Tell us what you did today on your Bearhawk Project

[jaredyates]

I used the laser cutter at our community workshop to cut out and engrave these nifty sun visors.
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[corefile]

any update on this Jared - would love to see how you attached this.

[wpackard]

I used the laser cutter at our community workshop to cut out and engrave these nifty sun visors.
[ATTACH=CONFIG]n23678[/ATTACH]

They look great! How are you planning to attach them?



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[jaredyates]

I'm going to start with magnets and see how that goes.

[JimParker256]

Not exactly Bearhawk progress, but closely related:
This week, everything finally came together to get started on my tailwheel training in my "new-to-me" '65 Citabria 7ECA with O-200 engine. Two hours on Tuesday, and another hour today, and I'm starting to get the hang of 3-point landings. We even had a 5-knot crosswind today, so it was a perfect "next step" from the dead calm air we had for the first flight. Having tons of fun!

[Chris In Milwaukee]

Congrats on your step forward! I trained in a Citabria with an IO-320, I believe. Loads of fun!

[Chris In Milwaukee]

My favorite local CFI just sold his Citabria and bought a 220 Stearman. Dying for the opportunity to get up in it!

[JimParker256]

Yeah, my hangar mate has a CH-750, and flies up to a grass strip near here all the time. One of the guys up there has a Stearman, and about 2 weeks ago, my buddy got a flight in it. Said it was a "big round airplane, with a big round engine, that flies big round maneuvers very gracefully." I thought that was a pretty cool description.

[Bdflies]

A milestone, of sorts... I've covered everything, short of the fuselage. So, it's time to tackle the fuselage! All the little bits have been an adventure and I've honed the rusty technique, to the point that I'm comfortable taking on the biggy. BUT, before covering the fuse, a rotisserie is a must, so create a rotisserie I will!

And yes, Jim. Tailwheel familiarity does count as progress on the Patrol! In my book, anything that gets you closer to flying your plane, is progress!

Bill

[whee]

Working on struts for H-stab. One done. I was concerned about the difficulty of making these struts so have been putting it off. Turned out to be an easy job.

[Bdflies]

I know exactly what you mean! I've come across more than a few tasks, that I've avoided, either due to apprehension about my skills, or just plain not wanting to screw something up. So far (fingers crossed) each task has proven to be no big deal. I suspect much of this, is because I think it to death! But, that's how I work...
The strut looks mighty fine, Whee!

Bill

[whee]

Thanks Bill! I agree that the extra thought that goes into the parts I avoid help make it go better. But sometimes you just have to dig in a get it done.

[rv8bldr]

Finally got the gumption (and courage) to start tackling the engine mount. I built a heavy duty stand to hold the O-540 at a reasonable height to work on it, and just got started. So far, I have made the mount ring and will be starting the actual ring-to-fuselage the tonight. As Bill and Whee said, there are areas/steps that get put off due to any number of things, but in my case, it is mostly from fear of the unknown (i.e. I'm not sure how to do something or figure it is really hard and I will screw it up). Although the ring mount is pretty simple, I got an inordinate amount of satisfaction of completing it. I'm really looking forward to getting at the next part of the mount!

[rv8bldr]

Whoa! Now THAT is an engine :-)

[Bdflies]

Well, Chris, I may have some good news for you! In a previous life, I was building a Murphy Moose, that was to be powered with a M-14P. I had the engine and prop. If you get a new engine, as I did, the engine comes mounted, in the crate, with a mount ring attached. You still need to build the support structure that bridges to the firewall, but you don't have to figure out all the geometry that actually attaches to the engine... Or, you could get in touch with Jim Kimball, in Florida. Those guys are the Guru's of M-14's, IMHO.

Bill

[Chris In Milwaukee]

The Kimballs are definitely in my address book :-)

[jaredyates]

I'm rebuilding the lower cowl section, mostly because it didn't turn out great the first time. Now is a handy time since I'm also changing the exhaust system. In the wee hours tonight I worked on the fiberglass portion that covers the FAB, and hopefully it will turn out better this time with me having a bit more fiberglass experience. The plane has been out of service for a month through this process, and when the second edition of the exhaust arrives tomorrow, I'll find out if it fits. If it doesn't, I'll start to get worried about having it together in time for Oshkosh. This was not a good time of year to undertake this process.

[Rollie]

Here is a deviation from the plans that anyone who has spent any time upside down under an instrument panel should appreciate. Tomorrow the sheet metal gets prepped, primed and painted. I don't know why it rotated toe one photo.

[Bdflies]

Not really progress on my Patrol, but progress on Ron B.'s Bearhawk. We picked up the seats for Ron's project! Man, they look nice! The pictures don't do them justice;

Bill

[JimParker256]

Nice seats. I'm doing something similar for my Patrol, but maybe two shades of grey.

[Chris In Milwaukee]

Put together a couple of temporary work tables in the garage so I can cut the 4x12x.125" into capstrips and spar plates. Not enough room in the basement, so off to the garage with me! A little bracing to go, and then ready for business.




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[JimParker256]

Finally found the plans for the EAA "Wing Rack" and am building them to hold my wings until I'm ready to mount them.

[Bdflies]

Whew! Pushed pretty hard this week (and enjoyed every minute!). Finished the initial taughtening of my fuselage. Still have two more ironings and LOTS of tapes. But 'phase one' of covering the fuselage is done!

Really enjoying this!

Bill

[Glenn Patterson]

Not today but last few days. BH727 finally emerging from the shop for final assembly a week ago. Happy Day!

[Battson]

Very interesting build! Looks like you've removed the Bearhawk hump, and you're using a stinger?

[Glenn Patterson]

It was the way it worked out for us. The top of the cabin follows the wing profile and flows into the fuselage. We were frustrated with the huge tail spring & tail wheel so we decided to give the stinger a try. We started out with the Scott's Iron Design tailwheel that we bought before the Bearhawk wheel came along. We did not care for the big tailspring arrangement. We talked with Scott's and exchanged the tailwheel for the stinger arrangement. He made the assembly for us with the mounting plate shipped loose so we could set the mount angles to get the correct caster.

Time will tell how the stinger will work out. The engine is a Continental IO-360 210 hp that eliminated the air inlet on the lower cowl. My partner wanted to have the sloped cowl similar to a Sherpa as he thought it was STOL friendly. The nose bowl is the typical MC3A but I had to build a new bottom half to be flatter to stretch over the bed mount so he got the sloped under cowl.

[Battson]

I think you'll be in good company with that stinger.... time will tell.

[Glenn Patterson]

Bearhawk 727 finally got its wings finalized on Thursday.

We hit a self inflicted snag. The wing skins were extended 1/2" at both ends for nut plates. The problem was that the skin extension did not leave any finger room between the wing and fuselage. Wings back into the shop. Inboard skins trimmed back to ribs & nut plates reinstalled. Much better & the way it was intended.

The fuselage was leveled side to side with the water level. The gear was solid blocked and hard shimmed to get the fuselage level. if we needed to slide a shim under the tire was aired up & then the air let out so the weight was on the blocks. It stayed dead level through the process. The right wing was raised with the drywall lift & preliminary level set. Then the scaffold was erected around the end of the wing with out the x brace on the inboard side. We used a 3" ratchet strap & a piece of styrofoam board to hold the position. The left wing was set in position with the drywall hoist as we wanted to do both wings at once. We used a 4 ft level with a spacer block to set the preliminary angle. To get the block height at the 46" edge is simply 46 x 2 x Pi divided by 360. A couple tries on the table saw to get the right thickness for the digital caliper. The left wing needed a minor adjustment to get the water level reading while the right wing was on the money.

The drilling of the attach holes made us think a bit and went easier than expected. We were fanatical in building the fuselage that carried into the measuring & setting the fuselage attach points exactly where they were needed. When we were assembling the fuselage we used a lot of string lines and plumb bobs to get top and bottom fuselage frames running on top of one another. We put light punch marks on the tubes that go across between the attach points as centerline references for measuring the attach points so the centerline was not lost. The fuselage was dead straight post welding thanks to our welder partner so getting the wing attach alignments worked out. We ran a rod through the fuselage attach points to mimic the Bearhawk and Newton's method of aligning the wing attach holes.The spacing on the front set was size for size and the rear set had an extra 1/16" added to give wiggle room. We loctite glued the shim washers in before clamping and drilling. The wing was built level & square with the attach holes offset 3/8" similar to Russ Erbs method so the bores did not align. The fuselage was drilled at 1/4" and the wings at 3/16" so a little head scratching on getting the different sized holes aligned. Some of the best things happen by accident. We used 1/4" x 3/16" id tubing to make bushings for the backside attach holes. We wiggled the 3/16 bolt until it centered on the side where the drill was to start and then clamped the assembly tight. We measured from the same outboard points on the wing to the same place on the tail post to have about an 1/8' difference.
The first pass was with a 1/4" bit that pushed the 3/16" bolt out and stayed centered as it backed the bushing out. This set the aluminum wing hole at the same angle as the fuselage attach. The attach holes were drilled out in steps and then reamed. The bolt hole center to center distance measured exactly the same on both sides.

It feels good to have this done and behind us.

[Glenn Patterson]

The prop is an 82 in. McCauley C203. We had the tail raised to level to make it easier to work on the wings so it is sitting tail high in the pictures. The tires are deflated to sit the gear on hard shims to level the airplane left to right. The prop is long & the attitude may make it appear longer. It will have more clearance on the 26in tundra tires or the skis. You probably can see it getting close to your rocks.

I did a fair bit of research on STC's etc upgrading aircraft Cessnas Stinsons etc with the Continental IO-360 210hp. The STC's all have 80in & the McCauley application guide has the 80in or shorter for most of the Cessna's using the same engine. I inquired of a couple places that installed these engines for upgrades and spoke to an AME that did a few as well. The AME told me that the STC's called for 80in but he installed a longer one on his personal plane. He did the change under the radar and used a longer C203 prop that ran great. The consensus among the fellows that did these engine upgrades was that the 82in would work well. The MacCauley application guide had a couple hotter versions of Cessnas with the 82in prop. The 82in is peak efficiency for the rpm & just below Mach1 for this engine. The 82in looked like a good start with for the engine.

[whee]

Looks great Glenn! The C170 STC allows a 82" C203 with the IO360. The Maule IO360 guru has installed several 82" props on Maules and a few 84" props. He says the 82" is about right but the 84" works well too. We are planning to use a 82" but if I have to buy a new one I'm buying a 84".

[Glenn Patterson]

Whee. Thank you. We thought about going 84 as well but arrived at the 82”. I did not know a what over length prop will be hard on the crank and bearings. No one could tell me either. I think the 82in will work good for you.

Our engine is an IO-360G from a Cessna 337. One fellow that did the 82in upgrades said that we could go longer being non-certified. I asked what length & what was too long for the engine. He was not sure. Then said it likely was best not to get too extreme. The 84in at full rpm has a tip speed exceeding thrust efficiencies speed. http://pponk.com/props/#1463774934977-1d7f57b4-6b2b
This is interesting read on prop thrust values. http://pponk.com/props/#1463774935085-a6c14c04-3b8d
The Continental IO-36OK series has the heavier crank and bearings that in the Cessna is 195hp engine but the Isham STC boosts the engine to the std 210hp and uses an 80in prop. If any engine can take a long prop the K series should. The XP modifications used 82in for most of the IO-360 engine series but there are not many around as the owner had financial and regulatory issues. The XP STC's covers both 170's and 172. I could not find enough info on the XP's. One AME put on a longer prop said his neighbours hated it. Our flying club had a member with an over length prop that was loud that caused complaints to the flying club & the police.

It has been a long time since I had my head in these things but I know there are Cessna IO_360 variants which may be the French version that used the 82in prop.
The IO-470J is 225 hp and a stronger engine that uses the 82 in at 2550 rpm. The typical IO-470 is 260hp/2600 rpm with the 88in prop. My partner wanted to start at 88in but that was too excessive.
The 82in prop is in the maximum thrust efficiency range for the rpm. HP is hp when it comes to a fan, pump impeller or prop. Longer prop finer pitch will consume same hp as slightly shorter prop with wider pitch to move the same air with the same hp.

I had a project with a large prop fan that ran for years that suddenly let go. It literally let go with fragments through the fan casing in every direction including the outside wall. The fan bent a 4 in shaft. It was a good example of what happens when a prop fan gets unstable. Adding an inch to a fan blade at same rpm draws a lot more hp and it is not a linear calculation. I think it best to have a fan or prop to run at max efficiency and as stable as possible for a reliable and safe operation.
We decided at the outset that we would be experimental in name and build to certified or better standards. The 82in prop is the upper limit for the engine with a known history .
The 82in was a matter of the better compromise for optimum efficiency & reliability. In the end it is what a person is comfortable with.