Chine reinforcing

[Dsoc]

I have sanded my 1965 Sunfish hull and ground the bad spots on both chines. Everything looks good I took a look inside and it is dry. I would like to reinforce both of these areas after the initial repairs are completed. This is at the widest spot on both sides. My plan is to gelcoat the top and the Hull. Any suggestions are appreciated.

 

[mixmkr]

Youtube, these forums and dont look back.

 

[LVW]

I have sanded my 1965 Sunfish hull and ground the bad spots on both chines. Everything looks good I took a look inside and it is dry. I would like to reinforce both of these areas after the initial repairs are completed. This is at the widest spot on both sides. My plan is to gelcoat the top and the Hull. Any suggestions are appreciated.

I gather you have openings so you can see inside.

Since the chine area is commonly damaged and could use more strength, I'd add strengthening materials before you start "initial repairing".

Fiberglass battens are frequently suggested, but I'd consider sections cut from "donor" Sunfish. (Usually, when I find a "donor" hull, I end up restoring the entire Sunfish!)

Add a wire or screw to act like a handle, lather with resin, and pull tight with a bungee cord. This can be done in conjunction with layers of a conventional cloth (or tape) repair, but you'll wish you had three hands!

(For the latter reason, I use "slow-set" catalyst).


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[Nicholson58]

If you can get to the interior then use glass and epoxy from US Composites on line for all of your fillers, reinforcement, epoxy. There is a tutorial posted on this forum for separating the deck and hull so you can repair from the inside. Otherwise, grind, layup, fair, longboard from the outside. I use US Comp sourced 3-M micro balloons as filler for fairing compound.

scarify the interior to get a good bond.

I use only US Composite 635 THIN resin. On line purchase. Buy the dispensing/measuring pumps. Excellent wet-out, slow cure, long working time, zero blush so multiple layers are easy. soap and scrub clean up but wear gloves. I get 9 mill pro gloves at Harbor Freight, durable and affordable.

for your repair I would apply serious layers inside. Use a 1” throw away chip brush for mixing and applying. Use the brush to smooth out the patch and to exclude the air. Pre-wet the surface before the first layer. Pre-cut all planned patches before starting. You can buy glass tapes in various widths Or cut to fit from cloth.

when the inside is done, flip the hull, grind a tapered depth into the broken old fibers maybe 2 inches either side of the crack. Fill with glass mat and epoxy. You can promote a smooth finish by pressing a thin polyethylene film sheet onto the surface. Stretch the film flat and painter tape the edges to make the film stay flat. If you do this carefully the surface will be nearly glossy when the film is pulled and near net shape. Work the air out. Later, If you need fairing, mix in 3-M micro balloons from US Composites to a stiff creamy consistency. Easy to long-board.

cure time on the resin is 2-3 days for sanding. I said it was slow. Working time is 2-6 hours depending on temperature.

 

[LVW]

As to polyethylene film, it seems most "plastic films" won't stick to one's repair (and will work). For example, ordinary grocery bags will work. I save the stiffer films from Breyers ice cream, as those stiff films give an automatic smooth finish--with less handling. Depending on the repair, you may have to eat a lot of ice cream!

The above advice to "Pre-cut all planned patches before starting" is an important consideration.

But cutting the glass will take the sharp edge off your good scissors. I buy cheap $1 scissors at Dollar Tree and re-sharpen them on my bench grinder. (Approximate the angle). You'll have created two very amateur coarse edges, but these "reclaimed" scissors will cut through fiberglass cloth even better than the new ones!

In a pinch, I've used a knife sharpened in the same manner. Stretch the cloth across a narrow seam in your picnic table and saw away. No picnic table (?) use a narrow seam in your sun deck.

 

[Nicholson58]

The bags you name are polyethylene. Most plastic bags are PE. There are some films that become permanent and would need to be sanded off. My favorite is high density PE if I can find it. It crinkles like cellophane but is immune to glue while retaining a bit of stiffness.

Your fix for cheap scissors is good and yields a similar edge to serrated. I’ve done this with a right angle grinder and flap wheel. Whatever, the serrations prevent the glass strands from slipping along the edge. This pair has lasted me years without resharpening. They are also great for cutting the spines off lion fish