B model Tank sizing

[Wyo Johnson]

Working on B model...Ran into something that caught me off guard:

Page 25 of "The Bearhawk Book" it discusses general make-up of the main fuel tank...24" fore and aft measurement. Then the rub comes in when you look at drawing 3B and measure the Center Rib from the False Spar to the Main Spar and its a shade over 23"?

I double checked the dimension from the Rear Spar to the False Spar (Drawing 15B - Support Tube 7.75") and the 23"+ is accurate, is there a Beartracks or something that has updated B model Fuel Tank Drawings?

What am I missing?

Tank Space.jpg


Thanks,

Andy
1423B - Scratch
Derby, KS

[Wyo Johnson]

Drawing 2B shows the tank at just under 21" long (fore/aft)...good thing I didn't cut those forms!

Tank Length.jpg
The Aux tanks measure 29 in the 2B drawing...

Andy
1423B - Scratch
Derby, KS

[way_up_north]

I appreciate you posting this...don’t hesitate to post anything else you find

[johwiltb]

So I think I just found something...In the

Model "B" Bearhawk Book Supplemental that's included with the plans, it has the drawings for the Patrol fuel tanks. Since the Model B wing is the same as the Patrol, this is probably more accurate. It shows that the width of the tank is actually 21 1/4". Hopefully that helps. Took me a bit to come around to that, too.

[Wyo Johnson]

John,

Geeze why didn't you say "hey dummy look in the Model "B" Bearhawk Book Supplement"...

So now both books are together in the same binder and I'll spend an additional hour researching before I post!!! lol

I trust the design, it just takes me awhile to find what I'm looking for.

Thanks again

Andy

[johwiltb]

Lol no worries, I’ll be honest I was following this thread just because I had the same thought! I bumbled my way into that supplement today looking for something else completely (engine mount design stuff) and saw it and the light bulb popped up! So we both learned today

[Wyo Johnson]

My "day job" is working in aerospace and the drawing systems I use are 3D and all linked...I learned to draft in high school in the mid/late 80s but its been a long time since have to jump around in the paper drawings and books to find data. I don't have a lot of time to build with work, and I know people have strong opinions about CAD/CNC etc...but for my time schedule its the fastest way for me to scratch build. So I was just going through my CAD drawings on the wing tooling and thought "I better check the fuel tanks fits...and that sent me down the rabbit hole!

The upside is my form blocks are good and at the machine shop now...in line with a number of small jobs...Wichita has lots of machine shops and some of them will take "off the street" business...it just sometimes sits behind Boeing, Textron, Airbus, USAF, etc. etc.