Laminate schedule for fins.

[SURFnTURF]

Anyone know what weight of glass and how many layers  the pros use to make fins?   I'm starting a project and I've got 6 oz cloth and resin research epoxy.  I'm thinking 12-16 layers?
Thanks...

[Dwight (DW)]

Hint. they use polyester resin in most fins. Windsurfers use epoxy in some, but not surfing fins.

[Wood_Ogre]

Its hard to do fins with epoxy use polyester resin.

[Wood_Ogre]

Oh ya, forgot.  4oz cloth 34 layers. 6 oz cloth 22 layers. 7.5 oz 18 layers.  

[SURFnTURF]

Thanks for the input.   I'm assuming I should use surfboard  laminating resin.  Any particular brand or style that gives more favorable finished physical properties?  I'm going  for clear. 

[SURFnTURF]

Well, I used 22 layers of 6 oz cloth with an injection epoxy from ILL Street composites in Charleston, SC used to make carbon car racing parts.  It's really viscous!   This may account for the fact that when I trimmed it, it was only about 1/2 as thick as it needed to be.  DAMMIT!   So I used 2 layers of 1708 just on each side of the base that goes into the box, then 2 more layers of 6 OZ over each entire side.
   This Epoxy requires autoclaving for 2 hrs at 180 degrees.   So I popped it into the one We keep next to our refrigerator and DAMN!   It is as stiff as were full thickness throughout, but really light!!!
     So It appears that Pro Box Larry doesn't want to give up his laminate schedule, but Me thinks  it's about 40 layers of 6 OZ, at least with this epoxy or the suggested polyester resin that I was too impatient to wait to be delivered., It would have been closer to 30 with RR epoxy, I'm thinking.
    The benefit of using epoxy over polyester is that the epoxy doesn't shrink, thus a much shorter cure time on the laminating table.   Drawbacks:  Well...  I knew this going into it but it's not slippery like polyester, so more care must be taken while squeegee-ing out any air.

[Larry Allison]

Well, I used 22 layers of 6 oz cloth with an injection epoxy from ILL Street composites in Charleston, SC used to make carbon car racing parts.  It's really viscous!   This may account for the fact that when I trimmed it, it was only about 1/2 as thick as it needed to be.  DAMMIT!   So I used 2 layers of 1708 just on each side of the base that goes into the box, then 2 more layers of 6 OZ over each entire side.
   This Epoxy requires autoclaving for 2 hrs at 180 degrees.   So I popped it into the one We keep next to our refrigerator and DAMN!   It is as stiff as were full thickness throughout, but really light!!!
     So It appears that Pro Box Larry doesn't want to give up his laminate schedule, but Me thinks  it's about 40 layers of 6 OZ, at least with this epoxy or the suggested polyester resin that I was too impatient to wait to be delivered., It would have been closer to 30 with RR epoxy, I'm thinking.
    The benefit of using epoxy over polyester is that the epoxy doesn't shrink, thus a much shorter cure time on the laminating table.   Drawbacks:  Well...  I knew this going into it but it's not slippery like polyester, so more care must be taken while squeegee-ing out any air.

LOL I didn't know you were asking me! I don't use 6 oz my friend. 32 layers 7 1/2oz. The Benefit of epoxy is cure time ONLY correct. But the negative is flex and rigidness which translate to performance.

A short look at some laminating going on at our factory i the video clip. Enjoy the ride!

[blackeye]

But the negative is flex and rigidness which translate to performance.

Larry, I don't quite follow.  Do we want flex or rigidness to get performance? Which is more flexi - epoxy or polyester?

Also, I presume your layup schedule would be adjusted for whether you are using cores or not. 

Thanks for your willingness to answer everyone's questions.  Its a great way to build a brand for you. 

[SURFnTURF]

Neither epoxy or polyester, or vinylester for that matter, is inherently more or less flexible.  All can be formulated for variing degrees of tensil strength, stiffness, elasticity or other properties.   The key is to find a balance of the desired properties.   Too stiff and the product is brittle, so a little flex is not a bad thing. 
     Polyester, even low shrinkage tooling resin products can post-cure, deforming after its seemingly cured.    I've seen it happen in sailboat decks up to 10 days after coming out of a mold.    For something as small as a SUP fin, 3 days is safe, less for smaller ones.
      Polyester is probably a  more  popular choose for fins not just for its workability, but it's significant angle less expensive  than epoxy.   This doesn't make it a lesser product, just the right choice, all factors considered.
     I chose this particular epoxy as I happened to have some on hand.  It's price at over $100 a gallon makes it cost prohibitive for production use but ok for 1 fin.   Even though the body o  the fin is only about 1/2 as thick as it should be, it's pleanty stiff after autoclaving, and its weight rivals a cored fin.

[SURFnTURF]

On a side note, I'm.sure Larry  has chosen a resin with optimal properties for fins  if not having a custom formulation.

[Larry Allison]

On a side note, I'm.sure Larry  has chosen a resin with optimal properties for fins  if not having a custom formulation.

You are right my friend. All 3 of these fins are a Polyester Blend which we made back in 1988 before Future and FCS were even thought of. But as the Push for overseas building and prices driven down later by companies like Future and FCS certain resin blends became discontinued because of manufacturing demand, one being the blend I used in these fins here.

[Larry Allison]

But the negative is flex and rigidness which translate to performance.

Larry, I don't quite follow.  Do we want flex or rigidness to get performance? Which is more flexi - epoxy or polyester?

Also, I presume your layup schedule would be adjusted for whether you are using cores or not. 

Thanks for your willingness to answer everyone's questions.  Its a great way to build a brand for you. 

Blackeye, Flex and stiffness in right formulation is important.

Epoxy has a higher tear resistance in a easy term, which makes it somewhat elastic soft.

Polyesters are in the cast family which makes them harder, but without structure make up of some sort they can be brittle.

Flex with a proper fiber glass make up and foil creates a "S" flex, like the pic below. This flex is where the bottom 3rd section of the fin stays rigid and the top 3rd section twists off releasing pressure. Most Fiber Glass fins are high glass contents and low Resin, which is why they react differently than composite fins.

Most of the composite fins laterally flex. What I mean by this comment, is when the fin loads up it laterally flexes from tip to base losing the power at the bottom 3rd section of the fin. This occurs because the coremat core has a chain link effect allows the Epoxy to run thru not allowing for a "S" flex but lateral flex. Most composite fins are high Epoxy low fiber fill, which is why lateral flex is greater and this make for lack of drive in a fin.

What I find funny is when you sale a carbon composite Fin and then posts directions how to fix it when it splits. And that is even funnier because how do you fix a egg when it cracks?

[blackeye]

And that is even funnier because how do you fix a egg when it cracks?

Well I suppose you laminate on more shell, no? Or just eat it.

I'm getting the picture - like any other foil in water or air, the flexible fins dump load and are more forgiving, and the stiff ones load up and are more responsive.  To an expert, the flexi's feel mushy and to a beginner, the stiff ones feel uncontrollable. 

So how does that apply to flatwater boards? Being low speed applications the fins are large and being so I can imagine they are flexible.  I would think a really stiff fin would be desirable even for beginners, whether it be laterally flexing or S-flexing. S-flexiing might return a tiny bit of power as it snaps back to alignment with the base. Interesting stuff.

[Larry Allison]

And that is even funnier because how do you fix a egg when it cracks?

Well I suppose you laminate on more shell, no? Or just eat it.

I'm getting the picture - like any other foil in water or air, the flexible fins dump load and are more forgiving, and the stiff ones load up and are more responsive.  To an expert, the flexi's feel mushy and to a beginner, the stiff ones feel uncontrollable.  

So how does that apply to flatwater boards? Being low speed applications the fins are large and being so I can imagine they are flexible.  I would think a really stiff fin would be desirable even for beginners, whether it be laterally flexing or S-flexing. S-flexiing might return a tiny bit of power as it snaps back to alignment with the base. Interesting stuff.

Quote:
I'm getting the picture - like any other foil in water or air, the flexible fins dump load and are more forgiving, and the stiff ones load up and are more responsive.  

Correct comments in this sentence my friend.

Quote:
To an expert, the flexi's feel mushy: Correct again

Quote:
 and to a beginner, the stiff ones feel uncontrollable. :
 Not correct, on the contrary the stiffer fin for a beginner feels the best and most comfortable with better control like my Bat Fin.

Good observations blackeye. I will come back to finish up tomorrow getting late and just came on for a moment to answer some of your reply.

Mahalo,Larry

[Larry Allison]

And that is even funnier because how do you fix a egg when it cracks?

 

So how does that apply to flatwater boards? Being low speed applications the fins are large and being so I can imagine they are flexible.  I would think a really stiff fin would be desirable even for beginners, whether it be laterally flexing or S-flexing. S-flexiing might return a tiny bit of power as it snaps back to alignment with the base. Interesting stuff.

Blackeye,
Flatwater the object is less drag with best projection like this unlimited with a small ventral and 5" Elliptical Keel at the rear.

Or 4" Twins with med. Ventral like this 14' Hovie.

Or 5" Elliptical Keels by themselves like on these unlimiteds



Or the Gladiator Pro at 7" and the Ninja Fin which is large in plan shape but because of S Flex feels like a 8" fin on full volume tail boards.
 
These are the some of the best flat water set ups my friend.