Building a high performance whitewater kayak- going to need some help

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#1

Hey guys!

I tried posting a thread in the newbie forum, but it hasn’t gone through. :o

I am working on a pet project I have been researching and planning for a few months and could definitely use help with from experts. I am completely aware of the risks, and learning curve when working with composites, and will be working my way up to a large scale infusion through a couple of basic but practical projects leading up to the boat.

My single biggest issue has been on selecting a layup. Originally all whitewater boats were actually glass and kevlar garage projects, where you would rent the mold and build your own boat. In the early 90s advances in plastics moved the sport away from composites, but in recent years as we, like other sports, are pushing the limits we have returned to composites for lightness, stiffness of composite boats.

I am very much a tinkerer, and pick up new skills pretty quickly. So far though the information is daunting and pretty confusing I have been able to sift through it pretty well and have a pretty good idea of where I am headed.

As of right now the industry standard seems to be a carbon/kevlar with core layup. I am just trying to figure out the best lamination schedule for my project for a durable and high performance hull. (Remember this boat will occasionally hit rocks).

Plain weave Kevlar would be the logical outer layer for abrasion and impact resistance, but if I am going to make/ own an carbon boat I am going to be flaunting it with a visible outer layer of twill carbon.

I was thinking about doing 6oz twill Carbon (0*), 6oz twill (45*), core (what would you reccomend?), and then 2 layers of Carbon Kevlar Hybrid for the hull. To save wieght I was just going with C/K/C with core key areas for the deck. I change my mind every time I think about the layup so that part is still making me very nervous and I am sure shows my unfamiliarity with the materials.

Thoughts? Any help would be awesome!

Oh and what is freestyle kayaking you ask? Here is some footage from last week in WV:

[ame=“http://www.youtube.com/watch?v=NDdpSEMiUFE”]YouTube - New River Dries[/ame]

Ben is paddling a composite (Infused C/K with core) boat and you can clearly see him explode off the water on impact with the green water. For comparison the design is the same as the blue/white boat.

#2

Sorry about that Kayakdude. This forum as heavy anti spam filters for new users but the restriction drops quickly. A couple more posts of yours might be filtered depending on the content but after that everything will work.

#3

Thanks. I think at this point everything has gone through, but I am not getting any responses.

Can someone tell me what they think of my planned layup and give me an idea of what a good core material would be?

Also is there a reason that no one uses male molds? I am not casting a complex form, and I would save myself a lot of labor and cost by vacuuming at least the hull straight to the plug. This is going to be a one-off so the mold would be scrap anyway.

#4

male molds leave the outside an unfinished surface… you could however finish it but would create more work.

best thing is to make a mock up and make good quality molds that reflect the shapes you want…

your laminate schedule sounds good using carbon and kevlar. using a core definately has its benefits.

as far as engineering this project i suggest you go to youtube and look at what guys are doing when making their boats.

if you model after a boat you have already there is no need to build a plug… you can mold off it. hope this helps a bit.

#5

That does help!

How rough a surface is it really going to be? I was assuming that a few layers of clear coat and some buffing and I would be good to go.

I am pulling off a boat that I own, however I am going to be altering the shape with clay to remove indents for unnecessary bolts and handles as well as changing some contours to soften hard edges since I have read that those are weak spots and are risk areas for bridging. This also allows me to sufficiently alter the shape to avoid legal issues, and tailor it to my personal taste.

The issue is that like most other industries no company is willing to make public thier layup, and no two are doing the exact same thing. Some offer full carbon and carbon/kevlar options, but that is about as much as I can gather other then from photos. I am otherwise winging it.

Is it overly ambitious of me to go more or less straight to infusion? My logic is that it allows me the most control to set myself up perfectly without committing if something doesn’t go as planned. I can take my sweet time and do a pressure drop test before mixing the resin, reducing the chance of a mishap.

Thanks again!

#6

i dont recommend infusing on the first try either… but you will need to use vacuum for sure to get any performance outa this project.

a good plan would be to go ahead and make molds of the top and bottom. its pretty easy to do and can be done fairly cheap. specially that you have something to go off of.

then join them. easier said than done. but you can easily do this if you approach it right.

#7

Yeah that is the plan I am just trying to make sure that I am not going the long way about things.

There is a xxxxpit rim to consider here which means that the hull has to be done either in two parts fused together, or in 1 part out of a 2 piece mold. This is the 2 piece method- not really a fan. I would rather spend my time making an extra flange and do a two part mold then deal with this mess.

The plan is to lap-joint the two halves of the boat- add a rim to the hull which makes it wide enough that the deck will just fit straight into it instead of having to spend hours trying to align and tape the two halves together. Then I will just glue them at the seam and apply a few layers of kevlar tape from the inside.

#8

you got the right idea…

thing is that cawkpit ring looks to be two pieces with a black seal at the joint. im thinkin 3 molds… top and bottom halves and the ring.

dont think you really have to get too much into putting kevlar at the seam. there are plenty of adhesives that are super strong for a mate like that.

there is a real easy way to do a slip joint and it involves using sheet wax. that way you dont have to engineer a mold and all that mess to accomodate the mating surfaces.

the sheet wax goes on one mold. then the laminates get layed over the wax thats placed along the rim of the mold. when the half cures the wax comes right off and there is a relief where the wax was that the other half slips over.

#9

Man I wish I had taken some pics from ben’s boat, but the above method shows an overly simplified xxxxpit rim in my opinion. In a plastic boat the curve looks more like this:

The full curve works to give a better seal to the skirt. If I don’t have a good seal I will be leaking water at a good clip, ruining any weight gains I started with. By casting the deck in two halves going down the length of the boat I can perfectly mold the rim as is for my final piece and safe weight on the final part.

The kevlar tape is a last line of defense from impact. I noticed that Ben’s boat which used the same technique was missing quite a few chips at the joint, which could be potential leaks if not sealed from the inside.

Dallas you are the man! Do you have a link or more info on that wax technique? That would be a major time savings!

#10

um… not really… its a trick of the trade.

you can buy sheet wax any where and its very cheap. the blue kayak has a negative contour on the rim… that would require advanced tooling…

shoot for three molds.

the thing with sheet wax. is to match the thicknees of the sheet wax to the thickness of the laminate. for a flush overlap

#11

lets see some progress on your part with this build and im sure more people will get involved in helping you… there is alot of very very skilled fabricators in here and some very knowledgable people as well. alot more so than me im sure of that.

good luck and keep trucking… man.

#12

I am picking up the boat for the plug Sat. Then the fun will begin.

#13

I am in the process of getting my materials in order to start molding the boat. My plan is to start by casting and infusing a few helmets, and maybe make a wakeboard before I go to the boat.

The single thing that is the most frustrating right now is a lack of a workspace. I can’t find an indoor space that is clean and dust-free that isn’t also the intake for a central air system. Hopefully something will come together when I move in a month.

Also does anyone know of a good writeup on how to do a gel-coat with an infusion?

#14

Since your plug is another boat. I don’t think your going to want to try infusion for making the mold. I just think that would be asking for trouble. I don’t even know where to start on making a flange that would be able to handle vacuum. The plugs I infuse are all machined out from Ren tooling board, which allows me to machine the flange into the plug. Once I have a plug that can handle vacuum…

[ul]Tape the perimeter off, this is the area you will stick the double side bag tape too. You don’t want release agent or surface coat here.[/ul]
[ul]Seal and release coat.[/ul]
[ul]Spray Gel or Epoxy Surface coat and pull the tape off carefully then let tack.[/ul]
[ul]Now you can stick your bag tape to the clean perimeter.[/ul]
[ul]Layup… Glass or Carbon, peel-ply, flow media, spiral wrap, and vac bag.[/ul]
[ul]Pull vac, do leak test, leave vac on to boil off any remaining moisture. I only wait 20-30min. I have heard of others waiting hours… :wondering:[/ul]
[ul]Mix resin[/ul]
[ul]Infuse[/ul]
[ul]Cure[/ul]

Done!

#15

Nice! Sounds pretty standard, although taping the flanges before spraying I somehow hadn’t thought of yet.

Another thing I just wanted to throw out there just in case: No matter how much I baby the plug boat it is going to get scuffed up a bit and I will need to do some buffing for a perfect mold. Should I just do what I can with the boat and spray a little extra gel coat before laying up the mold so I can polish out any imperfections? We are talking very small scratches from rubbing on the bed of my truck here.

#16

As long as you took proper steps there would be no problem infusing that. You just need a good flanging material such as MDF or other ridged material, and make sure you seal it good against the plug. Duratec after will fill micro purosity and pinholes. And when you lay the surface coat or gelcoat for the mold you seal it even more. Obviously you should do a vacuum check before getting to that stage, but its not that difficult over all.

#17

I’ve been working on choosing an epoxy system. I’ve been looking at marine grade systems, but does it really make a big difference? West Systems is a name I know, but I have also been looking at MAS. Anything else anyone can recommend?

#18

If I do infuse a mold is it worth looking into an epoxy specifically made for the job like ToolFusion? http://www.resininfusion.com/toolfusion.html

Also how sturdy would my flanges need to be?

#19

well it depends what type of mold you are making, high temp ones you would want to use a infusion resin specifically designed for tools with repeated high heat cyles. A regular VE or PE or epoxy would be sufice for the standard room temp(or slightly higher) molds. As for the flanges they should be sturdy enough that they wont move and crack, creating a leak. Biggest thing with infusion is very good vacuum integrity both in the bag, but also the plug/mold. Best to do a vacuum check first on the plug/tool before.

#20

Thanks Hojo!

Still trying to decide on an epoxy. I need something that will be tough, clear, UV resistant, and be able to deal with being immersed in water.