Outboard motor drag

[Peter Kozup]

Have any of you with outboards in a well, like on a CD25 or CD26, figured out a convenient way of cutting the drag of the outboard while sailing? It is difficult (impossible!!) to pull the motor up out of the water because the well cover is in the way. I'm very aware of how much drag the outboard must cause while sailing. but can't figure out a way of reducing or eliminating this. Anyone have any thoughts or ideas?
Thanks, enjoy the down time and fair winds.
Peter K.

[Ron M.]

I had a CD25 / longshaft (25") outboard and sailed it with the motor in and removed a few times. My recollection is that it was a negligible difference. The stern was a bit higher and lighter but not much.
Overall I would say it was not significantly faster. My feeling is to enjoy the sail and not fret over a half knot lost to lower unit drag. Perhaps a larger head-sail ?
________
Vapir Oxygen

[Gary M]

Peter,

I once owned a Columbia 26 Mark I which had an outboard well. The drag your talking about always irritated me, along with the lazarette filling with water.

I used it this way until I sold it with out ever finding a good solution but other owners would use a 2 HP outboard to get in and out of the slip then store the outboard in the lazarette while sailing. The Columbia came with an engine well plug that could be installed closing off the well.

This is probably as close to a solution as your going to get.

Gary

[Tod Mills]

this guy, Bob Wessel. His boat has an outboard well and he's been developing a way to get the outboard up out of the water. Last I heard, he was looking at a vertically-sliding motor mount.

If you click on "Send E-Mail" at this post of his.....

http://bbs.trailersailor.com/forums/tra ... 537532,Bob

[Ron Brassord]

Iowned and sailed two CD 25s and found that a long 25" shaft engine was not necessary. The standard shaft gave much less drag, and worked in all conditions. I also learned that it was more important to have an engine small enough to turn in the well for steering the boat in close quarters.A smaller engine with the shorter shaft was more easily lifted out of the water and stored horizontally in the top of the well for long passages and storage.
An important trick i learned from this forum was to insert a pipe in the exhaust vent on the upper backside of the lower unit to take that exhaust under water and out of the well. This allowed the cover to be fully closed with out choking the engine'
I found that a 9.9 was too much engine, an 8 2 stroke about right and a 6 enough in most conditions.
Good sailing Ron B

[Carl Thunberg]

Peter,

The prop drag may not be as serious an issue as you might think. First, the prop is in the shadow of the keel. As much as we'd like to think we have laminar flow across our keels, the reality is, the flow is quite turbulent. Turbulent flow creates flow separation on the downstream side of the keel with vortices that shed off in an alternating pattern, left, right, left, right, etc. This creates a low pressure zone on the downstream side of the obstruction (in this case, the keel). The prop is located right in the middle of this low pressure zone.

An extreme example of this is a boulder in a fast-flowing stream. Any fly fisherman knows the trout hang out in that eddy because the flow stalls there.

Obviously, I've simplified the hydrodynamics considerably here, but the principals are sound. Just something to think about.

[mgphl52]

My second CD25 came with a VERY heavy 9.9 outboard (as did my first 25). However, I had started racing when I bought Brigitta and YES, the drag is anything but negligible (in my opinion). Plus, I kept her in a salt water marina year round, aka lost of extra maintenance on the water pump, etc. My solution was a Nissan 6hp 4 stroke that easily fit in well, was only about 60 lbs, easy to pull out or replace even in "bouncy" conditions and it stowed very nicely on the cabin sole while racing. Since I am also a rather lazy sailor, that motor spent far more time in the cabin than the well - we would just sail in and out instead of motoring.

[Dave H]

I sail a Typhoon Senior with 5 hp Honda 4 stroke in the well. I also believe the loss of speed is negligable. However, in racing nothing is negligable. I remember hearing that 1/100th of a knot over a 4 mile course is 15 seconds at the finish line. I'm not enough of a mathematician for verify that. I also remember hearing that you can get a different PHRF rating depending on whether you leave your motor in the well or not. If that is true, we could look at the two ratings and tell in seconds per mile what the difference has been calculated to be.

[Neil Gordon]

I remember hearing that 1/100th of a knot over a 4 mile course is 15 seconds at the finish line.

Using 4 knots as compared to 3.99 knots, I got a difference of 9 seconds. At 3 knots and 2.99, I get 16 seconds.

[Brian A.]

The Eastern Long Island Yachting Association measurers deducted 12 seconds from my PHRF rating when I elected to race without the engine in the well. An experienced racer advised me that the benefits of the reduced drag far outweigh the penalty. After sailing both ways, I agree. In addition, I have found that even a slight coating of slime on her bottom will cause a noticable drop in performance. Stowing the outboard and keeping the bottom clean helps me arrive at the bar before last call on Wednesday nights. Drag is bad for both racers and cruisers. My 2 cents: Reduce it any way you can.

[Dave H]

Hi Brian, Do you know how the use of spinnacker or asymetrical sails effects your PHRF rating? What is the typical adjustment in PHRF rating for spinnacker or asym? I'm thinking about moving my boat closer to home. It would be a racing club. Thanks. Dave

[Brian A.]

Hi Larry: I posed your question to a measurer for an advisory opinion. This is what he advised: "a CD25 with a standard size chute (max. girth no greater than 16.2 feet, pole length no greater than 9 feet, will take a 19 second penalty". Your local folks may or may not agree with this, but it gives you some notion of where you'll end up. I hope this helps. Simpatico is rated at 278, engine stowed, non-spin, max hanked-on headsail 135%. I think this is a pretty fair figure. Cheers, Brian