Tinbuzard - One off design

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Jman

Site Developer
Joined
Oct 22, 2002
Messages
1,881
Location
Pacific NW, USA!
Jeff Schroeder (Tinbuzzard) was good enough to send some pictures and a description or the incredibly unique design he is working on. Here is what He wrote:
Known to close friends as the Tinbuzzard, I started this one off project in the early 1980s. It has been built, modified, and rebuilt numerous times as I've learned more and more about aircraft construction. It is now getting to look enough like an airplane that people are thinking that I might actually finish it. It has been a personal goal of mine to design and build an airplane, I'm not enough of a sadist to offer plans or a kit!

The Buzzard is an all metal, two seat tandem pusher with retractable gear. Length is 27', wingspan 30'. Planned gross wt. is 2,500 lbs. wing area is 135 sq. ft. Design goals were to have excellent visibility, good low speed handling, and to have something different. I'm hoping for Bonanza class performance. Planned engine is a DynaCam DC-375. This is a twelve cylinder barrel configuration powerplant with double ended pistons driving a swashplate. I have a mockup of the engine in the plane now, and am hoping to get the real one this year. The airframe is all flush riveted, with butt seams between skin panels. Most of the metal and fasteners come from various aircraft surplus houses here in Southern Calif. The structure is admittedly overly complex, with 500+ bolts and over 15,000 rivets so far! The only airframe part that I havn't made myself is the nosecone, it's a prop spinner off of a DC-6.

Jeff Schroeder











Thanks Jeff!
 
Last edited:
T

Tinbuzzard

I'm about 70% finished on the airframe and perhaps 30% on the various systems. Elevator and rudder control, and nosewheel steering and retract systems are done. All fuselage and tail metalwork except for the engine cowling is complete. Unfinished items are canopies, electrical and all engine systems, leading edges and control surfaces on the wings, and brakes and maingear retract. Panel and radios are about 1/2 done.

I actually had a rebuildable J-69 turbine many years ago, but abandoned any thought of using it when I realized it would drain the tanks in less than an hour! (Cap. 60 gal.) It's also just about the loudest turbine ever made which would have made me very popular if I had been able to afford all the fuel.
 
T

Tinbuzzard

Hi, Scott:

Yes, I fabbed the gear. The maingear struts are machined out of 2024-T3 blocks and the half forks on all three are 7075-T6. I have a good local source for surplus aluminum, and access to a machine shop as well as a small mill of my own. All of the fittings and parts on this airframe are homemade except for wheels, bearings, brakes, rod ends and fasteners. (+ engine, instruments, radios and so on) This may be taking homebuilding to an extreme, but I have always loved doing things myself. Even back in my model airplane days, I usually built my own rather than kits. Actually, one of the reasons that I started a scratchbuilt project was that I couldn't afford a kit at the time, and still wanted to build.

Jeff
 

orion

R.I.P.
Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
Hi Jeff;

That's quite an ambitious project. Congratulations on your progress thus far. Being a designer in this industry, I must commend you on the selection of your configuration as it folows some of my own thinking and prefereces. Should be a ball to fly.

I also like the selection of your trailing link gear design, the long tail booms for a sufficient amount of tail volume and the relatively robust looking layout of your wing structure.

As a designer though, I would also like to pose a few questions.

1) The wing on your airplane looks to be rather small with a limited amount of room for flaps. Despite the potentially higher wing loading though, the pictures you show depict very little or no root incidence of the wing. If you are predicting a very high cruise speed, especially at lower altitudes, this is probably OK but if your performance does not come up to snuff, you may be flying a bit nose high all the time.

2) There doesn't seem to be a lot of room for flaps (short span). This could lead to a relatively high landing speed, requiring a relatively high angle of attack prior to touch-doiw.

3) Number two leads to this: Although this is difficult to judge from the pictures, it seems that your tail (the bottoms of your verticals) is sitting pretty low to the ground. What is the allowable geometric angle of attack of the airplane on the ground (and relative to the ground plane)with a flat tire and the gear struts fully compressed? Ideally this number should be at least ten to twelve degrees, maybe more. If it's less, you may have to modify your vertical geometry and/or put sacrifitial tips on the bottom of the verticals.

Anyway, just my two bits worth.

Bill
 
T

Tinbuzzard

Hi, Bill:

Thanks for your interest in my project! I realize that it can be difficult to tell much from a few photos so I'm happy to answer questions about what I did.

First about the wing: Its actually fairly large, with a root chord of six feet and a span slightly over thirty feet. The centersection between the booms is unflapped, and has an incidence of 4 degrees relative to the fuselage. The outer panels are set at 2 degrees, and have a further washout of one degree. The leading edge (not yet built) has a straight sweepback of ten degrees fuselage to tip, while the trailing edge is nearly straight. The overall sweep of the wing is about six degrees. This was done to get the CG, aerodynamic center, and main gear in the right relative positions. The outer panels will have single slotted flaps with a 7.5 foot span on each side. Flap width is slightly over 25% of the chord.
Without the leading edge or trailing surfaces built, the wing looks smaller than it really is. Actually, I have enough flap that I might have to limit deflection somewhat to avoid overpowering the elevator in the landing flare.

Planned wing loading is around 17 to 18 pounds/sq. ft. Airfoil is the Riblett GA37-215 I had originally planned on using a GAW2 foil until I realized that the large pitching moment would get me in trouble. Twenty years ago, when I started the design of this project, I read all of the NASA and NACA reports that I could find, and was sucked in by the performance claims. Further learning on my part, and the less than stellar performance of some planes with the GAW airfoils, convinced me to alter my wing design before it was too late! Luckily, the middle of both airfoils was similar enough that I didn't have to change the ribs between the spars I'd already built!

My estimated cruise speed for planning purposes is 160 knots. Using the Airplane PDQ program, I should have a level or slightly nose down (1 deg.) fuselage attitude at cruise. The program also indicated that my elevator position would be neutral at cruise as well, so I must be close on the stab incidence too.

You're right on about the tailbooms. I wish that I had raised the tail two or three inches. I'm just okay with prop clearance with a compressed gear and the bottom of the verticals touching. (following the guidance in Pazmany's book on landing gear design) Notice the small articulated wheels under the tails to take care of overrotation. I can get to a 14 degree angle of attack before the tails touch. (around ten with flat gear) However, in a gear up landing, the bottom of the verticals will touch first and slap the belly down. There are stainless steel skid strips on the belly of the plane under the rear spar, and the bottom front corner of the verticals is light foam and glass. It should tear away until the small tailwheels touch. (interesting note: I put similar skid strips under my BD-5 and USED them! They saved the bottom of the plane) The nosewheel on this plane is about one third exposed when retracted against a firm stop, and this gives the nose something to roll on while sliding down the runway.


Jeff
 

orion

R.I.P.
Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
Hi Jeff;

Sounds like you did your homework. Good choice of section too - you're right, the GAW series (1 and 2) were dogs.

It is important to keep in mind that NASA's definition of general aviation is a KingAir, not a Glasair. The GAW sections were designed to work well at about 50 psf loading, not 20.

If I recall correctly, the engine you're using will put out about 200hp. Based on your layout, I would be surprised if you wern't able to get better performance than 160 kts with the gear up.

Programs like PDQ are OK for conceptual layout and idea work but may not have sufficient refinement for gaining detailed information. You might want to get a more refined analysis of your layout done so you have a better and more accurate idea of the characteristics.

Bill
 
T

Tinbuzzard

Project Update

Since posting a description and photos last spring, I've finished cockpit side consoles and throttle quadrant, along with the seats. The wings now have leading edge ribs (15 per side) and ailerons. The outer three ribs between the spars have also been remade to match the GA37-215 airfoil. (I was going to shim the originals, but realized it wouldn't work well) As soon as the pushrods and bellcranks for the ailerons and flaps are in, I can finish skinning the wings. Still waiting on the engine.

Jeff
 

W.M.Patrick

Member
Joined
Aug 3, 2003
Messages
5
Location
Madison, Mississippi
Timbuzzard-One off design

your pictures and design is very close to what i had in mind in asking
about a pusher versis tractor configuartion. I am not as brave as you
in that i have a mustang II wing that falls close to your design. cord is
about 5 ft. and length about 26 ft. made in three pieces like you picture.
I expect you did your homework where the twin boom tail and pusher
offers much more drag than the tractor design. My present mustang II
does 200 mph on 200 HP low and 200 kts. at altitude. Landing gear
tucks in much like you have it pictured. Maybe you can shed some light
on my proposed project. I intend to use a modified 302 Ford engine
which will put out 300 plus h.p. at 4400 r.p.m. and weigh under 500#.
This should fall within the weight limits of what i am presently flying.
your design looks great and i look forward to seeing it as you progrress.
 

orion

R.I.P.
Joined
Mar 2, 2003
Messages
5,800
Location
Western Washington
If I understand your comment above, you indicated that a twin-boom pusher would have a higher drag count than a conventional layout.

Although there are some design considerations, in general, actually the opposite is true. There are two factors to consider: The first has to do with the overall layout. If we normallize several vaiables (equate them from one layout to the other), the twin-boom pusher configuration will generally have a smaller wetted area than a conventional layout. Yes, the difference can be minimized if particular attention is paid to this part of the loft (for the conventional layout) but as a general rule of thumb, eliminating the tailcone and the sizeble nose engine cowl does result in less area, especially for tandem aircraft.

The second detail is the effect of the propulsion installation. In a tractor configuration the high energy air is directed onto the wetted area of the structure. As such, there are energy losses that result in a slightly lower efficiency number for the prop.

In a pusher, the flow is of course into free air. Furthermore, the effect of the prop flow also reduces the boundary layer effect generated by the fuselage. Coupled together, there could be significant propulsive efficiency differences between the two layouts with a significant benefit attributed to the pusher configuration.
 

Tamecat

Active Member
Joined
Oct 23, 2003
Messages
33
Location
Teaneck New Jersey
Pusher Designs

:ban: The pusher design has merit :ban:

Hey Orion, I am building a large scale L-39 to see if it can be done! I'm going with a gas engine and the plane will be huge. (Still not convinced it could carry over to full scale, but at least this is the least expensive way to find out.) Consturction will start as soon as the engine comes in.

Hey Tinbuzzard, Great Job Man!! We are all very impressed! Do you have any more Pics? And if anyone else is doing a pusher design, show us your progress I'm am very interested.
 
T

Tinbuzzard

Here are a few more photos of the work I've done. Ailerons and their control systems are finished. Leading edges are done, and I'm doing the wingtips now. Even with the top skins incomplete, there are over 3,000 rivets in each outer wing panel.


Jeff
 
Last edited by a moderator:
T

Tinbuzzard

I finally got the photo situation sorted out. The following series shows about one years worth of work on this project. The leading edges were horrible to do, fifteen ribs on each side and all different. Boys and Girls, Hershey bars are much more enjoyable to build!! (I've helped buck a couple of RV-4s) Smart people build a Van's design, dumb ones do the following!
 
Last edited by a moderator:
T

Tinbuzzard

This is the aileron structure before skinning. Notice the counterweight rod sticking down, it will fit entirely within the wing without protruding.
The aileron is top hinged with ball bearings in a bracket at each end.
 

Attachments

Last edited by a moderator:
T

Tinbuzzard

Here I am riveting down the outer .025" skin on the right wing. I made it in one piece from the lower main spar cap, around the LE and back to the rear spar. This was to avoid having a joint in the upper surface in front of the aileron. It wasn't really worth the effort, as it made the riviting more difficult!

The wooden frame against the particle board behind me is for a Davis DA-2 cockpit mockup being made by one of my hangar partners.
 

Attachments

Last edited by a moderator:
T

Tinbuzzard

Here, more of the right wing leading edge is being fitted. I've been making butt joints between skin panels wherever I can, more through stubborness than anything else. I'm my own worst enemy with regards to build time.
 

Attachments

T

Tinbuzzard

The last right wing leading edge skin, (.032") is being fitted up to the center section of the plane. It was VERY gratifying to find that it matched perfectly, considering all of the opportunities for tolerance stackup, layout and fabrication mistakes! That included changing the airfoil partway through the wing build.

Notice the tabs along the centersection top skin (grey primer). They interleave with similar tabs on the underside of the outer panel skin. This allows a joint that is merely a line between butted skins. Access to the four bolts that hold on the outer wing is through a removable panel on the bottom, also with tabs and a hidden hinge to secure it.
 

Attachments

Last edited by a moderator:
T

Tinbuzzard

The left wing with aileron is seen here attached to the center section. The beginning of the L. tailboom is near the lower left of the photo. The top of both outer panels will remain open until the flaps and their control mechanism are installed. The aileron pushrod runs in front of the main spar. I'm now building tips that will extend beyond the ailerons about one foot. Total wingspan will be 32" 0".
 

Attachments

Top