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Old Mar 06, 2010, 08:35 PM
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Originally Posted by nick_75au View Post
Does anyone have any suggestions on building a vang from scratch, currently I gave a couple of 4-40 ball links and an aluminium bracket bolted to the mast that I beleive is hanging up in places as I sail.

Nick
Here is a nice little design from Graphite.

Could be engineed slightly bigger. Ball Raced as well & usese a simple turnbuckle arrangement.

..
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Old Mar 06, 2010, 09:11 PM
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Quote:
Originally Posted by Islander51 View Post
:

I think that you could do it with levers.

The power of lateral thinking!!

Thank you in anticipation,
Edward.
Edward

Perhaps I might have a shot. Like I said previously some automatic Latch/switch systems (pre-modern age) were tried and found to be useful in some circumstances.

Your idea on face value appears to be workable. My only visual question is how would the Jib be released for normal function. ie back to pre latched positions. & adjusted easily..

Similarly & perhaps more of a more standard use of TX & RX, I note that most skippers tend to sheet in fully to a pre-set maximum closehaul, leaving little travel on the Trim Tabs to allow for even closer haul positions. Stops overloading of system & a bit of a failsafe..

I have seen in a Marblehead a spring/cord type arrangement in the Main that stopped any overload when close hauled.. When closehauled the spring would activate & not allow the main to travel in further beyond a certain point regardless of the TX movements. There was some lever system that allow more play in the main sheetline while maintaining its position. Under the deck there were lots of levers & pullies & it looked very complex

I noticed that the Trim Tabs were then used to alter the slot from the Jib. The Jib with this fine adjustment could be trimmed to almost nothing or back to original setting. Once released by the sticks or tabs everything returned to normal with Trim Tabs used rather than sticks when beating upwind, most of the time.

This was about 15yrs ago & quite complex. Not sure how it could be done in miniture to save size & weight inside an IOM.. But it worked well in the larger class from a standard long arm winch.

The skipper worked on the two channnel radio because of cost, disability, an engineering background and just for fun as he put it..
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Old Mar 06, 2010, 09:11 PM
k4s
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Sorry ,don't mean to hijack.
Robert,I was following along with your expandable foam build but now can not seem to find it.
How did the second attempt go?Did you figure out how to adjust for the amount the foam expands?
It was an informative thread,but now seems to no longer exist.
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Old Mar 06, 2010, 09:16 PM
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Thanks Mike, what profile is the vertical part?
Waboats looks fantastic only, how would I build that? looks to be moulded.

Nick
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Old Mar 06, 2010, 09:17 PM
k4s
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Gary,
Just ask the questions you want answered.Pretty sure an answer will be forthcoming as there are plenty who have, or are building IOMs on line.Sirit over on RC UNIVERSE has a build going right now that has answered a few for me.Pics show alot more than just words and so far he has done a great job,imho.
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Old Mar 06, 2010, 09:30 PM
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Originally Posted by nick_75au View Post
Thanks Mike, what profile is the vertical part?
Waboats looks fantastic only, how would I build that? looks to be moulded.

Nick
Nick

yes it looks to be carbon moulded but as not allowed in IOM, fabrication out of light Ali shouldn't be too difficult. Simply wrap shim around pipe or rod & fix together with eyelet & small amount of resin. Eyelet can act as guide for cunningham.. Internal diameter for mast, outside for bearing.. Not sure if the Bearing Running directly on the mast is allowable as yet. Ball-Raced Goosnecks are a recent (last few years) development in the IOM class..

Booms are hollow with small plug with slot cut in end. Fixed with small nut/bolt.. Same for Turnbuckle Vang..

Jib can be done similar with slot cut for forestay attachment & counter balance fixing passing through the solid plug in the end.

All looks neat & tidy which is a good thing to avoid lines getting caught up during racing.

There appears to be a lot of Sails Etc influences in the design so I would perhaps get a rigging diagram for their standard Gooseneck arrangement.

Old Days was pure rigging cord & bowsie.. Now just a Turnbuckle of varies sizes & shape (stops slip & more reliable).

Cheers

John
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Old Mar 07, 2010, 05:48 AM
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Quote:
Originally Posted by Islander51 View Post
To: Mr. R. May.

Dear Mr May,

I would be most grateful if you would reply to this previous post:

I think that you could do it with levers.

With a double arm, when full in, the jib controlling arm just touches a peg sticking up from the lever.
Add one click on the trim, lever moves over, other end of the lever also has a peg just touching the jib sheet, so this moves also, making a longer run for the jib sheet and bringing it in just a wee bit.
Still too much slot? make that two clicks.

If properly set up, mainsheet movement would be minimal

This should also weigh less than another servo.

There may be something in the rules that says you can't do this??

Edward.

The power of lateral thinking!!

Thank you in anticipation,
Edward.
Hi Edward

Without a drawing I think understand how that would work as an adjustment for trimming the jib and could be made to be proportional too, it won't give me quite what I am after which is to achieve far more steering from the sails.

I read your post before walking the dog this morning and it made me realise with the typical IOM race layout the main sail has only two positions, in and out. If the main can be set in either position the jib can become fully proprtional. I haven't figured out how I can achieve it yet but your idea has certainly triggered a new lateral though process of my own.

All the family are here abouts today so I will catch up with the other posts in the morning.
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Old Mar 07, 2010, 10:27 PM
k4s
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Well its less than 2 weeks(12 days) until the NZ IOM Nationals kick off.
These are being held in Tauranga,on the sunny east coast of NZ's north island for the first time.
The regatta will be held in a relatively new man made lake in the LAKES SUBDIVISION with an incredible amount of support from the developers,GRASSHOPPER DEVELOPMENTS,They have supplied free of charge,1 The lake
2 All materials for the dock and a subsequent extension to the original as the fleet locally has grown.
3 A portable office delivered to site for the event.So a huge thanks to them.
The entries to date are 44,so this means that three heats of 18 boats will be sailing.Will make for some interesting starts and possible muddle at the top mark for the first leg.I can"t wait.Very exciting.
For a look at the venue and other details....
http://www.ohope.co.nz/iom/index.html
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Old Mar 08, 2010, 04:31 AM
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Most folk growing up have, at some time or another, had a small free flight glider. The instructions normaly contained a simple diagram how to get the glider to fly well by adjusting the position or amount of weight on the nose. Too little weight up front or the weight slid to far back and the glider would pitch up and stall, the nose would drop , the model would then pick up speed, pitch up and stall again.

With too much weight up front or the weight slid too far forward the glider would just dive into the ground.

Here is a very familiar drawing to the one on the instructions of a glider and it best explains why trimming the boat for the conditions is vital for maximum boat speed. It should also shows why it is essential with model yachts that invariably get rigged and un rigged every time you travel to the lake or pond, that you record the distance from the mast head to the transom and check it is correct every time you sail. Establishing the measurement is down to your particular boat and requires one to sail and adjust until you can get the boat balanced.

If anyone reading this deliberatly sails with weather helm please post how and why you are doing so. But for my benefit andothers who are sailing IOM how do you go about establishing the optimum amount of weather helm.

I have only shown mast rake being used to affect the sweet spot. Moving the mast foot and or the jib swivel will also move the CE of the sails.
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Old Mar 08, 2010, 05:55 AM
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Robert,
I totally agree with you about the sweetspot and mast position. One thing baffels me though and I think Richard will agree with me. Perviously on the Tempest, Richard has his mast position well foward of the "sweet spot". Assuming it was nuteral helm, when moving it back to the current position now , one should get severe weather helm and yet it does not. The mast rake is VERY pronounced to there is more to counter the weather helm than just moving the mast foward. Closing the slot too I find will reduce the wether helm effect.

Can anyone comment?

Cheers!

Ervin
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Old Mar 08, 2010, 07:06 AM
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Moving the mastfoot a lot and raking the mast can have almost no affect at all and mast rake should be used a real fine tune of the rig. If there is a noticable weather helm I would start by moving the foot of the mast forward (upright) and move the jib deck swivel forward by the same amount.
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Old Mar 08, 2010, 07:50 AM
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Robert,
I agree with your statement however keel stepped masts dont always have the ability to move foward as you mentioned. Moving the jib foward will help combat the weather helm but also increases the distance of the jib from the mast which in my opinion is not a favourable option. I try to keep the jib position as close to the mast as possible so you get a more constant apparent wind thru the slot. By raking the rig foward you are changing the center of effort in relation to the centre of lateral resistance and hence the helm of the yacht.

For my setup where the foot of the main is 1/2 that of the jib, she sails with fairly nuteral helm with a hint of weather helm to hunt for the best line. When I incease the foot of the main to match that of the jib I get more weather helm, faster acceleration but lower top speed.

This is personal preference but I prefer to point high and can usually duplicate the acceleration effect by sheeting out a little, get it moving then sheeting in and pointing.
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Old Mar 08, 2010, 08:28 AM
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And that is where effective use of the tell tales comes in. Once the boat is fundamentally trimmed with correct and known helm it is then possible to adjust ones point of sail for or sail trim for;

1. acceleration (after tacking or choppy conditons) Inside (Weather Side) tell tail straight back (outside TT dipping and dancing)

2. Max speed, both TT streaming back and horizontal

3. Flat water pointing, Outside TT back and horizontal, inside TT horizontal and lifting up to 45 degrees

4, emergency pinching, making a bouy having mis-judge last tack or un expected windshift, forcing another boat (on Port) to tack rather than allowing them to cross ahead. outside TT horizontal inside tt Vertical up. Don't keep this up for long it is not fast or effective. If the Inside TT lifts like this and you are don't need to pinch you should consider tacking.

If you are steering a good course to your next mark and the Outside TT flutters you should let your sails OUT. If the Inside TT flutters you should sheet IN

If you get this under your belt have a look at the luff of the main (its belly) You might have the jib set beautifully but if the luff of the main is backing a lot of speed is being sacrificed.
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Old Mar 08, 2010, 08:37 AM
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Quote:
Originally Posted by scully View Post
Robert,
keel stepped masts dont always have the ability to move foward as you mentioned. .
This where I get irritated with some of the commecial hulls that have been designed with a single predominent set of conditions in mind. Buy and sail them outside those conditions and you end up with a boat that is incredibly difficult to tune. And is where the level playing field takes on a nasty tilt. A deck stepped mast or mast slider and chocks is my preference.
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Old Mar 08, 2010, 09:20 PM
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