Foil now re shaped, cut out removed and fitted to the board. It now weighs 1.2kg. How many layers of glass would you recommend and approx how thick would them layers end up so I know how deep to make my bevel. Mike or Pepe please.

Years ago I used to have a wave fin with a slot down the front made by F Hot. It worked realy well in preventing spin out. This may be a bit extreme.

depends on glass weight of course but I work on 3 layers per mm.

So you need to do fangys flex test. If there's no flex, there's no load on the glass, and you can get away with 1 layer and small bevel. If the fin is flexing, then there will be load on the glass, I'd go for at least a 20m wide bevel 1-2 mm deep and 3 to 5 layers of glass. If that gets you close to the leading edge, then make that a rebate instead of a bevel

Thanks for the advice guys, will do more work on it next week as the wife will have me doing more useful work over the weekend. I already have plain weave glass and epoxy at home so will probably use that. Unfortunately that rules out the gap filla . I am thinking of using balsa for the core as it will be relatively easy for me to shape and I have no blocks of foam or polystyrene at home. I was thinking 3 layers would be enough. As for fangys flex test I don't want to end up with a kanting keel like the barge so testing on the water only. I doubt very much it will flex, it is still about 22 mm thick at the front.

As long as it's one piece of balsa and not the end grain patchwork Basil has. That's a real bugger to shape as the density varies a lot.
And why does epoxy rule gapfiller out?
Epoxy works with anything, it's polyester that doesn't work with styrene.

I wasn't seriously recommending fangys jump on it test, but you could try putting it over your knee and see what happens in a controlled way.
You won't get a permanent deflection until it's bent a few mms. If you really are worried about that, then a light glass job will lead to the center popping out.

decrepit said..
As long as it's one piece of balsa and not the end grain patchwork Basil has. That's a real bugger to shape as the density varies a lot.
And why does epoxy rule gapfiller out?
Epoxy works with anything, it's polyester that doesn't work with styrene.

I wasn't seriously recommending fangys jump on it test, but you could try putting it over your knee and see what happens in a controlled way.
You won't get a permanent deflection until it's bent a few mms. If you really are worried about that, then a light glass job will lead to the center popping out.

Just goes to show I know nothing about resins and Compatibility with materials, I was just assuming from what Pepe said about polyester and using a different foam yesterday that epoxy might react with gap filla .
The piece of balsa I have looks decent and is big enough to fit in one piece.
There is no way I am even going to attempt bending the fin over my knee, I know my kneecap will break before the fin flexes. If the centre pops out its not a biggie, just go back to drawing board. At least it wont be another fangy fin lost at coodanup. We will have to have a treasure hunt for the two that have been.

swoosh said..
Back of envelope maths, you could apply say 180kg to the side of the cutout fin before it permanently deforms. At which point the tip will probably have flexed about 4mm.

Solid, I reckon easily over 1000kg to get the same deflection.

Actually seeing as I have the CAD, I could FEA it, but anyway, noone would want to see that.

Only 180kgs, that counts Swindy out as a crash test dummy.
if FEA is finite element analysis: I love those things, they remind of all the Rubriks cubes I never mastered :-)

Smiles on Dials Peter! I will post something a bit more substantial, later, because at the moment I have just got home from a concert gig and should not really be posting anything at all! Concert was great tho:-)

Thanks windy, it will be interest to know what 75-80 kg sailors are using too.

Peter, I was really close to 80 kgs in early high school. Now I guess that me and my kit are closer to 120kg all up, so what I post here may have close to zero relevance for you, but at least it may give you a worse case scenario as far as the fin/ sails combo's are concerned.
Firstly, my boards are vintage and as such tend to the long and narrow form. Eg. my widest board ( The Barge) is three meters long but only 61cm wide. The others are in the 53-54 cm wide range and all of them require a forklift crew to lift out of the trailer. So for me, it's more a sail size dependant decision.

The Barge - 8.0m -10.0m sails I use the FF28. I have used a 7.5 with the FF28, but once above the 32-33 knot mark, the combo is so 'locked in' that it feels lifeless and the the vertical lift becomes a bit of a handful as well.
The Barge - 6.5 -> 8.0 m sails I use the FF24 .

My other boards are Vintage Windtech and Mistrals ( 53-54 wide),that I use with sails less than 6.6m and in this case I can use the FF20. For me the FF20 really only begins to do its thing once I am at the top end the 6.6 wind range, as in my hands it needs to be moving quickly to generate enough lift to counter my weight/sail leverage. Having said that, it has the approx the same area as a Delta 16 (which was close to useless with my level of ability) so the fact that I can use a fin this small at all is a surprise to me in itself. For me, the FF20 doesn't spin out and misbehave when underpowered, it merely doesn't allow me to point high enough to enjoy my sailing. But please remember, part of the fin behaviour may be as result of my boards all being skinny hips and tails sorta gals.

Once the FF22 casting is popped out of the moulds, I expect it to be the fin I use with my 6.6 sail most of the time, as the jump down from 24 to 20 is simply too large for my weight, ability and fitness.

The fins were designed to be skewed toward the greater lift end of the spectrum and not expected to be used when a PB max speed is on offer. However, as a point of interest, on the above combo's I have recorded;
- FF28 peaking at about approx 33 knots
- FF24 peaking at approx 37 knots
- FF20 peaking 39 knots ( Jonski has done 40+)

could have done with a 26 this morning, lucky for me I'm making my own. With the 70 wide board and the 7.9 when the wind dropped off a bit going up hill was a bit of an issue with the 24 but fine when well powered up. But I am fat with a heavy back foot. Not quite the 180kg mentioned above though.

keef said..

Swindy said..

fangman said..
Tips - Neighbours get tired of listening to angle grinding when they are watching TV at night.
- You have really bad lawn beetle.

I was thinking of using an inverted bevel, that is, undercutting at least the leading edge section and the base. The idea was to provide a physical lock for the foam/resin and also provide protection for the resin joint (as per Decrepit' s technique with Stainless steel leading edges.) But I am happy for you to try all options/techniques Swindy, and simply let me know what works.

Is it worth the extra greif of trying to tuck wetted glass into the internal bevel as it is not the leading edge. With an external bevel it will still be locked in. Also it will be realy hard to bevel the inside all the way round with such sharp corners.
This is why I wanted you to do yours
first but I cant wait that long.

Compacting glass and into tight corners, did you use a fiberglass wheel

No glassing has taken place yet Keef, but the way I intend to do it wont involve sharp corners. No glassing will be going on in fangys shed for some time yet as neither of us know what we are doing he is allowing me to make all the stuff ups first. He's good like that.

Looks excellent, he's probably got wood over your timber

Thanks guys. The only mistake I have made so far is forgetting to make some templates of the foil shape before cutting out the centre. Now having to shape it by eye and feel.

Great work Roger, a bit of bog and some spray putty, could be better than the original.
Big question though, how much weight have you saved?