[Rhodes22-list] How to improve Rhodes 22 upwind performance?

[ROGER PIHLAJA]

Hi Dennis,

When I first got S/V Dynamic Equilibrium, I did some experiments with my outboard motor, a stopwatch, and a measured mile on Sanford Lake where I live.  Specifically, I was trying to determine what the “best” fore/aft trim was.  I moved ballast around to cause the boat to be 10 degrees down by the bow, level on the waterline, and 10 degrees down by the stern.  I had a graduated cylinder rigged up to measure fuel consumption and an accurate digital tach so I could reproduce the same engine RPM’s.  I choose the engine RPM to yield ~5 MPH to simulate sailing fast, so the effects of hull form wave making would be in the same range as sailing.  I made repeated runs over the measured mile at slightly different engine RPM’s until I found the engine throttle setting that yielded 5 MPH (actually a time of 720 sec over the measured mile with a running start) at each fore/aft trim setting and then measured the fuel consumption.  I did the experiments on a calm day when there was no other boat traffic and my lake has no currents.  I was trying to separate out drag from all the other factors, measured in terms of small differences in fuel consumption.  What I found was; down by the bow fore/aft trim was slightly better than level on the waterline and both were better than down by the stern.

I think it’s a question of drag.  Think about the hull shape behind the shoal draft keel back to the transom.  You want this part of the hull to smoothly direct the flow coming off the keel back to merge with the surrounding water.  When the hull is down by the stern, it acts like a set of landing flaps on an airplane wing  - lots of drag.  The difference between 10 degrees down by the bow to 10 degrees down by the stern is about 3% more fuel consumption and, I presume, that much more drag.

However, there is a big caveat to this experiment.  In waves, the boat depends on having sufficient reserve floatation in the bow to be able to punch thru waves.  Without this reserve floatation, the bow may submarine and you are in danger of pitchpoling, definitely the start of a bad day on the water!  But, for racing, especially on smooth water, slightly bow down trim is faster.

Yes, I know I’m a nerd!  But, a guy should be able to play with his toys, right?

Roger Pihlaja
S/V Dynamic Equilibrium

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From: Dennis McNeely<mailto:mcneelyd at site-solutions.com>
Sent: Sunday, March 20, 2022 7:36 AM
To: 'The Rhodes 22 Email List'<mailto:rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] How to improve Rhodes 22 upwind performance?

Greetings all -
One other thought... if you don't have enough weight forward, the bow of the boat can't provide enough lateral resistance to counter the force of the sails.
Put differently, if too much weight is aft, the wind will push the sail, mast, and boat forward - but it will also push it sideways. That lateral push is countered by your rudder and centerboard, but it's also countered by the submerged bow of the boat. If the bow is too far out of the water or the stern is submerged too much, trying to balance your rig is a non-starter.
Stated differently, if the stern is weighted down and the bow is riding high, you'll be continually pushed off the wind, because you won't be able to get the center of effort (the place where the force of the wind pushes your boat) over the center of resistance (the spot on the keel where the water resists force from the wind).
The tighter you sail to the wind, the worse the effect will become.
Having said all the above, I'm back to lurking :)
Dennis McNeely

-----Original Message-----
From: Rhodes22-list <rhodes22-list-bounces at rhodes22.org> On Behalf Of ROGER PIHLAJA
Sent: Sunday, March 20, 2022 8:47 AM
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] How to improve Rhodes 22 upwind performance?

Mike,

Here’s an experiment to determine if you have too much mast rake.  Assuming light to moderate wind so you can put up full sail, establish a close hauled point of sail, and trim both sails as good as possible.  Take note of how much weather helm you have.  Assuming you have the IMF mainsail, reef the mainsail a small amount, say 6 inches.  Reestablish a close hauled point of sail and trim the sails as good as possible.  You should now have less weather helm or maybe neutral or even lee helm.  Keep reducing mainsail area until you have eliminated all the weather helm.

By shortening the forestay, the weather helm can be tuned out of the rig.  I like the helm to be neutral to very slight lee helm in light air.  As the wind strength builds, the hull is going to heel over no matter how much rail meat you pile onto the windward rail.  I won’t go into the physics of why and how; but, the asymmetric wetted shape of the heeled over hull just naturally generates weather helm.  You counter this tendency towards weather helm by reducing mainsail area.  This moves the rig’s center of effort forward and reduces weather helm.  You want to leave the foresail at full area as long as you can keep the boat sailing on her lines and use the mainsail area to balance the helm.

In light air, there is very little feel to the helm no matter how the rig is tuned.  The easiest point of reference is to have the rig tuned for neutral helm, especially for a novice helmsman.  So, even though the helmsman isn’t getting any feedback thru the tiller, he/she knows to simply center the tiller, and the boat will go straight.  As the wind strength builds and sail area is not reduced, the hull will begin to heel over, and weather helm will build.  The helmsman is now getting plenty of feedback thru the tiller.  If the weather helm gets to be tiresome; then, the mainsail area can always be reduced to take the pressure off the tiller.  Even a few degrees of rudder angle off center develops an amazing amount of drag.  This slows the boat down and reduces pointing ability.  Remember, the boat is making leeway even when the tiller is centered, and this leeway is enough for the shoal draft keel, centerboard, and rudder blade to work together to develop the required lift for the boat to be able to point.

Roger Pihlaja
S/V Dynamic Equilbrium

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From: ROGER PIHLAJA<mailto:roger_pihlaja at msn.com>
Sent: Friday, March 18, 2022 7:32 PM
To: The Rhodes 22 Email List<mailto:rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] How to improve Rhodes 22 upwind performance?

Mike,

A couple of things to check:

1.   Is your centerboard all the way down?

2.  Is your rudder blade all the way down?

3.  In 5-15 knots of wind, you should use the mainsheet and traveler to center the boom.  Make certain the boom is not rising up and there isn’t too much curl on the leech.  Make certain the mainsail foot out haul is tight.  Without battens, there is only so much you can do with mainsail shape; but, this will set you up to do the best that is possible.

4.  Use your backstay adjuster to get the sag out of the forestay.  It takes quite a lot of tension on the backstays to remove the forestay sag.  Don’t be afraid of cranking on the backstay adjuster.  A mast head rig needs the forestay to have little sag in order to properly form an efficient slot with the mainsail.

5.  Refer to my rig tuning procedure in the archives to adjust the tension in the standing rigging.

The Rhodes 22 sails best to weather if it is regarded like a big sailing dingy, as upright as possible.  There should be zero to very slight weather helm.  If you have too much weather helm; then reduce the mast rake angle.  ie Make the mast rake more perpendicular to the deck.

My guess is you have too much mast rake, which is giving you a lot of weather helm, and killing your ability to point to weather.

Hopefully, these suggestions help.

Roger Pihlaja
S/V Dynamic Equilibrium

Sent from my iPhone

> On Mar 18, 2022, at 1:49 PM, mm.bizlist1 at gmail.com wrote:
>
> Hi All,
>
> Now that I've been sailing my Rhodes for about a year, I'm starting to
> focus on getting the best performance out of her.  While I mostly sail
> for fun, I do race every couple of weeks and want to be more
> competitive.  In particular, I have found that she does not go to windward very well for me.
>
>
> I have a 130 genoa and the IMF mainsail.  Until very recently, I have
> been routing the jib sheets outside of the outer shrouds and
> handrails. That limits how much I can trim the genoa. Consequently, I
> can only tack through about 100-120o.
>
> Recently, I tried running the jib sheets between the outer shrouds and
> the inner shrouds.  That definitely improved my pointing ability
> significantly at the expense of less than optimal headsail shape on
> some off wind points of sail.  However, this configuration lets me use
> my jib cars to adapt to wind strength and whether or not I am
> partially reefed.  I think this will retain the ability to use a whisker pole on downwind legs.
>
> I did briefly try both of the inboard jib sheet fairlead/cleat
> alternatives but using those would seem to require having a second set
> of jib sheets and probably going on the foredeck to switch between
> them after rounding a mark (I often race solo).  Also, those options
> eliminate the ability to control the sheeting angle to the clew with the jib cars.
>
> I'd greatly appreciate your thoughts and comments about what you have
> learned about how to optimize your boat's performance.
>
> Thanks,
>
>
> Mike McKay
> s/v Liber (2006/2018)
> Allatoona Lake
> Acworth, GA
>
>