Hatz Biplane Association

Below are some of the Hatz Classic Plans discrepancies taken from the archives. Please feel free to add to this thread as necessary.

From Jeff Cattrell:

Spar Fittings:
Sheet #06
Center Section Fitting FSTW1 and RSTW1, the dimensions from the end of the spar should be 1" instead of 3/4" as shown. These are meant to be measured from the 1/4" end rib. This is noted on another sheet but not this one.

Sheet #09
The fitting on the root end of the rear spar is shown to be located with the holes 3/4" off of the bottom of the spar, this dimension should be 1". If left at 3/4" the wing will not line up with the center section.


Ribs / Spar Taper
The spar tapers I used do not match the ones shown on the plans, I couldn't get the #10 rib to work with the tapers that they showed.


Aileron Spar
Sheet #07
The aileron spar dimensions are wrong, the taper as shown will put the aileron in a bind. I made mine from several pictures of completed planes and it seemed to work well. I will try to post some dimensions of what I used.

Aileron Spar:
On sheet 7 of the plans the dimensions for the aileron don't quite work out right.
I used the following:
Center of the tip...3/4" down from the top
tip width is still 3/4"...I made mine a slight bit wider to sand down to the wingtip...
Top taper starts 7 3/4" in from tip
Bottom taper starts 21 1/4" from the tip.
these dimensions worked great into my tips and the aileron can use almost a full length hinge with no bend....

Just noted this today.
Trim tab dimension error: There is a trim tab detail which shows the trim tab at 1/2" scale. The measurements are all wrong on that detail, don't use it. It looks like he drew the detail to double scale from the rest of the page but dimensioned based on 1/4" scale.

Nick

Aileron Idler Brace/Bracket. This is a support piece for the compression tube that the Aileron Idler is attached to. It was left off the plans but appears on a couple photos on the Makelan CD.

Please see the following post for details:
viewtopic.php?f=8&t=364

Center section sheet 3 on the left side, the nose ribs have a notch to sit on the base of the center section. The nose rib drawing does not have a notch (the tail pieces do). You have to make that notch.

Sheet 5 calls for 8 of part 5 (PEM), but looks like you would need 10. The PEM part number is S-0524-2 (zinc plated), NOT S-0528-2 as printed on the plans. Sold at McMaster-Carr http://www.mcmaster.com/#pem-style-nuts/=lvq5xp

Wingspan is depicted as 25', but actually measures out closer to 26' in the finished build.

Discussion here: viewtopic.php?f=8&t=475

The roll wire lug/fitting is depicted in several sheets:
23, 23R, 15 and 12. The correct depiction is in sheet 12 (IMHO).

More Discrepancies between sheets 23(R) and 12 are regarding the "disks" that are welded on to the lower corners of the fuselage front end (station 0-5), directly on to the rectangular gussets:
Sheet 23 mentions a thickness of 0.090" (zone D-2), sheet 12 specifies a 0.125" thickness for this part (zone D-1). Since the roll wire fitting is 0.125" thick, and is a similar spacer between the firewall and the fuselage, I expect 0.125" is the correct thickness to use.

Details A and B on sheet 23 have some wrong dimensions on them. I suspect all dimensions need to be divided by 3, for example where the sheet specifies a 4.5" measurement, it is actually 1.5". I base this on the fact that these details are 3:4 scale.

On sheet 12, the "Full Scale" depiction of the trim handle pivot is actually larger than full size. the dimensions are probably right, but the drawing is too large.

Would a set of plans purchased now be revised to correct these discrepancies?

You would think so but I doubt it.

On sheet 19, part #BRKPED1 lists 2 required and #BRKPED2 lists 6 but the quanities are reversed.