Jetski Hull Layup Schedule

General Composites Discussions Composites Talk
#1

my plug is almost done, then flange time and molds.

this post pertains to the layup schedule for the final part and whether to use a core material or not - would like to build the whole hull out of carbon.

i have one buddy who used 15 layers of 6k/11oz carbon fiber, alternating the weave pattern between layers. costly, but has held up for him. i have another buddy who used coremat as a core material, but he stated after a few seasons it started to delaminate inside the engine bay.

others i have spoken with who have worked with core materials (i personally never have) said stay away from a core material for the bottom of the hull for fear of delamination. i was thinking of using 1/8" Divinycell though as i know one reputable builder is using it (wouldn’t say where/how), his hulls are SUPER light and strong (but he won’t give out his layup schedule which I totally understand as he is business to make money, I am doing this for my own personal benefit).

i know a lot of large boats use a core material, but most hulls are V shaped whereas this is more of a flat bottom.

i plan on building my first hull out of 12oz biax to “season” my molds and figure out the best pattern for the layers (that and it will be cheaper/safe to build as my first part and i have a layup schedule someone else has used that has worked for them).

after that i want to do the carbon hull. weight and strength are the two agendas here. i plan on vacuum bagging. infusion would be cool, but i do not have enough experience in my mind to jump to that.

wondering what weight fabrics, weaves, core material or core material?

i know the top and bottom with by completely different layups. the bottom is what i am most concerned with as it takes the most abuse, and the motor/pipe will be attached to it. i plan on building some test plates, but even with a small test plate, it is hard to know (for me anyway) how it will work on a much larger part.

thanks all for your time / input.

-Andrew

below are pictures of my hull before turning it into the plug:

#2

Hey, Nice hand warmer option…

Here’s a picture of my cheap gel coat gun, on the last post http://www.compositescentral.net/showthread.php?t=2509&page=4(it was actually free)I’ll get over to the shop and measure the nozzle.

Keep up the good work!

#3

Hey Mr. FX-1 Mafia Boss :cool:

I looked you up on here and saw that post of yours with the gun your using a week or two ago.

I have a cheap HVLP gun I was thinking of using - used it to paint a couple race bikes - leaves a lot of orange peel no matter how I set it up so I figure it would be a good sacrifice :rolleyes:

I have not ever used a pressure pot though…that is new to me.

I have a little bit of Duratec left I should throw in and shoot some test panels / see what happens.

-Andrew

#4

The 6k twill weave i use is 11oz weight i believe. It is about
.015" thick. With three layers i can make a part that will hold up the urethane bumper on a car.

Most composite supply places have a chart that states the thickness of each layer of cf. So even when you compress it with vacuum it will be that thickness. Like 3K 6oz is .009" thick. Figure out how thick you want your hull to be and that will get you how many layers of cf you need. I personally would use core material and that will cut down on how much cf is needed.

15 layers of 6K sounds like too much, but then again if your scraping the hull on the bottom of lake rocks… just add more layers of cf where the bottom will rub rocks. Saves weight, time, and money.

Hopefully that helps some. There is also a composite boat building forum online.

#5

While I can not advise on the layup sched, nor where/how to add core…i will say, if the bottom keel(?) does get physical abuse, add a layer or kevlar/vectran down there. You can, and maybe should add a layer of kevlar/vectran to the bottom somewhere near the surface (ie: if not surface layer, next next layer would do) This adds abrasion resistance. if you gouge the carbon 5 plys in, you are screwed. kevlar should prevent that.
Hardpoints should have NO core. Add up layers of carbon/glass/G10, even sometimes hardwood blocks to have mounting points. You can’t tighten bolts to a foam core area! In general, if you are going to have something mounted on the hull (even if a secondary bonded bracket), reinforce that area more. Also, make sure your resin has a high enough service temp for engine/exhaust areas. Don’t want to burn up the resin :slight_smile:

#6

that is exactly what i have been doing - adding the posted thickness to come up with a layup.

last night i laid up 6 or so test panels in all sorts of variations - can’t wait to get home and check them out! (is weird i want to rush home to checkout cured test layups? haha :p)

do you have a URL for this site you speak of?

yes, i will plan to use a layer of kevlar/carbon weave on the outside for this reason. one company in the industry is doing this on there carbon/kevlar visual hulls. The rest are primed and painted that they produced.

mounting and hard points no core - got it. i should have stated that in my last post - that much i do know. :huh:

#7

You forgot to mention to the folks here that the ski you have is powered with a 1000cc engine, basically 200hp on a surf board…:eek::eek: lol.

How’d those test panels come out?

#8

No! I’ve been late to class numerous times because I’ve stopped by the lab to pull out a part I laid up the previous day. One time I left class halfway through to check on a cured part before rushing back mid lecture. The suspense of seeing how a part turned out makes me quite anxious.

#9

Roo I’m very curious to know what you decided on. I am at the same point in my thinking through my schedule.