Thread: Goat Island Skiff
23rd May 2008, 04:48 AM #76
Howdy Larson! And Welcome!!!
You really won't need the extra thickness. Half Inch is way overkill - it will end up weighing the same as all those other boats that you didn't buy the plans for!
12mm will be Eight times stiffer than 6mm. Not double - but eight! and the chines - the only place it can possibly break will be the same size anyhow (but they won't break either)
Nice thing about the Goat is that built as per the plans it is a reasonable weight for two adults to handle on the shore. Increase much at all an it all becomes a big chore.
And of course the sailing performance won't be the same either.
If it makes the difference between building or not building the boat then go for the thick stuff - providing the rest is the plan spec. But if you want a thing less ordinary - build it as per the plan.
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23rd May 2008, 08:55 AM #77
To satisfy yourself, fix a piece of 1/4 ply to a timber frame about 18" square (that's more than the biggest span on the GIS), put a pair of steel capped boots on, and TRY to kick a hole in it. DON'T do it with elbows, you'll break bones.
When the ply is contained by the structure, it is immensely strong, and there's no risk of it puncturing from a human falling on it!
I agree entirely with Michael regarding the weight too, you may not be disappointed, but you'll never know what you are missing out on.
23rd May 2008, 02:14 PM #78
I love the pics and video of her sailing but do you have any of her being rowed or motored? and how many hp? She appeals.... and the GF says she doesn't want to sail on her own so a GIS is looking better than 2 PDRs'....
Hell I wish the shed was happening.
23rd May 2008, 04:05 PM #79
Dave's boat was used for a year or two in this configuration before he built the rig. He may pop in and correct me, but I think he had a building project on one side of the lake and it was the barge? Mik?
I don't have any pics rowing, but use a pair of 9' oars and it rows very easily. I used to (haven't for a while) row regularly from our place for about half a mile to a low level bridge, once under it I'd rig and go sailing out in deeper water. It's all a bit of good fun really. Usually I carry a couple of others with me and it's no effort at all.
Mik's done that solo a few times too, he may care to comment from his perspective.
23rd May 2008, 05:27 PM #80
As far as the robustness of the GIS's bottom you might like to read this from my web pages.
Can the GIS carry a load?
From Leigh Hemmings on Scotland Island
Hi, from Scotland Island.Today we used our light fast and pretty Goat Island Skiff as a concrete, blue metal and sand barge. Previous days have seen it used as a timber barge -- powered by an electric outboard!. When not in this guise it's main role is our commuter boat. But, once our renovation is a little further down the track, our Goat Island Skiff will once more become light fast and pretty sailing craft. Trust you are well and enjoying life.
More on Motoring
The boat balances quite OK if there is someone else in the boat to sit on the front seat with the driver on the rear seat. When by yourself the boat will balance better if you make up a tiller extension for the outboard so you can sit on the middle seat.
A tiller extension for the outboard can be made of plastic pipe to fit over the outboard tiller.
What sort of Outboard works OK
Not too big - you won't go any faster and it might put too much load on the boat.
Perhaps you can use a slightly larger outboard, but generally outboards don't take too well to running at low revs all the time - and it is another heavy bit to carry round.
Be aware too that outboard weight is a whole field to itself. Generally a manufacturer will use the same engine as the basis for 2 or 3 models. So you may see an three different horsepower outboards all with about the same weight - ie they all use the same block and other internals.
So do some checking before buying.
23rd May 2008, 05:58 PM #81
23rd May 2008, 06:16 PM #82
Remove the pin and you could turn a 6 into a 9.9 or a 9.9 into a 15.
I believe motorcycle fiends turn this into an artform - anyone want to get a moped up to 100kph?
23rd May 2008, 08:47 PM #83SENIOR MEMBER
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- Portland, ME USA
The Torqueedo electric outboard would be a great fit for a family in a GIS
Any one tried it?
RE: Robustness of bottom> not cheap but some folks in the Pacific Northwest laminated Kevlar onto the bottom of their dories for ultralight abrasion resistence of the bottom plank. I've never laminated with Kevlar.
Last summer I became a yawl advocate after a local Raid event at Woodenboat. I think the mizzen makes life very simple. What about adding one to the GIS, offset of course...just a small 9-11 SF or so one that will get the boat to point into the wind, heave to when necessary. I'd envision the mizzen to be used for longer sails or with new crew to help "park" the boat to deal with issues, reef underway, or just have a drink. Maybe you guys could comment on a mizzen. It'd add no weight to the hull...should change the CE negligibly, I would think with it being such a small mizzen.
24th May 2008, 08:53 PM #84
Kevlar is awful to handle - the midge once built a 30ft cruising racing cat of the stuff.
I've used a bit and it is a pain - hard to cut, hard to wet out, impossible to sand.
Exactly the qualities you need to avoid abrasion. But it is massive overkill.
If you have mostly sandy beaches or soil and grassy edges - no problems ever. Concrete ramps are no problem either - particularly if you put some brass strip on the bottom skids. Midge did that with Gruff and geez it sounds awful when this beautiful timber boat gets dragged up a concrete launching ramp!!!
If your shores are rocky then my feeling is light glass does almost as good a job as much heavier glass - but remember that most goats have had no glass. The epoxy coating is enormously flexible and can handle all sorts of knocks without cracking and seems to stop most surfaces from "digging in".
We have been using 2oz (75gsm) for some boats where the plan specifies 6oz and found that it provides an awful lot of protection.
As far as yawl GISs. I like yawls too (refer Beth), but two sails would add about 60% to the cost of the existing rig - and the GIS is very stripped out - I have taken pains to keep stuff out of the boat. Which is why it is so light and has so few pieces.
Also adding a mizzen means the centreboard has to move further back or the main mast move further forward. Both are bad choices.
One will make the boat pitch more in waves - at the moment it is quite OK because the pitching from the mast being in the bow is damped adequately by the flat bottom (that's something people never mention when they worry about whether flat bottoms work - even catamaran design is heading the same way with much flatter sections under the bows - mostly to damp pitching as well) and moving the centrecase moves the seat too far back forcing the crew too far back in the boat. REally bad for performance.
Could do it starting with a clean (metaphorical) piece of paper - but the goat is a goat is a goat.
24th May 2008, 09:11 PM #85
Torqeedo looks like a nice unit
This one is also positive, but I find the claim doubtful. He is using the torqeedo on a 35ft yacht (a light and narrow one for sure, but still 35ft) - I think he is talking about zero wind conditions. Against a wind and sea I suspect he would be sailing. But there is a review on use on an inflatable at high speed and low speed which sounds quite believable in terms of drain.
25th May 2008, 02:38 PM #86
Michael, with the price of fuel going through the roof at the moment, especially for those of us who live in the country, a boat like the lovely GIS whch can be used under sail or with a small outboard looks more and more appealing. As her designer, what horsepower motor do you recommend? What changes need to be made to the boat to accept a motor? I don't know how she would go when pulling the cray pots but she looks as though she wouldn't be too bad for sneaking around for a few Sweep and she appeals as camp/tourer for the Murray where a shallow draught is getting more and more essential.
25th May 2008, 07:30 PM #87
Nice to run into you again! I'd be very surprised if you could use more than just a couple of horsepower on the goat. Leigh Hemmings who sometimes uses his as a gravel barge (!) generally gets by with a 2.5 or 3hp four stroke (I almost typed three stroke). Much more and efficient low speed hullforms want to stand up on their tail. You can see this a bit on pic above (transplanted to here)
The pic is one of my USA builders for the Goat David Graybeal. Even a couple of horsepower can be pretty effective - you can do 3mph in a calm with oars quite easy. So the mechanical horse will do a lot better.
In general I would probably not think of sailing with the motor on the back. It would probably be safe ... but ...
And it would raise the centre of gravity a bit - and it would already be up with the mast in place.
27th May 2008, 10:53 AM #88SENIOR MEMBER
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- Portland, ME USA
27th May 2008, 12:22 PM #89
The transom, though it is quite thin is heavily braced by the top stiffener and two big knees. It also has the rear seat supporting the middle section. The stiffener up the middle is just somewhere to clamp the outboard (David Graybeal put it to the side) and also to transfer load between the stiffener and the rear seat.
29th May 2008, 08:01 AM #90
I have nothing of value to add to this discussion, but I had to post anyway.
DHL just dropped off a box of epoxy and tape from Duckworks. I've got confirmation that my sail is being made (also by Duckworks) and will be available within a few months. I've found a local source for high-quality Greek okoume ply (US$110/sheet due to the recent fall in the US dollar -- ouch!!). And I've cleared space in my garage for the build (a monumental archeological undertaking involving several days of work and multiple trips to the dump).
In short, by the time my son is out of school in a few weeks, we should be ready to begin construction on our GIS. I can't wait.
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