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Re: Strip: Seam strip fiberglass
By:Laughing Loon CC&K
Date: 9/18/2017, 8:43 am
In Response To: Strip: Seam strip fiberglass (Aaron Potter)

I put fiberglass tape on one of the outside seams between the deck and hull and I'm not happy with the results. The weave is very evident on most of it, so much that from a distance it looks like cloudy patches. The tape is 3" wide 6oz tape. The temps yesterday were in the 80's and I had a light on the MAS resin and slow hardener. The mixed epoxy was noticibly thinner than when I had applied in my basement at cooler temps. I put masking tape on both sides of the seam, applied a thin coat of resin, rollled the tape out then applied resin to wet out the glass. When the wet out coat was still tacky, I used a box cutter to cut the glass to the masking tape and applied a fill coat. The cut edge turned white as I was peeling back the cut edge and didn't go clear with the fill coat. Now I have a wide semi-cloudy strip with two white lines.

I'm sure the 6oz tape didn't help. It seemed thicker than the 6 oz cloth I used on the inside of the kayak. I've read a lot of posts about getting a clear finish on the boat and I tried to follow that advice. I have two questions:

1. How do I avoid this on the other side? (unfortunately the other side is the one that got too much heat in one spot when I was repairing an issue inside the hull so it will have an obvious repair visible on it)

2. If I decide not to live with the seam as it currently appears, how do I go about removing the seam tape. I'm assuming I would have to sand it away without sanding into the cloth on the deck and hull. Is there a better way?

Few people understand that sheer clamps and laminated stems where used by some builders, without a second reinforcing layer of fiberglass, to avoid cloudy looking second layers of fiberglass at the stems and hull deck joints.

#1 Don't heat your resin and hardener with a lamp or water bath.

You have no control over just how hot the resin/hardener will be. If it's hotter than 80˚ it will cure faster than anticipated and will not have enough time to wet-out the glass fibers for good transparency.

Don't use seam tape. It has finished edges and just doesn't work as well as the glass used for the rest of the boat.

MAS epoxy cures in half the time of System Three. This is why I use System Three for all my exterior glassing. I use MAS for interior work where speed and transparency are not an issue.

Nick seems to do okay with MAS on his boats but I'm not sure whether and how he does his stems and hull/deck joints. Perhaps he'll chime in on this.

I use 5" wide strips of non-bias cut glass straddling seams with 2" masking tape on each side. This allows me to cut glass for seams off my 60" wide cloth so I only need a few pieces. Wider seam glass helps hold the glass tight across the joint when wet-out and makes trimming and lifting the waste easier. You must wait for the epoxy to cure to a very firm leather hard stage before cutting/lifting the waste so the epoxy is not torn away from the glass fibers as you experienced. Since MAS recommends applying new coats over a tacky coat this is a problem with using MAS since you would have to wait beyond this stage to trim the glass and then sand the epoxy before applying fill coats.

You can see how I do my seams in this video -
https://www.youtube.com/watch?v=60FGkJ4iArY&t=205s

#2 You may be able to remove the bad seam glass with a heat gun but you'd have to be careful to not overheat the underlaying glass. Or you can sand it off using 60 grit in a ROS.

In either case close attention and finesse is required to keep from damaging the underlaying wood.

Messages In This Thread

Strip: Seam strip fiberglass
Aaron Potter -- 9/17/2017, 5:49 pm
Re: Strip: Seam strip fiberglass
Laughing Loon CC&K -- 9/18/2017, 8:43 am
Re: Strip: Seam strip fiberglass
Jay Babina -- 9/18/2017, 3:31 pm
Re: Strip: Seam strip fiberglass
Aaron Potter -- 9/20/2017, 9:28 pm