New Patrol Scratch Builder

[Mountainhead]

Hello all,

I just wanted to introduce myself. My name is Drew and I am slowly working on a Bearhawk Patrol scratch build. I have Plans # 421.I greatly look forward to getting advice and insights from the wealth of experienced builders on this site. I am not new to fabrication and design although I don't claim to be an expert either. I have built Jeeps and Landcruisers, but never an airplane. In terms of tools and space, I have a decently equipped 2 car garage with MIG/TIG/OXY welding rigs, plasma cutter, a Bridgeport and an engine lathe, sanders grinders and woodworking tools.

I bought my plans earlier this spring and have spent the time since I bought my plans form Bob, studying and visualizing the parts and assemblies in the plans. I have been drawing up parts in Solidworks and find that to be very helpful in visualizing these assemblies and their construction. I have also been exporting flat patterns and having some parts laser cut from 4130 to reduce some of the hand fabrication necessary. I plan on building the "kit: parts first and moving on to the bigger components as I finish the smaller fabrication projects and clear more space in my garage for the big bench needed for the larger structures. I am not trying to rush the build since I want to learn as much as I can through the process and want my build to be safe and well thought out.

I am also a new pilot. I was working on my private pilot license and had just attained my student licence and solo endorsement when Covid hit and my FBO shut down for a bit. I have a disabled son who has a weaker immune system than most of us, so I am having to put my completion of my license on hold for a few more months until the situation improves in my area. This keeps things happy at home by not stressing out my better half too much. Beyond that, I plan to build time (on rentals) and get continuing training and look forward to the day that I have my own patrol to explore the country in. I have never actually flown in a Patrol (or even seen one in person), but I know someone who is finishing a 4 place Bearhawk and after looking at lots of different options for planes to build, I feel strongly that I am making the right choice in selecting the Patrol. I was hoping to get to check out some Patrols at Oshkosh this year, but that sadly didn't happen...

I look forward to getting to know you and learning form your experiences as I work on my project. This is very exciting time for me and I want to get as much out of the experience as possible.

Wishing you all the best,
Drew

Patrol #421

[Bcone1381]

Welcome Aboard!! You have a lot of experience and equipment to take the scratch build to a very high level. Keep us updated!!

[Bacon]

Welcome Drew! Fellow Jeep builder here (06 TJ, awaiting some big Danas and possibly a diesel swap 🦾 tired of these weak D30/35’s and open diffs/crap fuel econ, bet you already know though 😆😆😆)

I too am new to the airplane game and in a similar position with licensing/training and covid. Hang in there bud.

Where about in the world you building this bird?

[Mountainhead]

Thanks for the nice words guys. I live in Northern California near Sacramento.

I know its unrelated to building airplanes, but my Jeep is a 91 YJ on Corporate 10bolt/12bolt full width axes, spooled with Chromoly axle shafts, 4.88's and high steer knuckles and links, "twin sticked" Dana 300 t-case, SM420 transmission, stretched frame and wheelbase, fully caged on Dick Cepek 40's. Everything was made not bought. It has lots of other goodies too, but it doesn't see much action anymore. I love flying so much more than wheeling, its not even funny. I also restored an old FJ40 for my dad years ago and built rigs for friends along the way too..

It was all great preparation for building a Bearhawk! I'll have to start a thread detailing my build since I have already started receiving parts form laser and am getting ready to start welding. I plan on starting with controls, brake pedals and other linkages. I'll work my way up to the bigger stuff.

All the best...

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Drew
Patrol Plans #421
Scratch Build
Northern California

“When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.”

[Mark Goldberg]

When you cut 4130 sheet with heat (laser or plasma) it leaves an edge that is not good. It is OK if the entire perimeter is welded afterward. But if not you need to remove some material where the edge was heated. Perhaps you already know this. Mark

[Mountainhead]

Thank you for your input Mark. I am not an expert and don't pretend to be one. I regard you as an expert and highly value your opinion. This is actually something I have been curious about and have asked a few folks I know. It has been difficult to get a straight answer.

I have no intention of laser cutting any structural parts. So far they have been tabs and components to make the control sticks, torque tube and pedals. Its been many years, but I once took a materials science class and learned about carbon precipitation, pearlite and martinsite in carbon steels (and other topics). My thinking was that I would try using these laser cut parts in areas not seeing high loads where carbon embrittlement could play a dangerous role. I don't see any visual indication of a thermally effected zone along the edge of the laser cut (like I do when i use a plasma cutter), but I acknowledge that does not mean that there is no TEZ. I do have a small kiln and could bring these parts up to the transition temperature and stress relieve them before trying to use them. I have also considered over sizing them slightly and sanding away the outer margin to remove some of the heat stressed materials. In the case of brake cylinder tabs and control stick/linkage tabs, I will be welding most (but not all) edges/surfaces and would certainly be getting the whole part up to a solid red glow. I am thinking (perhaps incorrectly) that this will cause the 4130 to normalize as it cools, thereby stress relieving the cut metal. If my logic is flawed, I would love to be pointed in the proper direction before I make too many parts. They are also good practice parts if I decide not to use them in the end.

This is just the kind of knowledge I was hoping to gain by being involved in these forums. Thank you for taking the time top share your thoughts with me. For what its worth, I plan on buying your wing spar kit and possibly your cut fuselage tube package as well.

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Drew
Patrol Plans #421
Scratch Build
Northern California

“When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.”

[Russellmn]

One option would be to go with a waterjet shop instead, this would eliminate the concern altogether.

[spinningwrench]

Since you already have a Bridgeport you might want to consider a CNC retrofit. I make many small parts and little things for my Patrol build that way. No thermal issues to consider. Water jet is another option but it’s hard to find shops willing to do non production work. I have modeled my Patrol in Solidworks as I build. If your stuck on a particular assembly possibly I can help.

[Bcone1381]

This kind of work could (will?) revolutionize homebuilding. Its untapped readily available right now....it could be revenue for any kit designer and I hope our design might see that some day. I imagine a designer or an approved person making CAD available for the builder. The builder sends off the design code to a fabricator and then parts are being delivered by UPS, or making the drive to a nearby fabricator to pick up the parts. Its like moving a factory closer to a shop. It moves that CNC Bridgeport instead being an unjustifiable cost of dollars to making Sense (cents). I can see a Spar web could be done that way. The factory owns the design, sells the right to fabricate one set to a builder, and the builder has no shipping cost if its made near home. Thats exciting... spars, hydro-formed ribs, Everybody wins.