Side Slip

BPowell · Post by **BPowell** » Sun Dec 19, 2004 3:51 pm

I have noticed that there is a fair amount of side slip when sailing my 2002 26X with 150 Genoa full ruders and centre broard. (Dog tracking some call it) Do people sail with the motor down or has anyone else noticed the same?

Bruce P

Dan B · Post by **Dan B** » Sun Dec 19, 2004 4:27 pm

A few things to consider -
1) Weight distribution of passengers and cargo
2) Amount of centerboard down
3) How tight your sails are trimmed (tighter than necessary adds more to leeway and heel than it does to foward power.)
4) How full (or flat) your sails are set.
5) Direction you are sailing against tide or current

They all add in some way to slippage.

BPowell · Post by **BPowell** » Sun Dec 19, 2004 6:05 pm

I have rented and sailed other boats Hunter, Catalina etc. but my Mac seems more so than others. Heal I can take care of and enjoy most of the time but with Full centre board and rudders as described before in my last post it seems to much. It seems I need 50% more centre board than I have most of the time when on any reach. Just looking for what others thought, or if any one has done any MOD's

Bruce P

Dimitri-2000X-Tampa · Post by **Dimitri-2000X-Tampa** » Sun Dec 19, 2004 6:49 pm

I don't think a Mac should side slip any more than any other retractable board boat. Maybe there is something keeping your board from dropping all the way. On my 26X, virtually all the blue line (up to the knot) is used to get the board all the way down.

Fixed keel boats are going to have a lot more resistance to side slipping as a general rule, but you have to make it up by lifting your board for extra speed as you approach a downwind course!

I don't typically sail with my engine down unless it is a fairly short distance. In the past, I have found that my bigfoot lower unit dropped my sailing speed by about 0.2 mph but yesterday when I was beating upwind, it seemed to be closer to a 0.5 mph reduction in speed when I dropped the motor.

Moe · Post by **Moe** » Sun Dec 19, 2004 7:09 pm

Leeway - the usually undesired sideways movement of a vessel due to wind (and/or current). When it comes to wind:

The flatter the hull bottom, the greater the leeway

The shallower the draft, the greater the leeway

The softer the chines, the greater the leeway

The higher the freeboard, the greater the leeway

I see a few reasons the Mac hull would have considerable leeway.

--
Moe

MAC26X · Post by **MAC26X** » Fri Dec 31, 2004 1:13 pm

I agree Moe, and because of that I find the leeway is reduced by over-tightening the sheets a bit. This increases the heel which reduces the amount of flat bottom and presents somewhat of a "V" edge.

Moe · Post by **Moe** » Fri Dec 31, 2004 2:05 pm

I'll have to take your word on that. If I'm not mistaken, heeling is generatlly considered to increase leeway because of reduced centerboard effectiveness. But this is on round hull boats that don't change the hull profile much when heeded. That's quite different from going from an 8 degree deadrise flat-bottom to a near 45 degree super-deep-V as you could on a 26X.

--
Moe

Dan B · Post by **Dan B** » Sat Jan 01, 2005 2:12 pm

Did some testing while out on the lake yesterday, winds were 10-15.

Sailing upwind with full main and full genoa out - lots of heel. Rolled in enough genoa so that it was just barely larger then foretriangle and sailed upwind again. Much less heel, speed a bit less, but track lines on my GPS show I was able to point about 5 degress higher.

Catigale · Post by **Catigale** » Sat Jan 01, 2005 3:17 pm

Reef early and often....

INteresting that pointing got better - I imagine the genny furled up to almost storm sail size has a really crappy shape..

..in my beginners opinion I wonder if you could point better because you got you heeling down so that your rudders worked better, less windage, etc..

Jealous of all you guys in warm climates still sailing...

Catigale

Tom Spohn · Post by **Tom Spohn** » Sun Jan 02, 2005 1:21 pm

My experience with the X is similar to Roger's advice from the "How to sail section of the website."

"The time to reduce sail area is when you first think that it might be necessary. Even with less sail, the boat will be faster if the heeling angle can be kept below 25 degrees. Beyond that, performance goes all to hull."

We try to keep the boat at 20 degrees or less when we sail. I suspect that at more extreme angles the center board and rudders lose some "bite".

dclark · Post by **dclark** » Mon Jan 03, 2005 8:39 am

I have a couple questions...

Maybe it's because I haven't really sailed anything else, but how can you did if and how much side slipping you are doing?

I agree performance goes to hull at much more then 25 degrees. And I'll add that at much more then 30 degrees my boat will probably (depending on sail direction) round up into the wind. If I already have the forestay as tight (short) as it will go, then how much benefit (if any) will there be if I go through the work to further reduce mast rake (shorten the forestay or raise the tang on the mast a couple inches)?

Tom Spohn · Post by **Tom Spohn** » Mon Jan 03, 2005 9:59 am

Dave,
Sounds to me like your boat is already pretty well balanced. BWY recommends keeping the mast rake between 3 to 6 degrees, with the M on the 3 side and the X on the 6 side. If you are in this range, why change anything?

Moe · Post by **Moe** » Mon Jan 03, 2005 10:20 am

Being out of this sailing thing for many years, having a boat the size of the X round up rather than knockdown sounds like a good thing to me. It's one thing to right a small daysailer in warm Florida waters, but I'm sure it's a lot less fun with an X in sub-70 degree waters.

I understand the drag of rudders fighting weather helm, and there's some effort at the wheel to keep them over (without no-feedback steering), but for us old, slow folks, it sounds like a reasonable compromise.

--
Moe

Duane Dunn, Allegro · Mon Jan 03, 2005 12:50 pm

6 degree's is way to much rake for anybody but a beginner. And even for them the frustration of constantly rounding up won't help them learn to sail very well. They need to get a feel for the boat and when to crack off the main some to control the heel rather than be constantly spinning out into the wind.

Go for 3 degrees or less rake on an X. You'll find you need far less helm to hold your course and that will equate to reduced drag and better speed.

I haven't shortened my headstay but have it cranked down almost closed. I only round up in really big puffs. In most puffs now the boat just heels more, drops it's nose some, and presses on without having to correct at the helm. This is the behavior you want.

If however you are getting pushed over beyond 25-30 degrees it's time for a reef. She is far faster sailed on her feet with less sail area. Don't try to be macho and sail with full sails in a blow. Eventually you'll heel so much you will likely be going backwards.

My next trip out in strong winds I want to experiment with a second sheet run to the cabin top track. I think with the genoa rolled in just forward of the stays and pulled inboard more the boat will go pretty well in higher winds. I still need to get that intermediate reef in the main. The factory one is just way to large.

MacGregorSailors.com

MacGregorSailors.com

Side Slip

Side Slip