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7th December 2009, 11:09 AM #76
Mick, I have been thinking of a way to easily change the flexibility of the spars without stuffing up the finish too much.
For my second set of spars, as I have a router, I am thinking about making them hollow from 2 pieces.
The nice thing about the router method, is that the wall thickness can easily be varied relative to the top and sides of the spar, so that more vertical stiffness can be achieved relative to sideways stiffness. If I need more flex, all I need to do is split the spar along the glue line with a Japanese saw and rout out some more wood, then stick the 2 halves back together again (adding lightness!). Likewise, extra stiffness can be easily added where required by adding some lightweight Paulownia infills where required.
As for the boom, do you think there would there be any benefit in leaving the forward section of the boom solid, to just aft of the downhaul attachment? Or should I go hollow for the whole length and control the bend with the wall thickness?
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8th December 2009, 10:56 AM #77
Howdy Clint,
This is an old bit of boatbuilding lore appearing. Either epoxy works as a coating on wood or it doesn't. If wood needs to "breath" then there would be tens of thousands of epoxy built boats with serious problems now.
However the glass coated ones have proven themselves to be very durable over the last 40 or so years.
Of course people can coat or not coat as they like ... but it is down to personal preference, probably with considerations of maintenance and longevity topmost for those who choose epoxy.
If a boat is traditionally finished then ventilation becomes important as the main method of reducing the risk of rot. I think that might be where the breathing idea came from - but it is well shown to be incorrect.
MIK
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8th December 2009, 11:03 AM #78
Howdy, I think it is possible that the aft most spacer will have to be removed as it may break when the tiller arms are bent to fit around the rudder box. Might be OK, but probably a good idea to do a trial before mixing glue.
Glass is a really crappy way to improve the stiffness of spars if it is cloth and wrapped around them - because the glass is heavy and it has half the threads going in the wrong direction and it is over the whole surface.
Placing a narrow strip of unidirectional glass on the top and bottom faces of a yard, gaff or boom is quite an efficient way to stiffen up a softer spar compared to making a new one. Probably a good idea to measure the bend with a standard weight before and after to see the difference and keep a record to add to the database we are talking about.
MIK
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8th December 2009, 11:10 AM #79
The wall thickness is not a very efficient way to control the stiffness of the spar. It is a great way to control the weight though! The outside diameter, particularly the depth is the best way of controlling the stiffness.
I would probably suggest making a series of simpler booms - probably just square section with radiussed corners and once the right stiffness is found then it might be time to make the routered out hollow spars.
I am chronically lazy so would probably go the timber top and bottom with ply sides for the boom - with some taper and rounded corners, I don't think it would be too obtrusive as the boom. But that is me!
My feeling about the boom is that one one side you want it visually unobtrusive but on the other you want it pretty stiff. If the foot is laced on some extra flexibility toward the back end is not harmful at all.
Best wishes
MIK
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8th December 2009, 12:27 PM #80
Hi Mick, One of the first things I checked was that the tiller would fit squarely around the rudder casing using a piece of timber to simulate the casing. It does so without a problem as there is a good deal of flex in the horizontal direction. I thought about making it fancier like Peter's tiller, but in the end went with the simple ladder type, like the plans. It's light too.
Thanks for your thoughts on the boom. I'm with you on the simplicity aspect, especially because simple is always easier and often just as good, so why take the longer and harder road to achieve the same result?
The good thing about the boom is that it's so simple and quick to make and so between us all we should have some useful data before too long. The yard, well things could take a little longer...
Mick, do you have any records about the the lightest recorded Goat hull ever made? I want a target to try to achieve.
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8th December 2009, 11:09 PM #81
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9th December 2009, 04:25 PM #82
Rudder fittings
As most of you will know, Ronstan and the Danish firm Frederikson have merged and so Ronstan are not making some of their range of fittings any more. (If you’ve been trying to get hold of rudder fittings, you’ll know what I’m talking about) This is what the Chandlers told me, so I guess it's because they have duplication in some of their lines. The problem is that some fittings are now very scarce here in Australia so they are obviously having some sort of supply problem. The chandler had a stack of yellow stickers on their price tags, which they told me was their code for discontinued lines and there are no more available.
Items as 7.9mm pins such as RM148 are now unavailable, so you need to make your own or try to buy second hand.
I have just paid AU$175 for my rudder and transom gudgeons, as there is not much other choice available here with 8mm pins, well nothing else in fact. These are the ones I’ve bought, and will need to modify these a bit to fix to the spacers in the stock. Easy enough seeing as they are alloy and not SS. I really should have considered making my own aluminium ones with nylon bushes as my brother in NZ has done on his Paper Tiger, but I don’t like metal work much.
Attachment 123816 Attachment 123817
As for the tiller extension, I’ve stripped down an old carbon fibre fishing rod. As you can see, it fits the Ronstan PU universal joint perfectly. I have not pushed it in all the way yet as I still have to clean up all the old glue from the extension and then paint it. It even has a knob on the end which was the base of the rod.
Attachment 123818 Attachment 123819
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10th December 2009, 01:10 PM #83
Howdy,
The lightest I know about was Peter Hyndmans that just came in under 130lbs before painting, varnishing and fittings.
Also Peter is from a racing multihull sailor and builder so the principle of reducing weight and leaving stuff out is well ingrained. (he was famously tough on his racing crews about carrying a minimum of stuff and keeping stores and water weights down - consistent with safety).
However it was built when Gaboon was really Gaboon and the light Western Red Cedar was used for everything except the gunwales and inwales. Only glass tape.
I think the weight of the boats has increased as the variety of building materials has become more restricted. I would not be surprised if most boats are about 10lbs heavier than this now.
Good, glad you checked out the tiller. I was doing a double check for you!
With the rudder fittings - it is a bit of a pain in Australia because everything has become so race oriented. Duckflat had some old style stainless pintles and gudgeons made up and have those in stock and they are cheaper than alternatives.
The Goat can get away with lighter rudder fittings than many boats this size because the rudder evades the loads of hitting things quite nicely. If using lighter fittings though I do like to see a one piece pin going through all the pintles and gudgeons.
The standard Ronstan in the modern style will be fine of course if embarrassingly expensive! Not that the simple stainless ones are spectacutlarly cheap!
Best wishes
Michael
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11th December 2009, 05:28 AM #84Senior Member
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I have found the same issue in obtaining rudder- fittings in my area.
Duckworks USA have some light and very affordable fittings ( Joost has them on his GIS )
Attachment 123937
and I have found these locally. about 55 Euro, 10mm pins (probably a bit oversized) with 35mm inside ( that's the minimum you need on GIS rudderbox ) Attachment 123928Attachment 123929.
I have been thinking about using standard stainless steel hinges. These are very strong, inexpensive en easy to get ( at least in my area ). Using these means a more or less permanent fixation of the rudderbox to the transom, but that's not a big issue if you remove the foil on your trailer. To do so you need to change the rudder-box design, so you can fit these hinges in a way that they work well. A 45 degr angle in both sides of the front-piece of the rudder-box could do the job (?)
MIK,
it could be worth to consider this?
Rudder fitting are pretty expensive and it would be a great design feature to be able to use standard hinges ( stainless steel, brass or copper ) . I did not yet sort out how to do this, but since I did not finish my rudder-box yet I will probably try a few options.
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11th December 2009, 07:08 AM #85
Hi Ralph
I did not think these types of fittings with the integrated pin would work due to the transom cut-out. These types are in more plentiful supply, but it's the restriction at the transom cut-out that stopped me buying this type. If it can be confirmed they do indeed work, then I think a lot of the problem will have been solved!
As for the SS hinge, they can be made to work, but at considerable effort. Better to work out a way to , SS is not easy to bend over a short distance without destroying the fitting.
Other possibilities are these gate fittings, which are cheap:
Attachment 123939
Or these which are easily made, but are so cheap it would not be worth the hassle:
Attachment 123940
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11th December 2009, 08:31 AM #86Senior Member
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Hi Woodeneye,
You are probably right about this transom cut-out, and I remember Joost telling me he had made this slightly bigger to match these fittings. I already changed my rudder cut-out for several reasons due to my outboard cut-out.
About using standard stainless hinges, I was not thinking about bending them but about changing the woodwork to be able to use them standard. I am not shure about which model hinge or in what direction changes could be made......but it would be nice to have a simple set-up using standards stuff in stead of expensive marine hardware. It would certainly match with GIS overall "Keep It Simple" filosophy'.
I will give things a tought.....I will probably have plenty of time for that, since we are getting towards <5degr temp's here. So my epoxy-work will slow down for next few month .
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11th December 2009, 08:40 AM #87Senior Member
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Just a little additional info about this rudder cut-out change;
The overall height of the cut-out needs to match your tiller height ( in the cut-out area, in my case 40mm ) plus the lenght of the fixed pin ( in my case 35 mm ) plus a small gap needed between the tiller bottum and bottum of cut-out ( f.e. 5 mm ) . So in my case the cut-out is about 80mm high.
You mount your rudder-case in a way that there is a small gap between the tiller and the bottum of the cut-out. This will give you sufficient height to lift your rudder-case over the fixed pin.
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11th December 2009, 09:21 AM #88SENIOR MEMBER
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11th December 2009, 10:51 AM #89
That's good info guys, that cut-out is fine. My brain is very visual, and sometimes I can't imagine something working until I see it. It's a handicap for sure
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11th December 2009, 01:52 PM #90SENIOR MEMBER
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Joost what is that strip planked hull in your photo set???
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