Typical mast-rotation settings (Inter17)

I was wondering if anyone could provide with with some details on typical settings for the mastrotation, and/or the operation of the mast-rotator(?) in general.

Kind regards,
Martijn

Hi Martijn,

The Taipan website gives a pretty good explanation on rotation and some other stuff.

Go to www.taipan.asn.au
then at the top Click on Tips and Tricks
click Cat 4.9

Tom Turlington
I17R #124

Tom,

Tx! I have printed the pages and will readup tonight.

rgds,
Martijn

I still have some questions on the rotator javascript:void(0)
:

Does anyone know why the Inter17 does not use a rotator limiter? Or is it just that I have a model without them?
Should I install them?

The other thing I do not get is how it actually works: I understand turning the mast nakes it easier to bend, by bending the mast I create a flatter sail. But why would I rotate going downwind, would i not like to have a full sail isntead? Would I not rotate going upwind instead to get a flatter sail?

Many questions here, sorry. I have not got this rotater thing sussed yet.

Refer to this thread linked below and this image that was posted by Luiz. It's all about creating an efficiently shaped airfoil.

Rotation Thread

The fact that the mast stiffness is different in its long and short cross-sectional axis is purely a secondary issue. The primary one is of course effecting a smooth transition between the edge of the mast and the sail on the lee side of the rig. Since the sail is set at diferent angles to the boat at different points sail, the mast angle must change too, if a smooth transition is to be maintained. Also the farther off the wind you sail, the fuller the draft the sail is trimmed for and therefore the more severe the angle of mast rotation needed. The differential in bending stiffness in the fore and aft mast axis can work for or against you depending on the boat and conditions. Diamond wire/spreader adjustments are the usual ways this bending is managed, though rotation can be a complicating factor here, so that a compromise between the needed rotation and desired bend has to be reached.

Jimbo

If you really want to get deep into the subject of rotation/prebend go to

Landenberger-sailing.com
tuning guides
A cat tuning

Be prepared to read and reread ...........

Tom

Tom: Excellent reading, thanks for posting! Andrew have obviously re-vamped his website since last time I visited.
The other articles/guides was very good as well.

Thanks everybody, great links and info. Will try things out on the water during the weekend.

TX!
Martijn

Yes, install one.

But as a general guide

Downwind (with Kite I assume)
90 degrees or very slightly less.

Upwind, 90 degrees till trapping out, then point to the shrouds till overpowered with max downhaul, then ease the traveller and pull in the rotation until sailing in very high winds (35+) the mast should be pointing at the back beam.

These are the my starting points, you might want to go +/- a little on them for your own style of sailing/ weight

mbalhuizen,

I am amazed that your boat didn't come with a rotation limiter.
The Inter 18, 20 and Nacra F18 have one.
Does the mast have two through holes just above the boom mount?

Without a limiter your mast must be be rotating way too far forward when going upwind and killing your performance.

Actually, the I 17 (I17R) has the same set up as the I 20. You can set rotation anywhere from about 0 degrees to 90.

Tom

Martijn,

A good place to start would be about 45 degrees for upwind (and decreasing as the wind comes up)and about 75 or so downwind since you will be wildthinging I'm guessing. Some of the others sailors may know better on the downwind. I have been sailing with a spinnaker the last three years.............

The Taipan website above spells it out for light, medium, and heavy winds.

Scooby,

My 2000 I-17 aluminum mast boat has a mast rotation device as stock equipment.

Are we talkng about the same thing?

There is a stainless 'arm'( pointing aft) about 12 inches long attached to the mast about 4 inches above the boom attachment.

Then the pulley system and line, that adjusts the whole deal, attaches to the aft point of the rotator arm, to pulleys on the boom,..then the line goes down to tne tramp,..under the tranp,..to exit at cleats port and starboard..just aft of the side shrouds..

..you do not have this set up stock?

regards,

Bruce
I-17
( on the beach at Tampa )

Yes I have this, woiuld not sail any boat with a rotating mast without it !

IMO it is a stock item.

Are you guys talking about rotation limiters or rotation inducers? If you have a boom equiped rigg, a rotation inducer is not required (the boomless 6.0 required one). Typically, the angle and pressure from the mainsheet will tend to rotate the mast so all you need is a limiter.

It seems there is some confusion about my question, sorry about not being clear.

I do have a rotation arm as described by bruce, it is indeed a stock item.

What I do not have are the two lines, one each side of the boom that run through a alu cleat limited by a black ball.

The manual for "Inters and F18" states:

Tie the 5/16" rotator limiter lines to the diamond turnbuckels and lead them back to the clam cleats on the boom, and install the stopper balls.

It them goes on the explain the rotator setup bruce described.

I am stil not sure weather I would need them or not. I have noticed that the mast does not easily rotate to 90 degrees I have to force them by hand, especially with light winds. More wind makes the angels easier to setup.

I also find that they are not so easy to adjust while trapping.


Thanks for all you time and info,

Martijn

Tx Simon,

Yes, I am sailing with the kite (3 years now) and immensly enjoy it. It was the main reason to go for the I17, the FxOne was still to new (=expensive 2nd hand).

I have started using the figures you have described. I got them of the taipan website I learned about from an earlier post.

regards,
Martijn

Martijn

How old is your boat, my boat is riged so that the controls of the mast rotation come off the boom, down thru 2 holes in the tramp and then out to the side decks. You can just see them here :







Do you know anyone in NL looking for an Inter 17, I am selling mine ?

I have sail number 35. That would make the boat 5 years old?

I have included a picture to show you what lines I am asking about, the yellow lines.


Your boat looks great!

Matrijn

The Taipan often runs with less rotation than other boats. The tips giving in the taipan tuning guide are good but you may want to increase the rotation a little beyond what is stated there on your boat. Note that the two boats are using different mast sections; the crosssection of both is noticeable different with the I-17 being teardrop shaped and the Taipan mast being oval shape. The Taipan mast is much thinner (63 mm to about 90 mm on nacra masts).

Wouter

The Taipan often runs with less rotation than other boats. The tips giving in the taipan tuning guide are good but you may want to increase the rotation a little beyond what is stated there on your boat. Note that the two boats are using different mast sections; the crosssection of both is noticeable different with the I-17 being teardrop shaped and the Taipan mast being oval shape. The Taipan mast is much thinner (63 mm to about 90 mm on nacra masts).

Wouter

Wouter, tx for that.

The main thing I have picked up so far is the difference between masts using diamond stays vs masts that do not. My understanding of the effects of mastrotation dated from my diamond-less masts - H16. It seems the effects are the other way round for masts with damond stays.

groet,
Martijn

Martijn,

Nope, 35 is a fair bit older, mine is 76 and is 5 years old in Aug, I would guess 35 is more like 7-8 years old.

The yellow lines are indeed rotation inducers, I've not used them as I find they are usually more trouble than they are worth ! As you can see from my piccies, I do not have them on my boat. I sail on a lake most of the time and so don't get much in the way of waves in light wind - the rotation inducers would be useful to keep the mast rotated in the light stuff in waves !

>Nope, 35 is a fair bit older, mine is 76 and is 5 years old
>in Aug, I would guess 35 is more like 7-8 years old.

Ok, good to know that.

>the rotation inducers would be useful to keep the mast
>rotated in the light stuff in waves !

Yes, that would help. I will look around to see how other
do this.


Martijn

I that case you'll be alright.

Going from a diamond wireless mast to a prebend (with diamond wires) rig is a big step.

Wouter

You only need to worry yourself with THOSE rotation inducers in very, very, light air. I actually refer to those as "anti-bing-bong devices" because they keep the mast from swinging back and forth in light air and chop. You shouldn't need to use these if you have any breeze.

Jake, I think we need one of those anti-bing-bong devices on this thread. I got dizzy trying to read it.

mbalhuizen,
We definitly have some confusion.

The yellow lines in your picture are mast rotators/overrotators/inducers, not limiters.
The striped line attached between the boom and the mast rotator wishbone is the rotation limiter.


General comments as to use.

Most boats have a rotation limiter of some type.
They usually have settings for upwind and downwind.

Mast Rotators are used downwind and/or in very light wind.
In light wind, there isn't enough pressure from the boom to keep the mast fully rotated,
so the inducer prevents the mast from "banging".
Most sloops don't produce enough boom pressure when running downwind to overrotate the mast to 110 degrees.
A mast rotator is usually needed.

A boat running a spinnaker needs to rotate the mast past 90 degrees to prevent mast breakage downwind.
Since they usually keep a tight mainsheet and don't travel the mainsheet very far down,
there is usually enough boom pressure to overrotate the mast properly.

There are two types of positive rotators/overrotators/inducers, manual and "automatic".
Manual rotators include the type on the boom, shown in the picture,
and the type which use an additional wishbone mounted on the front of the mast (see Murrays catalog, page 27).
This type must be manually released and then reset on each jib or the battens can get broken.
Many boats use an "automatic" rotator built from bungee cords.

Hello All,

Those yellow lines, nope, do not have them on mine.

I suspect they would be nice in light air applicaitons, if that is your conditions.

Scooby, nice pics,...your boat looks like new.....compared to a new one, yours is a bargin, do the wheels come with the price? (..do I get my commission if this post sells her?)

..

no really, both your boats look in great shape....how a boat looks new out of the box,...and 5 years later reflects on the worth of the product..

I have sail # 50, however, being on this side of the pond, my sequence may not coincide with yours, it is a 2000.

regards,

Bruce
I-17
St. Croix

Yes, the Wheels are in the price, and yes, some sort of commission could be sorted out

Large crate of beer is the usual around here.