and difficulty where possible and practical. By low level technology I am referring to CAD, laser, waterjet, CNC. For example:

• I have purchased a complete wing spar kit from Jerry Kerr.
• A rib kit from Mr. Bartoe.
• Brunton Flying Wires and Drag wires from Harvey Swack.
• A CNC profiled fuselage kit from VR3.

In addition I have converted all of the wing fittings, brackets, links, lugs etc. to CAD and had them cut by water jet. I have designed a laser cut wing spar drill template/jig which positions the five spar components so that all of the holes can be drilled in a complete spar as an assembly. I plan to continue converting as many parts as I can to CAD so that I can reduce the "hand-made" components to a minimum. While it takes a little time, converting the design to CAD is a great way to truly understand the drawings.
The Skyote is uniquely suited for conversion to CAD in that a "computer" was used in it's original design. I have read that Mr. Bartoe used a HP calculator to "compute" the design and dimensions of the Skyote. The plans show all of the critical dimensions to three decimal places for X,Y and Z axes.

Amazingly, when I put the design into CAD the results agree out to Mr. Bartoe's third decimal place about 99.9% of the time. I have found a few small discrepancies but usually less than 0.030"! Some of these may be due to my erroneous interpretation of the drawings!

If you want to build your Skyote as cheaply as possible, or if you enjoy handcrafting the same parts over and over again then my approach to building is not for you!

 If you want to build your Skyote in the minimum possible time with highly accurate parts then this approach may be the answer. I personally get a lot of satisfaction out of organizing the project so that it can be produced  accurately. Hopefully some of this work will prove useful to others.