Folks,
First of all, hello
My first post, and Im not even close to building anything .
Got interested in building about 8 months ago; got set on a bipe a bit later, and got dead-set on an open cockpit aerobatic bipe after a ride in a Steerman about a month ago. Skybolt choice naturally came very fast.
No shop and no tools so far, but planning to start a build in about a year. Meanwhile, studying plans and reading books, this forum, etc.
Anyways...
I know this question was discussed a few times, but I haven't seen specific answer to what I have in mind... please excuse me if Im asking something obvious.
When looking through plans and reading around this forum about pitfalls with 1:1 plans (shrinkage, etc), decided to take the measurements. Used lower wing plans.
1. According to the plans, the rib's 42" long. If I measure on a 1:1 plan, it's more like a 42 1/4.
2. If you do the numbers on the ribs' plans, the distance between spar centerlines is 23 1/16. Everywhere else on the plans (ie, fuse attach fittings, wing general drawing with rib arrangement) it's 23 1/8. And if measured, it's 23 1/4. Grrrr.....
3. Upper wing ribs vs. upper wing tip rib - distance between spar centerlines on two drawings (two different sheets) is 1/16th of an inch off between the two.
So this got me thinking, what to do about this.
Gutfeel tells me that building to 'fit in place' should just work. The way I see it is:
- Profile spars. Make them a bit longer, cut off the ends and use as profiles for spar openings in rib jigs (according to Beej's manual, great idea btw). Profile according to drawings on rib 1:1 plans, whatever the ##s end up being.
- Build rib jigs around plans and around spar cutouts. Build ribs.
- Wherever the spars are misaligned on tip vs. other ribs, make sure to mod the jigs to keep them aligned.
- Watch for the ribs to be able to create one uniform curve on the back of the wing that will 'blend' in with ailerons and the bow (that I have to scratch my head about a bit more.. need to factor in hinges to have the trailing edge of ailerons flush with wing's trailing edge, and make sure to maintain the uniform curvature of the tip bow on ailerons and wings).
---
But. The perfectionist and engineer in me says 'Stop!'. In addition, Im thinking of Delta; and in Delta upper wings have to mate with a center section, and center section ribs' drawings are done differently.. in different times, and will be inaccurate in different ways possibly.
So, other options:
- Redraw the ribs. But the Skybolt's plans are missing ALL vertical dimensions (and I can't trust the ones I measure off directly off the plans). Well, I have Firebolt's plans as well (bought them primarily for reference and much better quality drawings) which has exactly the same rib and 1-inch grid around rib's profile. CAD, print, etc.
- Even better, generate the airfoil using proper math equations (airfoiltools.com came up as a very cool tool, + there should be some simple math behind standard airfoils.. need research). Import the points into AutoCAD, add truss structure according to Steen's plans at appropriate stations...
I know at least some of you built ribs just to plans, with dimensions being slightly off (I think someone quoted 1/16th of an inch).. but 1/4 in my case?
Am I overthinking?
First of all, hello
My first post, and Im not even close to building anything .Got interested in building about 8 months ago; got set on a bipe a bit later, and got dead-set on an open cockpit aerobatic bipe after a ride in a Steerman about a month ago. Skybolt choice naturally came very fast
. No shop and no tools so far, but planning to start a build in about a year. Meanwhile, studying plans and reading books, this forum, etc.
Anyways...
I know this question was discussed a few times, but I haven't seen specific answer to what I have in mind... please excuse me if Im asking something obvious.
When looking through plans and reading around this forum about pitfalls with 1:1 plans (shrinkage, etc), decided to take the measurements. Used lower wing plans.
1. According to the plans, the rib's 42" long. If I measure on a 1:1 plan, it's more like a 42 1/4.
2. If you do the numbers on the ribs' plans, the distance between spar centerlines is 23 1/16. Everywhere else on the plans (ie, fuse attach fittings, wing general drawing with rib arrangement) it's 23 1/8. And if measured, it's 23 1/4. Grrrr.....
3. Upper wing ribs vs. upper wing tip rib - distance between spar centerlines on two drawings (two different sheets) is 1/16th of an inch off between the two.
So this got me thinking, what to do about this.
Gutfeel tells me that building to 'fit in place' should just work. The way I see it is:
- Profile spars. Make them a bit longer, cut off the ends and use as profiles for spar openings in rib jigs (according to Beej's manual, great idea btw
). Profile according to drawings on rib 1:1 plans, whatever the ##s end up being. - Build rib jigs around plans and around spar cutouts. Build ribs.
- Wherever the spars are misaligned on tip vs. other ribs, make sure to mod the jigs to keep them aligned.
- Watch for the ribs to be able to create one uniform curve on the back of the wing that will 'blend' in with ailerons and the bow (that I have to scratch my head about a bit more.. need to factor in hinges to have the trailing edge of ailerons flush with wing's trailing edge, and make sure to maintain the uniform curvature of the tip bow on ailerons and wings).
---
But. The perfectionist and engineer in me says 'Stop!'. In addition, Im thinking of Delta; and in Delta upper wings have to mate with a center section, and center section ribs' drawings are done differently.. in different times, and will be inaccurate in different ways possibly.
So, other options:
- Redraw the ribs. But the Skybolt's plans are missing ALL vertical dimensions (and I can't trust the ones I measure off directly off the plans). Well, I have Firebolt's plans as well (bought them primarily for reference and much better quality drawings) which has exactly the same rib and 1-inch grid around rib's profile. CAD, print, etc.
- Even better, generate the airfoil using proper math equations (airfoiltools.com came up as a very cool tool, + there should be some simple math behind standard airfoils.. need research). Import the points into AutoCAD, add truss structure according to Steen's plans at appropriate stations...
I know at least some of you built ribs just to plans, with dimensions being slightly off (I think someone quoted 1/16th of an inch).. but 1/4 in my case?
Am I overthinking?
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