Noodling Bearhawk Weight and Balance, Part 1

Source: 2006 Q4 Beartracks, Rob Gaddy. Part 2 is in 2007 Q1.
What do I need to know about Bearhawk Weight and Balance? If you are still reading I will assume you have an interest in the subject also, so come along for the mental trip and we will see if we learn anything.
Let’s start with the basics; here is our Bearhawk, figure 1. Let’s assume we have finished it but haven’t flown it yet. It has all equipment installed and engine oil, but not fuel. I want to know two things, first what does it weigh, and second where does it balance, hence Weight and Balance or W&B. To answer these questions let’s put some trustworthy scales under each tire to find what the weight is on that particular tire. Let’s level the fuselage, it is important later. We will use the W&B for N33RB as given in the October 1999 Bear Tracks, page 6 for an example. Continue reading →

Corvette LS1 Engine Updates from Ed Schweitzer, Late 2006

Source: 2006 Q4 Beartracks, Ed Schweitzer
LS1 Engine for a Bearhawk
Hello:
READER BEWARE. THIS GOT TOO LONG AND DULL. The transmission weighs 64 pounds complete for bolting on to an engine. I designed it so it can be used on any engine. The engine is a Corvette LS1. Aluminum block and heads. Its weight is 370 pounds. The prop will be in the same position as the prop of a Lyc O540. It has 350 hp at 5600 rpm. It has 350# of torque at 4200 rpm. (approx numbers).
The transmission swings the prop at 2700 when it is in low and the engine is running at 5600. The prop also turns at 2700 when the transmission is in high and the engine is at 4200 rpm. The concept I followed was to load the engine with the pitch to avoid over revving in high gear. The concept worked as predicted on my Q-200 and a Subaru engine before I learned that the fuselage was destroyed by invading gas. I did several taxi tests WITH A FIXED PITCH PROP.
The concept I followed is to allow an auto engine to work like it is intended and to avoid any modification. Auto engines have advanced so much while the A/C engine has the basic 1940’s design with a few “changes of an unsubstantial nature”. This must be so to avoid developing a new engine and keeping the old Certificates from FAA. If I am wrong about this correct me. They still use nitrite Hardening and magnetos as well as updraft carbs. I cannot see any difference between my fathers 1935 Case tractor carb and the carb on my previous O-200 Continential. I took both apart and reassembled them. The Marbel Schebler trade make label is even the same.
The reason I choose to use an auto engine without any mods is my belief that the auto makers want the greatest reliability in there engines. Too many dead cars on the shoulder will cause a question in the minds of new car buyers. The aircraft engine has some of the same features of a diesel, like low rpm for peak torque. This is necessary when swinging a direct drive big prop and not having mach tip excesses. With the 84 inch prop my Bearhawk prop will be at mach .94 when the plane is traveling at 170 mph and 2700 rpm. RED LINE rpms. I have worked on this transmission for 15 years , the last 4 years full time. Now I must finish the Bearhawk and test it in flight. I have a lot riding on this. I invite luck and constructive remarks. You are the unfortunate ones to see the first public pictures.
Ed Schweitzer
LS1 Engine on a Bearhawk

Gerdes Brake Master Cylinders

Source: 2006 Q4 Beartracks
The Bearhawk builder’s community has long relied on the long shaft Gerdes master cylinder sold new/surplus by B & B Aircraft Supplies for the Bearhawk. Unfortunately, Dan Brown of B & B has finally run out of stock. However, a good solution has been worked out by Bob Barrows and AviPro Aircraft, Ltd. in conjunction with B & B.
B & B retains a large stock of SHORT shaft Gerdes master cylinders. They are more than adequate for the job except the length of the short shaft would require changes in the Bearhawk drawings. The solution Bob worked up involves the machining of a “clevis fork end” that extends the short shaft and makes it dimensionally the same as the long shaft cylinder. No “off the shelf” part had the correct threads and bore size.
B & B will now supply the short shaft Gerdes to AviPro who will then offer the master cylinders and clevis fork ends to Bearhawk builders. The price will be $110 (plus $10 shipping) for two of the master cylinders with their clevis ends. As this BearTracks goes to press, the clevis ends are being machined. The master cylinders and their clevis ends will be available in Janaury. To order, you can email aviproaircraft@hotmail.com, or visit http://bearhawkaircraft.com.

Correcting a Heavy Wing- The Washer Method

Source: 2006 Q4 Beartracks
The following info was developed by Jim Clevenger, owner & builder of the just finished Florida demo Bearhawk – plans serial # 448 (prototype kit). If your plane has a heavy wing in its initial flights, after checking the flaps are inline on both sides, and you notice that when flying hands off one aileron is high and one low. Continue reading →

Rib and Spar Wing Kit

Source: 2006 Q3 Beartracks
Following a suggestion from Bob Barrows, AviPro Aircraft now offers to scratch builders a new package of wing parts. The purpose of this package is to eliminate some steps in building your wings that many builders find difficult. Finding an eight foot brake you can use and then bending up your spar webs to match your ribs can be a lengthy trial and error process – hard to get right. If the spar web heights do not closely match the ribs, your wing skins will not look so good. After more than eighty sets of wings, our factory wing team does these bends very precisely.
This package includes the bent spar webs for the main spars, rear spars, false spars, aileron spars, & flap spars. Also included are the only other pieces that require bending on an eight foot brake. These are the aft wing skin stiffeners in the flap area (4 pieces) and the trailing edges for the aileron & flaps (4 pieces). This package includes all the ribs as they come from the factory that professionally hydrforms them. These are 48 nose ribs, 16 main ribs (.025), 8 main ribs (.032), 16 aileron nose ribs, 16 aileron ribs, 26 flap nose ribs, 18 flap ribs, 6 trailing edge ribs, 16 aileron pocket ribs, and the 4 false ribs. All ribs have their lightening holes cut and flanged. The ribs still need to be straightened (fluted), and have their vertical angle stiffeners riveted on. The price for this package is $2350 + shipping/handling/boxes.
The ribs are drop shipped from Oregon, and the spar webs are shipped from Texas. If interested, call or email Mark at N95MF@hotmail.com or 512/626-7886
Continue reading →