Notes/Updates

UltraCruiser Construction Notes & Updates

May 2002

The following plan updates apply only to plans dated prior to May 29, 2002.

SHEET # 1

· Overall length of motor mount box should be 22” (from bulkhead A forward).

· Motor mount box—for easy assembly, it is advisable to split the part at the middle bend line. Each side is then riveted to the 1 x 1 x 1/8 angle.

· Engine should be offset 1° to the left to compensate for torque. This is easiest measured from the back of the engine to the firewall. The left side should be ¼” closer than the right.

· Engine location, or arm, is critical to a good weight and balance. We suggest starting with the back of the engine 10” forward of the firewall.

· Outer tabs on bulkheads B, C, D, and E should be 3” wide to allow for 1½” rivet spacing. Bulkhead A should have 2” tabs for 1” spacing. Bulkhead F should have 1” tabs for 1” spacing. You’ll need to trim the tabs to clear the fin spar.

· Lower cowl brace is difficult to make as shown. After bending edge, notch to ¾” tabs and shape to fit. Then cut a doubler from .040 material and rivet to tabs.

· Cooling baffle—cut a 1½” radius semicircle from center of aft edge. This allows access to drain plug on ½ VW.

· The tail doubler (.125 6061T6) must be 16.250” overall length not 14”.

· 6-32 oval head machine screws are adequate and lighter to save weight.

· Side rail can be bent gradually rather than sharply at B. This also gives more room in the cockpit.

· Bulkhead A and bulkhead B flanges face aft—not as shown.

SHEET #2

· Bulkhead F is difficult to form with 2¼” tabs. We recommend splitting each tab and rivet on 1 1/8” spacing. The plan shows the top tab bending forward. This is not necessary and it interferes with the E to F stringer. Simply cut it off to allow for the fin spar clearance. All rivets in this area are high shear Avex 1682-0412 or equal.

SHEET #3

· 1/8” nylon push/pull tube guides should be fastened to bulkheads with 1/8” aluminum mandrel rivets to save weight.

SHEET #4

· It is not necessary to make 2 rib jigs. Simply fasten the cut outs to the back side of the plywood.

· Rear flange on nose rib should bend up. The rest of the nose flange bends down.

· Ribs should be assembled with solid rivets or aluminum mandrel pop rivets.

SHEET #5

· Center panel spar cap. The notch to allow for access to the attachment bolt should be 1 3/16” wide. Take care to polish and radius this area.

· The diameter of the largest lightening hole in the wing tip spar extension (not labeled) is 4.250”, not 2.50”.

SHEET #6

· All access covers should be fastened with #4 x .250 oval head sheet metal screws to save weight.

· Drill spar caps on web side at 1” spacing using drill jig (be very careful to keep holes vertical to each other during assembly of web).

· Use 1/8” aluminum rivets with aluminum mandrels on 3” spacing to fasten: skins to ribs and wingtips.

· Take care to drill a .250 hole in rear spar prior to cutting notch. It is very important to polish and radius this inside corner.

· Locate front spar 10” aft of bulkhead B. The rib will extend approximately .625” aft of C. If you have attached the skin to C, see attached drawing. If not, adjust the angle of C to correct for our error. Take care to maintain the bottom of ribs parallel to the side rail.

SHEET #6 cont.

· The control attachment nut plate on the inboard aileron rib should be 10-32, not ¼-28.

· The lower spar cap is bolted (2-AN3 bolts) to the two .063 x ¾ angles running from bulkhead A to C 4” apart on the bottom of the fuse.

· The ¾ x ¾ x .063 angle from bulkhead B to across the top of the spar should be 14” long, not 8” long.

· To allow for fastening wing skin at fuselage side, add 1 nose rib and 1 aft rib against fuselage on each side.

· The overall length of the trailing edge spar should be 83 7/8” (bolt center to center should be 82 ¾”).

SHEET #7

· The .040 doubler on the inboard stab rib is bent 90° and bolted to the stab spar with 2 AN3 bolts. The rib is not bent with the doubler.

· The stab incidence slot needs to allow for more negative incidence. The slot should run from the centerline to approximately 1” above the centerline.

· Rivet spacing for tail skins and stab spar web is 2”.

· The tail spring is 7.250” between bolt centers.

· The vertical rivet spacing on the dorsal fin is 1”.

· Omit the two AN3 bolts on the vertical fin root rib and replace w/ rivets. Also rivet the rear flange to the vertical spar.

· Replace the 2 inside horizontal stab doublers with two (2) ¾” x 6” .040 doubler located on the inside of bulkhead F flanges. The rectangular doublers are difficult to fit between the skin and F.

· It should be noted that the horizontal stabilizer and vertical fin ribs are symmetrical; therefore tab directions are not critical.

SHEET #8

· Control tube weldment bearing—the 7/8 x .058 bearing tube should be 1” wide, not ¾”. Flat stock is then also 1” wide and remains 1¾” long, assemble with cam grease. Fasten to the carry thru with two (2) 8-32 machine screws tapped into the angle.

· Push rod inserts are available from Hummel Aviation and can be ordered through the flyhummel.com website.

· Omit the seatback bulkhead. The seat back is to be made from 1/8” birch (5-ply) and hinged at the bottom with a 3½” long hinge.

· Install a piece of .016 from the rear of the control box aft 13”, and rivet to bottom skin. This serves as a partial seat bottom and can be cushioned appropriately (sitting on the skin will give you more room).

· The landing gear gusset bracket has developed cracks on the prototype (we believe this is mainly due to a rough ride to Sun-n-Fun in a trailer). See attached drawing. This gusset is also easier to fabricate and positions wheel properly at 2” aft of datum (leading edge).

· Filler neck should be 4” from front of tank, not 6”. Also, the front of the tank should be 2” from bulkhead A.

· Gas tank front should be 16 5/8” wide, rear should be 19 1/8” wide, height of each end as shown is correct.

· The aileron bell cranks mount to the landing gear support.

SHEET #9

· “Bottom canopy strip” should read “Windshield strip”.

· When riveting the canopy to the bows, rivet spacing is 3”.

· Windshield material is 1/16” lexan.

· Trim canopy extension to butt, not overlap (easier to fit and close).

SHEET #10

· The splice from the aft wing root fairing to the rear wing root fairing is at bulkhead C, not as shown.

General

· Change aft CG limit to 16.2”. When determining the original CG limits the symmetrical shape to the stabilizer was not considered.

Click on thumbnails below to view sketches that were included with these updates.

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