mixing kevlar with glass matt and rovings in a lamination.

I would have thought that you would put the Kevlar on the outside ( just under a skin) to get the best impact resistance?

 

I have system three silver tip epoxy, biax 17oz, 45/45 and 18oz, 90/0 will go on top of the kevlar wet on wet. I'll have a male mold , foam and glass hand laid. So for puncture restance Kevlar inside or out? Rick

 

Lets back up a little why so worried about punture resistance ??? Been boating just about all my life and never hit a single thing ever anywhere . to me its a non event so why bother !! anyway to be really resistant you'd need more than one thin layer !! probabply 3 or 4 maybe to work properly !! S glass with epoxy resin is a better deal maybe !! It need to be the skin not under the skin !! Its to protect the glass and core etc etc !!At speed if the water gets in to the foam core with hydralic pressure it will peel from end to end !! foams like that its peel resistance is very low and really scary .
Balsa or solid glass in the bottom below the waterline, and core from the chine up the top sides !!

Would be easy to learn to drive properly pay attention and take a little more care !!

 

Fabrics intended to improve puncture resistance (Kevlar, spectra, etc.) are best oriented as far from the impact site, within the laminate as practical (distance from the center of gyration). It's simple physics folks. Abrasion resistance is the exact opposite, naturally. Floating fabrics isn't an uncommon issue and there are a few different ways to handle it. You can put some more fabric over it and with Kevlar, a good idea, because of finishing issues. Bagging, weighting, peel ply and other tricks can be employed too. Folks that have bad experiences with Kevlar, usually have it exposed or are trying to grind into it or fair it. Some think it's a great abrasion strip, which it is, but you have to consider all the physical properties, when designing or modifying a laminate schedule.

 

One layer lapped on the keel will give me two layers where I think I will need it. I hope to be as good a boater as you one day, but untill I learn to sail I will need a little kush. Again removing the mat from the schedule has given me a stronger, lighter, but thinner schedule. I know the kevlar is stronger on the inside as the last or near last layer, but for puntures? Rick

 

I would have thought the physics say the opposite?
If the weaker layers are outside during an impact they will just be ripped apart then you get to the kevlar which is stronger.
If the kevlar is on the outside its yield strength will go up as it has support behind it?

 

I would be trying to stop anything punturing and from getting into any part of the glass behind and specially the core for sure . putting the kevlar away inside is totally defeating its purpose of being there as a puncture resistant layer .
Have you ever seen a cored hull bottom come off ??
first the boat hit a wave at speed and the foam core sheared , then it began to flap and in a short time fractured and cracked and once the water pressure got in it blew up and exsploded like a balloon filled with water and totally peeled from end to end Lucky the core did not go round the chine or the ballooning water pressure would have taken the topsides out as well right to the gunwhale .
Like i keep pointing out many many times you want to see what lets go and what stays together go look at some broken boats , TAKE A CAMERA WITH YOU !!! look and understand why some things stay and others dont .

 

Yep
take a look at a failed feretti built Bertram plenty of how not to do it design there

 

I wont be building a plaining hull , a nice old designed not to slow trimaran. The kevlar is stronger as an inside layer, as far as adding strength to the schedule, but simply as a puncture resistance may be best outside lay up.

 

You guys ought to make several test laminates and break them.
First just see how much it takes to bend and break, then drop a ball from increasing heights to see about puncture.
Weight the panels before you break them.
Too many theories with no facts.

Personally I would trust PAR, but you need to prove things for yourself.

 

How the hell you going to make a ball make a hole in a panel you could drop it from space . Puncture you need something sharp !! puncture ,as in making a hole .
And if the kevlar is at the back of the laminate behind the glass and behind the core and what ever else is in the way it will be destroyed before it gets to the kevlar !! wouldnt you say ?????so wouldnt you say its in the wrong place ???

 

Tunnels,

One of the standard tests in aerospace is to use a ball to check puncture damage.
When you want to test for exploding rockets you use something with a sharp edge. I doubt you need to worry about that, but if that blows your skirt up, use a cube of steel.

The point is the test not your silly little quibbles.

If you want puncture resistance you need to decide what your goal is.
1. Do you want to stop any damage to the panel? Extremely difficult and heavy to do. You might start with steel on the outside, however the Concordia had steel and was still penetrated.
2. Do you want to stop the panel from being penetrated in order to keep from sinking the boat? I.E., are you willing to fix the boat after you have gotten it back to shore? This might be do-able, sometimes. I doubt that Kevlar would have helped the Titanic.

Nothing you can do will protect a boat in every situation. Pick your battle.

You have won again, I quit this discussion. Common sense eludes you everytime.

 

Been doing a little research (ref. Fiberglass Boat Repairs--Roger Marshall) apparently there is a combined product on the market: a mixture of S glass and Kevlar unidirectional fibers. It was developed for high strength and impact absorbent qualities. Regarding where in the lamination it should go ???. I have a gut feeling that for best results of these exotic lamination mixing the order of the day might be vacuum bagging. I for one not having the experience nor close at hand supply will remain a "One Trick Pony".

 

As stated earlier there's no point to use kevlar.
Inside the hull the damage is done before the layer of kevlar and outside it just doesn't work. Better might be skin on frame, kevlar alone with film...

 

What structure are you adding impact resistance to ?