Can you help me with some prints or rought dimensions:
Friend will try to make me weed speed fin. So, I need it for my lake, to bi around
25-27cm to cover range like slalom fin around 33
need to dive in the water as small as possible
Some prints or suggestions are welcome
thanx
Thinking about some vector delta weed prototype or similar fin
What method is your friend using to make the fin? Hand shaping, cnc milling or else??
as i know he can do g10, and carbon, don't know for method, but i think that he have some hand skills.
I am interest to have similar fin like vector delta weed speed 27
I don't know for angle degree and what you sugests
Lake is very tricky, grass, maybe few tree parts under water, never know what you can pickup :)
he also have some new system we would like to try
wood furnir into glass fibre
much stronger then g10, and look killer like
He made lots of fins, and he have excellent finish
He use autocad for measure design
On pictures my custom delta looks mean
wood inside, and orange glass/carbon outside...
Only need to find good angle and size
to cover like my slalom cca 33cm, even 31
Have you follwed Lelos's posts, he's just made a 21cm speed weed that holds his 7.5m sail!
Sorry it's in this thread.
www.seabreeze.com.au/forums/Windsurfing/Gps/Fastest-Weedfin/
I've posted a foil profile at the bottom of page 1, lelos12345, fin starts in page 2, it's worth reading the whole thread, a few real experts like slowboat, give us some of their wisdom.
Looking at weed fins in general the leading edge angle is about 45 degree. So i suggest you stick to that.
If your friend can handle 3D files with his autocad version I can make a 3d model for you. A simple outline and constant profile over the fins span would not take a long time for me to make the 3D model.
About the profile. I don't think you should use the eppler foil, a simple naca 0009 looks better and the SD 8020 looks even better than the naca. See: http://www.worldofkrauss.com/foils/show_compare?sform_contains=&items_per_page=-1&commit=Compare&id[]=616&id[]=1132&id[]=1744
But for a wide base speed fin maybe you should go for a relative thickness of 6%-8%. With a base width of 145 mm (approximately equal to the vector weed speed) this would results in a physical thickness of 8.7 - 11.6 mm. For comparison: the physical thickness of a SL7 31 cm at the base is approximately 9 mm. But the sl7 has a base width of only 95 mm.
testing the new one tomorrow 25kn hopefully crack 40..
wkc read the post have a think, do what seems right to you, and do it thats what i did and its worked out real good... gone from hating weedy's to quite honestly its the best fin i have in my quiver are the one I have Made...
and i cant stop !! itching week in week out !!
hehe, yess
thanx 2 all
we will try to produce something
i hope, i will put some pictures of final products here ;)
hope i will "crank" 30, yeah, at last
I was thinking more of the eppler 297.
speed fins operate at a lower angle of attack. (especially where you walk back upwind), so don't need a stall resistant thick leading edge.
Apart from that the negative pressures are lower and more evenly spread out over the foil width.
this lessens the likelihood of ventilation and or cavitation at speed.
so
thickness 6-8%
rake 45 degrees
and what size you recomend me for 6,8 sail and 100 litres board ???
21 or 23 ???
I'd go 7.5% to 9% for a weedy, it doesn't want to have any flex.
If you're only aiming at mid to low 30s, 8.5 to 9.
If you think you'll get in the mid to high 40s then 7 to 7.5, but then they have to have a lot of carbon to keep them stiff.
Probably 23, for low to mid 30s, much above that you could go to 21, but if it's choppy, you're better going longer.
23 as long as it's also wide, (full length of box), if you have a more conventional profile, keep the same area by going longer.
yep, that looks about box length.
But I haven't tried a fin like this, so I'm only trusting on other's comments.
if I get it right on english
width of the fin must be like width of the box
there is no problem that fin is mooved from box saddle, right ?
The reason the fin is off set to the front, is to get the center of effort of the weedie about where a normal fin would be.
I don't like the idea myself, as I've seen too many boards damaged by the sticking out point.
with a 23cm fin, I don't think the difference in center of effort is worth worrying about.
But then I put my fin boxes 1cm further forward in the board to accommodate the weedies I normally use.
so, you suggest that fin is positioned like tuttle box, not set to front
here is a rough print what is the plan
Personally I like the bottom 1, but I think Lelos would like the upper 1.
It would be interesting if you made both, and see which you end up using the most.
The only thing I don't like is the sharp point at the tip, that looks deadly.
I prefer a flatter tip (parallel to the base), than those, (very close to your deign), but just with the sharp point rounded off.
ok, thanx, if I get right my english
all like on picture only upper right point little rounded, not like knife
right?
looks good ! wkc good luck with it hope its as good as mine.
30kn will not be a prob !!
I did a 31.16 nm the other day on mine loved every minuite ! and a 37.98 2sec
the new one i did seems faster at an angle of 50 and a thinner profile and 19cm
held my 6.3 no prob and i hope to run the 6.7 on it this kicked out in marginal winds 4 runs around 34kn and felt solid just need to refine the profile a little.
look forward to seeing the result
Yes, you are probably right. The difference in RE between the data available and the real life situation is too big to make an honest comparison. I should have thought about this earlier... Do you know if there is any data available for high RE?
I'm also doing some CFD on fins. But I look at a 3D case so my results cannot be compared to the available data of 2D analysis. I'm still in the preparation phase, so I did not yet compared different foil sections in my simulation set up.
