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Thread: Goat Island Skiff
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25th June 2007, 12:36 PM #31New Member
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MIK, I'm very interested in your boat. Having built and owned a Bolger Featherwind (a skiff made from 1/4 ply), I hated the oilcanning of the bottom because it was not stiff enough. I've heard no complaints about the GIS in this regard, is this a concern? Also, the boat looks to be pretty high sided, sort of unconventional for a skiff. How deep is the GIS? Finally, I'm a fan of the sprits'l and was wondering how easy it would be to fit that particular type of rig on the boat. Thanks, TDO.
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25th June 2007, 01:14 PM #32
Gidday TDO and welcome,
No oilcanning at all. That's because the structure is cunningly designed to keep the span of the ply down to a minimum.
The boat may appear high-sided, but it's a nice utility skiff, and the gunwhales are a comfortable height for sitting on while sailing, and that's a great spot to perch, giving the helmsman a perfect view of his surroundings and the sail. It also means that the angle of heel can be pretty large before she ships any water over the leeward side. In fact it just never happens, not even with the leeward gunwhale on the water!
I'll let MIK answer the sprit question, it doesn't seem like a big deal to me, but the sail would need to be designed with it's centre of effort in the same spot as the other alternatives.
cheers,
P
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25th June 2007, 08:46 PM #33New Member
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Thanks, Midge. I hope I didn't come off as criticizing the design with regard to the "high sides". The waters where I sail don't get too warm and the what I perceive from pics as higher sides on the skiff is a benefit, although I can't say that perching on the gunn'l looks too comfortable.
Regards,
TDO
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25th June 2007, 09:05 PM #34
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26th June 2007, 12:57 AM #35
Howdy dumbox,
(I feel quite guilty calling you that!!!)
I like sprit rigs too but the advantage of the balance lug is that it allows the 105 square feet of the balance lug to be carried quite low down - so not as much heeling moment as otherwise. You would have to reduce the sail area with a sprit and lose some of the light wind performance that the lug is capable of.
Also as far as strong wind goes the lug reefs really easily with no extra gear required.
Like I said to Midge many years ago now ... if you like sailing fast try the balance lug rig rather than worry about all those battens and high tech spars and sails. In fact I've said that to everyone who had doubts about he lug rig - and they have all been more than happy with the way the rig works in its modernised traditional form. Did you see the pages on my website (accessible from the GIS page) about setting up lug rigs - I've learned a lot about making them perform really well.
The high sidedness of the GIS is quite cunning (if I say so myself). As per normal it gives a much greater reserve stability - the boat goes over a long way before the water starts coming in - but at the same time I fluked it a bit and produced a boat that doesn't look at all high sided - very sleek looking from almost every angle.
The high sidedness almost conspires to make the boat look a lot narrower than it actually is.
Hope this helps
Michael
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26th June 2007, 02:34 AM #36New Member
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Hi, Michael, Thanks for the reply. I have been sailing with an 86sqft spritsail (quadrilateral, not the leg-o-mutton sharp rig shown on one of your PD racer's pics) on my current boat and just love it. I recently added a 21 sq ft jib to it (unstayed) which has made it zippier all around and surprisingly closer winded than I expected. Winds over 15knots require that I stow the jib since the mast bend pretty well spoils the set of the jib. Anyway, in contemplating a new build and not having a lot of money, I was considering the possibilities of using my current rig on the GIS.
A couple of things, keeping in mind that I have read your sight on sailing the GIS several times. First, I sail regularly in 2 foot chop on large inland lakes (this is not motorboat slop) and was wondering if you think the GIS would handle such conditions well. I've not seen much written on its rough water capabilities.
Secondly, I see that you are contemplating a longer GIS -- a raid boat? Have you thought about a less specialized, but longer daysailer type to compete with Reuel Parker's Small Ohio Sharpie (19.5ft x 5.5')?
Lastly, sorry to bug you with the questions. You are the first person I've found who appears to sail flat bottomed craft regularly and can give me some insight into the nature of their handling in a variety of conditions. My first boat was a Bolger Featherwind and I've been bitten by the skiff bug since. I did not think highly of that design and I have been searching since for a skiff that would do the type justice.
Thanks,
Dennis
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28th June 2007, 09:12 PM #37
Yep - that form of the sprit makes more sense - but if it doesn't have a boom you lose a lot of the performance. I keep meaning to do an article to show why boomless rigs are so poor in terms of performance - it is pretty easy to explain. But a sprit rig with a boom would work OK but you would have to make sure it balances over the same centre as the original.
I would also be concerned that the bigger, more powerful (more stable) GIS may break your existing mast.
A couple of things, keeping in mind that I have read your sight on sailing the GIS several times. First, I sail regularly in 2 foot chop on large inland lakes (this is not motorboat slop) and was wondering if you think the GIS would handle such conditions well. I've not seen much written on its rough water capabilities.
Secondly, I see that you are contemplating a longer GIS -- a raid boat? Have you thought about a less specialized, but longer daysailer type to compete with Reuel Parker's Small Ohio Sharpie (19.5ft x 5.5')?
Lastly, sorry to bug you with the questions. You are the first person I've found who appears to sail flat bottomed craft regularly and can give me some insight into the nature of their handling in a variety of conditions. My first boat was a Bolger Featherwind and I've been bitten by the skiff bug since. I did not think highly of that design and I have been searching since for a skiff that would do the type justice.
MIK
Sailing the skiff
The skiff will sail much the same as most boats its size, but there are a few peculiarities that come with the flat bottom.
As with almost all boats the skiff will sail fastest if sailed level - with little or no heel – the exception is in very light winds when you are struggling to get up any speed at all the boat can be heeled over to 20° This reduces the wetted surface by around 25%. As soon as the boat has achieved any sort of consistent speed it should be brought upright.
When the water is very choppy the boat may slam badly if sailed upright. A small amount of heel will smooth its movement considerably. The minimum amount of heel that stops the worst of the slamming should be adopted.
The forward and aft buoyancy tanks are designed for use as seats when rowing. The boat will perform best sailing with crew weight concentrated around the middle thwart.
The final difference with many other boats is because there is no jib. This means that the mainsail boom should not be pulled in tighter than 10 degrees from the centreline of the boat.
Rowing the Skiff
If rowlocks are to be fitted they need to go 300mm behind the back edge of the centre seat. The oars need to be 9ft long.
Shorter oars can be OK if you only want to go short distances with low efficiency, but if covering real distance and planning to go out in stronger winds then the longer oars are highly recommended.
I have drawn up a set of classic oars for free download that will suit the GIS but with laminated plywood blades to make the blades highly robust.
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21st September 2007, 03:33 PM #38New Member
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Sprit Sail Question
I am looking at a suitable boat to build for myself and my two young boys, 8 & 10, to learn to sail in, go camping, etc. Just the things the GIS seems so suitable for!
I have been looking at the Jordan Wood Boats, "Footloose". I even went so far as to order plans. But, the finished weight of 300 lbs puts me off when I compare it to the GIS ~130 lbs. As I look at the plans I also think it is more difficult to build than the GIS and would require more woodworking skill than I possess.
I have to say that the sprit sail used on the Footloose interests me due to the lack of a boom. With my complete inexperience and two young boys I fear somebody getting hurt by the boom....just out of sheer inexperience.
Would it be difficult to set up a sprit sail on the GIS? I realize it would cost some performance but a lug rig could be fitted later could it not?
Thanks,
Murray
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23rd September 2007, 01:22 PM #39
Howdy,
I really, really don't like boomless sails.
There is an argument for them in rowing boats where a small, simple auxilary sail is be be added. The prime use is not sailing and the whole thing packages away very easily. Oughtred is a user of this type of rig for this purpose - and it is a very good choice.
But for a good sailing boat they are a very poor solution.
A boom like the one on the GIS is quite light and small (1 3/8" diameter if I remember) and in the body of the boat is quite high up compared to the floor of the boat - the GIS is extraordinarlily deep in the hull - but it is camoflaged by the curve of the sheerline and the pretty lines of the hull. Also the balance lug rig is very docile and unlikely to do anything sudden.
The only place boomless rigs work well is with certain catamaran rigs where the boat is wide enough for there to be a curved traveller to keep the mainsheet at the correct angle to the foot of the sail at all times.
The main problems are to do with the sail twisting heavily when the sheet is eased.
Upwind - you get a gust that threatens to overpower the boat. The natural response is to ease the sheet. The bottom part of the sail immediately becomes much fuller producing MORE power rather than less.
Reaching - The top of the sail twists out at a crazy angle reducing the projected area - less area to "catch" the wind - so much less speed. Also the sail shape is unstable and will twist further with every gust - the rig "bounces areound a lot. This reduces reaching performance substantially.
Running - when the sail is well eased for running the top of the sail can swing forward of 90deg to the boat reversing the heeling forces. So you get a gust and the boat heels to leeward initially but a bit more wind and it suddenly reverses - leading to a heavy roll every time a gust hits.
Also you are much more likely to do an unintended gybe because the bottom part of the sail is much closer to the centreline than would otherwise be required - making it easy for a small wind direction change or steering change to allow the wind to get in behind the bottom part of the sail and flip it over.
There are people who talk about "Performance" of boomless sails - but it is the "sales pitch" getting a bit past the theory and practice of sailing. Or they just haven't done enough comparitive sailing tot know!
The biggest single performance and safely enhancement in racing boats in the last 60 years has been the boomvang to reduce the twist and shennanigans I talk about above. Every racing boat has one and every successful racing sailor uses it - quite hard at times to hold the boom down.
The balance lug rig gets the same effect from its basic setup so there is no extra cost or complexity in keeping the boom down.
(I hope I didn't sound like I was being grumpy at you ) The grumpiness was directed at those who push boomless sails. I will put them on some boats - but they do have serious drawbacks.
I have retrofitted a boom on several boomless rigs (the first one was a Murray Isles "Swallowdale" and ince little rowing/sailing hybrid) for various clients over the years and all have been very pleasantly surprised about the improvement in handling and performance.
Best wishes
Michael Storer
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25th September 2007, 04:53 PM #40New Member
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Boomless sails
Michael,
Thank-you for your long and informative reply. It really was most helpful. My kids are just going to have to learn to keep their heads down when changing course. (I also just came back from a performance by the Shaolin monks and after watching them break iron bars and wooden poles over their heads I have a greater appreciation for what sort of blows the human skull can withstand.)
I will be downloading a set of GIS plans in the near future. Thank-you very much!
Best regards,
Murray
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26th September 2007, 11:38 PM #41
The first three kung-fu lessons are free!
MIK
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27th September 2007, 12:32 PM #42New Member
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Kung-fu and material selection
After three lessons they should know enough to duck!! I hope I learn that quickly!
I downloaded my GIS plans today and managed to find a few minutes during work to call around to track down some marine plywood.
The middle of the Canadian Prairies isn't the best place to look for marine plywood....There is one place in town that has marine plywood and all it has is Douglas Fir "marine grade" sheets.
Is this ok to use or should I try to find a source for Okoume plywood?
Thanks, Murray
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28th September 2007, 06:05 PM #43
sorry about being slow to answer this.
Fir ply tends to check (crack) on surfaces over time. Gaboon or just about anything else is better.
Michael
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1st October 2007, 05:50 AM #44New Member
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Thanks Again!
Michael,
Thanks again for the advice and help. I'll track down another source.
Cheers,
Murray
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1st October 2007, 06:41 AM #45
Murray,
Welcome, and don't forget to post pics!
P
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