Replies to This Discussion

Permalink Reply by tungsten on January 11, 2013 at 3:03pm

Well this is what confuses me,its only here on drift boat forums that say Kevlar has a use.Anywhere else says its not useful and a waste of money.I'm just like most others ,kevlar has to be good heck it stops bullets.But,the balistic material is different then what we put on boats in fact if you were to put epoxy on balistic kevlar it wouldn't stop bullets anymore.Its the stretch that does the work.

So from what i've read and understand is, kevlar is a stretchy material and one would think that mixing materials with different properties would be a waste.plywood is stiff,kevlar is far from that so putting it beside wood is like putting rubber beside steel.So the wood and epoxy break well before the kevlar has done anything so again kevlar is a waste.

But then we have a very well none boat builder that does a test showing that kevlar on plywood is good so this is what confuses me.

Its funny how people test things,we always reach for a hammer and swing as hard as we can.I'm guilty of this also.But nowhere we fish does a guy come running out of the bush and start hitting our boats with a hammer.Our boats go 2-10 mph we weigh on avearge 600-900 lbs.So maybe a different kind of test would be a little more helpful since a hammer goes about 70 mph.No beercan size rocks are going to hit our boats at that speed.

Another thing that i understand is kevlar wicks water like a sponge so again not  good to have it beside wood.

 

Tungsten: still confused.....

 

 

 

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Permalink Reply by tungsten on January 11, 2013 at 3:10pm

Rick,

Yes stretchy resin would be good with kevlar but byitself not against stiff plywood.

S glass is from what i've read very compareable to epoxy so this is the right choice.But no one knows what it is,Kevlar on the other hand is well known so it gets used without people fully understanding its properties.

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Permalink Reply by Lawrence E. Long on January 12, 2013 at 5:30am

Tungsten:   From one of my suppliers:  Kevlar has superior impact,tear and penetration strength than FG. Specific gravity of 1.45 vs 2.2 for FG Tensile strength 400,000 lbs /sq. in. vs 250,000 lbs/sq.in. for stainless steel.  Used for canoes, kayaks, racing shells- products requiring high strength and lower weight.  Don't know about the water "wicking"  but I doubt it is true-considering where it is used.

I have been confused most of my life- but still keep going along enjoying it.

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Permalink Reply by Joey on January 12, 2013 at 5:59am

Here is my plan of attack, please shoot holes in it if need be.

Outside bottom: 2 layers of 8 oz S-glass

Inside bottom: 1 layer 5 oz Kevlar, 1 layer 6 oz E-glass

Sides: 6 oz glass inside and out

Chines: 6 oz 6" followed by 4" inside and out. Have had one        suggestion to go to bi-axial tape on chines. Any support for that over e-type? 

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Permalink Reply by tungsten on January 12, 2013 at 9:14am

Joey,regular woven FG tape has 2 layers(toes) i think there called, 1 running along the length and one going the width so 0 being the length and 90 the width.So when its used at a seam the 0 follows the seam not doing much as for strength,the 90 crosses the joint.With biax 45/45 so one layer on top of the  another.This tape is much stronger since both toes,cross the joint.The tape because of how its is stiched also goes around curves better without the pucker.

There are plenty of boats built with the standard woven4- 6" tape on there seams.It still works just harder to work with and not as strong for the same weight as biax.If you can get your hands on some biax for a resonable price then i would say doit.But if you already have the woven tape then thats OK too.

Permalink Reply by Phillip Westendorf on January 12, 2013 at 6:42pm

Joey,

From where I am sitting you have a very workable plan.  Seems like it'll be plenty tough to take on what most rivers will throw at you. 

I'd keep going as Tungsen says, including the homework on Kevlar.  Keep us informed and post some pics as you go along.

G'Luck

Dorf

Permalink Reply by tungsten on January 12, 2013 at 9:51am

For those interested give this a read,

http://web.mit.edu/roylance/www/allred_83.pdf

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Permalink Reply by Rick Newman on January 12, 2013 at 10:16am

Tungsten, even with four college degrees the MIT paper is tough reading. For those that want a less difficult but still informative treatise on materials I found some info from Fiberglast. It also shows that Kevlar has a potential issue with water. However from the quick reading that I did I would have to suggest that the reduction in strength would be minimal and for most of the boats we are building of little consequence. Secondly for the rivers that Joey is boating he shouldn't have to worry. Perhaps when he is building his Grand Canyon / New River whitewater boat in a few years it might matter. 

http://www.fibreglast.com/product/the-fundamentals-of-fiberglass/

Joey, I think that your layup will be just fine, it will protect your boat and give you experience in working with the materials. Speaking of experience, how much river reading experience do you have? Your boat will be strong and a great vehicle to explore and fish. A big part of the experience of running rivers is learning to find your path, whether it be through the details of building your boat or your way down the river. Obviously each boat and each river will provide new experiences and adventures.

Rick Newman

Permalink Reply by tungsten on January 12, 2013 at 11:58am

Rick,agreed a little hard to read.But it confirms that kevlar does absorb water.A simiple google search of "does kevlar absorb water" will also confirm it.

Another search of'" kevlar and plywood"  will give some interesting reading.

 

Permalink Reply by tungsten on January 12, 2013 at 12:28pm

Rick i got your message,not sure how to reply,i'm not use to the way this forum works.So i'll respond here.

I understand the properties of kevlar.The point i'm trying to make is its use on plywood and weather or not there is any benefit.

From what i've read it has no use in a wood boat other then add weight and make your wallet lighter.

 

Joey.Sorry for hijacking your thread,i thought it was a good topic for discussion.

Iff you do use the kevlar ,please read up on how to apply it as its different then FG.

Permalink Reply by Joey on January 19, 2013 at 3:05pm

Well, 

   I learned a valuable lesson today. I was by myself working on the boat today as usual. I layed out my kevlar which took 2 pieces because of the width I had. Because my topsides were already stitched up it made layout extremely difficult. I rolled up the cut kevlar on a cardboard tube once i had the pattern cut out. I put on a layer of epoxy and rolled out the kevlar on top. WOW!!!! It didnt even come close to going down the way i took it up. I tried brushing out but nothing i did got rid of bubbles or the fact that i was taking the 90 degree weave out of the fabric. Ultimate result: i pulled up the kevlar after the complete wet out process. I will have nothing on the inside of boat as far as any cloth is concerned. I dont have the money to keep making this mistake. Will my boat still be ok with only glass on the outside??

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Permalink Reply by tungsten on January 22, 2013 at 5:52am

Sit back, take a deep breath,drink a beer.Your boat will be fine.

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