C-Forum

Could someone tell me the proper technique for installing a new outside seam tape on a composite boat. The original tape was coming up in many places so I have removed the entire thing. It easily pulled off in one piece.

I have both fast and slow West System epoxy and enough bias Kevlar tape (1.5" wide I think).

Thanks,
Matt

Being able to pull off the seam tape with little difficulty is a good indication that the outside seam had not been properly prepared (not sanded enough) in the first place. There may be lots of installation methods. The following is what John Sweet taught me when I was at Penn State 20 years ago.

Measure the width of your seam tape and place two lines of glass strapping tape from bow to stern each equidistant from the seam line (above and below) with the space between 1/2" wider than seam tape. Glass strapping tape the is relatively clear tape that has fiberglass threads running down its length (the kind that you can't tear easily with bare hands) that is often used for securing packages. This tape is much more durable than masking tape and the reinforcing fibers will be helpful in holding the tape together in later stages when you go to peel it off.

Take coarse sandpaper and sand heavily between the tape (heavy enough to go through the gel coat and into the fibers of the first layer underneath - you need to expose the fibers to get good adhesion - this is what was probably NOT done when the original seam was installed. You can also use a sanding disk for this task, but watch out - if you do, you'll need a light touch as the sanding disk can cut through layers very quickly.

If you've done your sanding job well, you've probably nicked the tape in several places with the sandpaper. Run another line of tape overtop of each previous tape, but extending another 1/8" in toward the seam (covers your nicks along with the thin line of hull and deck that you didn't sand because you were trying not to make any nicks). Make sure that the inside edges of the tape are pressed down thoroughly on the hull and deck as you don't want any resin to get underneath.

Cut your seam tape to the precise length needed. If you are doing a two-layer seam, one layer should be narrower than the other to minimize stress risers. When doing a two-layer seam, I usually sew the layers together once down the middle with a sewing machine to make it easier to keep them aligned and apply them together. However, Kevlar is much harder to wet out in multiple layers than glass so you might want to apply layers separately for a multi-layer all Kevlar seam.

Prop the boat up on the opposite seam so that the seam your're working on is exposed on top (make sure boat won't move when you work on it); we'll be doing one side at a time. Place lots of 2-3" lengths of masking tape lightly on the hull and deck from bow to stern where they will be easy to grab for use in the next step. Double the number of pieces of tape you've just laid out (you won't have time to put out more when you need it). Cut long strips of plastic about 6" wide in enough quantity to run more than length of the boat. I use white plastic garbage bags because the plastic is thick enough to handle well without breaking and the white is easy to see air bubbles through. A clear plastic of similar weight would be good too, but don't use black! Lay these strips, and everything else you'll need close at hand before you mix your resin.

I would use the slow West system, at least for your first seam, until you are sure that you'll be able to work fast enough to manage the faster mix. My seams have all been vinylester, so I can't comment on whether the fast West system gives you enough time to install an entire seam on one side. There's nothing worse than have the resin go off on you before you've got the seam fully down. If you wish, add pigment to your seam such as those that you can get from John Sweet. Mix up enough resin to be sure of being able to wet-out the entire seam; you don't want to have to stop in mid-installation to mix more.

Apply a layer of resin to the entire seam from bow to stern. Apply the seam tape carefully. Wet-out the seam tape thoroughly (apply multiple layers if you're doing more than one). As soon as the seam is applied and wet-out, strip off your gloves and grab the first strip of plastic. Strength a short end of the strip across the seam and tape it on deck and hull. Then work down the length of the plastic strip stretching across the seam and taping it to deck and hull as you go. As you go, press the stretched plastic down onto the seam and force any air bubbles and excess resin to the outside, onto the strapping tape. When you finish one plastic strip, start the next overlapping 1-2" with the previous strip. Once you have encased the seam in plastic from bow to stern, go back over it to work out any last air bubbles or pools of excess resin before it gels. If you have a problem with a plastic strip tearing, just stretch another one over top.

TAKE A BIG SIGH OF RELIEF if you've finished this job before the resin has gone off.

After the seam has cured, pull the plastic and masking tape off. Then pull the strapping tape beginning at one end. If you have a particularly thick pool of resin or a stray strand of Kevlar that's been pushed over the edge of the tape, you may need to carefully cut it with a razor knife before pulling past that spot.

Repeat this procedure for the other side.

Admire your handwork!

John,

Thanks for the quick reply and all of the details. I plan to try it tonight. Also two more questions.

1). Approx. how long does it take to do each half (to help judge which epoxy to use)?

2). Is it ok to work outside in the carport (~35 degrees F) and when finished move the boat inside (~70 degrees F) to let it cure? Will this affect to integrity of the cured epoxy?

I would like to use the fast epoxy if possible because I want to paddle on Sunday.

Thanks again.

Matt

Matt,

John's description is perfect. The only difference is that I just use Handy Wrap or Glad Wrap to cover everything. I start from one end of the boat and run the roll all the way to the other end. I then stretch it from side to side and tape it using masking tape. To get rid of the bubbles I cut little slits on top of the bubbles but always in the same direction. I then roll everything with a wallpaper seam roller.

I always use West Systems fast curing hardener. It still sets up slower than Vinylester. Working outside in colder weather might make the resin too stiff to wet out the cloth properly. I've always had plenty of time to make a triple seam at 70 degrees.

Jim

Matt:

I'm not sure that I've ever timed it, and I have to say that I haven't done a full outside seam in several years. I would probably guesstimate about 20-30 minutes per side for the actual layup, assuming that you've prepared and laid out all your materials carefully. Check your West System literature, the difference between fast and slow curing may impact pot life more than the overall cure time, but I haven't used the slow cure enough to recall clearly. With vinylester, you can easily control cure time by the amount of MEKP you use, so my experience with relative speed of curing vs. West System fast cure is exactly opposite to Jim's (i.e. when doing finicky work like an outside seam, I tend to mix a slow batch of vinylester to ensure that it doesn't go off too early).

If you decide to use the fast curing epoxy as Jim indicates he does, then just be aware of the state of your resin. Typically the pot will go off first. If you see this happening, you know that you have only a short time before the seam gels. At that point you'll need to quickly assess how much of the seam you can completely finish before it gels and abandon anything beyond that. You don't want it to gel in half finished state as then you'll just have to grind it off and start over.

Jim's suggestion of Handiwrap should work fine and might be an even better choice. However, I would use the practice of slicing the wrap to release air bubbles as a last resort. In my experience it is preferable to retain the integrity of the plastic and just move the air bubble outside the seam and onto the strapping tape. Only if you can't do that (e.g. too little resin, seam beginning to gel) should you cut the plastic.

I agree with Jim's assessment. Cold will slow down the gel/cure rate, but 32 degrees might make the resin too viscous to wet-out easily. You could try a small test batch just to see, but if you attack the seam without a test, Iwould at least move it into a garage with some space heaters to bring up the temperature somewhat. Certainly you'll eventually need to bring it above 60 degrees for a good cure.

John

You have received very high quality advice in these posts.

This thread is a good candidate for an archive on how to build or repair composite boats. If only Walbridge had had such clear instructions to edit for his Boatbuilder's Manual!

I would only add the following:

Since surface preparation is the most important part of a good seam job, and the part that takes the majority of time (and makes the most mess in your shop) being in a hurry to paddle this weekend sounds like a mistake to me.

Working with cloth and resin in 35 degree weather is just looking for poor results in a seam job. You need at least 60 degrees to properly wet the cloth, especially Kevlar. You can sand outdoors, but layup inside with plenty of heat and ventilation. Use heat lamps to obtain a cure. Allow a week for the stuff to cure before using it on the river.

Slap some duct tape on if you have to paddle sooner, or if the seam line doesn't leak, paddle it "naked." Just remember to let the boat dry out for about a week before you try to seam it.

Hey, hows the weather in BC.

I haven't gotten to paddle the "Cream Sickle Atom" since we spoke.

If I ever need a repair, I am calling you. HOw about that boat we spoke about????

Chuck

I'll add a few things:

First, I reccomend taping off the entire deck and hull with masking tape (or masking tape and plastic) to prevent any drips, smudges, etc of resin from getting on them while working.

I've always used the fast epoxy and never had a problem with it going off. the batches needed for seams are usually pretty small

If you have lots of ugly bubbles, wrinkles, etc in the seam after you pull off the plastic (ie, you didn't get them out before the epoxy gelled), you can sand it down a little bit and then paint on another coat of epoxy for a nice smooth seam. But If you just use kevlar tape, it'll fuzz when you do this and make your life miseralbe, so if you want to try this, add a layer of glass over top.

Has anyone tried perforated release film (for vacuum bagging) to tape down the seams? It seems like it would work pretty well, leave a good finish, and make it easier to work out the air bubbles. Just a thought, I haven't tried it.

Jeremy

I ran into two problems with the seam this weekend. First, I only ordered half as much kevlar tape as I need. And second, I underestimated the amount of preperation work envolved. I did get it masked off and about half of it sanded down. I just had to take a different boat out Sunday. Now I can just take my time and do it right. I think I'll use the slow cure epoxy just to be sure.

Thanks again for everyones inputs. I let you know how it turns out.

Matt

I have always used a layer of Handi-Wrap over the seam. To minimize tears while removing air and excess resin (with my hands) I lubricate the seamline with hand lotion.

If a tear happens anyway (usually when stretching the plastic film real tight to get rid of the "wrinkle-ridges") I just recover the area with another Handi-Wrap layer.

Minimize the number of pieces of plastic used on each seam. Pay attention to removing wrinkles once all the air bubbles have been moved to the tape lines.

Have some heat lamps available to get your mix to go off when you are satisfied with the job. About 18 inches away from the seam will be about right. You want about 120-130 degrees to set things up. Avoid more heat by monitoring things while the lamps are lit. You can burn the boat pretty badly, to say nothing about your shop/garage/basement/home!

Thanks to everyone here on Cboats.net, my new outside seam is curing. It was more work than I imagined, but it looks like it'll turn out ok. It's not really pretty, but I think it's strong and won't leak.

I followed the above instrunctions as much as possible, but also had a few detours.

I sanded outside and did everything else inside as it just got cold (28 degree F) here in Dallas.

Since I had to order more tape I got some black pigment as well. I like the way the black seam looks.

I decided to do all of the seams at once (right, left, front and back) with one piece of tape. This is how the seam was taped orginally. I did this with the boat upside down on a table.

I masked everything with straping tape, per the above instructions, and used an random orbit sander with 50 grit paper to prepare the surfaces. Even with the sander it took about 3 hours to sand down to the cloth. The gelcoat or whatever it was on the outside was very thick.

Next I cleaned the seam.

Next I filled a few voids with thickened epoxy.

Then I brushed epoxy on the prepared seam.

Then I layed the tape down on the seam. This was easier than I thought it would be.

Next I wetted the tape. When wetted, the tape really layed down nicely and stayed put even around the four corners. About 3/4 the way around, I notice my epoxy was starting the get a little thick. I quickly mixed up another small batch and finished wetting the tape.

Now I stretched the saran wrap across the seam. At first I was taping it in place, but I noticed the saran wrap would stick to the hull and deck without the tape, so I finished without using tape.

Next I tried to work the bubbles out. I think my saran wrap was a little to thin or my epoxy got too stiff because I had a hard time getting the bubbles out without deforming the wrap. I finally decided to leave the bubbles and fix them later. I also had a lot of wrinkles.

I waited for epoxy to get stiff (like hard rubber), but still tacky and then I took the saran wrap off and brushed on a coat of thickened expoxy to fill in the bubbles and wrinkles.

Now, since I had a pretty thick coat of epoxy on the masking tape, I decided to only wait for the epoxy coating to gel (instead of fully curing) before removing the masking. This worked as the masking came off easily and the seam line looks nice.

Looking back, I would only do one seam at a time and prop the boat up on edge and I would used stronger plastic wrap (like trashbags).

Matt

I practice veterinary medicine for a living and often do fiberglass repair on horse hooves. I use to use Saran as a cover for epoxy to be able to "trowel" it smooth and work out the bubbles. I have recently swithced to mylar strips and they are far superior; much stronger, doesn't wrinkle and is just as transparent. I haven't used it yet in boat repair but certainly will in lieu of Saran because my last job ended with the Saran coming apart before I had all the wrinkles smoothed out. I don't know if Sweet's carries the Mylar or not, but any farrier supply will have it and it doesn't cost much more than a roll of Saran.

Matt:

One of the reasons that I've always used the trashbags instead of Handiwrap is because it's a little heavier and less prone to wrinkles or to getting tears as you work out the air bubbles. Mylar might work well, too; I've never tried it. You can indeed sand out the wrinkles after the fact and then, if needed, paint the seam with a final coat of resin to eliminate the sanding marks. Getting out air bubbles after the seam gels may be a bit harder. If they are merely surface bubbles in the resin, you should be able to treat them like wrinkles. However, if the bubble is imbedded in or underneath the seam tape, as is often the case, then sanding through the seam tape in that location is the only way to remove them. This of course will weaken the seam at this location and leave a void that needs to be filled.

You've identified one of the solutions should you do this again: tackle the job in halves so that you can give the bubbles more attention before your resin gels. The other solution is to make sure that you've applied enough resin to have some extra to move around and fill the bubble. Unlike the original layup of the hulll and deck when building the boat, where you want to have only enough resin to just wet-out all layers without any extra, on an outside seam you want some extra resin to move around and then enough time to move it (and the bubbles) onto the strapping tape so that the final seam has "just enough" resin and no bubbles.

Also, if you find stray resin on areas of the hull or particularly the deck (because it doesn't get stratched as often) that you didn't sand, you may be able just pop them off with a putty knife. Frequently stray resin won't adhere well if you haven't prepped the surface first.

Hope the seam works well for you!

John

Thanks John.

It seems my bubbles are all on the surface along with the wrinkles. I did use plenty of epoxy. I think is looks pretty good, but I may sand it a little to make it a bit more smooth. I can't wait to get home to see how it looks cured.

Matt

Yesterday, after the seam had fully cured, I masked off each edge of the seam with tape and sanded it smooth with 200 grit sandpaper. I never got into the Kevlar tape.

After I removed the masking tape and cleaned off the dust, it looks pretty good.

I definitely think it'll stay put and I do like the black color.

I'll see if it leaks on Saturday.

Matt