I have just finished a 20cm 47r fin for dezzas new red falcon 49, I haven't used it but I used the plug for the mould yesterday on my naish sp 80 and 5/8 n/p rsr, I was way over finned and a tad over powered with the sail , I was trying to sail off the wind to get to primbee too get the same fin but thinner but was to bugged by the time I got back to head out again
I have 4 versions of this fin, a thick and a thin forward boxed and the same normal boxed , I haven't used the others but arky posted close to a 37knts the last time he sailed with the thinner normal box
theres no weed at primbee this year so there for more chop, so last years 17 & 18 cm fins are on the back burner until the weed comes back
so the ideal fin depth for primbee this year is 20cm+ at 47deg to 45deg , a 20cm fin at 47deg will still get you into some shallow water but much safer in chop
I didn't have any great speeds (32.08 ) mainly because of the power of this fin , the fin has the power of 20 wind turbines and a similar foil ,

Keef what sort of depth water are you talking about sailing in with this fin & is it only sandy muddy bottom?

nice fin Keef,(and nice mold). I made a similar one to that recently but my trailing edge went to back of the base and it had a pointier tip at 22cm.

I think your planform should be better. mine has too much area close to board and not enough at the tip so it doesn't lift the board as I would like and gets a bit scary in chop.

Glynn basically you can go into the same depth of water as a delta but not as heavy weed as the delta, this fin will produce heaps more lift as a 20cm delta and totally safe off the wind , I had the fin totally powered up off the wind and my back leg screaming out with pain , there were a few times the tail was skipping off the wind in chop and the fin was as solid as a rock where most fins would have let go,
you can go into some sandy gritty bottoms with out to much trouble ,the leading edge has approximately 40 strands of woven roving's with crushed grit protecting the outer layer , a friend told me it was tungsten carbide but gustbuster phill said it was sandblasting grit (same as in the mould ) what ever it is you cant sand it it has to be filed ,
the trailing edge at the base it is extremely sharp tapering out to being thicker at the tip, not a lot more but it's noticeable,
if your looking for a similar fin in g10 send bushfire a PM he is working with MXR fins , they have a similar forward base at 50deg and I believe with those guys anything is do able
heres the grit in the mould I used for the leading edge

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yoyo said...
nice fin Keef,(and nice mold). I made a similar one to that recently but my trailing edge went to back of the base and it had a pointier tip at 22cm.

I think your planform should be better. mine has too much area close to board and not enough at the tip so it doesn't lift the board as I would like and gets a bit scary in chop.

yoyo try thinning out the back of the fin and beefing up the tip , don't use bog use woven roveing or singular carbon strands ,lay them down with a wheel then stick some stiff masking tape over, then use a profile gauge to get your foil, I wouldn't go wider in the tip just a bit thicker

yoyo the original fin was the grey normal boxed pointy fin on the right , from there we have various sizes and rakes , I imagine it is similar to the fin you made , the fin on the top right is the plug I did for the red fin , so basically it should cover sails from 4/6 to 6/7 from 19cm to 22cm , note all of the fins have a fuller foil on the starboard tack and flatter for the port tack , as the NM at primbee is running from windang up to primbee with the port tack also at sanctuary pt

Looking good there Keef.

I'm looking forward to giving that fin a go keef! Might be turning me from a careful lady driver into a racer

Dezza with that falcon you wont have a choice , they have two speeds STOP and GO , the thinner foil fin mite suit the falcon better , just need some wind for a test run
paul these fins will be better suited for sanctuary point next year , I should have a couple of 22cm and 24cm fins off the other mould by then

envious of Mike cruising around on glass I decided to knock up a 55 degree fin . this one is 19cm deep.

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yoyo said..
envious of Mike cruising around on glass I decided to knock up a 55 degree fin . this one is 19cm deep.

looks good yoyo with a nice strait profile and looks perfect for that board , the fin mike is using is 50degree rake and 17cm, when I sent it to him I had built the leading edge up to 47 deg , he has brought the fin back to 50 deg there for it has now got his foil and the reason why its going so well,
you should ask him for a loan and see how it goes to windward , i find with the strait trailing edge your foot is over or behind the center of the foil which gives you the power to windward and reduces spinout and at 50geg feels very safe off the wind
here's a pic of a 21slingshot and the same fin as decrepits , you can see there isn't a great deal of difference between the tip of the 50 deg and the slingshot
the delta is in well need of a facelift but still performs well

It came out a bit bigger than I had planned when I based it properly. 19.6 deep and 252cm2 area but still 55 degrees.



That 17 you sent Mike has become legend. Goes upwind far better than a fin that size and rake has a right to do and feels too big when he gets it lit. Mike finds the vertical trailing edge puts the area a bit too far forward requiring rebalancing mast track etc. Mine has a better balance but the raked trailing edge makes the 1/4 chord rake much more raked and may kill the windward performance somewhat.

Maybe a planshape 1/2 way between the 2 would be optimum.

Originally I was going to make the fin 17 but decided to make it bigger knowing I can cut it down a lot easier than trying to make it bigger.

Will try it today and see how it goes.

PS the above board is 54 wide, the first photo was in a 58 wide board

the smaller board makes the fin look bigger, i'm sure it will drive a 6.5mt sail with ease in shallow water,you made the rite choice by going bigger because it doesn't take long to wear carbon fins down

the second fin i sent to mike is the in between profile your talking about and the better fin of the two, it's still wide for 2/3rds and a thick foil for lift and is 19cm but it's smaller in area than the 17cm
like i mentioned earlier in the post about dezza's fin, it has incredible lift for the rake but can be over powered easily, but after saying that you can use a sail 1mt larger and still get into shallow water with a smaller fin ,
dezza was over powered and over finned with the fin i made her with a n/p rsr 5/0 ,so we stuck the smaller fin in 19cm ( like the smaller fin i sent too mike ) and much better
for shallow water sailing i would go for the fin with the most lift and when your overpowered change the fin rather than the sail
heres a pic of the second fin i sent mike

Must get around to using the smaller one, but at the moment I think it's 45deg rake isn't enough for the horror rope weed out there.

Thanks love the info I have made a few fins some good some bad its funny we are in a position at present to try and design a fast shallow fin 21 cm or less that gives heaps of lift and does not spin out and will suit a 59cm slalom board. still waiting to find it.

Got 34.8 out of it yesterday. It didn't seem go upwind very well at Fangy's compared to my smaller delta. Maybe the extra tip area just causes it to flex and depower and increase drag. Though it seemed to go better upwind at Liptons this morning. I am more familar with that locale and a bit more time on the fin helped. It also worked on the 58 wide board quite well.

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yoyo said..
Got 34.8 out of it yesterday. It didn't seem go upwind very well at Fangy's compared to my smaller delta. Maybe the extra tip area just causes it to flex and depower and increase drag. Though it seemed to go better upwind at Liptons this morning. I am more familar with that locale and a bit more time on the fin helped. It also worked on the 58 wide board quite well.

i'm not sure if it would make much difference but I did make a change and i'm not sure if it would make any difference , what do you recon ,
34.8 isn't a bad speed for a test run

Neat work Keef, yep that looks better. But not so easy with Yoyo's method of manufacture

Was thinking of doing something like that,Keef. I think there is enough layers of carbon and the tip came out quite thin so reducing the chord and tip area may improve it. But it seemed better yesterday so I'll leave as is for a while.. Today I will try it in the iSonic 87. Looks about the right size in that board (56cm wide). I don't use it much because I find it uncomfortable to sail but is reasonably quick.

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yoyo said..
It came out a bit bigger than I had planned when I based it properly. 19.6 deep and 252cm2 area but still 55 degrees.



That 17 you sent Mike has become legend. Goes upwind far better than a fin that size and rake has a right to do and feels too big when he gets it lit. Mike finds the vertical trailing edge puts the area a bit too far forward requiring rebalancing mast track etc. Mine has a better balance but the raked trailing edge makes the 1/4 chord rake much more raked and may kill the windward performance somewhat.

Maybe a planshape 1/2 way between the 2 would be optimum.

Originally I was going to make the fin 17 but decided to make it bigger knowing I can cut it down a lot easier than trying to make it bigger.

Will try it today and see how it goes.

PS the above board is 54 wide, the first photo was in a 58 wide board

Good looking board! Lovely shape.

Keef, Mike and I have been spending time lately working on the idea of stainless fins or at least a stainless leading edge so we don't have to keep repairing the leading edge of our fins after a day running through the weed. We have different manufacturing methods so while Mike was panel beating and grinding 1mm stainless I was wondering if I just had 1/2 mm stainless ruler (KMart $1) centred between my 2 half shells I might get all the benefit without much more difficulty in construction.



In the end I decided to make one without the stainless first. I join the 2 half shells at the leading edge with carbon.



Then make a similar join at 1/4 cord using the same method. In this case the width of the carbon strip was too narrow and it ended up more like 1/8 chord which required additional reinforcing ( and weight) later.
I then taped the trailing edge together and put the blade in the sun for the carbon strips to set. After trimming I had my 18cm @55 degree blade.



It looked pretty good in the 54 as well



It is only marginally less area the the 19.5 but the shorter length may help on the shallow days.

the fin looks great yoyo, your definitely on the right track and nice and simple I got a sheet metal shop to cut 30cm wide strips but it was hard to get them flat, the ruler sounds great , I decided not to make any more stainless fins after decrepit's but I mite give your method a go ,I will grind the surface of the ruler and drill some holes to stop any delam , THANKS FOR THE TIP

Great idea with the ruler yo-yo. Do you think that you need the whole 12" or could you get maybe 2 for one? A 6" insert for 2 foils?
Cheap bastard aren't I..

Pepe, in the heavy weed the leading edge gets serrated over it's entire length, maybe you needn't bother too much with the first cm, but the transition between the two will stand out after a while, and probably catch weed. I think the whole length is best.
I think the ruler is too thin, it's only going to protect the first mm or so, wear goes in 5mm at least, then you're also going to get the ultra thin layer of resin/cloth at the junction chipping/peeling away. What I want to do, is get some 5mm material about 20mm wide, and get a 1mm step machined into it about 5mmback from the edge. That way your cloth has something to butt up to and shouldn't chip away. It'll probably still need to be repaired occasionally, but no where near as often, and much easier, because there's a defined edge to work to.
My experiments with a stainless skin, is a bit disappointing, I still think it's possible but you need a press to shape the stainless.
My attempts at hand panel beating are very amateurish, it wouldn't be too bad if you could bog it, but that defeats the whole purpose.

here's an interesting thought, if you could make a weed speed fin with a stainless leading edge that was indestructible and was capable of 40knts+ do you think a production fin manufacture would put one on the open market
if they could make car or truck tyres that was indestructible would they put it on the open market

with the stainless leading edge we are 95% there , the only thing that's holding the project back is impact , if you hit a solid object it's like a log splitter it wont split the fin but will do a lot of damage , a normal production fin will be bruised to the extent it can be repaired ,
I've been working with some plexithane 80 resin the same consistency as a break shoe peddle and believe it or not it is compatible with epoxy
here's another thought has anyone on this site tried to sand a beak shoe pedal , urethane by it self has to much flexy but i'm working on it

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decrepit said..
Pepe, in the heavy weed the leading edge gets serrated over it's entire length, maybe you needn't bother too much with the first cm, but the transition between the two will stand out after a while, and probably catch weed. I think the whole length is best.
I think the ruler is too thin, it's only going to protect the first mm or so, wear goes in 5mm at least, then you're also going to get the ultra thin layer of resin/cloth at the junction chipping/peeling away. What I want to do, is get some 5mm material about 20mm wide, and get a 1mm step machined into it about 5mmback from the edge. That way your cloth has something to butt up to and shouldn't chip away. It'll probably still need to be repaired occasionally, but no where near as often, and much easier, because there's a defined edge to work to.
My experiments with a stainless skin, is a bit disappointing, I still think it's possible but you need a press to shape the stainless.
My attempts at hand panel beating are very amateurish, it wouldn't be too bad if you could bog it, but that defeats the whole purpose.

Mike, Stainless steel work hardens, so bending & beating it makes it harder to work with.
You can anneal it by heating it up after working it for a while to bring it back, you can even quench it which won't affect it.
Working it hot is another way.

Ideally what you need is a flatbar the thickness of the fin, radius the leading edge & machine a step back from the LE to start the carbon.
Drill a heap of holes right through the stepped area (perforated) so the resin will go through & grip.

Have you tried any of the ceramic coating available, unfortunately some need to be baked on I think & also hard to get a smooth finish.

We do a lot of stainless steel work for aviation fuel facilities and what Paul said is correct.
what I would suggest is learn to swim and sail in deeper water.
Occasional sailing in shallow weedy spots is dangerous enough. Trying to spend all your time there is increasing your exposure greatly. Is it a risk worth taking just to hit 30 knts.

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DarrylG said..
>>>>>>
what I would suggest is learn to swim and sail in deeper water.
Occasional sailing in shallow weedy spots is dangerous enough. Trying to spend all your time there is increasing your exposure greatly. Is it a risk worth taking just to hit 30 knts.

Darryl, I'm sure you mean well, but I find your comment a tad condescending.

Are you saying all the guys who sail Lake George shouldn't?
(although you don't need stainless at LG, the weed isn't abrasive)

Firstly the weedy areas we sail in can be up to waist deep, no shallower than the non weedy areas.
And I have much more crashes in choppy water than I do in dead flat.
Catapulting head first into a sail in deep water, is every bit as dangerous as crashing in knee deep water.

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Paul Kelf said..
>>>
Mike, Stainless steel work hardens, so bending & beating it makes it harder to work with.
You can anneal it by heating it up after working it for a while to bring it back, you can even quench it which won't affect it.
Working it hot is another way.

Ideally what you need is a flatbar the thickness of the fin, radius the leading edge & machine a step back from the LE to start the carbon.
Drill a heap of holes right through the stepped area (perforated) so the resin will go through & grip.

Have you tried any of the ceramic coating available, unfortunately some need to be baked on I think & also hard to get a smooth finish.

Thanks Paul, I've given up on the idea of shaping a skin. I'll see if anybody around here can machine a step into a bar.
But I'm sure the bar doesn't need to be fin thick, as I said 5mm should be enough, but I haven't done any measurements, it may need 7mm to get back to 5mm from leading edge.

Don't get me wrong Decrepit, I think there is nothing better that making and sailing something you make your self. I just don't like the idea of delta style fins so people can sail in shallower water. If I am touching bottom in 30 cm of water I am touching cloth and get out of there quick. Stories of people grinding down 19cm fins in shallow water just has me concerned.

Well Elmo would certainly agree with you, and yes sailing in 19cm water is experimenting with disaster.
But we're grinding the whole leading edge of the fins in waist deep water. It's due to abrasive weed not the bottom.
And the high rake and shortness is for less weed drag, not necessarily ground clearance.
Although it's easy to get carried away by all that flat water, it's a matter of discipline I guess.