lifting line theory

for a while i have been trying to understand the lifting line theory. this has many benefits over the basic aspect ratio corrections for the calculation of CL and CDi including:

• Non-elliptical planforms
• Twisted sections (AoA varies along span)
• Section changes along span
• Wing tips (probably - see below)
  

it took me a while to work it all out because i didn't want to pay for a textbook and most of the internet references i found would either:

• have no nomenclature
• have errors
• after stating the method equations declare the solution too hard
• give the results for a single (not very useful) case only
• not have a worked example to compare results to.
  
• obviously every website has minor differences in nomenclature and assumptions
  

Yesterday I had an epiphany and remembered what a Fourier series was and the pieces fell into place and allowed me finally understand what was going on. I won't repeat the procedure here but I will give 3 useful links for people who do want to attempt it themselves.

Best description of method
Example to compare your results to
Simple Matlab code

A few notes on solving Fourier terms:

• In the matlab code the line 'a=b\rhs' is matrix maths and means [An] = [b]^-1 . [RHS]
• Look up MMULT and MINVERSE in Excel help, makes solving linear equations sooo easy and makes anyone who has coded row reduction methods in excel feel stupid.
  

I can supply my spreadsheet by email if anyone is interested.

Note on wingtips analysis:

I am not sure whether this is valid or not yet. Probably valid enough for anyone satisfied with a Lifting-Line theory result.

1. Design a wing with wingtips
2. Fold these wingtips down so they are in plane with the wing, adding to its span
3. Twist the wingtips so that they produce zero lift, independent of the wings AoA
   

gearing

click me.



easier to adjust than M2.
if your bellend isn't inside the CB

First

Guess who was first to do a foiling gybe on SLINO...?

Guess who is owed a rum...?

Started out with 20 knots today so decided on the chicken rig. Markla was first but had a couple of big crashes early with a tangled wand not working properly. Ended up being about 12 knots by the time we were off the water. The chicken rig still faired reasonably well in the lighter wind except for trying to stay deep downwind, that was a bit of an effort but to be expected.

Narkla hit bottom, hard, while going into a tack on foils. Water was only about thigh deep...doh! No major damage (slight chip on one tip) but these foils of Al's are really taking a beating well. They've hit bottom at pace a number of times. Bit of a drag to get back to deeper water only to have some shunt jetskier spray me from within a boat length, TOOL!

Still lacking a bit of height so the plan is to add a little AOA to the mainfoil and see what happens.

two videos

don't watch them
i don't watch yours
moth videos are now boring

me trying to gybe
and me failing into into the poontoon
and nick failing fend me from the poontoon
and nick failing to film me crashing into the poontoon




n4rkla sailing a bit


lots of training recently

one interesting mod, in these videos we have removed the shockcord that self-centres the rudders. the boat is much more vibrant to sail without the shockchord. it is easier to sail thru the maneuvers too. Alan mentioned that the fast australians are going back to shockcord on the rudders to help them fack. even so i think it will be a while before i put it back on

worth noting that the boat crashed with a very loud bang (1:35 in first vid), but there is not a sign of damage. i didn't even bring it back to shore afterwards.

nationals results

Go Alan!

Something strange is happening (lotta bad links) with the imoth-wa website but i did find some results here:
http://nsigns.com.au/moth/results/
Just click any of the date modifieds after 1.Jan.10.

This appears to be more of a workaround than something right so I don't know how long the link will work for.