Thread: Son of Goat project

Originally Posted by woodeneye

Hi Mick

The beam seems to be spot on.

What about a smidgin more sail area? Maybe something like 85sq ft? Go for grunt

Also, with the skipper in place do you think the decks will drain to the cockpit? It's hard to tell.

Also, are the foils the same as for OZ PDR?

Howdy,

It is easy to add or remove sail areas to lugs drawn this way. Just by adding more at the bottom (or removing it in the case of reefing). Boat stays in balance quite well.

It is also a 12ft mostly singlehanded boat and has close to the sail of a Laser (which is a foot and a half longer. Woodeneye, you are a mad sail carrier like me - and here I am going against my grain and trying to be sensible! Ha

As far as water off the decks, there is a bit of guesswork involved and I haven't pinned things down quite yet. The advantages are that the maximum width of the boat is well back and the pitch doesn't change a lot when the boat heels so if the boat does heel the water should run back to the cockpit (mostly).

Also goat like ... it is fairly high sided for a 12ft dinghy so hope not much water will come aboard - just like its big daddy. The mast is also significantly lighter and I have tried to keep it out of the bow as much as possible so hoping it will be a pretty dry boat.

MIK

Originally Posted by MiddleAgesMan

Very very nice, MIK. He's a real Son of a...gun? Goat? If we build one will we have to learn to refer to it as a him instead of a her?

A question about the GIS/SOG rudders. The angle of the transom puts the bottom of the rudder out in front of the transom. Does that give you the same effect as a balanced rudder shaped to have some portion ahead of the gudgeons?

Not it doesn't MAM,

To get balance depends on the rudder blade going forward of the rudder pin line.'

As far as whether boats are male or female - I've put the fox in amongst the pidgeons there! But the USA has quite a strong tradition of giving workboats male names ... so I am you will be able to cope!

If you like you can consider it a case of me having a postmodernist shot at boats having a name or a gender. But I believe that as much as I believe postmodernism.

MIK

Hello,

Sitting at home recuperating from (kneehole) surgery on my left knee (third operation in one and a half years time so let's hope it will be working properly after this one) and having ample time to think about the SoG design.

Dimensions, sheer line and sail plan (also the sail area) look spot on to me.

Brian made a very good point about the internal layout and the lacking of a thwart in the middle of the boat. In the Goat the distance from the tiller to the mid seat is too big, unless having an extra long tiller, to have the helm comfortably take his/her seat there (awkward angle with regard to the tiller extension) and you have to move from sitting on the bottom of the boat just after the mid seat to the gunwale. The crew, if any, usually sits on the mid seat in most conditions and the thwart divides the boat in two separate cockpits: one for the helm and one for the crew.

Now coming back to the SoG, a similar layout as in the GIS for this smaller boat would allow the helm to sit on the mid seat if sailing solo (distance tiller-thwart will be a lot shorter than in the GIS giving a more or less normal angle for the tiller extension) and would allow the crew its separate part of the boat when sailing two-up.

There is of course one disadvantage: more volume in the boat as the flotation boxes will be a lot smaller as now drawn.

Looking at photos of Brian’s old scow, the internal volume of that boat is diminished a lot by boxed in side benches. These would complicate the build a bit and add some weight, but perhaps it could be a worthwhile idea for at least the aft part of the cockpit (up to and including the thwart)? The front dock would in that case have to be shorter but perhaps can be brought to gunwale level to increase volume of the front flotation chamber (like in the Eureka canoe)?

Just throwing around some ideas.

Best regards,

Joost

Joost, I hope the knee is feeling better. You didn't injure it watching the WC on a 3D TV did you?!

This is a great discussion, and some good thoughts put up.

I think there needs to be an early call from Mick whether the new design is for a dedicated single handed boat or one whose main purpose will be for singlehanded sailing with an occasional crew along for the ride. To me, the GIS fills the latter role.

Personally, I like the fact that the new design does not have a centre thwart, but I guess that might change as Mick thinks more about the market it will be pitched at. I like that it reduces the cockpit volume, so less water would be retained following a capsize. (Callsign would sure approve also????!!!!) It might eliminate a bulkhead too, but I’m not sure.

A gunwale seat that Joost (and I think Brian) have hinted at is another one to consider carefully. Of course a seat feature will add some weight, but a seat that continues around joining the front and rear tank tops might be worthwhile thinking about as an option for some folk. I would not choose it, but it would definitely suit someone like Brian and I can see the general appeal of it. This is entirely possible because it would be non-structural.

A drainage plan involving tubes would also be nice as this takes the hit and miss out of getting it right for builders who want to add tubes like Ralph did. However, getting it right the first time without building a prototype is a bit of a challenge. Maybe if the cockpit is kept small, a double bottom and a completely dry boat becomes feasible too without too much of a hit on weight?

Joost, you will be happy that the new boat won’t need such a long tiller! I’ve always had longer tillers as I’ve always been a sailor who moves around a boat, shifting weight a lot. Sailing dinghies in big seas requires this jumping forward to catch waves to surf down, and then quickly back again to keep the bow up down the other side and maintain the plane as long as possible. I had a reputation for off the wind sailing in big waves, and for me it’s always been one of the big thrills of sailing, so a long tiller extension is a necessity. On my GIS, my tiller extension extends past the back edge of the rudder stock. But for cruising I can see the need for a much shorter one.

Originally Posted by woodeneye

A drainage plan involving tubes would also be nice as this takes the hit and miss out of getting it right for builders who want to add tubes like Ralph did. However, getting it right the first time without building a prototype is a bit of a challenge. Maybe if the cockpit is kept small, a double bottom and a completely dry boat becomes feasible too without too much of a hit on weight?

I'm not so hot on double bottom. More work, more complications, more materials, and then there's the other set of complications that arise when repairs are needed to the hull.

Speaking of design and bottom,

Mik, why do you specify 6mm on the bottom and not 9mm ply, especially since you also advocate not glassing the bottoms?

I ask because I know that most plans I've perused usually specify thicker bottom ply pieces, whether a Michalak design or the CLC Dory and Skerry.

Besides weight, is there some factor to the design that you're looking at?

Just curious. As I'm sailing along the 6mm below me feels mighty thin and I keep thinking of those big ol' Maine rocks...

Originally Posted by Joost

Hello,

Sitting at home recuperating from (kneehole) surgery on my left knee (third operation in one and a half years time so let's hope it will be working properly after this one) and having ample time to think about the SoG design.

Dimensions, sheer line and sail plan (also the sail area) look spot on to me.

Brian made a very good point about the internal layout and the lacking of a thwart in the middle of the boat. In the Goat the distance from the tiller to the mid seat is too big, unless having an extra long tiller, to have the helm comfortably take his/her seat there (awkward angle with regard to the tiller extension) and you have to move from sitting on the bottom of the boat just after the mid seat to the gunwale. The crew, if any, usually sits on the mid seat in most conditions and the thwart divides the boat in two separate cockpits: one for the helm and one for the crew.

Now coming back to the SoG, a similar layout as in the GIS for this smaller boat would allow the helm to sit on the mid seat if sailing solo (distance tiller-thwart will be a lot shorter than in the GIS giving a more or less normal angle for the tiller extension) and would allow the crew its separate part of the boat when sailing two-up.

There is of course one disadvantage: more volume in the boat as the flotation boxes will be a lot smaller as now drawn.

Looking at photos of Brian’s old scow, the internal volume of that boat is diminished a lot by boxed in side benches. These would complicate the build a bit and add some weight, but perhaps it could be a worthwhile idea for at least the aft part of the cockpit (up to and including the thwart)? The front dock would in that case have to be shorter but perhaps can be brought to gunwale level to increase volume of the front flotation chamber (like in the Eureka canoe)?

Just throwing around some ideas.

Best regards,

Joost

I am still thinking about it all. Remember too I thought some time ago that I might do two 12ft boats using the same plan.

I kept thinking that the current goat owners find sailing two up quite easy but the boat can be a handful (and a lot of fun) singlehanded. So this version of the SOG is much more towards singlehanding with enough space for a second person.

Am still thinking about the layout though.

The only real observations I have about Joost's points (which are good) is that side seats add a lot of parts to the construction. And the aim of the original Goat was to minimise the number or parts. Two sides, three seat tops, a bottom and four bulkheads and not much else. So that is one thing I would try to preserve.

The second is more technical - that making the forward tank taller won't make any difference to the stability after capsize because the water inside the boat won't come up over the tops of the existing tanks. Tanks low down and out wide are what give a boat enough stability and less bailing when righted from capsize.

So continuing to think
MIK

Originally Posted by woodeneye

Joost, I hope the knee is feeling better. You didn't injure it watching the WC on a 3D TV did you?!

This is a great discussion, and some good thoughts put up.

SNIP

It might eliminate a bulkhead too, but I’m not sure.

That's what i am thinking through too. There is probably a bulkhead needed near the mast and maybe one at the front of the centrecase.

A gunwale seat that Joost (and I think Brian) have hinted at is another one to consider carefully. Of course a seat feature will add some weight, but a seat that continues around joining the front and rear tank tops might be worthwhile thinking about as an option for some folk. I would not choose it, but it would definitely suit someone like Brian and I can see the general appeal of it. This is entirely possible because it would be non-structural.

I have a really strong reaction to these sorts of seat. There generally tends to be most of a sheet of ply in them and also less knowledgeable sailors tend to think that everyone should sit at the back on both sides. So that infrastructure is created but it is not really suitable for use. I have thought about a C shaped mid seat, but I think it quickly goes back (for a 2 person boat) to a mid thwart for the crew and the helmsperson on the gunwale most of the time and occasionally on the floor.

A drainage plan involving tubes would also be nice as this takes the hit and miss out of getting it right for builders who want to add tubes like Ralph did. However, getting it right the first time without building a prototype is a bit of a challenge. Maybe if the cockpit is kept small, a double bottom and a completely dry boat becomes feasible too without too much of a hit on weight?

It is another half or three quarters of a sheet of ply by the time the other stuff is put underneath. One of the lessons from the RAID is that double bottoms almost double the building time if extensive. Poor Chris and Brian ended up with a simple looking boat that took a long time to build in that case. I think the labour that they went through could be reduced using cable ties and fillets to put the sub structure in place but then you add all the stringers to support the foot loads and it becomes quite labour intensive compared to the spareness of the Goat and hopefully the rest of its family.

I would like to achieve that if possible.

Great points - they are helping me think this through more thoroughly.

Cheers
MIK

Originally Posted by callsign222

Speaking of design and bottom,

Mik, why do you specify 6mm on the bottom and not 9mm ply, especially since you also advocate not glassing the bottoms?

I ask because I know that most plans I've perused usually specify thicker bottom ply pieces, whether a Michalak design or the CLC Dory and Skerry.

Besides weight, is there some factor to the design that you're looking at?

Just curious. As I'm sailing along the 6mm below me feels mighty thin and I keep thinking of those big ol' Maine rocks...

Perfect question. (leading to something of a rant ... enjoy!).

We use or used 4mm for raceboats in Australia. Even all our crazy skiff classes. Boats like the Moth dinghy before it went fully composite was down to 0.7mm ply except for the cockpit that was 1.2mm with some 2oz glass under so feet didn't go through.

The Jarcat 5 which is quite popular here uses 4mm ply with 2oz (75gsm) glass over the top. It is a substantial boat.



I would say someone has the thicknesses wrong in terms of strength and it isn't the Jarcat which has several hundred boats built.

It also shows that much kayak construction is hugely overweight with 4 or 6 oz glass over 4mm ply and some kit and plan producers saying that the glass needs to be on the inside too. Sigh.

Bolger pioneered the modern plywood sharpie style of boat and always used a good bottom thickness to help ballast it. He always made a point of that and you can see it on his larger boats. But look at his smaller boats and they are the same ply thickness all round. Usually 6mm.

Why? With a much smaller boat this extra bottom thickness has much less of an effect as crew weight is completely dominant and the 5 or 10 or 15 extra pounds of the slightly thicker bottom doesn't make much difference to the sailing apart from when you have to lift up the boat.

Thats another thing that is often not realised ... that a ten percent weight increase doesn't just mean that the boat is 10 percent harder to pick up. It might mean it is impossible.

From my own racing experience i know that manhandling a 170lb boat into the water takes three people to lift. A 140 lb boat requires two and I dont want to lift a boat onto a roofrack if it weighs much more than 100 lbs even with help. For a singlehander like a canoe or the PDR to get it down to 50 or 60lbs means there is a break even chance I can get it over to the car and onto it by myself.

Two people can carry a 140 lb boat but have to be really strong to pick up a 160 lb boat.

In each case less weight makes the boat much more useful and practical and more flexible in use. It also brings it into the point where you don't have to be hairy chested to get the thing into the water. When we got involved in the PDRs the current trend was to build out of 9mm ply and 12mm ply because of worries about damaging the boat and also the lack of torsional rigidity. We went to 6mm for the bottom and 4mm for the hull with built in buoyancy that made the boats utterly rigid. At less than half the weight. There were other light PDRs around at the time but they didn't push home the point.

With the Goat my objective was to get the sailing performance of a modern OZ sailing boat. I knew the 4mm would be kinda OK but require too much internal structure to support which would add too much labour. But I had realised by then from cutting up lots of kits over the Duckflat benchsaw (when I was an employee in the early 90s) that the best way was to support the skin transversely on the inside of the boat with the bulkheads (which also form a monocoque seat structure to give huge torsional rigidity). Then on the outside a pair of bottom skids (if needed) break the bottom up into very small areas. The Australian designer Murray Isles was good at that as well as Bolger.

the seat boxes also mean that the buoyancy is built into the boat.

If you look at most of the other designers they don't really use that approach consistently so they need to have thicker bottoms and I think they have never really looked around much to work out what the best practice is. I only really realized the lessons of the Jarcat structure about three years ago myself. But my instinct was in that direction already.So apart from the thinner ply lesson it also shows that having some glass is as effective as having heavier glass. Kayaks with two to three times the amount of glass compared to the Jarcat!?! I am left scratching my head.

If concerned about rocks I would put 2oz glass over the bottom to an inch past the chine so the glass tape can be eliminated. If you can damage that then i think it is pretty likely a heavier structure could have been damaged too. Dragging the boat across rocks should be avoided whatever the construction but the light glass would reduce the potential damage when it was accidental or unavoidable.

There are several designers that come from racing boat backgrounds or have some broad experience. Bolger, Welsford, Selway Fisher and you don't often see 9mm ply in their sub sixteen foot boats until the displacement is quite high.

Also I think that the point is not to build boats so heavily that there will never be any damage as this focus on about 1% of the sailing experience has such a drastic effect on the other 99% plus the handling on shore that it is a Devil's bargain. I think it is better to accept the likelihood of repair.

So that provides me with my context for design.

Best wishes
MIK

Would be great if the build could follow the Quick canoe style rapid build. Keep her as empty as possible. That would be bulkhead for mast holding up, and brace for dagger. Buoyancy bags can do rest and make hull completely open. Use upside down bailer bucket to sit on anywhere in the hull.

She could then be car topped. I car topped a Mirror on a Citroen Dyane, which has a canvas roof, for 270 miles when I came down south. Combi's are very expensive these days. Could the design include a simple trolley

Talking of bailer buckets, I read recently on the sailing canoe forums that a bucket hanging over the opposite side in the water can act as an anchor and help climb back on board.

Also, talking about Mirror dinghies, there is a great example to bench mark against. Plus Ian Proctor's flat bottomed 12' SigneT design.

So, absolute minimalism, as per Goat but even more so? I suppose as a designer you have to build in safety tanks - although non in QuickCanoe.

Brian

Brian,

I think what MIK tried to say in his earlier posts is that the internal structure is needed to give the boat its shape and to make it strong. The internal structure that needs to be in the boat anyway can than easily and without much weight penalties be used to make make flotation tanks that act at the same time as seats for the crew.

I like this approach a lot in the GIS: simple, effective and good looking with the bits of timber in.

My guess is that perhaps to much consideration is given to the buoyancy: the tanks in the Goat do work (as proven a lot lately by Callsign ). I really like the GIS layout and think it can be easily transferred to the smaller boat (thwart may be less wide and perhaps made of timber attached to cleats on the boat's side). It would be fairly easy to include one separate building plan sheet for people wishing boxed in sidebenches.

The SoG will be really aimed at sailing solo (with the opportunity to sail it two-up) and the sailarea will match this idea. Hence it is not very likely that she (or he for that matter) will capsize often anyway.

The chinelog method works very well for the construction and is not that much slower in the build. It also ensures that the chines are nicely and evenly curved without any bumps or lumps. If I were to build a quick canoe, I might consider this method over the tape and glue method.

Best regards,

Joost

Hi MIK,

Great design as you made it, espcially for single-handers and occiasional 2people. I like the enclosed front deck as it will certainly minimize bailing out. For me that is a mayor safety factor for inexperienced single handed sailers. You could even add draintubes and perhaps through-hull selfdrainers if you like it.
Attachment 141937
It still gives a nice rowing position on top of the centerboard-case and place for two (with one facing backwards on the deck and another on the side )
I guess you will make a bulkhead just in front of the centerboard case, leaving two tri-angular open storage spaces left and right of it? ( Nice for a bucket! )
This set-up also makes it easy to return lines from the mast to the back of the frontdeck, for easy single handed acces.
No double-bottum ; that only works with open transom and in general boats tend to go up-side down with it after capsizing ( if you lost contact with the boat and did not get on the centerboard in time) It's better to have the boat deeper and keep water deep inside after capsize.
No side decks, keep it simple! I my GIS ( still not ready to launch ) I used 28mm spacers for wider seating, you probably could go up to 40 if you want to further improve that.
Attachment 141936
A local foam padding ( as used in Finn-dinghy could also improve comfort.
Attachment 141934

Saildesign with 2 reefs seems very good to me, I personally would like a loose-footed version and perhaps a standing-lug version? The boat at the picture is also a 12ft dinghy. This could improve tacking?
Attachment 141935

If I will not be able to manage my GIS single handed, this will certainly be one of my choices for a next build!

Best Regards
Ralph

Originally Posted by Joost

The chinelog method works very well for the construction and is not that much slower in the build. It also ensures that the chines are nicely and evenly curved without any bumps or lumps. Joost

Hi Joost, yes, I am sure you are right about this. You reminded me of when we were assembling the hull and the shape was very floppy and looking nothing like a nice curve. We clamped on the chine stringers and the shape was tramsformed.

Brian

Great explanation Mik, thanks a lot!

Originally Posted by Watermaat

If I will not be able to manage my GIS single handed, this will certainly be one of my choices for a next build!

Best Regards
Ralph

I'm telling ya, 100 lbs (50k) of ballast and you'll be all set, the Goat is great single handed. You're going to have to find another excuse to build SoG, like that fact that you just want to build one!