CB-1 fuselage extension

[bwwillis]

I was corresponding with fellow in Fresno last week who had a CB-1 project for sale. He said the fuselage was extended 9 in. to allow for larger pilots and the Lyc O-320 engine. He had plans for this drawn by Kelly in 2003. Also he had the original plans for the shorter fus. I'm wondering what version the Hatz Assoc. sells. I was not the high bidder so some else gets the details on this one. My CB-1 plans show very little for the O-320 engine version and my Classic plans which uses the O-320 is a couple inches shorter than the CB-1. Someone please educate me on the versions of the fuselage.

[dougm]

The Hatz Association sells the standard CB-1 plans. If this fellow has a set of plans that includes drawings of a fuselage extension, then I would think that is a custom, one-off set. I don't have a set of CB-1 plans to compare to the Classic (someday I will do a comparison... I keep threatening this but it hasn't happened yet), but my understanding is that the exterior dimensions are the same (length, width, height, etc.) and that most of the changes involve relocation of components between the firewall and the rear 'pit to allow for more room. These include:

Cockpits: Front - Pedals moved forward 2" and seat moved back 2" and more reclined; Back - Pedals moved forward 3" and seat moved back 4" and more reclined. Pedals also moved outboard to the lower longerons.
Stringers: more stringers were added to give the fuse a fuller, more rounded shape and to increase the space between the fuselage tubing and the fabric.
Gear Legs: lengthened approx. 3"

There are many other differences related to control linkage, ailerons, emmpanage, landing gear, cowl, etc.

[hatz215]

If that was the one on Ebay with the wire wheels and odd shape tail surfaces (he used a flying pic of my airplane), the way I understood it was, his original set of plans was a very low number (under 100) and he had an update to lengthen the fuselage which was incorporated into future plans. I was unaware of this, but you would think the plans would show all updates. I noticed he took the auction down, it doesn't come up in completed listings.

Steve

[bwwillis]

Steve and Doug,
Thanks for the information. Every bit helps me make decisions on my project.
The recent ebay auction project was serial #99 according to Rick the seller. The bid closed last Sat. about 3:30 PST and went for $5100. Another interesting thing about the tail group was the airfoil horizontal stabilizer shape. I didn't see either a jack screw or trim tab in the pics. Was there a plan version that didn't have elevator trim? The seller posted to me a note that the lengthened fuselage would eliminate the need for added ballast
in the tail. My observations at Brodhead a couple years ago was that no two Hatzes are the same. The Warner powered ship has a tail post full of lead. The O-200 powered ones seem to have a longer engine mount than the O-320 versions. An author in Sport Aviation mentioned that his first O-320 powered Hatz flew level with the elevator not streamlined so he changed the incidence on the elevator on his second one. So many details and choices. I appreciate all those willing to share their ideas and the reasons behind them.

[hatz215]

BW,

We put an O320 in ours in the early 80's. Our plans # was 215. We had conversations with Dudley to determine where to locate the engine. As I recall we just put it as far back as possible. We blocked it into position then welded our own mount to a dynafocal. No lead in the tail.
I did notice those airfoil shaped tail feathers on the auction site. Someone spent some time on that project.

Steve

[bwwillis]

Steve,
Your approach to the installation of the O-320 sounds reasonable. Do you recall the weight of the pilot and if the elevator was streamlined with the horizontal stab. in level flight?

The symmetrical stabilizer airfoil on the ebay project seemed incomplete without any material between the top and bottom members. It appeared to be made of tubing which I thought would cause a problem for the rib stitching. Here is my real question about stabilizers, why is the stab on the Stearman made with a tail lifting airfoil? I've seen and flown many aircraft with an airfoil shape that "lifted" down in opposition to the wing but only the Stearman with it lifting the same direction. Of course it could and I imagine it does pull down or lift down in level flight but why build the airfoil to be better lifting up? This upside down stab. camber on the Stearman is usually missed by the casual observer. Typical cubs and Hatzes are symmetrical, flat.

[hatz215]

I don't recall pilot weight, but every in flight photo I have of our ship shows a little down elevator. Can't answer the Stearman question but in normal flight you have a download on the tail.
I think ribstitching would be fine with the tubular airfoil tail surfaces. I would say it's pretty sturdy.

Steve

[Bill Rusk]

The first Hatz, Happiness, was several inches shorter than the later ones, and it is noticeable in flight. I don't know if the plans ever had the short version or not. Mehlin lengthened the fuselage for the Brodhead Hatz 8 inches, all of it aft of the rear cockpit. He did it mostly for looks as at that time he was not planning the Warner engine, he was going to use an 0-290 that he already had. Lengthening the fuselage has the dual benefit of improving the looks a bit and also helps the stability about the vertical axis. It is fine as it is but a little better with the longer fuselage.

The wing and stab incidence is optimized for the 0-200 engine and a cruise speed of about 85 mph. With the larger engine 0-320 Hatz the cruise tends to be over 100 and as a result the stab is streamlined better with the logitudinal axis in cruise flight by changing the stab incidence as on the classic. My opinion only.

Bill

[mtaylor]

My Lauzon frame was welded up with the horizontal stab fuselage attachment welded in place. I cut the top half of the attach point from the fuselage, welded steel tube bushings
inside the two parts and bolted them back together. This way I can add or subtract washers to change the pitch of the stab. In flight, my Hatz flies with just a slight bit of nose down trim so I don't feel it's worth the time and trouble to go in there and fumble around with trying to add two washers.

[alvinsager]

Hi,
My current ride is a Cygnet, which flies with up trim, or more up trim. I will put the stabilizer more negative when I re-assemble after covering. I suspect that the area of the horizontal stab is on the small side. My previous plane, a Citabria, needed a bunch of nose down trim in cruise, but not being an experimental, I didn't do anything about it.
As far as the Stearman, I am guessing that the lifting tail is to compensate for the added lift the wings generate as airspeed goes up. Old modelers would recognize this approach from free flight and early RC.
Al