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Zarathu 06-21-2016 10:18 AM

Outboards and sailboat balance question
 
Does having an outboard on a small sailboat unbalance the boat and cause pitching?

I was told in another place that having a 90 lb outboard on a 19 foot sailboat would unbalance the boat and cause pitching and hobby horse actions.

I have not noticed this with a 60 pounder and two people at the stern in the cockpit, but again I don't tend to sail in conditions where the wave heights are high enough to cause pitching because my only sailing partner is the admiral, and conditions like that scare her.

Can this be balanced by adding movable ballast forward to the center post or to the bow, or by hiring a 65 pound kid to move around inside the cabin?

deniseO30 06-21-2016 10:46 AM

Re: Outboards and sailboat balance question
 
Most sailboats have what is called a "displacement Hull"
the more horsepower used to push the boat the more it will "squat" in the water and not really go faster 19ft boat probably only needs 3- 5 HP and guessing the 90lbs is 9 or 10 HP? Which will make the transom"sink" when the extra HP pushes the boat against its hull speed. When sailing, I doubt you will notice much if you aren't racing or into performance sailing. You do want to be mindful of the boats "freeboard". Since the o/b is like another person's weight

olson34 06-21-2016 11:04 AM

Re: Outboards and sailboat balance question
 
The boat's NA designed the boat for XX number of pounds of aux. engine. The hull displacement took this into account, whether it's an inboard engine or an OB mounted on the transom.
Lots of smaller sailboats had the weight of an OB factored in to their displacement calculation, whether planned to be on the transom or in a well.

I have only seen one 19' sailboat with a large OB, and that was about 40-ish hp. This was an early model MacGregor motor sailer, prior to their 26 footer.

What kind of boat are you looking at?

Loren

Zarathu 06-21-2016 11:41 AM

Re: Outboards and sailboat balance question
 
Quote:

Originally Posted by deniseO30 (Post 3547794)
Most sailboats have what is called a "displacement Hull"
the more horsepower used to push the boat the more it will "squat" in the water and not really go faster 19ft boat probably only needs 3- 5 HP and guessing the 90lbs is 9 or 10 HP? Which will make the transom"sink" when the extra HP pushes the boat against its hull speed. When sailing, I doubt you will notice much if you aren't racing or into performance sailing. You do want to be mindful of the boats "freeboard". Since the o/b is like another person's weight

That's what I figured. The 90 lbs is a 6 hp 60 lb Tohatsu Plus a 30 lb Torqeedo 1003. Each used for different things. The tohatsu is needed when I need to run back to the beach launch, often through rough seas, pulling a 10 foot walker bay dinghy, or for running back to the mooring from an approaching storm when I need to do hull speed, or hiking out long distances in a short time period, or motoring at night back from the fireworks trying to avoid a dense field of lobster pots.

The torqeedo is for anything else(getting out to better wind, coming into the mooring or dock, or just quiet motoring to get somewhere when I'm not in a hurry, and as "kicker" back up for when the gas engine decides to fail---as I have experienced int he past in dangerous circumstances.

I have a huge 24 inch freeboard, and the boat sails best and fastest in not more than 5-10 degree heel.

Thanks for your help. You confirmed my thoughts.

Zarathu 06-21-2016 11:45 AM

Re: Outboards and sailboat balance question
 
Quote:

Originally Posted by olson34 (Post 3547858)

What kind of boat are you looking at?

Loren

See my answer to Denise. I've not noticed hobbyhorse pitching with only the 60 pound previous Honda and three people in the cockpit. I tend not to be sailing when the weather gets difficult, and unless I got caught, the biggest waves I get are about 18 inches, not really enough for hobbyhorse pitching. But I can move ballast to midships to balance if necessary.

deniseO30 06-21-2016 12:14 PM

Re: Outboards and sailboat balance question
 

Zarathu 06-21-2016 12:50 PM

Re: Outboards and sailboat balance question
 
Quote:

Originally Posted by deniseO30 (Post 3548098)

Yeah it looks like a miniature CG boat. We have someone in the WWP19 who put a 40 hp OB on the stern and it will plane and do about 35 MPH.

zedboy 06-21-2016 01:05 PM

Re: Outboards and sailboat balance question
 
I had a 10HP 2-stroke Mariner that probably weighed 50-60lb on my Siren 17. Never felt it caused balance issues - don't see why it would, considering it was right off a square transom and 150+lb adults sat right next to it (on a boat that weighs 750lb dry, just over half a WWP 19!).

It was far more horsepower than needed for hull speed. The Siren will plane (or close) but the rudder became impossible at high speeds due to prop wash.

aloof 06-21-2016 03:27 PM

Re: Outboards and sailboat balance question
 
Weight in the ends has an insidious effect on the boat. Its symptoms are not obvious. The best advice is to do what you can to keep weight out of the ends. If you need motors aft and perhaps an anchor with chain ready at the bow, so be it. Just know you have seriously degraded your sailing performance. The only way to demonstrate it is to one day remove all the heavy gear fore and aft then go for a sail. Or just sit on anchor with waves running. The difference is usually significant. That is why racers do what they can to avoid any extra weight in the ends. All these little things add up. Does it make a difference? Certainly. Do you care? Perhaps not.

OP asked if the weight aft might be compesated for with weight elsewhere. No it cannot. The weight needs to be either removed from the boat or moved towards the center. Fuel tanks and batteries might be moved. Crew can sit more forward.

Zarathu 06-21-2016 05:56 PM

Re: Outboards and sailboat balance question
 
Quote:

Originally Posted by aloof (Post 3548370)
That is why racers do what they can to avoid any extra weight in the ends. All these little things add up. Does it make a difference? Certainly. Do you care? Perhaps not.

Everyone who was complaining about this in a West Wight Potter was talking about degraded performance. That's kind of ridiculous in a boat whose top speed is about 5.5 knots, so that its degraded to 4 knts. Big deal. People who buy WWP19's didn't buy them for speed, they bought them for stability and the pocket cruising. And they generally(unless the sail in the really choppy San Francisco Bay) don't sail in enough chop to be worried about hobby horsing, because in those conditions they are either reefed a lot, or they are actually using the big engine that they have hanging off the stern starboard.

Racers don't own west wight potters in the first place.


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