Ultralight Board II – SUP Foil Bumblebee

[Dwight (DW)]

I talked to TJ yesterday about the boards on the market. His opinion matched what I thought about them by simply looking at the shapes.

His personal DW board was the Armstrong. Most stable. Parallel template indicates this just by looking at it. He switched to the KT Dragonfly. Easier to paddle up. But less stable. Again, looking at it, you’d come to the same conclusion.

I’m going to take more inspiration from the Armstrong than the other shapes.

Barracuda and Dagger fall into the less stable group also.

Naish is most stable, but at what cost being 25 wide!

[PonoBill]

I think some folks might be missing the key point--it's XPS, which is closed cell foam. Water leaking through pinholes has nowhere to go. It won't gain weight and won't delaminate because delams are caused by water in the foam getting hot enough to release lots of water vapor and pressing against impervious layers of hotcoated glass. I'm going to have to build one of these. SHIT! I don't need another project.

[Dontsink]

I think the point was that kevlar absorbs water but innegra does not.
Innegra has excellent impact resistance  and is probably the lightest fiber out there.

If i was going to use minimal amounts of resin (or GGlue as i think Beasho is using) i would definitely go for a waterproof material.
Water is very dense and even a little amount seeping into the Kevlar fibers during the sesh will add weight.

[Vancouver_foiler]

 Beasho did you leave the bottom.with peal ply texture?
Similar maybe to sharkskin denticles?

quote author=Beasho link=topic=38521.msg440762#msg440762 date=1690303624]

Quick question. Why Kevlar? It's a hydrophilic cloth meaning the cloth itself will absorb water. It is also has a higher density than Innegra. Innegra is hydrophobic as well as being lower in density. I cant be sure, but you could possibly shave a few ounces off with different materials as well as avoid possible water intrusion into the fibers.  It's only a guess of course, but id be curious to find out.

The primary objective was to be "light in the ends."  Similar to America's Cup boats that were illegally fast because they had reduced swing weight back in the 1980's. 

The secondary objective was to be ding proof.  On my first board I used 1.4 ounce/Yard fiberglass.  The lightweight glass was intended to keep the XPS from flaking off over time.  However it does ding, or puncture, with sharper impact.  Even my big toe.  The Kevlar, on test samples, proved to be very ding proof against acute impact and was only 2.2 ounce/Yard.  Semi affordable @ $32 per yard from Fiberglass supply.  I would use Innegra if available, or affordable (??). 

The hydrophilic/hydrophobic didn't necessarily apply because I am not making my XPS boards waterproof.  To do that takes too much time, material, weight and quality control.  Ironically I have found that the moisture, if any in the fiber, serves as a natural evaporative coolant to keep the XPS from baking in the sun.  Although I have kept the boards out of direct sunlight when not in use. 

Between the 2 boards I have > 120 sessions combined and they are both holding up with no random XPS delamination that people seemed wary of. 

Now when I look at a board with full Carbon layers tip to tail I just see unnecessary dead weight.  The nose and tails of SUP foil boards serve no purpose but for flotation on takeoff.  They only need to be strong enough to not to randomly snap off.  The America's Cup'ers were pushing the limits of this idea 37 years ago, and I remember some boats did break.  We will only know we've gone too light, too far when things start to break off.   

IMO most production boards are way too heavy focusing on aesthetics and given the amount of box failures NOT investing in Track strength.  I went the other way and Invested heavily on deck structure and in the track support with carbon rods and XPS infrastructure but still less than a Full Divinycell high density stringer design.  I Divested of strength in the ends, waterproofing and showroom finish.  This board ended up 2 to 5 lbs lighter than comparable 115 liter boards. 

In a world where people are talking about 1% improvements in foil efficiency its crazy to me that board weight, meaning advantages of 15% to 50% are largely ignored.

https://www.latimes.com/archives/la-xpm-1986-12-23-sp-122-story.html

"The fiberglass boat was found not illegally light in the ends, unfairly enhancing its speed, and was not in violation of the rule prohibiting a more beneficial weight distribution than an aluminium yacht."
[/quote]

[Beasho]

I think the point was that kevlar absorbs water but innegra does not.
Innegra has excellent impact resistance  and is probably the lightest fiber out there.

If i was going to use minimal amounts of resin (or GGlue as i think Beasho is using) i would definitely go for a waterproof material.
Water is very dense and even a little amount seeping into the Kevlar fibers during the sesh will add weight.

Both Gorilla Glue and Epoxy have a specific gravity of 1.1 meaning 10% heavier than water.  So, if there is any water seeping into the fiber it weighs LESS than the Glue would otherwise weigh permanently bonded into the fiber. 

Said another weigh, porous fiber will always be ligther than glue filled fiber whether or not it takes on water.   

[Beasho]

Beasho did you leave the bottom.with peal ply texture?
Similar maybe to sharkskin denticles?

Yes.  With all my final lamination layers I never added any 'clear coatings.'  So I would just vacuum bag with Peel Ply and call it finished.

The carbon comes out very sleek looking.  The Kevlar has a slightly burlap, or sharkskin, texture.  Smoother to the touch than it looks.  BUT definitely not a polished finish. 

[Vancouver_foiler]

 

I think the point was that kevlar absorbs water but innegra does not.
Innegra has excellent impact resistance  and is probably the lightest fiber out there.

If i was going to use minimal amounts of resin (or GGlue as i think Beasho is using) i would definitely go for a waterproof material.
Water is very dense and even a little amount seeping into the Kevlar fibers during the sesh will add weight.

Both Gorilla Glue and Epoxy have a specific gravity of 1.1 meaning 10% heavier than water.  So, if there is any water seeping into the fiber it weighs LESS than the Glue would otherwise weigh permanently bonded into the fiber. 

Said another weigh, porous fiber will always be ligther than glue filled fiber whether or not it takes on water.

Hang on a sec here-what are you using Gorilla Glue for?

[finbox]

I purchase some innegra from https://compositeenvisions.com/ it is a 3.6 oz - they have a 2 oz listed but it is out of stock. From the Easy Composites youtube channel they did testing on different composite layups for a snow sled. The Kevlar had good impact resistance and also had strength to it. I think with innegra it lacks stiffness so it needs a structural layer, member DW used to make boards with innegra & fiberglass.  I was told on hand layups the innegra will float and needs a fiberglass or other layer to hold it down.

[tarquin]

https://www.easycomposites.co.uk/learning/choosing-composite-reinforcements-for-impact-strength

[PonoBill]

I purchase some innegra from https://compositeenvisions.com/ it is a 3.6 oz - they have a 2 oz listed but it is out of stock. From the Easy Composites youtube channel they did testing on different composite layups for a snow sled. The Kevlar had good impact resistance and also had strength to it. I think with innegra it lacks stiffness so it needs a structural layer, member DW used to make boards with innegra & fiberglass.  I was told on hand layups the innegra will float and needs a fiberglass or other layer to hold it down.

Generally, a layer of fiberglass is used with innegra to decrease the spring back (less of a problem with bagging) and provide a sanding surface. If you touch sandpaper to Innegra your day just got a lot worse.

[clay]

Both Gorilla Glue and Epoxy have a specific gravity of 1.1 meaning 10% heavier than water.  So, if there is any water seeping into the fiber it weighs LESS than the Glue would otherwise weigh permanently bonded into the fiber. 

Said another weigh, porous fiber will always be lighter than glue filled fiber whether or not it takes on water.

Well this is an interesting point.

So a board's skin/laminate soaking up water is lighter than a board's skin that is fully wetted out with gg or resin?

[Vancouver_foiler]

Both Gorilla Glue and Epoxy have a specific gravity of 1.1 meaning 10% heavier than water.  So, if there is any water seeping into the fiber it weighs LESS than the Glue would otherwise weigh permanently bonded into the fiber. 

Said another weigh, porous fiber will always be lighter than glue filled fiber whether or not it takes on water.

Well this is an interesting point.

So a board's skin/laminate soaking up water is lighter than a board's skin that is fully wetted out with gg or resin?

I don't get it, is Beacho using gorilla glue(GG) to laminate fibers? Further to the point,  how in the world is GG specific gravity compared  to water  in fibers relateable to anything?
I'm just diving into an 8ft xps DW board, no fill coat -raw dog peal ply finish board and don't want to miss any pertinant...stuff.

[Beasho]

Yes!  Beasho was using Gorilla Glue to laminate fibers.

The dream was that Gorilla glue would be more accessible, and faster given its 1 part nature.  AKA no more mixing epoxy for perfect cure . . . .

My first board I used Gorilla Glue to laminate the majority of the nose and tail.  On this board I used it on the tail.

The good news is that it worked.  The downside was that it tends to set up too quickly, making it a bit hard to work with large patches of fiber lamination.

The other benefit is with Ding Repair.  You can just slop on some gorilla glue, cover with Tape and go surf 1 hour later.  No worry about making it water proof because the whole board is porous anyways.

[tarquin]

I did a load of laminate test patches with PU glue and various fibres. Couldn't get any real strength. I eventually made a paddle blade but it had Paulownia veneer that gave it the strength.
 You can get other brands of PU glue, not just Gorilla glue and some are slower at going off.
 I did some flax and recycled PVC tests with PU. Very impact resistant but no real strength.
 If you vac bag the PU you can get most of the bubbles out and end up with a pretty smooth plastic like finish.

[tarquin]

I cleaned out my work shop ages ago and threw a lot away. This is armacell recycled foam with cork, glued with PU. I did a few different lay ups with flax, innegra and glass in the middle. None gave any real stiffness but the innegra and flax would never catastrophically fail. The fibers would hold together. Very impact resistant and easy to repair.