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**rodsmith** · 01-17-2023, 10:45 AM

I'm also in Colorado, home airport is 6400'. While a turbocharged engine is enticing, it comes with a big weight and complexity penalty. I believe yours would be the first turbocharged 540 in any of the Bearhawk models (I could be wrong about that). You would want an intercooler, there would definitely be cowling mods involved and you would be on your own there. I think you would find that a 300HP angle valve engine in the Model 5 would have pretty good high altitude performance. If you had to have a turbocharged engine, maybe something like a Continental TSIO-360 would be a better fit weight wise.
Covering: I personally have experience with Poly-Fiber and Stewarts covering Systems, both are great, most people with no experience find them easy to learn. A lot of Bearhawk builders are using Oratex and are happy with it. Plenty of info about their experience on this forum. As far as bird strikes, most likely bird strike would be the windshield or leading edge of wing which is aluminum. If a bird did hit a fabric part, would be a much easier repair than on aluminum.
Tire size: No best size, totally depends on how you will use the plane. 8.50x6 will handle a lot. If you need floatation for soft fields or will be landing in large gravel or a very rough surface, then you are going to want something larger at the cost of speed and dollars. Again lots of info/opinions on this forum.
Ordering a Model 5 kit is exciting, enjoy the adventure. I don't think there is a better plane available in that size range for back country flying.

**Utah-Jay** · 01-17-2023, 11:55 AM

You can hit oratex hard with a hammer and it just laughs back. As rodsmith says above, highly unlikely you would get a direct bird strike on a oratex flat surfaced. Maybe the leading edge of a H-Stab/V-Stab

**marcusofcotton** · 01-17-2023, 02:32 PM

Let us not forget Airtech Coatings for quality fabric system. Good products, great training videos free on Youtube, small business owner Robbie Staton is very approachable and friendly to the bearhawk community.

**Redneckmech** · 01-17-2023, 04:29 PM

Originally posted by PilotDebug View Post

Hello Bearhawk People!

I'm currently getting ready for my private pilot checkride which should happen in a couple months. Ever since I started flying and became obsessed with backcountry flying, I knew I wanted to build a kit plane. I'm an engineer who loves to build things....what better way to get something brand new, be confident with how everything works, for the best price, and have a blast doing it? I've been very interested in the Rans S21 for its STOL and higher cruise speed capabilities but realized I could get the same performance out of a 4-seater. I found the Maule M7 very appealing but the price is crazy...then I stumbled across the Bearhawk 5 and HOLY CRAP! This plane seems amazing. Its unmatched in its STOL performance with the useful load and cruise speeds. Is there any backcountry planes with all three better numbers? I don't think so. I've sent an email to the info email and Mark to hopefully get my place in line for a kit.

I am going to be building/flying the plane out of rather high altitudes in Colorado. The density altitude here sucks in the summer and I want all the power I can get for mountain flying. So far I've been eyeing the Lycoming TIO-540. With high altitudes I know the turbocharged engines are the best. Is there another engine recommendation?

It seems for covering options it is between Oratex and Poly-Fiber? Can these coverings withstand a bird strike? That is one thing that I liked about the all metal rans s-21.

For avionics, I really like the garmin g3x. I want to be IFR-capable as well along with autopilot.

For tires, what is the best size bush tire? I was thinking 26-31.

I should not that I will be mainly flying this plane for fun in the backcountry here in CO and surrounding states.

Thanks for all the help!

PilotDebug

Welcome!

It seems we share much of the same background and reaction to the 5'! I had been looking at several other aircraft including the Zenith 801, until I too discovered the Bearhawk 5. There just is not anything that I have run across that compares.

They are expensive and not really proven yet but the Adept Aeromotive 320T looks very intriguing since it is turbocharged and lighter than an O540. I will be watching it's progress as I work through building my 5' and see how it proves out. FADEC control and liquid cooling are definitely appealing.

image.png

**Hewko** · 01-17-2023, 07:41 PM

I'm installing an chevy LS3 (430 hp, 365 when limited to 4400 rpm, 1.73 drive reduction, but the torque is what's really impressive) in my BH 5. Most builders will strongly advise against an automotive engine for several reasons although the LS3 is reliable and has had success in the Titan mustang and some moose builds. I'll be on floats and need the thrust, a 540 will lose reliability at the hp I need to get out of it. But it will add to my build time.

**JayDub** · 01-18-2023, 11:31 AM

Having spent over 1,600 hours behind different Continental TSIO-520Ms and maintaining 3 of those over 7 years, I would advise against going with the turbo Lycoming or Continental on the Bearhawk. There is the cost to purchase, the high cost to maintain, the extra cost and weight in fuel, and the extra complexity (complex often means reduced reliability, yes turbos fail in the air and create mega problems), plus extra things you'll need to do to get max performance like someone said intercooler. Yes, we had intercoolers that were under STC, remote oil coolers, etc to try to get the most power and get rid of the extra heat. Our base airport was at 8,360' and over 70F but we occasionally flew out of dirt strips at over 14,500' but it comes at great expense in weight and all the other reasons above. For commercial use, yes, but for personal use I'd stay way far away. That's just my opinion from my experience but I'm more of a KISS kind of guy.

If you are bent on getting max performance, I'm not sure the difference in weight of the O-540 and IO-540 but isn't the IO rated at 350hp at sea level instead of the 250/260hp? Can the BH5 airframe handle the weight and power of the IO540? I don't know much about the BH5 but if so, that might be a better option but I'm thinking it's probably overkill.

Even at Leadville (North America's highest public airport) the 350hp IO-540 reduced down for density altitude would be a rocket. Leadville is not even at 10,000'MSL. People fly C172s and Piper Cherokee 180s in and out of Leadville quite often. How often would you realistically even go there? The first time is a novelty, after that, meh. It really isn't that high compared to other places in the world. Realistically, a 250hp Bearhawk should have no trouble on strips up to 10,000' I'm sure.

I'll throw some eye-candy out there. This is of the TSIO-520M. The intercooler is to the right of the air filter box on the lower left of the photo but it's not much in the photo. There is an adapter plate where the factory oil cooler normally sits in front of the first cylinder on the right side (I think it's #5 IIRC). The remote cooler goes in the tunnel for the front landing gear where it can get more airflow and is quite effective.

CP2396 engine.png

You might want to get your licenses first then try to find some training for bush/back country flying though before you worry about engines. That will probably take a year or a few. Even building you will have plenty of time to figure that all out first.

Jay

**Sir Newton** · 01-18-2023, 11:51 AM

Yip, experimental experts ! all seem to have various opinions. However, you don't want to turbo charge an air cooled engine because you think it is cool!

**kestrel** · 01-18-2023, 12:31 PM

I can offer a few notes on Lycomings. The TIO-540 will be too heavy for good balance by the time it is a turbo system, though will generally make 350 hp. I've flown them a bit in Navajo Chieftains.

For normally aspirated, the issue is less O-540 vs. IO-540 and more "parallel valve" vs. "angle valve". In the former the valve stems and rockers are parallel and in the latter they are not. I believe that the angle valves variants are always injected. The angle valve breaths better and is heavier. The generic parallel valve variants go up to 260 hp and the angle valves are generally 300 hp.

If you are out for power and considering a Lycoming (I'm not getting into Ford vs Chevy type debates), then build an IO-540 angle valve with a cold air sump, a bit of porting and polishing and pick a compression ratio that suits the type of fuel you wish to burn. If you are all in on horse power and 100LL (or new unleaded variants), then go for 10:1 compression. I suspect you can approach 350 hp (sea level) without the turbo. The advanced electronic ignition systems (not P-Mag or Surefire) will advance the spark at the lower manifold pressures found at altitude reducing how much power is lost due to altitude.

I'm told that with electronic fuel injection and ignition, a ported, polished, cold air induction, 9:1 parallel valve 540 and safely produce 300 hp (verified on a dyno) burning auto fuel.

**Hewko** · 01-18-2023, 02:10 PM

Here's a 525 hp LS3 (must be the LS376) in a Murphy Moose on amphibs.

525 HP LS 3 Powered Murphy Moose on Floats

https://www.youtube.com/watch?v=SpLYp-qqV8E

A custom-built Murphy Moose on floats with a 525 hp LS 3 engine. 4-blade MT propeller with beta/reverse.For those interested in the engine and modifications...

**Sir Newton** · 01-18-2023, 02:46 PM

I was a big Murphy Moose fan & nearly an owner of this SR3500. I backed out of the deal because of maintenance issues & lack of record keeping with the plane. In my defense, the seller was doing his very best to cover up all the problems the plane had. Resulted in NO SALE. The reason I am high jacking this thread is because I really do know something about Moose & how much they really weight. They are heavy heavy ships. On 4000lbs amphibs 2990lbs dry weight. Just about make the aircraft useless. Believe when I say I have been down many roads. The BeaHawk 5 is the gold standard in this catagory. Hands Down

**kestrel** · 01-18-2023, 08:44 PM

Originally posted by Sir Newton View Post

I was a big Murphy Moose fan & nearly an owner of this SR3500.

Now that is interesting. Murphy says that the gross weight of a Moose is 3,500 lbs. This one is listed as 4,050 lbs. Are they claiming a 550 lbs increase for being on floats?

Page not found – Murphy Aircraft

https://www.murphyair.com/models/

Scroll down for the Moose.

Murphy claims useful loads greater than the Bearhawk 5. But it is my understanding that those empty weights are very optimistic. Maybe if Bob built one it could get close? ...and hand propping the MP-14?

...what does an air starter weigh? Anyway, there are 2 Bearhawk 5's flying to my knowledge and both have real useful loads in excess of 1,400 lbs.

That said, while I have no interest in owning a Moose, I'd sure love to give a go a flying one. We had one on our strip for about a year. It is a very cool airplane. The local owners decided it was "too much" to ground handle and maintain, so they sold it.

**kestrel** · 01-18-2023, 09:04 PM

Seems this should be a different thread, but I just tripped over some info on an LS3 powered Moose.

525 ponies Murphy Moose

https://www.supercub.org/forum/showthread.php?61626-525-ponies-Murphy-Moose

Engine sounds really good, sure to wake the neighbors backing up in the morning. Seems to stay on the water a long time.

525 HP LS 3 Powered Murphy Moose on Floats

https://www.youtube.com/watch?v=SpLYp-qqV8E

A custom-built Murphy Moose on floats with a 525 hp LS 3 engine. 4-blade MT propeller with beta/reverse.For those interested in the engine and modifications...

Note the enormous amount of water required for that thing to get in the air. ...read the comments.

This one claims 4,000 lbs gross,

**Hewko** · 01-18-2023, 11:09 PM

He must have Ray Watson's Moosemods fuselage upgrade kit for 4,000 lb gross, along with his LS3 packages with a reduction drive. Yep that Moose was extremely slow getting off the water, and his floats were digging in taxiing, maybe over floated or not be set up right or set up for a heavy payload, or possibly the throat angle is wrong, floats can be tricky to set up. I considered a Moose, since I'm flying it's little brother the Rebel, which is great on floats, but chose the BH5 for a few reasons. If the LS3 set up can handle that much power in the moose, It should be very reliable at reduced power in a Bearhawk.

**PilotDebug** · 02-06-2023, 01:48 PM

Thanks for all the replies! Finally getting my place in line today

I am so excited and cannot wait to get the kit and start building. Here is what I am thinking for options, but would like some advice:

1. YIO-540-L1C5 Lycoming Bob Barrow Rebuilt
2. Dual G3X with 3-axis autopilot
3. Tundra Tailwheel
4. Auxiliary Fuel Tanks
5. Fiberglass wingtips

Options I'm not sure of:

1. Windshield -- I've only ever used a clear. How much better is the tinted solar gray or green or UV protected? Does it make night flying less safe?
2. Main Wheels. I am probably going to start with the 8.5 while I'm going to be using normal airstrips when first flying this plane and then maybe upgrade to 26' later
3. Brake master cylinders - One set is included, what advantages are there for adding on the second set?
4. Prop - From what I have found is that metal is cheaper than going composite yet composite is lighter...I'm leaning towards the metal but maybe I'm wrong?
5. Covering - Is there a breakdown somewhere that compares prices/etc from all the different fabric options?

Thanks!!

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