JEM Watercraft

Ordered plans for the Sabalo 12 this morning. Time to replace the Malibu Mini-X I (stupidly) sold before moving to Atlanta. The -12 should be a big improvement though. Few questions about it:

1) 4mm ply vs 1/4" - Is the 1/4" going to be too thick? I have an okay source of decent 1/4", at a price cheap enough that I could build two kayaks, but obviously it's not worth the cost savings if I can't bend the parts. For that matter, would 4 oz glass suffice or should I still stick with 6 oz if I used 1/4" ply? Worst case I go over to AircraftSpruce and pick up four sheets of Okume.

2) Resin quantity. I've done some limited glass work before, so I'm not totally new to glassing and resins. I noticed that the standard Sabalo calls for 1.8 gallons, vs. the two gallons that the -12 requires. Why the difference? I also noticed that on the study plans the 15' Sabalo doesn't list glass cloth as a requirement. Was there a design change where it was decided to glass only the -12 and not the original, getting only a resin coating instead? I would assume at a 4mm ply thickness you would want the additional protection from the glass. Which brings me to...

3) Protection. Most of my yakking takes place in north Florida. Oyster bars, shallow water and winds abound. My Mini-X had about 300 cuts, some pretty deep, in the hull where it blew over and dragged across oyster bars. I'm not sure a graphite coating would provide enough protection. How about a few yards of kevlar? They weren't a big deal on the plastic kayak, but I'm nervous about breaching the glass layer and exposing the wood to saltwater. I'm leaning towards a complete kevlar coating on the hull, doing the topside in standard 6-oz glass. If I can get a wet-on-wet kevlar on glass layup on the hull then I may go that route instead. I don't want a cured base layer and only achieve a mechanical bond on the kevlar. I may even graphite on top of that, since I'm not building a stripper and I will probably end up painting everything above the waterline to get the added UV protection. Maybe some SeaDek as well.


I think that's it for now. Sure I'll have many more questions once things start to kick off. Great designs on here. Look forward to building this one.

Any thoughts on this stuff?

http://www.aircraftspruce.com/catalog/w ... iteply.php

The 1/8 inch is what we call doorskin, some have used it on boats, but if anything besides air and water touches the hull, there might be trouble.

The quarter inch would be nice, but wow, that price!

1) 4mm ply vs 1/4" - Is the 1/4" going to be too thick? I have an okay source of decent 1/4", at a price cheap enough that I could build two kayaks, but obviously it's not worth the cost savings if I can't bend the parts. For that matter, would 4 oz glass suffice or should I still stick with 6 oz if I used 1/4" ply? Worst case I go over to AircraftSpruce and pick up four sheets of Okume.

6mm might be tough to bend on the bottom panels. If you use full glass coverage with 6 ounce, the hull will be heavy.

2) Resin quantity. I've done some limited glass work before, so I'm not totally new to glassing and resins. I noticed that the standard Sabalo calls for 1.8 gallons, vs. the two gallons that the -12 requires. Why the difference? I also noticed that on the study plans the 15' Sabalo doesn't list glass cloth as a requirement. Was there a design change where it was decided to glass only the -12 and not the original, getting only a resin coating instead? I would assume at a 4mm ply thickness you would want the additional protection from the glass. Which brings me to...

I switched to listing 2 gallons because no one is going to go out and but 1.8 gallons. The quality of plywood has declined a lot, even in the few short years between the sabalo 15 and 12 release. So I switched to recommending full glass coverage.

3) Protection. Most of my yakking takes place in north Florida. Oyster bars, shallow water and winds abound. My Mini-X had about 300 cuts, some pretty deep, in the hull where it blew over and dragged across oyster bars. I'm not sure a graphite coating would provide enough protection. How about a few yards of kevlar? They weren't a big deal on the plastic kayak, but I'm nervous about breaching the glass layer and exposing the wood to saltwater. I'm leaning towards a complete kevlar coating on the hull, doing the topside in standard 6-oz glass. If I can get a wet-on-wet kevlar on glass layup on the hull then I may go that route instead. I don't want a cured base layer and only achieve a mechanical bond on the kevlar. I may even graphite on top of that, since I'm not building a stripper and I will probably end up painting everything above the waterline to get the added UV protection. Maybe some SeaDek as well.

E-glass or s-glass will be a lot easier to touch up than kevlar. Kevlar needs vacuum bagging or judicious experience fighting resin into it. Do some research on mixing in graphite for the bottom coats. A lot more effective.

Kevlar is more beneficial against puncture rather than scrape and scuff. When it is used, it's most used on the inside of the hull, not the outside.

As for graphite coating.
You can make a tougher graphite coating by adding silica.
Only my final coat is epoxy graphite. The initial coats are epoxy, graphite, silica.
There are numerous "recipes" out there for mix ratios you'll run across on boat building boards.
I couldn't tell you what I use. It's like making biscuits. All by feel.
I get the graphite and epoxy mixed and start adding silica. Silica will also bulk up the mix some allowing you put down a wee little thicker coat as well.
Silica makes it hard and durable. You'll figure that out if you have to sand on it much.

Once done with the coats I'll start sanding it with a 600 grit and go up to a 1000 grit. Slicker than frog snot on a lily pad.
Reason for the high grit is the last coat is just epoxy graphite. It goes down thin. You'll sand right through that quick with the typical 120-220 grits and the lower grits also leave scratches.

Some folks leave it jet black but it mars easy. Sanding makes it real slick. It brings the graphite in play. The slicker it is the less damage you'll suffer from scrapes and gouges.
Here is how I visually explain it to people. Walk out to your clean car, put your index finger on the hood, apply pressure and push forward. Your finger will slide for a bit and grab.

Now walk over to the sanded graphite bottom and do the same thing. That finger just goes and goes. It doesn't grab. That is the protection that graphite offers.

My concern would be freshwater intrusion rather than saltwater. Saltwater has preserved the wood decking on a many a ship.