Hatz Biplane Association

After measuring, I measured again using a different ruler. I ended up trying two straight metal rulers, and two metal tape rulers. All are different.

Hey John,
All measurements are just comparing one unit (length in this instance) to a "standard" length. Since you are not going to get the standard meter (or metre) from here: http://en.wikipedia.org/wiki/Metre, I suggest you pick one measuring device (tape) and stick with it for the entire project. If you are concerned about the first inch with the tip of the measuring tape and all, take your measurements from the first inch tick, not from the tip (but remember to subtract 1!!).
What is important is that you use the same measuring device throughout the project, so that 25" now will be 25" in a year. and it is not important that your 25" are the same as my 25" or someone elses 25". At some point you can also forget about the number of inches, and just make sure that the distance between the motor mounting holes is equal to that on your engine mount. Who cares if it is 25.0000 or 24.897? as long as it fits it is good.
Anecdote:
The Piper factory has a tolerance of +/- 0.125 of an inch in the welding jig of the fuselage. That means up to a quarter of an inch off and you are still OK. Surely a proud airplane builder such as yourself can do better!
Build on.

orchardair wrote:Hey John,
I suggest you pick one measuring device (tape) and stick with it for the entire project. If you are concerned about the first inch with the tip of the measuring tape and all, take your measurements from the first inch tick, not from the tip (but remember to subtract 1!!).
What is important is that you use the same measuring device throughout the project, so that 25" now will be 25" in a year. and it is not important that your 25" are the same as my 25" or someone elses 25".
.

Totally agree. Don't get hung up on it, just pick one and be consistent. Think about the planes built during the first 45 years of aviation, they didn't have the level of precision available to us today and they performed missions far more extreme than anything we will ask of a Hatz.

Build with confidence!

Excellent…I'll use the same ruler throughout. I guess I need to relax a bit…or I'll never get 'er built.

Hi,
After Formula 1 RC where planes had to be really accurate, working with a 4' chord wing felt like child's play. My first full scale had wings you could not twist with the struts (or wires) and flew very straight. Don't overthink the details!
Al