raising the boom

[mastreb]

Looking at some boats today.. I see some have their booms run "up" at an angle of say 8=12 degrees.. Mast to Stern.. It appears this is done to allow standing room at the Helm?
If so, can we 1. Cut our main sails at an angle
2. When we get a new main have it cut to fit etc. etc.
My real question is?? Could I have two different "style" Main sails ( foot ) and just allow the boom to swivel as needed...??

The gooseneck on the Mac will handle this just fine, and it's certainly the simplest mod to do to raise the boom discounting the cost.

From an aerodynamics perspective, you will loose a tiny bit of performance. The sail acts as a wing foil when close hauled or reaching, and by raising the back of the boom, you will put the boom into the slipstream of the bottom portion of the sail, eliminating that portion of the sail's wing effect and creating a bit of drag after the clew. Also you're likely to create a small vortex off the back of the boom because you're vectoring wind upward into the slipstream of the rest of the sail, which would cause additional drag.

All that said, the foot of the sail is the least effective portion anyway, the wind is slowest along the bottom, and the foot already has the most drag of any portion of the sail. Furthermore, it's likely that a sail cut this way would maintain a tighter leech which would improve the performance of the rest of the sail, offsetting this effect, perhaps entirely.

For running, the main acts more like a parachute than a wing, and in this case your performance will decrease linearly as a function of the lost square-footage of sail, probably about 10%.

Bottom line, it won't be faster, it will likely be noticeably slower, but it might be just be negligible, and it's almost certainly worth it if you want to boom raised.

Matt

[Divecoz]

Thanks ...to Judy and Mastreb both, for invaluable information and explaination.. I am presently in Florida ( using Moms Computer : ) I noticed a few sailboats ( Down Here...) running just such booms/sails and this seems like a good idea ( to me ) for a New Sail ..I'll keep Judy in mind for this purchase for sure.. I "believe " I would keep the old sail, as its still in very good shape, as a back up. I'd just keep it in a sail bag up in the V berth..

[Judy B]

Hi again,

I think there's very little aerodynamic downside to raising the end of the boom, particularly when the gooseneck position is considered in relation to the planform of the headsail.

The explanation can be found in the math that describes how the headsail and the mainsail interact. They behave as a unit, not as separate entities. The aerodynamics of a two-foil system are quite different than a single foil system. I haven't personally spent a lot of time learning specifically about the aerodynamics of raised boom-ends, but modern sail-design software can simulate it. It's an interesting topic to a sailmaker like me.

In practice, it's commonplace to design open-rule racers so that the gooseneck attaches down low on the mast, and the boom is angled up quite sharply to clear the cabintop and helm. It's a design found on racing boats like the Open 60's which are raced around the world.

Here are some pics:





Here's a link to some pics of Bruce Schwab's Open 60, "Ocean Planet", on my personal website, where you can see details of the "vang" and some exquisite rigging. Bruce Schwab is a friend of mine, and the Master Rigger who advised me about rigging my boats over the years.

http://blumhorst.com/potterpages/Photop ... aindex.htm

Fair winds,
Judy B


PS. Technical note: Google "modern sail theory" for more info. Be sure to visit Arvil Gentry's website - he's the grand-daddy of modern sail theory. Arvil's technical papers can be downloaded at http://www.arvelgentry.com/index.htm; they're for the mathematically inclined. For a less mathmatically taxing approach, I recommend The Symmetry of Sailing: The Physics of Sailing for Yachtsman by Ross Garret or The Art and Science of Sails by Tom Whidden)

[ronacarme]

Sliding gooseneck allows main halyard to raise main as hi as possible. Given that, pull down the fore end if the boom to pull the wrinkles out of the luff. If the boom seems low, duck thy head or spend $$$ and recut the main. If the latter, risk more heeling. Or get a different boat . IMHO. Ron

[zephyr101]

took it out sailing with the sliding gooseneck in place and the bimini up. boom clears the bimini. needed the shade today. every thing works perfectly you have to fold up bimini to raise main sail then raise bimini again . and if i want i can run with the boom in original position(slids up and down ) can even go lower then original. then bimini has to stay folded.boom rests in oriinal mount. cost about 4 hours labor and less then $50. for parts 1- longer 1/4" x 3" bolt 8-1/4 flat washers.1-new lock nut 1- sliding goose neck (used) new less then $50.labor to close up gate for sail slugs and open up new one lower. drill out rivits, ended up chiseling off, drill new hole for boom bale (to clear front of bimini)also replace bolt behind mast with eye bolt 3/8"x 3" had to drill out hole ,it was metric only a few thousants difference.block and camlock bought at tag sale(down haul) every thing new would be around $125.
HOWIE (zephyr )








0

[Highlander]

Il you move your mainsail center of thrust up the mast, the heel momentum will increase. The ballast will then become insufficient, the stays and mast not strong enough.

You will not have a MacGregor sailboat any more. The marine surveyor will notice and NOTE it. The insurance and the prospective buyer also.

This is a major modification, far beyond the reach of a non marine specialized engineer. I would not even raise the sails on such a modified boat without putting on a life jacket.

Hope you change your mind.

So basicaly what you are saying is that the boat manufacturer should not be selling the boat with a 350sq. ft Spinnaker . Think u should reconsider what u say before u say it !

J

[Highlander]

Annoying, but not unsafe.
mastreb
Captain

My Mac is not modified. I keep it on a 20 miles long, 1 mile wide lake, with nice mountains and cliffs. Real nice.

On a nice summer morning, at zero speed, I was enjoying the music, waiting for the noon breeze to kick in, all sheets out, taking advantage of any breath of wind as it would come. Actually, once in a while, I would move a little. I was alone.

At one point, I saw a nice little gust moving toward me on the glassy water surface. I prepared to take advantage of it to tack.

At zero speed (the boat would not round-up) the heel almost instaneously rose to 30 degrees, then exceeded the range well beyond 45 degrees, something like 60.
The speed still at zero.

I stood up on the side of the lower bench cover (starboard) holding to my dear life with my whole left arm on the port side of the ...hull. I succeeded at staying on board.

«Annoying», indeed, but not «unsafe» since I am a fairly good swimmer. Besides, my stays held just fine, since they were not prematurely worn out, being the appropriate gauge for the nominal heel of this boat.


Note: my editing is as frequent as the instances I wish to correct my English writing. Believe it or not, I am actually a pretty good writer.......in French !

Their is no way the boat will heel period with all the sheets out the sails would be just flapping in the wind , the sheets would have to be sheeted in tight with no one in control of them or were left flapping in the light breeze & aloud to get tangled in the rigging or was with no or not enough ballast either way thats not the boats fault, just a misgiuded inexperienced or reckless sailor . Ive sailed my boat with 4 head sails & main equaling up to 700sq ft of rags thats more than double the jib & main alone . no offence But ! Scaremongering without facts is not the way to go . I've sailed my @ over 65-75 deg. of heel for a very exciting ride & have posted the videos to prove it





Here's Beene's boat no problem coming right back up
http://s844.photobucket.com/albums/ab1/ ... 010128.mp4

J

[Doupirate]

Their is no way the boat will heel period with all the sheets out the sails would be just flapping in the wind , the sheets would have to be sheeted in tight with no one in control of them or were left flapping in the light breeze & aloud to get tangled in the rigging or was with no or not enough ballast either way thats not the boats fault, just a misgiuded inexperienced or reckless sailor

So flattering......Thank you!

So you say what happened didn't happen since it does not match your vast experience! Sorry, I was there and it happened as depicted. My ballast is full all season long as the boat sleeps home, at her own personnal dock.

I've sailed my @ over 65-75 deg. of heel for a very exciting ride & have posted the videos to prove it

You should not be so proud to show your boat clearly over-sheeted heeling about 45 degrees. When you heel more than 20 to 30 degrees on any boat, you slow it down and become the clown of the day. There are little holes rows in your mainsail. They are for reefing the mainsail. By heeling excessively as you are so proud to show us, you just decrease the mainsail effective surface, having it largely horizontal hence not facing the wind as it should. A reef or two would have the same end effect on the mainsail, but since the boat would straighten up hence not dragging on the water as much, it would accelerate.

Excessive heeling might impress some people but not everybody.

This YouTube shows the pros working hard to reduce the heel at the Cape Horn. On average they succeed at maintaining it at around 20 degrees. They run to win the race....

http://www.youtube.com/watch?v=zXuzy0k9mZQ

Besides, you should consider balancing your main and your furler so the rudder would stand at neutral. Your second furler looks excessive to me. Your boat will tend to turn downwind, you will have to constantly compensate with the rudders, hence slowing the boat further.

There are good sailing schools that could teach you the basics of sailing. I recommend you take advantage of their services the sooner, the better.

Regards,

[Divecoz]

First off........ I'm Now Home..
Needless tom say......Mom just didn't have the tools I needed, to experiment with ..
I need approximately 1 ' of additional height at the end of my 10' boom.. Sooooooo I took a 10' length of 1/2" EMT and with a ruler in hand , I raised one end 12" off the ground.. Then with just, so much as reaching into my , now handy tool box and retrieved my Johnson Angle Finder.. For 1' additional clearance? I find I need only about .... 8 degree's of lift.. I at least have done this numerous times, by just releasing the Vang and the traveler down haul..
Under most sailing conditions...This would not be advantageous...
I "think" I'll just risk the cost of having a sail made.. ( Judy Judy Judy) I think it will be best to call and actually talk with Judy on the phone..
As the wife pointed out.. ALL Your Toys are FREE! Well Yea.. kind of..

[Divecoz]

I watched the Video.. Numerous exceptions there to be seen..
#1. They were running between 36 and 39.. degrees
#2. They are running in ..Big waves Heavy seas... thats almost double 20....
#3. BIG Dollars on the line.. ( Sponsors ) thhhhrow money at... consistent winners.. they can get REAL stingy with 2nd 3rd and " only managed to finish"....
Clown.. aka Clowning around.. If you good enough you CAN Clown Around.. ( depending on your abilities)
I am just not good enough , to feel confident enough , to Really Have Fun ( Clowning Around) sailing... Jon / Highlander has " Shown Us " with Videos .. that he's better than most of us at sailing on these boats.. I used to "clown around " Water skiing and Snow skiing.. even in MMA's.. and I still clown around Scuba Diving... I feel that , implying that Jon was or is "a clown" out on the lake ? was at best, a poor choice of descriptors
As for where your boat calls home? That IMHO has nothing to do with how good a sailor you are.. Though many of those locations say.. Your yearly income exceeds $1,000,000.00 NET! or MORE!!!!

[Kittiwake]

I love it: reading this site is sometimes like watching a couple of spirited best-friends having their weekly friendly argument!
I know nothing about sails; but my guess is that, if 2 Mac owners seem to completely agree on some sailing issue, then one of them (likely both) is(are) just being polite.
You all seem to me to be making good points.
Cheers,
Kittiwake

[Judy B]

First off........ I'm Now Home..
Needless tom say......Mom just didn't have the tools I needed, to experiment with ..
I need approximately 1 ' of additional height at the end of my 10' boom.. Sooooooo I took a 10' length of 1/2" EMT and with a ruler in hand , I raised one end 12" off the ground.. Then with just, so much as reaching into my , now handy tool box and retrieved my Johnson Angle Finder.. For 1' additional clearance? I find I need only about .... 8 degree's of lift.. I at least have done this numerous times, by just releasing the Vang and the traveler down haul..
Under most sailing conditions...This would not be advantageous...
I "think" I'll just risk the cost of having a sail made.. ( Judy Judy Judy) I think it will be best to call and actually talk with Judy on the phone..
As the wife pointed out.. ALL Your Toys are FREE! Well Yea.. kind of..

In terms of measurements, what I'd really like is for you to give me three measurement from your rig so that I can precisely define the angle that you want for the boom compared to the mast. Your mast may be at a different angle than somebody else's. So I would need measurements from YOUR boat.

Attach a measuring tape to the head of the mainsail and hoist the mains and tape to the usual position on the mast. Position the end of the boom up where you want it by whatever means is convenient.

1. Luff: Measure from the head grommet to the top of the boom at the tack (front of the boom),

2. Leech: Measure from the head grommet to the top of the boomat the clew grommet (back end of the sail).

3. Foot: Then measure along the boom between those two points: from tack to the clew

You don't need to be precise with your measurements - a quarter of an inch won't matter because I'm not using these measurement to build the sail. I'll use the measurement to calculate the angle between the boom and the mast on YOUR boat, so it clears YOUR head

If you'd like to give me a call, I am working in the office today and am available.

Fair winds,
Judy

[Highlander]

Their is no way the boat will heel period with all the sheets out the sails would be just flapping in the wind , the sheets would have to be sheeted in tight with no one in control of them or were left flapping in the light breeze & aloud to get tangled in the rigging or was with no or not enough ballast either way thats not the boats fault, just a misgiuded inexperienced or reckless sailor

So flattering......Thank you!

Your Very Welcome . An unsheeted boat is basicaly the same as a boat mast up only , So please do enlighten me !
as to how this happened on relativitly calm water with a sudden gust with a boat dead in the water !, I've seen it happen in big water with huge swells mast up only

So you say what happened didn't happen since it does not match your vast experience! Sorry, I was there and it happened as depicted. My ballast is full all season long as the boat sleeps home, at her own personnal dock.

I'm still listening !



Nice pic

I've sailed my @ over 65-75 deg. of heel for a very exciting ride & have posted the videos to prove it

You should not be so proud to show your boat clearly over-sheeted heeling about 45 degrees. When you heel more than 20 to 30 degrees on any boat, you slow it down and become the clown of the day. There are little holes rows in your mainsail. They are for reefing the mainsail. By heeling excessively as you are so proud to show us, you just decrease the mainsail effective surface, having it largely horizontal hence not facing the wind as it should. A reef or two would have the same end effect on the mainsail, but since the boat would straighten up hence not dragging on the water as much, it would accelerate.

Well if you do not practice this you will not learn what your boat is capable of or know how it is going to react in this situation & you'll learn what not to do in a bad situation
which apperently happened to you !

Excessive heeling might impress some people but not everybody.

Yes. But boys will be boys ya gotta have some fun with yer friends

This YouTube shows the pros working hard to reduce the heel at the Cape Horn. On average they succeed at maintaining it at around 20 degrees. They run to win the race....

http://www.youtube.com/watch?v=zXuzy0k9mZQ

As for my sailing skills well my best was a race against 40ft hunter with my & I won the race & posted the video as proof !

Besides, you should consider balancing your main and your furler so the rudder would stand at neutral. Your second furler looks excessive to me. Your boat will tend to turn downwind, you will have to constantly compensate with the rudders, hence slowing the boat further.

My boat is rigged unique & will actualy sail higher into the wind than a stanard mac

There are good sailing schools that could teach you the basics of sailing. I recommend you take advantage of their services the sooner, the better.

If your going for sailing lessons a dinghy sailing class will teach you more & are better suited reguarding skills for beginners as our boats are basicaly big dinghies & I'm always learning

Regards,

Do not be offended by my dry sense of humor
Cheers for the new yr Guy's
J

[Crikey]

That was a nice picture!

Topping lift on an

(also Happy New Year - everyone!)
Ross

[u12fly]

Let's not get picky about who likes to sail on the rail with the sensation of speed and who wants to squeak ever knot out of the boat, I think there are times when we give and take one vs the other. I've not had my boat rails baptized yet, but I hope to get there one day. I think the angle trimmed sail is the way to go... I have a toping lift which gives extra space parked, but makes no differnce when it comes time to load the sail with wind.