Materials Selection - Fiberglass keel in female MDF mold?

[Jeff in Boston]

External keel surface = 10 sq feet.

I need to cover an additional 8 square feet to cover the exposed keel slot. So 18 sq feet.

 

[fallguy]

The keel slot is already formed up?

1.1 yards epoxy at 350 oz is only like 25# of materials

what am I missing

 

[Jeff in Boston]

You can see the keel recess on another P26 here: Keel and Keel Bolt Photos - Pearson 26 (pfeiffer.net)

I was calculating as if the whole thing was solid fiberglass.

I think you are about right that 25 lbs for the keel at 3/8" thick (and lets say another 25 lbs) to fill in the slot gets us around 50 lbs.

As for as no structural requirement, a keel this shallow will have very little side load and tensile load. It will almost entirely be in compression when sitting on the hard or a trailer. As I'm not trying to keep this light weight I can just go "way overbuilt" and I'm not worried.

 

[fallguy]

2 yards fabric at 7 layers is 175 ounce glass and 175 ounces resin@ or 350 ounces glass and 350 ounces resin or 3 gallons

 

[Jeff in Boston]

Thank you for your help on this!

 

[fallguy]

You'll probably be able to intertwine the csm and the canoe glass; this will reduce your resin to glass rate and improve the laminate. For example, a layer of csm would take quite a bit to wetout. But the follow on wouldn't take much.

I made a female mould for a very similar layup with hardboard. I made a flange for mine; perhaps different. The beaching keel mould had nice fillets in the bottom and was coated with duractec. Then waxed and sprayed with partall. Seven layers of 1700 and one layer of kevlar buried inside. A little more like 0.300".. Mine did get a little resin rich..but it was really hard to keep the resins from moving down the sides, so, be warned, you'll want to put some pieces in the bottom only; they take up the running resins

 

[Jeff in Boston]

Thanks!

If I want to use epoxy to glue the whole thing to the bottom of the (roughed up and acetoned) hull, should I put a layer of waxed polyester on the top of the keel and let it cure fully (and sand / dewax) before I use the epoxy?

 

[fallguy]

Thanks!

If I want to use epoxy to glue the whole thing to the bottom of the (roughed up and acetoned) hull, should I put a layer of waxed polyester on the top of the keel and let it cure fully (and sand / dewax) before I use the epoxy?

I would think that is needed. I don't use polyester much, but for any epoxy bond; you need no wax and mechanical key...40-60 grit.

 

[Jeff in Boston]

Makes sense.

Anybody got any suggestions on a good supplier for laminating resin? Total boat is $58 a gallon. Hi bond boatyard resin is $40 a gallon at Defender.

 

[Jeff in Boston]

I'm a doofus. Concrete would be a much better ballast. Denser, cheap, and I can pour it in one shot.

 

[comfisherman]

Bit of a resin shortage on resin at the moment. Deferring my larger projects until October in the hope that it resolves. Grateful for ordering as much as I did in 2020 in preparation.

40 a gallon isn't terrible retail currently. Obviously in larger quantities its better. My supplier isn't taking new customers, rumor is the other 2 major west coast are also only servicing existing customers. Tough time to need a lot of composites at the moment, it can go either way last fall it was the cheapest I've ever bought.