Source: 2016 Q3 Beartracks
Hopefully by now you’ve heard about the “Model B” package of changes to the Bearhawk 4-Place. If not, here is a link to the press release issued by Bearhawk Aircraft.
Bob first designed the Bearhawk 4-Place in the early 1990s, and he’s learned a lot since then. His Patrol and LSA have used his innovations that simplify construction and reduce drag, and the Model B package includes those changes applied to the 4-Place. These include:
1) New Riblett airfoil wings (30-413.5 airfoil same as the Patrol) with 5 more sq ft of wing area
2) In place of welded in place steel side and belly formers – on the Model B they are aluminum attached with stainless pop rivets to tabs welded to the fuselage tubing.
3) Shock struts with stronger tubing to better resist the compression loads when going sideways on the runway like during a ground loop.
4) A round tail spring of heat treated 6150 steel.
5) Horizontal and vertical stabilizers with airfoil shaped ribs in place of the original flat ribs.
All 4-place kits shipped from Bearhawk Aircraft going forward will include these changes. As of September 2016, new kit orders will be available starting in January 2017. Here are a few questions that have come up about the new package:
If I order a set of Model B wings can I bolt them onto an original 4-place? There are changes to the top of the fuselage structure and potentially a window hinge placement modification as well. The new airfoil is 1.5” taller from top to bottom compared with the original 4412 airfoil. Some of this additional size is above the wing spar attach points, and some of the additional size is below the attach points. On the fuselage top, the upper formers (where wing to fuselage fairings attach) have to be re-shaped to conform to the different airfoil shape. The small tubes coming aft of the windshield as stringers for fabric have to be raised a little. Below the wing, without relocating the hinges you might not be able to open the windows all the way to the bottom of the wing. This depends on placement of the tube where the window hinges are welded on. On N303AP this was dealt with by using light weight gas struts that hold the windows open.
Will Bearhawk Aircraft offer a rib and spar kit for the new wing? Yes
Will parts still be available for the original design? Yes, but it is conceivable that eventually some of the parts for the original wing and tubing kits for the original fuselage might be discontinued. But for the near future – all parts for the original BH are still available.
When will plans builders be able to purchase some of the more popular factory-built parts, such as tail feathers and fuel tanks? All parts for the Model B are now available as parts for plans builders. The wing tanks are the same now as the Patrol tanks. Tail surfaces are now available with the airfoil shaped ribs on the horizontal and vertical stabs. Since the new airfoil is common to the Patrol, the ribs will be the same, and a single style of wing tips will fit both airplanes.
I have a complete or mostly complete airplane but would like to add the Model B features. Can I do that? All of the features except the wing airfoil change are easy to incorporate. The complications of a wing change are outlined above. The performance gains are likely to not outweigh the effort required to make these changes for most builders.
I am a scratch builder just getting started and want to incorporate the Model B changes. When can I get plans and how much will they cost?
Bob is still finalizing the drawings, and expects to have them available in early 2017. Folks who already have 4-place plans will be able to order a duplicate set of drawings with the changes for $50. Once the new drawings are complete, all new plans purchases will include the Model B changes. Bob will maintain a few sets of original drawings for builders who are in progress on an original 4-Place and find need for a replacement set of drawings, for the usual $35.
There is always an urge to have the latest and greatest, but builders should keep in mind that these up-dates are intended to make modest improvements to future airplanes and simplify kit production. The old design is not obsolete, and there is no need to throw out your old ribs/wings and start over. The original 4-Place is still as capable as it always has been.