Vacuum Bagging - an experiment in cheapness

[Ross Leidy]

I let the pump run for about 5 hours, shut it off, and let the paddle cure overnight. In the morning, I removed the bag and the peel ply and then rough-trimmed the excess glass. A few hours later I popped the paddle from the mold. Overall, it turned out pretty well - only one small void that I fill later. I'll do another layup sometime this weekend.

Ross

[stumpy]

Looks great, Ross, I'm currently trying to figure out how to vacuum mold a coaming I have the form for, but have yet to try laying it up, ideally in graphite, for skin boats. So far, all I have is the form, layed up in plwood, and would be able to lay it up bt hand, but I'm thinking the vacuum approach would make things easier, and better

[Ross Leidy]

Okay, rope caulk is not the right product for sealing a vacuum bag. It works fine for sealing the tube to the bag, but it's just not sticky enough to use to seal the entire bag. Butyl tape would have been better, but I didn't have any of that lying around.

After my failed attempt with the rope caulk, I reverted to duct tape. I switched to a different roll once my green tape ran out. The new roll was stickier and worked better. Also, I found a roll of thicker plastic and used it this time. I felt that the thinner plastic might either be somewhat porous or could be developing small leaks from rubbing on the work surface. For whatever reason, the thicker plastic worked better. The seal was good enough that the pump was able to achieve the target setting of 21" Hg. It's cycling at 15 seconds on, 8 off, so there's still a leak somewhere. I spent some time trying to track it (or them) down, but didn't have a lot of luck. It was much better than the first go, so I just left it as-is.

Ross

[Seppy]

That really sucks Ross......

sorry, I just had to be the one lol.

SO...taking orders? Looks like you are a hairs breath from a very repeatable little setup there good buddy.

Looking forward to seeing the final product.

Rick

[Seppy]

I meant to mention, if you can get hold of a reasonable stethoscope..$20 job..you can track down those air leaks quite quickly.

Oh, and play Doctor in da house.

[Kayakkev]

This may not work, but we test windows for hurricane strength this way.

Put in a scrap piece of plywood, vacume it down, and then swab different areas with water using a slop rag. Start at one end and work to the other. If needed flip it over and do the same.

if you cant see where the water is coming in thru the plastic, then carefully open the bag and the plywood will be stained in that area.

KK

[Ross Leidy]

I took the paddle halves outside to dress the edges in preparation for gluing them together. I clamped an 8ft 2x3 in the Workmate and used that as a work surface. A bastard cut file worked great for removing the excess that was left by the rough utility knife trimming.

The first half I bagged with 1 layer of carbon and 6 layers of 6oz glass. After it came out of the mold, I thought it felt a little too flimsy, so on the second half, I used an extra layer of glass. To balance the two, I applied a final layer of glass to the first half. This I didn't bag, and you can see the difference in texture below (matte - all bagged, shiny - last layer not bagged). The difference in weight between the two halves is about 1oz. This is at least partially due to the hand layup on the last layer and possibly due to the higher vacuum I was able to achieve on the second half. Still, not too bad, the total weight of the two halves is under 26oz.

A stray strand of carbon found its way into the mold on the second half. The irony of this is that on the first half, I found the some on the interior and thought I better be careful on the second one that none get stuck on the outside. I checked as I was laying that first carbon layer, but it eluded me. With judicious use of the tip of the utility knife, I was able to scrape it off. On the finished paddle, the scar shouldn't be noticeable.

The minicel plugs are sound dampeners that Duane describes on his site. These add a whopping total of 0.04 oz.

I hope to do the glue-up tomorrow.

Ross

[Seppy]

You've made it look too easy Ross. I'm really looking forward to seeing the finished paddle.

What are the rough measurements?

[Ross Leidy]

You've made it look too easy Ross. I'm really looking forward to seeing the finished paddle.

What are the rough measurements?

So far, the hardest part was working through the issues with getting a good seal on the vacuum bag. Now that I've got two paddle halves, the rest *should* be smooth sailing.

I built the plug based the paddle shape specified in Brian Nystrom's book (http://greenlandpaddlebook.com/. It's got sharper edges than the Holst paddles I've built before. I'm anxious to see how it performs - it should have more lift.

I kept the length the same as my Holst paddles - 87", but I stretched the loom just slightly. I think it's about 19-1/2", but it's been so long since I made the mold, I'm not sure. I'll have to check. The tips are about 3-1/4" wide.

I thought of the stethescope idea, and I know my wife has one she keeps in a box of toys for visiting kids. She was out of town when I needed it and I couldn't find the box on my own, so I'll have to try it next time.

Ross

[Crashmo]

Maybe I have to wait for the next installment. I'm anxious to see how you join the seams. Any glass layer on the inside or out?

Duct tape!

Maybe this is why I failed shop class.

[Ross Leidy]

Maybe I have to wait for the next installment. I'm anxious to see how you join the seams. Any glass layer on the inside or out?

Duct tape!

Maybe this is why I failed shop class.

Yeah, I'm not sure duct tape is quite the right choice. Although the silver duct tape and black carbon would look good together.

I'll be joining the halves pretty much as Duane describes on his site: http://rollordrown.com/kayak/gstick.html. I'll use some slightly thickened and black-tinted epoxy right on the edges, and then bias cut glass strips straddling the seam on the outside.

Ross

[Ross Leidy]

The glue-up went quite well, although the fast hardener I used was a little too fast for me. By the time I got through painting the edges with slightly thickened epoxy, the remainder in the cup was already turning into a hot, solid puck. I had to mix a second batch to make a much thicker batch to make a 1/4" wide fillet in the very tips of the paddle for strength. Sorry, no pictures of that.

I used thick, doubled rubber bands to clamp the blades together - this was tight enough to provide good contact, but not so tight it squeezed the joint dry. The loom was sufficiently rigid that I could use a few spring clamps to hold it together.

I used a pair of mixing sticks clamped on either tip to help align the blades and ensure that the seam didn't have any twist along its length.

The edge closeup shows the color and consistency of the squeeze-out. I used a little graphite so that the seam would disappear and a bit of fumed silica for gap-filling and adhesive properties.

Next - sand and glass the exterior seams and fill a couple voids.

Ross

[Robin Boys]

Absolute Magic. I'll send my address so we can test it out
Robin

[Ross Leidy]

Absolute Magic. I'll send my address so we can test it out
Robin

Me first!

[Ross Leidy]

Tonight, I filed/sanded off the squeeze-out, washed off the mold release film, and applied some bias-cut glass strips to the edges.