Building a Carbon Fiber Forespar

After researching several ideas and building methods I’ve finally settled on a method and materials. The plans call for 6-foot long 4inch diameter aluminum un-stayed pole. 3 feet of the pole is inside the hull in a sleeve and the half is forward of the bow. Looking at several mast sections I found the wall thickness about 2.35mm I also find it easier to work in millimeters for the math.

Speaking with my NA the general rule of thumb is to go 30% over for Carbon if you do not want to spend thousands of dollars in mechanical engineering and testing. Simple math rounded up to 2 decimals gave me a 130% wall thickness of 3.06mm I went ahead and gave it a 150% factor of 3.53mm as my target wall thickness or .139-inch or just about 1/8” in a reasonable fraction. So I’m looking for a total lay-up of Carbon / composite of 1/8’” around a 3” - 4” molding surface.

I looked around for different type of material to build the mold such as aluminum, cardboard, foam, fiberglass, and PVC. The mold could be sectional several pieces, split two pieces, and solid - I thought about it a lot. I started to look for material and read all I could from others on tube building. I spoke to many people and each had their own idea some have built tubes and some have not, some have built boats some have not, some just like to give free advice and tell you how to do it they are the real jewels! But I listened to them all got to love it! The most enlightening conversion was with Kevin Cook on his method, wound fiber cord by hand and shrink tube. Written material was an article from West Systems here is a link to the article: http://www.epoxyworks.com/26/pdf/Building_composite_tubes.pdf I took a little from each plus my own spin. My final decision is a mold of a single piece of 3.5-inch schedule 80 PVC pipe. Schedule 40 is the type that you find at the local building supply stores - schedule 80 has thicker walls and you have to go plumbing supply houses to find it. Back to the math this pipe has an OD of 4 inches and a lay-up skin put me about 4-1/8 inches just about where I want to be. One reason for PVC is I usually never see Epoxy stick to unscuffed plastic.

I found a site www.sollercomposites.com/composites/carbon that sold the heat shrink tube and carbon sleeves like the “Chinese finger torture” toys. This is the material I decided to use to for my lay-up. I visited the site from my saved favorites and reviewed the supplies, then called and had a nice informational talk with the owner of the company. Looking at the tech sheet and my chat I had an idea of the size material to use, the stretch, fiber orientation, shrinkage, and ect…. I bought 30 feet of 5 inch Carbon sleeve that will give me 5 lay-ups plus more. I will be pulling the 5-inch diameter cloth down to 4 inches so it will "grow" in length up to 30% so I'll see what the real streach will be. I will have 1 lay-up of E-Glass on the outside for abrasion and impact to protect the Carbon. I also picked up 7 feet of the heat shrink plastic.

Now for the Lay-up I will make sure the tube is smooth and waxed with mold release. I will use a skin of the 3M film, then a thin lay-up of the 200 gram unidirectional carbon fiber most likely do two wraps and smooth it out with peel ply, then let it kick. Then I’ll give it a twist to see if it floats on the waxed PVC, if not I’ll cut the lay-up lengthwise and then it will twist. I’ll leave it on I just want to make sure it is not stuck. Once that is free I’ll be assured that it will not stuck to the tube. A light sanding and clean the blush then I’ll be ready to lay-up the sleeves wetting them out as I go. If I need a little more thickness I may do one unidirectional wrap in the middle of the sleeves Once it is wetted out I slip on the plastic heat shrink tube. Start heating in the middle and work my way out to the ends. The heat shrink tube acts the same as vacuum bagging. Each layer of carbon sleeve is rated at .53mm thickness the fiber sleeve is. 28mm. I figure I will get 5 – 6 layers of carbon and 1 fiber. I’ve ordered the composite materials I just need to pick up the PVC tube from the supply store now.

As usual I’ll take pics and post it on the web. I need to make the tube and sleeve for the tube with the Starboard side of the main hull as it gets molded into the hull. This will also be a test for the process because I need to make a 10’ boom and two 17’ connecting beams.

Later.

Last edited by TheManShed; 01/14/10 10:07 AM. Reason: changed link for carbon sleeves

Mike Shappell
www.themanshed.com
TMS-20 Builder
G-Cat 5.7 - Current Boat
NACRA 5.2 - early 70's