A forum about all aspects of the construction and maintenance of the Billy Dawson inspired modified Hatz Classic biplane. Here is the place to ask your questions and get the answers from the real experts.
ha622 wrote:PS: Sorry, but it seems that the upload of a pdf file is not allowed in the forum. Is there an alternate method to include/distribute non-jpg files? Does anybody know?
Hi Juerg,
I made some changes, please try again and let me know if it works.
Doug.
I checked the 25" dimension and it was accurate but then I started to build my rib jig and I noticed the spar height dimensions although correct in measure are not the same as the height of the classic spar.
The pdf front height is 123.9 mm or 4.878" and should be 4.842" not a problem.
The pdf rear height is 96.7mm or 3.81" and our spar is 3.699", this is almost 1/8", I think that might be a problem.
Please let me know if I missed something. Is the CB-1 spar different?
I know that the pdf file was for the CB-1 but I would have thought they both used the same spar dimension.
Last edited by Bitshifter on Wed Aug 29, 2012 11:29 am, edited 1 time in total.
Ed White
HC 154
"In life 10% wrong is failure, in school it's an A"
We plotted the Clark Y airfoil directly on to a sheet of plywood and built the rib jig on that. We did not use any drawings as direct templates for anything because the paper keeps changing due to humidity changes. You should use the dimensions provided on the drawings and build from that.
John Hanson HC-012
As a matter of fact, I have never compared these dimensions to either the CB1 or the Classic drawings up to now. The CB-1 plans give a spar height of 4 7/8" (4.875) for the front and 3 11/16 (3.6875) for the rear. The Classic plans show 4.842" and 3.699" respectively. So they are pretty consistent. My dimensions are 4.878" and 3.807". So you are right, my rear spar is slightly higher.
Yes, it will matter If you have the spar already made. In that case you will have to modify the ribs to make them fit. As mentioned previously this will not affect the aerodynamics in a noticeable way. I built the spar to fit my ribs.
