larrykin

Any IOM newbies out there ??? Having sailed other boats I find tuning an IOM to be quite different. Almost opposite to what I'm used to with USOMs etc. After a week of reading IOM forums on tuning and learning details from race champions I have gleaned some bits of useful information.

Being visual I did some drawings to reinforce these concepts and as a personal reference.
I thought I'd post them for comments and any more advice from IOM sailors on how to get the boats to sail in a reasonable straight line.


One drawing I missed was in gusty conditions DO NOT have a loose backstay. When a gust hits, the jib will "open up", and the boat will spin into the wind. Twas a bit hard to draw....

Larry L.

GLX

Hi Larry these are good drawing. WD

larrykin

GLX,

thanks for your thoughts and I agree totally. First up.... what is a "kicker"? I know all about a "cunni" but am guessing a kicker is the boom vang?
Today I spent some time talking to some 'old salts' who, between them, had been sailing RC yachts for over 50 years. We were racing IOMs. Their advice was get it right on your boat then leave well enough alone. They said they made tiny adjustments to backstay and headstay tension. Didn't use the mast ram. And gave a whisker's hair turn to their vangs for mainsail twist. Didn't use outhaul. Their boats were all flying and there were some club members who had raced for Australia in IOM events.
I have been overthinking this whole concept. Back to KISS - Keep it Simple Stupid - Now I'm just going to use the settings they suggested and sell my boat. Main advice was to begin by buying the best boat you could afford and follow the directions [sm=idea.gif] and then have fun.

Larry L.

GLX

Well Larry you're in the lucky situation that there are a lot of people in Australia that know about racing and tuning IOM. Here we apply our full scale experience in practice with our IOM but then learned the hard way what is different. We then learn more when we go and race abroad in the UK, France and at international events. This is because model boat in Ireland went from being an active fleet of c50 + skippers to only 3 skippers plus me who recently joined the IOM fleet. The marblehead class completelydisappeared. And together we re-build the IOM class and I'm trying to promote RC sailing here since.

I can second what the experienced IOM sailors said to you. In that yes you need to have the boat tuned up but you can spend your time tweaking tuning to get the most optimum tuning but if you think of it conditions change all the time so you can spend your entire day tweaking. Where I'm aiming to get the boat to a tuning level where I'm happy quickly then I focus my attention on boat handling and tactic since there is so much that you can loose there even with the perfectly tuned up boat. With experience you'll learn to have your boat relatively well tuned up quickly and though you may adjust some controls your focus will be on sailing.

Yes the kicker is the vang. Personally I tend now to play only with the backstay tension, kicker and mast ram and that's it. I may adjust the sail foot tension in extreme wind condition ie very light or very heavy but that's it.

At the end of the day there is nothing that beats time on the water... so I hope you'll enjoy sailing IOM and you'll have lot of fun

Happy sailing

k4s

GLX,
        Thats interesting stuff re the tuning techniques.That is the way I was shown when I first jumped into this RC sailing stuff(1 year).Get the rig looking right on shore and sail the boat as it is.Only very minor adjustments from there,mainly twist in the sails.
        Twist is certainly the BLACK ART of sail setting.Strange how twisting off the sails more is advantageous in both heavier and lighter wind conditions.Probably the first bit of advice I recieved from the sail maker was that  too much is often better than too little.
        The next most important thing is to NOT have too much halyard tension on both the jib and the main.A few wrinkles in the luffs is not a bad thing,especially in the light.
        Now MAST BEND,there is a mystery.How much and where in the mast.Experimentation is about the only way to figure that one out.

mfr02

I tend to the view that you start with getting the leading edges straight (assuming a straight mast), and adjusting the leeches through the vang in the case of the main, and the leech line in the case of the fore. The objective is to allow the right amount of shape while preventing the roach from fluttering.
After that, its just a case of figuring out which other suit of sails you should have fitted that day, and developing an eye for conditions. Getting the initial settings takes just a few minutes - finding out what tweaks works best on your particular boat in the days particular conditions becomes a lifetime hobby.

larrykin

You wrote one paragraph which looks straight forward, but, it takes a lot of time to get to such a simple place.
On my IOM to set-up. 1. Stick mast into through deck slot with zero mast ram. 2. Connect backstay and forestay. 3. Tension stays to get mast straight from side view. 4. Connect shrouds and tension to get straight mast from rear view.
Now, my shrouds are set 30mm aft of the mast. Once I tighten the shrouds I have raked my mast back. So I have to have a balance between headsail tension and shroud tension and the backstay is there to do very little for a straight mast.
With this set-up on my boat I still have a touch too much weather helm. Ends up as if 100% is guitar string tight my settings are backstay 20% shrouds 60% jibstay 90%. Mast ram is enough just to steady mast in slot.
Next time out what I'm going to do is slide my jib boom forward by moving my jib boom pivot back. This will move the sails CofE and hopefully reduce my weather helm. My sails, which I made, have my jib at maximum IOM size and the main at slightly under max. with the leech slot 10mm from mast. This could explain my helm problem.
Other good bit of advice I was given - when the wind picks up "open everything up". Those old sea dogs are so wise. [sm=bananahead.gif]

Larry L.

k4s

Other good bit of advice I was given - when the wind picks up "open everything up". Those old sea dogs are so wise. [img]../upfiles/smiley/bananahead.gif[/img]

Larry,this seems to apply to the real light stuff as well....bit of a mind bender eh?
It was explained to me that you want to keep the air moving across the sails so opening in the light allows the wind to flow while still remaining"attached" to the sail and having less turbulence thus less drag.In the heavier stuff opening is more about controlling the power.
I may have all that a bit "cock eyed",as I say...still a mystery to me...thats what makes it fun I guess.

GLX

Hi Larry,

I found that weather helm is mostly caused by too much mast rake, rig unbalanced, and having the leech of the main too tight. if you still struggle with that problem I would change the shroud pressure and look at having one more set of shroud attachment on the deck more forward, in line with the mast. If I understand correctly you have pushing spreaders and this will naturally cause your mast to bend and flattening the main.

Re what you were told to open as the wind picks up I wouldn't agree with that - I would say open the leech in light to increase air flow and reduce resistance to air whilst in heavy wind this will help to de-power but this is only true if you need to de-power but I do the opposite as I thighten the leech as the wind picks up until I need to de-power. Within reason off course as if you tighten too much you'll suffer from weather helm and poor speed plus your boat will point well but will slide sideways as the anti-derive is less efficient.

solution : I start relatively loose and I tighen the leech until i start to feel weather helm then I remove some kicker...

Hope this helps :-)

larrykin

G'day K4s,

how is your IOM design going? You saw my new Noux I guess. If not pics below. I've just drawn up some rough profile plans for my own IOM hull. When done will post here as a set construction plans as PDF. Probably next week. I'm cheating by using designs I know and my own thoughts . Specifically a flat bottom at the stern with chines. See attachment I found. ??? Copyright ???? My design is a cross between the Tonic and the Cockatoo. The stern will be box shaped.

Away from tuning have had the boat in the water twice now. Took on a bit of water first time. About 2 cups in 1 hour. Second time about 1 litre in half an hour [sm=drowning.gif] . Guy at the races said he had had same problem. He said to just fill her with water and see where the water comes out. Went home poured in 1 glass of water and boy [sm=cry_smile.gif] the water poured through the skin. Found about 6 spots that leaked.

Society is to blame!!!! Arrest them!!! What I had done on this build for the first time, was mix acetone in with the epoxy when fibreglassing. 1:10 mix. Worked a charm. Resin soooooo easy to work with and wet the glass. My previous builds I had not tried this. They didn't leak. My cure was ripped out all the electrics. Mixed a batch of epoxy with acetone so it was runny. The spent an hour sloshing this mix around inside the hull until it dried. Sat watching a movie doing this for about 45 minutes. 24 hours later put the hose inside the hull and filled her up. No leaks!!!! . Acetone was both the problem and the solution. The original thinned epoxy had not filled the holes in the weave of the glass. So I had thousands of invisible pin-holes. Worked out for the good. Now with the electrics out I'm repainting and installing new electrics. Not used ones from an old boat.

GLX - I will try some of your advice. Well, actually only one. I'll try reducing my "cunni" to see if that reduces weather helm. Last night I recut my mainsail to reduce draft. Why? Because I had too much. Will be test sailing in a fortnight as I await my new servo to arrive from Perth. The other side of Australia. Like London to Moscow.

k4s

http://c_r_y_a.tripod.com/Sterne%20How%20to.htm

GLX

Hi Larry,

Sorry to hear you had leaks !!! glad to see you managed to fix them though :-)

Loosening the Cunnigham will not help with the weather helm in fact it will most likely accentuate it. I normally tighten the cunni just enough to remove any horizontal wrinkles in the sails. Did you mean the Kicker or Vang ?

good sailing

larrykin

GLX,

if that is your real name ?

My mistake I misread. Thought we were back onto the "cunni". Semantics here - you call 'tighten the leech' I call outhaul and boom vang. I start with my leech tight and boom vang 2 turns loose, at home, then when I get to the water, if there is no wind, I reduce outhaul and tighten boom vang. So I get a curved foot and a tight leech.

Back to what you wrote before. Only 3 people in Ireland with IOMs. How sad is that. Do they sail another class? Or RC is not popular. Anything to do with Ireland's economy recently going down? IOMs are expensive.

From memory you've not posted photos of your IOM. Wouldn't mind a look .

Larry L.

Islander51

This is from Lester Gilbert's excellent site, and gives you a very good idea of where to start.
Hulls vary,so if you've got too much weather helm in gusts, then leaning the mast forwards usually helps.

http://www.onemetre.net/Race/Roughset/Roughset.htm

I agree with others here, get it pretty much right, then only tiny adjustments, and enjoy yourself.

GLX

Hi Larry,

No GLX is just my login but you can find my name and pic of my boat along with other IOM on my website www.iomireland.org. I'm looking after the IOM class in Ireland. I'm not sure how to add a picture to a post.

Along with 3 other people we kept model boat from completelydisappearingin the country. We then setup the Irish IOM NCA and as chairman I've been "working" on developing the class in Ireland. We know have over 18 active skippers spread in 2 fleets : one in the East and one in the South of the country. But my interest is not only IOM as I brought a maxiRC here : a replica of a VOR60 of 2.4m and I have an old Mini40 I've restored and a 1.7m of Jet Services IV.

When you click on Gallery look out for IRL41 : It's a white boat with a black mast and green sail number.

larrykin

GLX,
I'd like to look at the gallery. It's a flash presentation that does not play for me. Loads one photo over and over.

Larry.