Pat'
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The rib lengths are all known, now. Also, even though we don't yet know the shape or thicknesses of the intermediary ribs just yet the 'thickness stations' are now known because of all of the 'spars' we drew in 'bird's eye view'! Isn't that awesome? We know the symmetrical foil has a chord length line that bisects it into two equal 'top' and 'bottom' parts. It's symmetrical! The root rib has a chord length line from a midway point on its nose to the TE and it is NOT symmetrical! Trace the shape of your tip and root ribs somewhere onto the plan. I drew the root rib on the right, next to the root end of the 'fan'. Draw perpendiculars across the tip and root rib chord length lines at the just found 'thickness stations', i.e., where the 'spars' intersect tip and root ribs. Also, remember when we drew the line across the 'fan' that represented the rear edge of the 'D' tube? Use this station to align tip and root ribs relative to each other. Draw a convenient line with your straight edge. Mine was above the 'fan' design (the right angle ruler in pic above was covering some of the drawing) and the same width. It was easy to just extend the verticals upward. Measure each relative station on the tip and root for thickness and put the tip thickness on one end and the root thickness on the other. 'Connect the dots' and it will look like a tapered spar going from the tip to the root ribs!
One thing will be absolutely essential in order to plot the ribs and that is the location of the chord length line. At the tip of the 'spar' it will be a midpoint location because the tip rib is symmetrical. Measure it on the root rib and transfer this to the 'spar' at the root end then connect those two dots with a straight line from the tip to the root.
I numbered my 'spars' with Roman Numerals and made 14 of them. You can make more (more foil accuracy) or less... it's up to you! The left pic above shows the complete root 'spar' ends of 'X' and 'XI' and tip 'spar' ends of XII, XIII and XIV. Not so easy to see are how I numbered the ribs onto the 'spars'. Remember, these ribs were just the lines I extended up from my 'fan'. You could draw them elsewhere. I had to draw some elsewhere because my paper wasn't big enough. In left pic above for 'spar' X rib 1 (circled at top) is the known Go 549 root rib. The second rib station has numbers 34 and 40.5. These are the thicknesses I measured with a mm ruler. 34 is from the top to the chord length line and 40 is the total thickness. I put these thicknesses on a datum line. After plotting them all I used a French curve and English curse words to draw the foils!
See how the drawing develops? Four done so thirteen more to go!!! When all of these are done I'll trace them so that the tracings can be put onto wood for cutting. The originals can be referenced for placement of the 'D' tube rear edge, etc. Drawing ribs isn't difficult... just onerous!Leave a comment:
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How do you make tapered ribs if: 1) your threaded rods for doing the 'carve and sand' method aren't long enough, 2) the taper is too great to really sand accurately and you don't wanna waste wood or foam as spacers, 3) your dog ate the computer, 4) your Foil Plotting software was accidentally deleted and you don't want to buy it again, 5) you have Foil Plotting software but your cat coughed up a fur ball into the printer, 6) the printer is fine but you used all the paper for the bird cage?
Tah-dahhhhhh! Draw an egg crate! It's basically that simple.
This is a straight taper wing. The root rib is known. I'm using the scale Gottingen 549 foil but the tip foil will be symmetrical. If I build the tip at the proper incidence it will help with tip stalling. The thicknesses of the tip and root were obtained from the 3-view. If you erect the tip on one end of the board and erect the root on the other it is a simple matter to measure the height and length for a spar to fit between them, right? Now, you don't want the spar to go from the TE of one rib to the LE of the other 'cause it would have a weird curve develop on its edges. So that this doesn't happen the tip and root ribs need to be divided into equal 'segments'. But... you say... the tip is shorter than the root rib so you can't divide them equally. That's correct! Linearly they can't be divided equally but they can be divided into an equal number of parts! The tip length was divided into the root length to get a unit-less factor of 3.08 sump'n or other. So, for example, 1mm length on the tip rib is ~3.08 sump'n or other on the root rib and ad infinitum! (that's for JimD) Plotting a bird's eye view of the tip rib and root rib onto a datum line, in this case, the rear edge of the 'D' tube portion of the wing we get a nice 'fan looking' effect. Now, count up the needed ribs and space them equally if the wing had them spaced equally and draw them between the tip and root at the proper spacing. For the professor this was 79.3 sump'n or other mm. I just stored that in the calculator.
More to come!Leave a comment:
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Hey TJ, other than Charlotte this will be the largest I've built! I've been dreaming of this build for a couple of years, now! Thanks for looking! -
4m should be a sweet scale mike, will be following in the background!
StéphaneLeave a comment:
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Hey Jelly, " Rhongeist" would mean Rhon the area and Geist is ghost, maybe because of it's see through wing structure which would make it look ghost like in flight, just my thought!
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