Sunday, November 23, 2008


The topics of today's post: We've got a CNC table, Builder Contact.

CNC Background - After building the sub-kit for the Vert Stab recently, my focus in NorCal has shifted to getting the wing spar (center section and outter sections) into the wing jig. While Dave is back in FL practicing his riveting so he can start the vert stab assembly, I have run into the need to fabricate several steel pieces for the wing spar. Faced with the prospect of having to hack these parts out buy hand or trying to get set up to do these parts with a plasma cutter - we opted for the later.
If you recall, I mentioned in a previous post that John "Cabi" Cabigas is also building a Prowler. In fact, here's a link: . Cabi bought a CNC plasma torch a while back and I contacted him about making some of these parts. Turns out, he had already modeled several of the parts that I need to have made. One of the biggest pieces is the wing attach plate that is bolted to the center wing spar and us used to attach the outter wings (at the spar). These are the pieces shown on the right here:
We found a day we both had some time and I went to visit him. We spent the better part of a day trying to flatten the "learning curve" on using his setup. The parts are still being worked on, but after seeing his machine work I realized that this is the way to go - when it comes to producing Prowler parts.

Buying The Table - Dave and I discussed this topic for some time, weighing the pros & cons. In the end we decided to pursue getting out own CNC plasma set up. We started looking at the different companies and their machines. We found that their systems vary wildly in both cost and capability. Cabi has a PlasmaCAM system. It's a good system that comes standard with many features that are options with other manufacturer's systems. In the end, we were leaning more toward the Torchmate system. We were going to purchase a new 4' x 12' TM1 system, but found a used 4' x 8' system for sale in Fresno, CA. After nearly a month of negotiations, we purchased the used system. Turns out, it was very well built, it was hardly even used, it was fairly priced, and it is expandable to a 4' x 12' system. Here are some pix:

The table came with the computer setup, but has had the hard drive reformated and a new operating system installed. The monitor has been replaced with an LCD monitor. We still have a lot more work to do before this becomes a useful tool in the Prowler shop. First off, we still have to purchase a plasma torch for it. I have been trying to learn how to use the software and I'm having some modest success. I have modeled my own "sample" part using the Torchmate CAD software. I have exported this file from the CAD software as a .dxf and then imported it into the Torchmate software that actually runs the machine. This software converts the "sample" part .dxf file into something called "G-code" which is what actaully makes the table move in the correct way to cut the part.

The Production Plan - While we were discussing the purchase of a CNC plasma system, we reviewed the parts breakdown of the Prowler and came to the determination that upwards of 95% of the basic airframe parts for the Prowler are made from 2 dimensional patterns. These parts are then either bent up into shape, or are in some way welded or attached to other pieces to form a larger part or assembly. So, our goal is to go forward and use this system to build our first airplane with the result that when we finish we will have modeled each part of the airplane for future use. Essentially we need to turn each of the patterns in these boxes:
into one of these (a sample part file in Torchmate software):
When we get ready to make another airframe, it should simply be a matter of putting the metal in the machine, pull up the files, and hit enter. Without having done any in-depth research, the hope is that we (using our system and Cabi's system) will be able to satisfy our production requirements - when we get to the point where we can start selling airframes.

Builder Contacts -
Ray Siem - We have stopped by again to visit Ray. He has made some significant progress on installing the systems back onto his airframe. He has installed the fuel and hydraulic systems. His main and tail landing gear are installed. He is in the process of making final decisions on his instrument panel and systems. Compare these pix with ones from a previous post:
Ray has an extensive collection of pictures that he has taken while working on his airplane. His pix are a collection of shots of George's , Chuck's, and his airplane. They are a great reference for building one of these airplanes from scratch. We are in the process of scanning all these pix into data files for computer storage.

Chuck Westcott - We have a meeting sked with Chuck for Tuesday, Nov 25th. He is based at the Salinas, CA airport and is planning on the second flight of his Prowler just after Thanksgiving Day. We hope to be there when it happens to learn as much as we can and document the occasion. More to follow.

Bryan Davies - Bryan's mother has passed away recently. Our sorrow and condolences go out to you for your loss Bryan. He has had to put the Prowler on hold for a while while he works on settling his mother's estate.

Steven Rogers - We (including Bryan Davies) had planned to go visit Steve in Sept, but had scheduling problems. Once Bryan is ready to go again, we will work out trying to schedule a visit to see Steve. We are really looking forward to the visit Steve!

That's the big stuff for now. Thanks again for checking in on us.

Sunday, September 21, 2008


The topics of today's post: A visit to a builder; building a drill press bench; and progress on our center wing spar pieces.

Builder Visit - One day last week while sitting on-call Todd took a trip to visit a another Prowler builder. He went to see Ray who is building one of George's original kits and lives near Thousand Oaks, CA. Ray has been working on his airplane on-and-off for some time now, but the quality of the work is astounding. His precision and attention to every detail is producing the best Prowler we've seen so far. Here is a pic of his airplane fuselage in one of his garages:
The airplane is actually much closer to completion than it looks here. This is because most of the rest of the airplane parts and systems have been completed, fitted, removed from the plane for painting and then stored in one of his many shelves of boxes. He is hoping to finish the re-assembly of all the components to the airplane and have it out of the jig within the next year.

Ray has been already been a wealth of information about this airplane and provided us with much more insight about the aircraft. After talking with him, we found out that another builder has flown his Prowler. Chuck is also a builder of one of George's original kits and is in the San Francisco Bay area. We look forward to getting together with Ray again many more times. Great work Ray!

Center Wing Spar Progress - Now that Dave has a sub-kit to keep him busy in his shop, Todd has had some time to work a little more on the wing in his. If you look back in the posts, it been almost a year since we cut out the pieces for the center wing spar. Hard to believe that this much time has gone by, but now we're making more progress. After cutting with a metal band saw, the edges of all the spar pieces are left with a fairly jagged edge, so they needed to be trimmed up. Here's a pic from last year's post: Also, the pieces were scribed to the pattern and then cut just outside of the scribe lines. This leaves enough material to file down the edges to a smooth finish. Turns out this represents a lot of filing. So, on to a better way.

Sometime after cutting out the spar pieces last year, we mounted a router under one of our building tables and fitted it with a 3 blade, carbide tipped router bit with roller bearing on the end. This provides for a technique to clean up the edges of our spar pieces (raw stock) and make them match the patterns exactly.
Here's how it works:
1) Mount the router and put it in the straight cutting bit;

2) Cut two 1/4" spacer strips for each pattern. One spacer strip goes under the entire stack and provides room to have a counter-sunk bolt head. The other is to provide room between the roller bearing (that rides on the pattern) and the actual cutting part of the bit . This keeps the pattern a good distance from the cutting edges and prevents chewing up he pattern. See pic in item 4 below.
3) Drill selected holes into the raw stock using the pattern/drill guide:
4) bolt the "stack" together and adjust the router depth to get the correct height for the pattern to ride on the roller-bearing: 5) Make a ba-zillion tiny bits of aluminum foil and end up with the whole stack looking like this:
The next item to work on are the bearing blocks. They are rectangular blocks that surround the bearing and are clamped under the wing attach brackets.

Drill Press Bench - A small side project that needed to be done was to create a long bench with a drill press attached for drilling the numerous holes that must be drilled into each wing spar piece. A long bench is need to provide support for these floppy pieces of stock while being drilled. This was the solution we came up with:
By mounting the drill deck (table) under the bench top the drill can just penetrate into the bench top and (most importantly) the head of the drill press is now height adjustable above the bench top buy loosening the drill deck handle and adjusting it.
Make sure to square the head of the drill press to the bench top. We used a tri-square and make adjustments (shims if necessary) to get the press square to the bench top in both directions. It has worked great.
Another side project that is getting more and more necessary is a hardware/parts bin rack. We found an old bread rack dolly for $10 and have begun modifying it for parts bins.

Contacts - Todd and Bryan were supposed to go up to Seattle to meet with Steve who has the 4th flying Prowler this weekend. Unfortunately, scheduling issue came up and we weren't able to coordinate. We are going to try to resked the visit for sometime in Oct.

Thanks for checking in on us.

Wednesday, September 10, 2008


Welcome! Or, if you're keeping tabs on us, Welcome Back!

Well, we're managing to get another update done - and it's only been weeks, not months! But, that's because things are happening! Here goes:

Inventory & Parts List - It's taken several months to complete, but we now have a fairly accurate and fairly complete inventory of all the "stuff" we got from George. We have organized this information into a set of Parts List spreadsheets for the airplane. We now have one comprehensive document that contains information about each and every part of the airplane, what its name is, what it's pattern or template is, what it's material specification is, etc., etc. There will be changes, additions and subtractions to this set of documents as we progress, but it is a baseline to start from. Amazingly, this had never been done before, and until now all this information was scattered about in various places - or just didn't exist.

One of the biggest challenges was going through all of the old documentation and finding items that were represented as one part, but were actually made from several different parts and pre-assembled. For example, there is a short shaft that the gear are mounted to. It is "anchored" in the torque box and protrudes through the wing spar. In the old documentation, this was represented as one item. It is actually made from 8 different pieces of raw stock. For production, this information is important to know because it will affect material ordering, etc. Now we will be able to tell exactly how much 4130 (0.063) sheet steel is required for one airplane, for example.

During this process, we also accomplished two additional tasks: 1) matched up any left-over inventory with the patterns that they came from; and 2) divided all the inventory, parts, patterns etc. into seperate boxes (for now) for quick reference. So, we now also have a fairly accturate list of inventory we got from George in the sale and now know where to find it!
Vertical Stabilizer Sub-Kit - Armed with the new spreadsheets, we now have an idea of what inventory items currently exists in each sub-kit and what we will need to fabricate to complete an airplane. The first sub-kit on the list was the vertical stabilizer. Turns out that we had all but about 4 parts we needed to pre-assemble this sub-kit. As mentioned in the website, Todd is the "Production Guy" and Dave is the "Assembly Guy." The vert stab sub-kit has been produced and is now in final assembly. Dave will be doing a major over-haul on the assembly manual as he completes each sub-kit. So, in the end we will have a completely revamped builder's assembly manual.
The parts which needed fabrication included the vert stab skin, a mid-rib, a forward spar and a small angle clip. We used a vacuum bagging technique to fold and crease the skin, a break for the spar parts and the old fashioned "bang it out" technique for the mid-rib.

George came out to help get us started and guide us through the "jigging" process the first time.
Once that was done we drilled the skin and built a crate to ship it to the "Assembly Guy" - Ah, I mean Dave. Now it's on to the fabricatiion and pre-assembly of the horizontal Stabilizer sub-kit next.

Materials For the Plane - Over the past several weeks we have been sifting through the newly created spreadsheets and determining materials that need to be ordered to complete the first two groups of sub-kits. This material has been amassed and is now holding down a bench in the production shop.
This is the steel sheets, steel tubing, bearings, hardware, etc., needed to assemble the Tail Group Sub-Kits and the Wing Group 1 Sub-kits. Hard to believe, or maybe not, that including shipping this pile of stuff represents over $1K worth of materials. In some cases there is enough material to make more than 1 airplane, but some things have to be bought in a minimum order - so that's what ya get.

Contacts - We have contacted a few gents recently that are currently building, or have built a Prowler. In fact, we are going to visit Ray in the Thousand Oaks, CA area to see his project tomorrow (Sunday, Sept 14th). We can't wait, as he sounds like a really nice fellow. We have been very encouraged by some of the information Ray has given us with reference to the airplane, and several folks he's been involved with for the past (nearly) 20 years who know the Prowler and have information about it. We're sure we'll have a lot of info to put into a blog post after meeting with him. Much more to follow.
Also, as mentioned in an earlier post, we have been in contact with Stephen in Seattle area who has a flying Prowler. Bryan and Todd are going to visit with him on the weekend of Sept 20th. This is sure to be a major event in the process of expanding our knowledge of this airplane. Steve is an engineer in the field of airplanes and should have a lot of pertinent information to help us. Much more to follow here as well.
Thanks for stopping by. We'll try to get a post out after meeting the two fellows and tell ya what we found.

Wednesday, August 6, 2008


We received an email the other day from someone wondering if we were still working on this project. Well, the short answer is definitely - YES! For the long answer, keep reading.

OK - let's see if we can account for all the time that has passed without an update.

December to March - Most of this time was consumed by our day jobs. Both Todd & Dave recently moved to new positions and/or aircraft at the day job and a significant portion of our personal time went to completing training, etc. Oh, yeah, Christmas was in there too!

April to May - More of maxing out on the day job to help pay the bills. Most of the rest of available time was devoted to personal projects that needed to be done (stupid honey-do's).

June to Present - Day job is at peak of summer travel season, so guess what!?!? Yep, more of maxing out the day job. However, by taking advantage of as much down-time as possible, we have made a large amount of progress on aspects of "(re)building the company". So, even though we haven't gotten a great deal of work done on "building the airplane" - we have made great headway on understanding the processes involved with producing Prowler parts and then how they are assembled.

We have gone through almost every component of the tail and wing. We've analyzed and cataloged each piece and then considered how to mass produce each one. We've identified many possible simplifications and improvements that we will incorporate into our airplanes. Much of this work was done in collaboration with Bryan (see builder list) and we thank him for sharing his experiences and ideas.

This work will continue with the fuselage parts in the weeks ahead, but it's a pretty time consuming and intensive process. Also, since Bryan has not yet started his fuselage, we don't have the benefit of his experiences - so most things become more of a "what if" discussion.

All of this has an important purpose, and we'll keep most of this to ourselves for now - but suffice it to say that there is "solid" "works" in the Prowler's future.
We also managed to get a few days in at AirVenture 2008.

A Few More Highlights -

Bryan's Airplane: Bryan is making very good progress on his Prowler. He recently had a Tech Counselor review his work in preparation for closing up his wing. Here is a write-up that was published on his EAA Chapter's website:

Here is a pic of his wing (Top):

Here is a pic of his wing (Bottom):

Steve's Prowler - We've had some great email exchanges with Steve and look forward to more. We will be attempting to learn as much about Prowlers as we can with Steve's help. You might say that he is fairly skilled in the trade of engineering aircraft so we look forward to marveling at his insight. Here's a GREAT pic from his airplane's maiden flight:

George's Airplane Move - George has decided to move out of his hangar. So, we offered him storage in one of our sheds. Here are a few pics of "move-in day."

Here is a video of an engine maintenance run 5 weeks later:

This video was taken with a digital camera instead of a video camera, so you can see the camera "strobing" the prop. The prop is actually turnng around 1000-1200 rpm. You can see dust swirls as George cycles the prop. Believe us, there is a LOT of air moving behind that prop!

BTW - This airplane is FOR SALE. If you are interested, please send an email on the Contact Page of our website and we will put you in touch with George. Since it is George's personal aircraft, we will not even try to answer any questions about the airplane. We're sure that you'll understand why we say that for all of our sakes - "You'll have to talk to him." We will put you in contact with him.

The Look Ahead - Well, the busy summer travel season is drawing to a close and Sept is usually a slow month in the airline business. So, we will endeavor to get a few things done around the shop. We did get hardware at AirVenture this year to bolt and rivet the center section main wing spar together, so that is next on the agenda. We are also going to endeavor to assemble the Vert. Stab. Sub-Kit and "ship" it out to ourselves for assembly. Dave will be working on that in Fla. while Todd works on the wing spars in Cal. Of course, there is always more part cataloging of the fuselage to help keep "free time" to a bare minimum. Oh, yeah, did I ever mention 3 great kids.......

That's all the news for now. Thanks for stopping by to check out our blog. We'll try get back to making this a more regular event.