Just ran across this recent article in "Experimenter" about Bob Barrow's LSA and thought most of us would enjoy it:

http://experimenter.epubxp.com/i/108002

Makes me want one for sure but I'm too deep into my Patrol to turn back and I don't think I can build it light enough to take a pax and fuel. Maybe later, I have a C-90 that would be ideal. Nice pics in the article.

It is really tempting alright. I'll be watching the kit prices closely as it would take me too long to build one from scratch. It sure would be fun, though!

Good find blackrock. The performance is impressive for that horsepower. I wonder what pistons he uses in the C-85 and why he chose the 0200 camshaft. I've heard of people using the C85 pistons with the 0200 crank but I think they had to be machined for clearance, I wonder if that is what he is doing.

C-85 cranks are mostly gone, C-85 pistons give a nice CR increase, not aware of having to machine for X engine.

Looks fun. I still think the decision to omit the flaps wasn't that great, but it should be a fun flyer. I have no high hopes for Class 3 medical waiver proposal, so LSA is a good market for Bearhawk/AviPro to go after.

I like it! Simple, fun and light.

macktruckfarm wrote:C-85 cranks are mostly gone, C-85 pistons give a nice CR increase, not aware of having to machine for X engine.

I can't remember where I read it but they said the the top edge of the C85 piston had to be beveled for clearance because of the longer stroke of the O200 crank.

whee wrote:Good find blackrock. The performance is impressive for that horsepower. I wonder what pistons he uses in the C-85 and why he chose the 0200 camshaft. I've heard of people using the C85 pistons with the 0200 crank but I think they had to be machined for clearance, I wonder if that is what he is doing.

Whee,

I'm PM'ing you Bob's phone number. If you call him, please let us know what you find out. It is intriguing to me also. Bob is really good about answering questions. He can be hard to reach if he is out of town, though. Maybe he can stroke up the Luscomb for you.

Zzz wrote:Looks fun. I still think the decision to omit the flaps wasn't that great, but it should be a fun flyer.

I believe the logic was, if you get the stall down to 30-35mph, why have flaps? I've heard that omitting the flaps saved about 60lbs - a big chunk of useful load for an LSA. FWIW, the article doesn't mention it(prob'ly because Bob doesn't want it advertised), but the actual design gross is 1,500lbs, so there's a generous design margin not found in most LSAs.

Thanks Mike - another good read from Budd!

That 60 lb. number for adding flaps seems high, (and good call on that number being much more significant for an LSA then a larger bird, a lot of people ignore that, already some have talked about using an 0-320 if they built one!) but I guess he must be including a beef up of the rear spar to handle flap loads? That is probably much more of a factor with the single lift strut design. I really like the inherent drag lessening of the one lift strut, but damn, where I am I going to tie solar panels, snowboards and other external loads? Seriously.... though only needed a few times a year I like having the dual strut/external load option for loads too bulky to fit in the cabin. The best of both worlds I suppose would be a aux strut you could bolt on when needed, just for external loads.

I want flaps, I don't care how slow it stalls, just another tool in the box when on short final, especially off airport. Purely from a marketing point of view I'd like to seem him offer them, maybe if enough people comment he may?

This kind of nit picking has to drive airplane designers crazy..... and BTW many LSA's have a higher actual gross then the stated LSA max, that way they can also market to the experimental crowd, just like Bob is doing. In actual practice, many LSA's are operating over the LSA gross, or so I've heard

Too was surprised when I read the flaps would add about 60lbs. I was expecting something around 40lbs because that is how much flaps for a Luscombe weigh.

Yeah it is not insignificant - but Bob would know.
You can bet your bottom dollar he's either done the calculation or physically weighed something to come up with that number.

Looking at the design, you have the torque tubes, reasonably large supporting structures, return springs and pushrod drive system, control handle and brackets, fixtures, cables turnbuckles, pulleys and mounts, inspection panels, then they physical flaps themselves which could be heavier or lighter than the wing skin & ribs they replace.

From what I've seen on video and talked to Bob about, I don't think he's afraid to use a slip here and there. Maybe that features in his thinking? There is something about an old PA18 or J3 (flapless) which keeps you honest!

Edit - typo fix

A friend of mine did the O-200 crankshaft mod on an L-2. The bottom of the cylinder skirts have to be relieved to allow the rods to pass without hitting them.

If the LSA Bearhawk already lands at 35 MPH (and as such does not need any more lift), but Barrows feels he cannot afford the 40-60 pounds of flap-related structure (to stay within LSA), there is one other option that an old soaring pilot like Courierguy would appreciate: Spoilers.

For about 5 pounds (assuming EXP/amateur built), you can put pretty effective spoilers on the wing for glidepath control. You need only two 6 x 18 inch lengths of .040 aluminum, or better yet foam/glass sandwich panel, five or six hand sized .063" aluminum bellcranks and four similar mounting gussets, 30 or 40 feet of 1/16" trim cable, two 1/16" turnbuckles, a small handful of hardware, a couple of feet of aluminum tube, four rod bearings, and a lever.

One of my EAA chapter guys has aset of Bearhawk LSA plans. If anyone seriously wants to pursue this, I will look at the plans and sketch out someting for you... but it ain't rocket science. Any old broken down model airplane builder and sailplane driver can figure it out. And Barrows is surely more than capable of doing it from the "official" factory position.

Spoilers will not lower your stall speed, in fact stall with spoilers open will be a bit higher (less lift). But spoilers will definitely give you more powerful glidepath and touchdown control. On a light, high-lift LSA category airplane, spoilers will allow you to fly the airplane more precisely in real-world gusty and turbulent conditions.

I enjoy flaps for takeoff probably more than for landing. It's nice to be able to break ground quickly on rough or soft. BUT, simplicity and lighter weight are also nice.

Question time. On this particular LSA does the stall speed and rollout already match the lift off speed and takeoff run? In other words does adding spoilers create a plane that has a landing ability shorter than it's take off capability and is that necessarily a bad thing?

Had a very interesting conversation with Mr. Barrows. I called to talk about the 4-place Bearhawk but I was really curious about the C-85 motor he built for his LSA.

He chose the O200 cam so he could run higher rpm; redline for the motor he builds is 3000rpm. He tried the C-85 pistons with the required chamfer on the top and they worked ok. He is now running custom forged aluminum pistons that weight about 25% less. This allows for higher rpm without increasing the stress on the crank. Another feature of the piston I really like is the the piston pin has clips that hold it in place like a car engine and the pin is pressure lubricated. He is not selling these pistons as he is still testing them and he has not yet decided if he will sell them separately or just include them in engines he builds.

Very cool stuff.

Adding extra capability or performance can always be a good or bad thing.

As far as spoilers, they would allow more precise glidepath control and a steeper approach. Whether that turns a "landing critical" airplane into a "takeoff critical" airplane or vice versa, I have no idea. Don't know anything about the Bearhawks LSA at all.

I do have a few hundred hours in Taylorcrafts, and I can confidently say that they would benefit greatly from spoilers. In fact many of the Army L-2's had them. The weak spot of the T-craft is the poor ability to apply and modulate drag to fine tune your approach in gusty or changing conditions. You can do wonderfully spectacular forward slips in the T-craft, which gives you a half-decent descent rate. But putting the airplane into and out of these slips is not instantaneous, abut it picks up speed insta-freakin-taneously when you let it out of a hard slip. Being able to move a spoiler lever back and forth, in a lot less time, would allow you to hit the spot consistently, with the least excess energy.

I'd have to say the 3 American T-crafts I owned were a little more "landing critical". I would not hesitate to take off from a 500 foot clear strip even with 65HP, but approaching into a 500 foot strip would require much better (calmer) conditions. Gusts, thermals, even moderate chop could easily mess up an approach to where you'd go around and try again. The British T-craft (Auster) had reasonably good flaps and not an over-abundance of power... so I felt I could easily land in less than 500 feet but I could not guarantee that 500 feet was enough to get ouit of under all conditions.

Sorry to just get back to this, but I've been away the past week.

courierguy wrote:That 60 lb. number for adding flaps seems high...

Bob has a penchant for steel weldments. It's pretty easy to see how it would add up. The Patrol flaps are pretty big; quite a bit wider than the ailerons(104" vs. 66") and have three hinges each. The LSA ailerons are a similar percentage of span.

Here's a couple pictures showing the Patrol flap support and retraction springs:


You can see the flap torque tube in the photo above. It runs back to the wing root as shown in this photo(this is a Bearhawk, but the flap drive is nearly identical):


And the flap hinges - each flap has two two leg and one three leg hinge. In these photos, the bearings haven't been pressed in yet:



With all this steel and the associated control lever, pulleys and cables, you can see how you would get to 60 lbs. I think they're are probably ways to trim quite a bit off this, but I'm no mechanical engineer and I tend to trust Bob on these things.

I've got both the Patrol and LSA plans. I'm out of time this evening, but I'll try to post the wing layout for the two designs tomorrow.

edit to add - My apologies, the above photos are not my own but are from Eric Newton's most excellent Bearhawk sites, mybearhawkpatrol.com and mybearhawk.com