Hobie 18 Race Tuning Question

Hi Everyone,

I was hoping I could get some advice! I have been looking at this forum and hobie forums and with the change in hobie 18 mast design from full aluminum to the comptip I am not quite sure which advice to follow for tuning.

1. I have mostly been following Bob Milimitch Hobie 18 tuning guide. Can someone confirm if that guide is for a comptip mast and also if they are the latest and greatest tuning tips for racing?

http://www.fleet297.org/PDFs/Hobie18TuningGuide.pdf


2. Is this generally correct for a comptip mast:
Mast Rake ... Back = less power, fwd = more power
Diamond wire tension ... loose = less power, tight = more power. What does loose "look" like and what
does tight "look" like?
Rig tension ... no idea what to set this to? i heard maybe 4" of movement?
Outhaul ... what is the correct tension for upwind, tight tight or 4"?
Dagger boards ... is the strategy similar to F18 where full down is max power and moving them up
reduces power?
mast rotation ... i always read start at side stay and move backwards to reduce power but then recently I
found a post talking about lining it with the boom is a better sailshape? which is best?

3. Again, comptip mast. I have installed a 5:1 downhaul that i can pull from the wire and I just dont seem to feel the difference. How can I be sure the downhaul is performing the depowering and flattening that I expect it to? How far should I expect the sail to travel? It is currently travelling about 10cm (as far as it can go) but when I release it, it only raises up 5cm. I tried to pull it during a puff where we lifted the windward hull but it did not seem to stop that from happening. Am I missing something on how it is used?

4. These are my current settings, and sail shape for going up-wind. Note that I am solo here so no jib.

https://www.instagram.com/p/CBItsj-BTnF/

Mast rake ... using the trapeze wire, from the bottom of the jib furler to the back transom...lands 5" above
the transom
Diamond wire tension ... cannot touch the mast with diamond wires
anywhere
Rig tension ... wires move approx. 8 inches on windward side

5. Tell Tails
--Based on the picture are my tell tails in the right location?
--I read in a post that a set in the 2nd and 3rd panel from the top (i assume that means the first two light blue panels) is best because it shows you the twist and tells you how much more you can pull in the sail. If so, does that mean you have to keep those flowing at all times? How far from the luff do I install them?
--Are these top sets the ones to watch? I have typically used the lowest set for determining my sail shape, I assume that is wrong?
--i do have leach tells on the 3rd and 5th panels. I also keep them flowing as best i can, is that correct and does the 3rd panel leach tell all i need for confirming sail twist is ok?
is a set of streamers on the front bridal or side stays better for determining the 90 degree apparent wind for downwind? I have them on the bridal but find it difficult to tell if they are 90 or less/more.

6. Pinching vs. Footing
How do you really tell if you are in the "groove" or just footing? typically I can tell when I am pinching but I also cant tell if I am pointing high enough? As an example in the picture, although I believe I am upwind, I may in fact just be footing?

7. Jib luff tension
any advice on this? All i know is to set it once there is some tension on the mast so as to not put all force on the jib luff and still rely on the forestay (opposite of the H16 it seems?)

I know this is long but any help would be much appreciated!
-C

**Note i also posted this on Catsailor.com**

1) The guide still applies. The aluminum masts are stiffer, so they require more downhaul tension to get the same effect. However these differences are small relative to differences between what I think is tight and what you think is tight.

2) A sail with a lot of curvature is considered a deep sail. It develops more lift, aka power, but also produces much more drag. Flattening out the sail reduces 'power' and drag. When sailing downwind drag doesn't effect you much. Make your sail deep. When sailing upwind drag has a large effect. Flatten the sail to reduce it. If your boat is overpowered flatten the sail.

Sail tuning has 2 key aspects. Sails must be shaped to produce the correct balance of lift and drag, and they must be rotated to have the correct angle of attack. The downhaul and outhaul change the shape of the sail, the traveler changes the angle of attack and the mainsheet is a complex mistress that does both.

With that said:
Mast Rake primarily drives weather helm. Most H18s are sailed with a nearly vertical mast. Rake the mast back to get more weather helm.
Rig tension: You should be able to rotate the mast 90 degrees to either side. If you can't loosen your rig a little.
Daggerboards: Down when you don't want to slide sideways (traveling upwind) and up when you don't mind sliding sideways.

Everthing else, follow Bob's guide.

3) If you have too much load on the sail it can be hard to tension the downhaul, which sounds like what is happening to you. Try adjusting the downhaul tension on a beach with the sails pointed into the wind. Set the traveler and outhaul loose and tighten the mainsheet. Rotate the mast to one side. Haul in hard on the downhaul while looking straight up the mast. You should be able to haul in 25cm or more sail and see the mast bend.

4) The jib makes the boat much more balanced, helping you tack quicker and sail faster. If you can handle it I recommend flying it, even solo.

Hard to judge the rig from the picture, but nothing is horrendously wrong. Looks like you could use to flatten it out a bit. Increase downhaul and outhaul tension. If the boat is still overpowered travel out a bit. You should be able to bring the mainsheet in tight between the gusts without flipping. If you can't, travel out more. Sailing upwind is faster if you travel out rather than ease the mainsheet. Your diamonds sound tight.

5) Eh, there isn't really one right place for telltales. There are a few wrong places, but yours are fine.
Sail tuning is hard. Try to make all the tell tails happy.
Apparent wind isn't easy to observe. Those big sails on your boat will twist the wind no matter where you measure. I like the shroud mounted streamers, but don't be surprised when the leeward one streams in a different direction than the windward one. I listen to the windward one.

6) If you don't think you are footing you are probably pinching, especially in light air. The best way to find the ideal angle for the conditions is to be sailing next to another H18.

7) Follow the guide. Don't set tension without the mainsheet tight. If you tension the jib without the mainsheet tight the jib luff and halyard will take the load that was meant for the forestay. On the hobie 16 the Jib luff is a cable and is meant to handle this load. On the H18, it can't handle the load.

I raced H18 for many many years. Honestly, I don’t think much fine tuning makes a whole lot of difference (others may strongly disagree).

The comptip is more flexible than an aluminum mast. For this reason, and because we typically were in the 330-350 crew weight range, I always ran the diamond wires snug. Let the comptip do the bending and keep the power low in the sail. I am a strong believer in the telltails in the upper panels of the main. The primary purpose is to tell you if you are over sheeted (stalled). If you are underpowered, they will tell you how much more you can pull in before stalling.

Downhaul can be very effective, in fact I think the only significant adjustments on the H18 main are mainsheet, traveler, and downhaul. Everything else we run the same setting in all conditions. The downhaul adjustment will only be effective if your sail is in decent shape, not stretched out. If you only have a couple inches between min and max, then you aren’t really going to get the mast to bend much.

Daggerboards are very low aspect. They are never pulled up when going upwind in any conditions.

Jib luff tension makes very little difference. Pull on some mainsheet tension when on the beach and then set the jib luff to take out the wrinkles. That’s about it.

Rig tension. Basically just take out the slop, but not so tight that the mast won’t easily rotate to 90 degrees going downwind.

Mast rotation pointed about at the shroud going upwind all conditions. Fully released downwind all conditions unless it’s super windy, then don’t worry about it.

sm

I have loaded up many photos on my boats own Facebook page to answer your questions Photos include how to measure mast rake, diamond tension, jib luff tension etc.

SRM is correct with his comments.

The only adjustment upwind is mainsheet tension and mainsail luff tension.

Dont be shy on putting in heaps of mast rake. We are a loooooong way aft and the boat is a rocket ship.

Enjoy the many photo Albums.

_________________
John Forbes
Hobie 18 Reimagined
Sail # 490
Boat name: 18@heart
http://www.hobie18.fun
https://www.facebook.com/Hobie18catamaran/

Hi all,

Thank you for replying!

I have a couple follow up questions.

1. For the downhaul I seem to be limited by the boom connection point. When putting the sail in and getting the wrinkles out I am already 4" below the sail entry point and there is only another few inches before the boom connection. Could someone maybe post some pictures of what full on downhaul looks like with maybe a newer sail?

2. John, what do you figure the mast rake is doing for you to improve performance? I noticed you have a full aluminum mast, is there any difference with the comp tip? I might try more rake but I figured that was less power based on the tuning guides and advice I have read? i will check out your page some more but have enjoyed seeing your pictures and advice. For mast rake right now I have 106" using the bow tang to 4' up the mast. Is this a lot, a little?

3. SRM, what does snug diamond wires mean? I cannot touch the mast at any point of the diamond wires. is that too snug maybe?

4. SRM do you put upper tell tales in more than one panel? if so, is the 2nd or 3rd preferred? Could you elaborate a little on what would show me I am under powered vs stalled?

5. I received advice on the H14 forum that the lower luff tell tales provide indication of angle (ie traveler position). I posted this there but will post again, I was out and it didnt seem to matter what traveler position I had, the windward tell would never stream aft?

Thanks again all,

Codie

Hi Codie,

The sail should be about 2-3” above the boom gooseneck when at maximum. With zero luff tension on it should be about 1” below the track opening. There is a Class Rule Black Band measurement that you should use as a guide to how low you can and can’t go. I moved my boom gooseneck attachment fitting UP the mast so the top of the gooseneck mast fitting was at the top of the lower black band line. That way the crew can get under the boom easier and the fitting acts as a mechanical stop for the black band rule.

I am not familiar with your method of measuring mast rake. On my boats FB page there is a photo Album about how I measure rake (which is the same way as most other classes) and where my mast rake is. Note that I made a new longer forestay to achieve my rake. The longer forestay also allowed me to eliminate the forestay adjustment chainplate.

You should be able to see how many telltales I have on the main, although I rarely look at them, I mainly look at the jib telltales and have put them in the correct place on the jib as the original Hobie position in the windows is not correct.

_________________
John Forbes
Hobie 18 Reimagined
Sail # 490
Boat name: 18@heart
http://www.hobie18.fun
https://www.facebook.com/Hobie18catamaran/

Codie,

I also have a photo Album on my boats Facebook page showing my diamond wire tension and what measurement I use. Once set, I never adjust the diamond wires. I leave it the same for all weather conditions and purely adjust the mainsail downhaul to power and de power the sail.

The large amount of mast rake I use will not change between an all alloy mast and a comptip mast. The extra mast rake does not depower the boat, it in fact makes the boat go much faster. There are many reasons for this including improved slot between the main and jib, centre of effort change, bows out to allow boat to be driven more, rudder helm, etc. I never change my mast rake for different wind conditions. It is set and forget. We move our crew weight around to cater for the different wind conditions. We race at 166kgs while most others are at 135-140kgs but we are still very competitive with the mast back all the way, even in light winds. Please remember, the more you rake your mast back, the more you must slide the jib blocks forward to maintain the correct jib sheeting angle.

If you intend to race then the absolute biggest improvement you can make is new sails. Hands down this is the biggest improvement as the main will have much better leech tension and the jib will be less bellowed. The other big improvements are having beautiful leading and trailing edges on the rudders and daggerboards. No slops in the rudder castings and daggerboard cases. Correct rake for the rudders. If these aren’t right then the boat will be constantly trying to stall.

Another important element that is always overlooked is the jib tack attachment. If it is not correct the. The leading edge of the jib won’t flow. It is the very first thing the wind reaches and if that ain’t right then the rest of the flow is disturbed. Plus, if it isn’t correct then it will be hard to steer the boat in the correct groove as that is determined by the first 6-8” of the jib luff.

Enjoy.

_________________
John Forbes
Hobie 18 Reimagined
Sail # 490
Boat name: 18@heart
http://www.hobie18.fun
https://www.facebook.com/Hobie18catamaran/

1. For the downhaul I seem to be limited by the boom connection point. When putting the sail in and getting the wrinkles out I am already 4" below the sail entry point and there is only another few inches before the boom connection. Could someone maybe post some pictures of what full on downhaul looks like with maybe a newer sail?

With a fresh sail, you will often have to use the downhaul to get the bolt rope pulled down into the track below the opening. My sail is far from fresh anymore, but it still has a good range of travel. We will pull the downhaul blocks within an inch or so of the gooseneck at max downhaul.

3. SRM, what does snug diamond wires mean? I cannot touch the mast at any point of the diamond wires. is that too snug maybe?

I would consider that to be snug. Basically cannot touch the diamond wires to the mast, but not so tight that you’re trying to induce prebend or anything like that. Tighten so there is basically no looseness or flopping of the wire.


4. SRM do you put upper tell tales in more than one panel? if so, is the 2nd or 3rd preferred? Could you elaborate a little on what would show me I am under powered vs stalled?

Yes, I use telltails in two panels. The panel below the first batten and then the panel below that one (I guess that would be considered panels 2 and 3). Underpowered would be when both windward telltails are streaming up or forward. Stalled would be when the leeward telltails are streaming up or forward. Underpowered is definitely preferred over stalled. Sails stall from the head down and the leech forward. This is why it’s important to have telltails all the way at the top of the sail.

5. I received advice on the H14 forum that the lower luff tell tales provide indication of angle (ie traveler position). I posted this there but will post again, I was out and it didnt seem to matter what traveler position I had, the windward tell would never stream aft?

I never really worry about the lower mainsail telltails. On the 18, it is the two sets of jib telltails and the upper main telltails that I consider most significant.

sm

If your tell tales are too close to the luff of the sail the windward side will never stream. Sails are not perfect foils, and the mast tends to produce a pocket of turbulent air. This pocket is largest at the bottom where the wind is the slowest and the angle between the sail and mast is the greatest.

see this writeup by somebody else for details:
https://sailzing.com/mainsail-telltales ... -approach/