Bearhawk Builder wrote:Whee, my opinion of course but I would build it to plans. I'm not sure why the builder felt he needed to lengthen the fuse but the Bearhawk is well known as an easy ground handling airplane. I jumped into my newly built 4 place with 7 hours total tailwheel time. As for the trim tab, again it's really a non issue to me, works well. It is sensitive but I actually like not having to crank away to make a change, small movements.
I've seen lot's of guys start heavily modifying their build but unless you're ready for the inevitable 'changing this changes that - oops how do you do that?' results I would stick with the plans, the plane is after all designed, engineered, tested and proven as is.
Here's what I fear - a major modification is made, then a builder wants advice on some issue. Normally a call to Bob Barrows who designed the plane or others who have built before you gets you a quick answer. But with a major structural change done who can blame Bob or anyone when they say you're on your own. I'm not putting words in Bob's mouth but who could blame him in the case of a design change. The best you might get from the Bearhawk crowd is 'that should work' but you are the designer, structural engineer and beta tester. Maybe that's your thing and power to you but my opinion is from the beginning be determined to stick closely to the plans for MAJOR airframe structure. There's enough work to do.

whee wrote:Haven't done anything yet besides studying the plans, ordering material and thinking about some things I might want to change/do different.The jig the airframe was built in was 2" longer in the tail. The theory is that it will make the plane handle better on the ground. In the BH I flew I didn't notice any problem with ground handling so I've been wondering if I should shorten the frame back to plans dimensions. Think I've decided to leave it alone. You can see where the tubes were lengthened to fit the jig.



I've also been thinking about the elevator trim; I don't like how the tabs servo. I'd like to use a Dakota Cub jack screw assembly and covert the tail to a trimable horizontal stabilizer. I'd have to eliminate the front tail brace wire and I can't do that without beefing up the horizontal stab. I ordered a stabilizer from Avipro and I don't want to cut into it so I think I'll just use a cable/tab system like a maule unless I come up with a good way to eliminate the front flying wire.

Material should be here Tuesday and hopefully some visible progress will made.

Brian-StevesAircraft wrote:I can't remember who makes it but there is a mod for Super a Cubs that adds a front brace to the elevator. The brace moves with the jack screw. Friend of mine has it on his amphibian Cub... You could probably fab up a system that is similar and have the trimable stab..

Bearhawk Builder wrote:Whee, my opinion of course but I would build it to plans. I'm not sure why the builder felt he needed to lengthen the fuse but the Bearhawk is well known as an easy ground handling airplane. I jumped into my newly built 4 place with 7 hours total tailwheel time. As for the trim tab, again it's really a non issue to me, works well. It is sensitive but I actually like not having to crank away to make a change, small movements.

bigrenna wrote:Two things that come to mind that I have learned... I don't know what I don't know, and it is truly amazing how big "little" changes can effect an entire system.

If it were to me, I would build to plans.

m_moyle wrote:Pat Fagan installed Morris control cables to actuate both tabs, and profiled stabilizers. Simple.. Says the beahawk flies like a 180.

whee wrote:

Brian-StevesAircraft wrote:I can't remember who makes it but there is a mod for Super a Cubs that adds a front brace to the elevator. The brace moves with the jack screw. Friend of mine has it on his amphibian Cub... You could probably fab up a system that is similar and have the trimable stab..

I've been thinking about how I could do that. I'll have to google it and see if i can find some pictures. Thanks.

Bearhawk Builder wrote:Whee, my opinion of course but I would build it to plans. I'm not sure why the builder felt he needed to lengthen the fuse but the Bearhawk is well known as an easy ground handling airplane. I jumped into my newly built 4 place with 7 hours total tailwheel time. As for the trim tab, again it's really a non issue to me, works well. It is sensitive but I actually like not having to crank away to make a change, small movements.

I too do not know why the builder of the jig decided ground handling was an issue; like I said I think the BH handles fine on the ground. Apparently this jig has been used on 10 different Bearhawks and no one has complained about the extra length. I still wish the airframe was according to plans and if fixing it was as simple as cutting out 2" I'd probably do it but it isn't that simple.

Pic of the airframe in the jig.


The trim does work well and I also like not having to crank the wheel a bunch when trimming. What I do not like is the elevator feel and I think the servoing trim tab contributes to this. If I can fix this issue without cutting into the airframe or horizontal then I aim to. To me it is a big enough issue to deviate from the plans to fix it. I wouldn't ask Bob why something isn't working right that he didn't design...that's what you guys are for

bigrenna wrote:Two things that come to mind that I have learned... I don't know what I don't know, and it is truly amazing how big "little" changes can effect an entire system.

If it were to me, I would build to plans.

I agree and that is why I don't want to deviate from the plans except to fix the trim and I want to do that with minimal changes.

m_moyle wrote:Pat Fagan installed Morris control cables to actuate both tabs, and profiled stabilizers. Simple.. Says the beahawk flies like a 180.

Morse push/pull cables are a good idea. I have been thinking about the profiled stabilizers a little and I'm not sure there is enough benefit to go through the extra work.

whee wrote:Mark, can you send me those pics of Pats setup? I thought you were talking about Morse/Telex push/pull cables.

m_moyle wrote:Cable on the top side of the elevator.

Zzz wrote:How exactly does this design improve upon the torque-tube actuated pushrods/trim tabs? I'm not clear on what this design change does.

From: Budd Davisson
Subject: fixed trim tab versus servoed trim tab

BH'ers, I just came back from flying Pat Fagan's rehabilitated Smokey Bearhawk and I just want all of you to know that his modification to the trim tab system has made what was a good airplane into one that is as nearly perfect as an airplane ever gets.

It's never been a secret that even though I've always thought the Bearhawk to be the most practical, best performing four-place homebuilt ever designed, I was never crazy about the fact that the trim tab was servoed. To clarify for any who may not recognize the term, a servo tab differs from a straight trim tab in that, when adjusted, it is not fixed in position in relation to the elevator: the trailing edge of the tab moves in relation to the elevator, when the elevator moves. The direction it moves determines whether it is "helping" the elevator, thereby making felt pressures lighter (like power steering), or "slowing" the elevator and making it feel heavier. In the case of the BH, it is making the elevator lighter. Bob will tell you that he didn't design it to servo, that's just the way the geometry of the linkage turned out. The amount of servo action is slight and something anyone can get used to quickly. However, I thought it detracted from the airplane's overall handling and gave it a vaguely "abnormal" feeling.

As designed, when in level flight and the elevator is pressured one way or the other, the trim tab servo action multiplies the effect of that pressure giving more elevator action than is expected. The result is a "pitchy" feel to the airplane. So, in cross country you're better off not touching anything or you'll slightly upset the stability. This isn't a huge deal, but in turbulence it can keep you busy. And it's not in keeping with the strong stability of the airplane on the other axis.

Pat's system uses a push/pull shielded cable to move the trim tab via the trim wheel and it stays stationary in relation to the elevator. So, right at neutral, when you move the elevator, you aren't getting the "power assist" from the servo tab. Where a BH usually feels unusually light in pitch, when compared to Cessna/Piper/Beech products, Smokey now feels just like any of the aforementioned Spam cans: it is now very normal in pitch.

I flew the airplane at the same time that long time BH pilots Kevin Deuscher (spelling?) and Scott Williamson did and we were all wildly enthusiastic about the improved handling.

On downwind coming back in to land, I said to Pat, "I now don't see why anyone would even consider building a four-place other than a Bearhawk."

I'm certain that given the reaction of three BH pilots known to him, Bob B will come out with a similar fix soon. He has already done the preliminary engineering for it so it should be a fairly easy project for him.

Anyway, just thought ya'll would like to know. Smokey is alive and very, very well!

Budd Davisson

Zzz wrote:Ahhhh... Thanks whee. Has Bob ever weighed in on this change?

OregonMaule wrote:Now we need a lottery on who will fly 1st. Zane, Whee or Pat. My money is on......

Halestorm wrote:You guys should just copy the otter. Jacking stabilizer, servo tab, and flap compensating tab, simple!

OregonMaule wrote:Now we need a lottery on who will fly 1st. Zane, Whee or Pat. My money is on......

Zzz wrote:Ahhhh... Thanks whee. Has Bob ever weighed in on this change?

whee wrote: ......The jig the airframe was built in was 2" longer in the tail. The theory is that it will make the plane handle better on the ground. In the BH I flew I didn't notice any problem with ground handling so I've been wondering if I should shorten the frame back to plans dimensions. Think I've decided to leave it alone. You can see where the tubes were lengthened to fit the jig. .....

175 magnum wrote:The only thing I caution is do not go with a small motor. Talk with Pat Fagan about travelling side by side with a 180 hp Bearhawk and who burned the most fuel.

Battson wrote:Whee - interesting nose bowl in the pictures you posted, is that the Bob Barrows design to fit a smaller 13" Vans spinner?

whee wrote:I've also been thinking about the elevator trim; I don't like how the tabs servo. I'd like to use a Dakota Cub jack screw assembly and covert the tail to a trimable horizontal stabilizer. I'd have to eliminate the front tail brace wire and I can't do that without beefing up the horizontal stab. I ordered a stabilizer from Avipro and I don't want to cut into it so I think I'll just use a cable/tab system like a maule unless I come up with a good way to eliminate the front flying wire.
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