[Rhodes22-list] IMF "Reefing"

Sat Feb 17 10:31:46 EST 2007

It seems to me that the difference between IMF and conventional from a
weight distribution standpoint is two fold:

1.  The furling tube which is negligible and the weight of the mast
extrusion, heavier than standard.  Both of these are fixed weights (fixed
height above deck with the mast raised in sailing position) and can be
approximated by a weight "x" at the midpoint of the mast (i.e., center of
gravity or CG).

2.  The weight of the sail (less than conventional, because it is smaller).
Since it reefs and furls on a vertical roller, the CG of the sail also stays
at the same height above the deck.  The center of effort (CE) of the furling
sail will move down and forward as the sail rolls into the mast.

Net effect, furling the IMF lowers the center of effort and not the center
of gravity of the mast and sail combination, while furling the conventional
sail lowers both the CG and CE.  The CG of the conventional mast/sail
assembly is lowered by the weight of the sail, which is not likely a
significant part of the whole.  

It seems then to come down to the additional weight of the IMF assembly with
sail vs. the conventional mast and sail.  I don't know this, but I am sure
somebody here does.  Likely windage of the thicker mast extrusion might be a
factor in some wind conditions.

For me, convenience trumps all.

Jim Connolly
s/v Inisheer
'85 recycled '03 

-----Original Message-----
From: rhodes22-list-bounces at rhodes22.org
[mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Bill Effros
Sent: Saturday, February 17, 2007 9:55 AM
To: The Rhodes 22 mail list
Subject: [Rhodes22-list] IMF "Reefing"

Wally,

Comparing "reefing" on standard sails vs. IMF sails is very hard to do when
discussing among sailors some of whom have never even seen an IMF.

"Reef Points" result in noticeable changes in sail size. The IMF is
infinitely adjustable. I often adjust my sail in increments of 5% of total
sail size. I suspect most IMF sailors change the size of their sails instead
of using the traveler. We don't think of it as "reefing" 
-- it is an adjustment the sailor can quickly make in response to changing
conditions.

The extra weight of the mast is insignificant. Remember that your sail is
larger, adding weight aloft compared to the smaller IMF sail. But, since the
boat is designed to be sailed upright, and can easily be trimmed to sail
upright, the difference in performance due to weight is probably no greater
in an IMF boat than the difference of carrying an extra bottle of rum. Or
not.

I carry my extra sail on the Genoa instead of the main sail. Both are
infinitely adjustable while single handing. When conditions change, I change
the set of my sails, all by myself, so easily that even a lazy sailor will
do it.

I think the biggest surprise about the IMF is how well it works
mechanically. The sail and mast are made for each other. There is no
compromise here, and it is easy to extend and retract the sail under any
conditions. My wife enjoys doing it.

Our harbor is busy on weekends with a very narrow neck, rocks all over the
place, and a 10 foot tidal variation every 6 hours. It is irresponsible to
sail into the harbor if you've got a motor, and most experienced larger boat
sailors take their sails down just outside the neck, and motor to their
moorings. We turn on the motor and don't even stop while we retract our
sails. When my wife sees other wives trying to control flopping sails inside
lazy jacks she shakes her head in disbelief. When other wives see my wife
roll up our sail they ask their husbands why they don't have sails like
ours.

Bill Effros

TN Rhodey wrote:
> Bill,
>
> Well I may be wrong here .....I guess it would depend upon how much 
> smaller the sail is verses the extra weight of mast. Way back when (on 
> the sailnet list) there was discussion about this. In my opinion even 
> if the mast weighed the same you still might need to reef sooner with 
> IMF. Pure speculation on my part and I will admit I may be totally wrong.
>
> The R22 is small enough to be quite sensitive to subtle changes in 
> weight and trim adjustments. You pay a price with IMF in mast weight, 
> sail cut, no downhaul, no cunnungham, no battens (except for the new 
> rev). If you know how to use all these controls you can create a much 
> flatter sail. You would be surprised at the difference adding a vang 
> made even with IMF. I could still flatten the sail enough to make a 
> big difference ...sailing much flatter, fast, and higher into the wind.
>
> Everything is a trade off and for me the pros for IMF are well worth 
> any cons.
>
>
> Wally
>
>
>> From: Bill Effros <bill at effros.com>
>> Reply-To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>> To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>> Subject: Re: [Rhodes22-list] Harken Lazy Jack
>> Date: Fri, 16 Feb 2007 09:02:30 -0500
>>
>> Wally,
>>
>> Why would a smaller sail need to reef sooner?
>>
>> Bill Effros
>>
>> TN Rhodey wrote:
>>> Joe, There are some performance trade offs with IMF. The sail is 
>>> smaller and I would think an IMF R22 would need to reef sooner but I 
>>> am just guessing. That extra weight aloft must have some effect on 
>>> balance.
>>>
>>> Wally
>>>
>>>> From: Joseph Hadzima <josef508 at yahoo.com>
>>>> Reply-To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>>>> To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>>>> Subject: Re: [Rhodes22-list] Harken Lazy Jack
>>>> Date: Thu, 15 Feb 2007 16:45:37 -0800 (PST)
>>>>
>>>> I've seen some other cool sail systems, some with sail covers so 
>>>> you only need to zip it closed. Several replace the slot in the 
>>>> main with a track system so even a kid could hoist the main, and it 
>>>> drops into right into the sail cover.
>>>>
>>>> A BIG advantage of the IMF (I believe) is the unlimited reef 
>>>> points. Another is that is remains protected in the mast during 
>>>> transport.
>>>>
>>>> I've only heard one mild complaint that the IMF mast is thicker, 
>>>> and thus hinders pointing performance a little, but like Stan says 
>>>> there are trade-offs ... unlimited easy to set reef points, or 
>>>> slightly better pointing with the possibility you'd need to bring 
>>>> down the main completely because you couldn't depower enough.
>>>>
>>>>
>>>> And I only had a minor problem with lazy Jacks where one of the 
>>>> lines got wrapped around part of the sail, and we had to lower and 
>>>> raise it again. But this was aboard a 65 foot Schooner with gaft. 
>>>> So it was a little more trouble than if it was a Rhodes with lazy 
>>>> jacks :-)
>>>>
>>>> Speaking of the A28 video ... I like the piston powered Hoyt Jib 
>>>> boom for down wind sailing .. very nice feature.
>>>> Notice it's a working Jib and NOT 175 gennoa!
>>>>
>>>>
>>>> --- "Michael D. Weisner" <mweisner at ebsmed.com> wrote:
>>>>
>>>> > While viewing the AE28 video, I was impressed with the ease with 
>>>> > which the owner was handling the main. He was using a Harken Lazy 
>>>> > Jack system (installation manual at
>>>> > http://www.harken.com/pdf/4058.pdf.) At West Marine, the small 
>>>> > Harken Lazy Jack is about $200.
>>>> >
>>>> > Has anyone ever used the Harken Lazy Jack on an R22 main sail? 
>>>> > Does it interfere with boom movement? Does it jam easily?
>>>> >
>>>> > I know, with IMF, you have no need for it. I still haven't been 
>>>> > able to justify the cost of the new IMF mast & hardware on our 
>>>> > R22.
>>>> >
>>>> > I was just thinking that the Lazy Jack looked interesting. Maybe 
>>>> > run the control lines (downhaul &
>>>> > halyard) back to the front of the cockpit, next to the pop-top, 
>>>> > opposite to Genoa furling line. Comments?
>>>> >
>>>> >
>>>> > Mike
>>>> > s/v Shanghai'd Summer ('81)
>>>> > __________________________________________________
>>>> > Use Rhodes22-list at rhodes22.org, Help?
>>>> > www.rhodes22.org/list
>>>> >
>>>>
>>>> __________________________________________________
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>>>
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