C17 in New Zealand.

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TomW1
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Re: C17 in New Zealand.

Post by TomW1 »

Please fill your compartments full of foam. Water condensing in your air space will be more of a problem than water getting into a compartment than is a properly sealed one. Make sure what ever foam you get is 2 part polystyrene and your Coast Guard approved. You would need a 4 gallon kit for a 1600lb displacement as listed in the study plans. Drill limber holes at the back of the compartment to drain to the center compartment which will then be pumped out by the bilge pump. The center of the frames should all have limber holes to drain water to under the motor well, this should be shown in the plans.

The foam will probably over fill the compartments as it expands. No big deal, just cut it off even with a saw.

Regards, Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

OneWayTraffic
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Re: C17 in New Zealand.

Post by OneWayTraffic »

Thanks all for the thoughts. The boat will be trailered, and never spend more than a day or two on the water at a time. Usually 3 or 4 hours, then weeks on land under a tarp or cover in a reasonably but not always dry climate. With hatches open and ventilating. If anything water vapour would be more of a concern in foamed compartments without limbers or inspection ports. I do want enough foam in the right places to ensure level preferably upright flotation which means above the floor if possible.

It's good to know that foams have moved on. Most the horror stories are to do with old boats, or poor workmanship. But it would bother me that I can't check. I'll think about it while glassing the inside.

TomW1
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Re: C17 in New Zealand.

Post by TomW1 »

OneWayTraffic to obtain upright flotation you need to add flotation under the side decks. Build a box frame to hold the foam, and then add the top to it after foaming. I don't remember how wide the side decks are on the C17 7 or 8 inches but 17' x 12" x 2" x 8" is 3264 cubic inches for x2 both sides or almost 4 cubic feet. As you can see I used 8".

With the foam beneath the sole this is enough to keep the boat upright. You still need the foam under the main deck, this is supplementary to it to keep it upright.

I hope this helps. do not worry about the foam under the deck. Make sure you have done a good fiber glassing job. Some of the boats that have been built by other builders are 24 years old this year. Make sure as I said before that you have a place for any water to go to another compartment through a limber hole. That is the secret to a dry boat. As I recall there are limber holes in all of the center compartment frames

Well I hope this helps you out.

Regards, Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

OneWayTraffic
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Re: C17 in New Zealand.

Post by OneWayTraffic »

That's pretty close to what I was planning. Great minds and all. :D

OneWayTraffic
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Re: C17 in New Zealand.

Post by OneWayTraffic »

Inside glass is almost complete! I have some bubbles to drill and fill from frames C and E today and Frame A to tack into place. Front of Frame B, I had done one of my best glassing jobs in the morning, only to have the sun come out and blow bubbles in it for me. :lol: The outside of the hull is gray epoxy and warms up nicely with the sun on it. I mucked around with trying to push them back into the gelled epoxy, then drilling and injecting but in the end, the SOB tool with a carbide blade and some patches of tape were the go.

I've just started my 4th batch of 24L epoxy. That's 72 litres used, and the BOM stated 60L. :doh:
I wonder if that's got something to do with building two transoms, 3 sets of stringers, double glassing then stripping half the hull once, light glass to the sheer, slightly more glass inside than specified or my first time fairing efforts? At least it's not all extra weight in the boat. I'm glassing the sole as well, and will probably use light glass on all interior surfaces so I doubt that I've ordered my last batch of epoxy. :D

I've sorted the plan for inside drainage. Five compartments under the sole, no limbers under the stringers. I have limbers cut in all frames except the sides of frame D, as I didn't preplan for that. Instead I'm running with inspection ports and rubber plugs, Bung down the centreline. All plugs and inspection ports will be protected from rain and other nuisance water. I'll about half foam fill the compartments with block foam and use that as extra support for the sole. I'll also put some very small permanent vent holes in unobtrusive places forward in the cabin to equalize pressure inside and out.

Only about a month of decent boat building weather to go, though I should be able to get some things done in Winter. Ordered some fast hardener for that.

I'll get some photos up on my phone in a minute.

OneWayTraffic
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Re: C17 in New Zealand.

Post by OneWayTraffic »

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OneWayTraffic
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Re: C17 in New Zealand.

Post by OneWayTraffic »

Spent a while mucking about with Ubolts. I'd read an old thread where Cracker Larry had made a drill jig on a 2 by 4, and clamped that to get the holes, so I tried it. Holes in transom were great, so I overdrilled to 13mm (0.5") and filled. Then used the jig again but couldn't get the holes right. Either the jig slipped, or I'd screwed up something, maybe in the overdrilling. So I got out the holesaw, drilled them all to 25mm (1") and tried again. Used the drill jig to put holes in scrap and fitted the Ubolts into them. I put hose and tape over the Ubolts to leave a wider radius. Then clamped into place and filled around the Ubolts. I'll remove tomorrow, fill the rest of the way with a Gflex mix around the bolts. Tape as a release agent so I can remove for painting.

Also drilled the front UBolt. No worries here yet, though amazed at the thickness of the hull on that front curve. 18mm thick!
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Dan_Smullen
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Re: C17 in New Zealand.

Post by Dan_Smullen »

Looking neat and clean!

I’m surprised the C17 has 2 stringers rather than 4. I assumed the C series boats were scaled versions of each other.

OneWayTraffic
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Re: C17 in New Zealand.

Post by OneWayTraffic »

Dan_Smullen wrote: Sat May 01, 2021 8:16 am Looking neat and clean!

I’m surprised the C17 has 2 stringers rather than 4. I assumed the C series boats were scaled versions of each other.
It's not so neat if you get close to it. :D I'm planning to have a sand and tidy up, then coat with tinted epoxy everywhere before I get the sole on. Not needed, but I'll feel better about it.

I have plans for several boats in that size. They all have two stringers: FS17, OB17, PG20, C17. The OB17 has a third central stringer. The C17 panel size is small enough I think, same hull thickness as the C19, but 10% smaller width. The skeg acts as a third stiffener down the keel, which is already thick and strong. Also less weight, and HP leading to a bit less speed. I doubt I'd go faster than 25mph for the most part.

To be honest I was thinking about putting battens down the middle of the panels on the inside or strakes on the outside as stiffeners. Now I've got most the boat structure together I really don't think it's needed. As you pointed out on your thread, this is the strongest thing I've ever made. Only thing I'd like to do differently would be to use 9mm bottom ply rather than 6mm. That's because I took so long to glass it the 6mm ply went a little out of straight, and I used a lot of putty and time fairing it. I don't know how bending 9mm would have gone, but I would have tried.

TomW1
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Re: C17 in New Zealand.

Post by TomW1 »

Do not worry about it, Jacques already over designs his boats. :wink: They will take a kicking and keep on ticking. :lol: A PH15 took a log all the way though the hull and upper deck and made it home just fine. Just use the glass called for 12os not 6oz, Biax not flat.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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