Would adding a mast reduce rolling on a motor cruiser

[Jcorstorphine]

35 years ago I built a small Seafairer 21 Motor Sailor from a bare hull which I always thought behaved well in all sorts of weather and did not seem to roll excessively in beam seas or passing wash. I have recently refurbished an identical boat but completed as a motor cruiser although it does have the deck fitting and mast support to complete it as a motor sailor.

My problem is that my new boat seems to roll unpleasantly in beam seas or passing wash even though I have the exact same amount of ballast fitted in the first Seafairer.

The only difference between the two boats is that the new boat does not have any masts whereas the previous one had two (in my “delusions of grandeur” I fitted it out as a ketch)

Is it my imagination or would a 21’ mast dampen the rolling due to the moments of inertia ignoring the steadying effects of have the actual sails set.

I have to add that between the two Seafairers I owned a 31’ Westerly Pentland so it perhaps I just became used to the motion of a bigger and heavier boat and that my first Seafairer rolled just as bad as the present one.

JC


Just updated this post, see No 8 J.

 

[wotayottie]

No. It would alter the frequency of the roll through altering the roll moment of inertia but would likely make it worse in amplitude by making the boat more "top heavy".

Try fitting some steel bilge keels to the hull to increase resistance to roll.

 

[fireball]

A mast in itself wouldn't dampen the roll - putting a bit of sail up too could though

 

[Twister_Ken]

Agree with wotayottie except:

It used to be commonplace to see displacement motor cruisers fitted with a smallish mast aft, carrying a 'steadying sail', cut flat and sheeted on the centreline. This - presumably - acted as air-brake to reduce rolling.

 

[Red Admiral]

35 years ago I built a small Seafairer 21 Motor Sailor from a bare hull which I always thought behaved well in all sorts of weather and did not seem to roll excessively in beam seas or passing wash. I have recently refurbished an identical boat but completed as a motor cruiser although it does have the deck fitting and mast support to complete it as a motor sailor.

My problem is that my new boat seems to roll unpleasantly in beam seas or passing wash even though I have the exact same amount of ballast fitted in the first Seafairer.

The only difference between the two boats is that the new boat does not have any masts whereas the previous one had two (in my “delusions of grandeur” I fitted it out as a ketch)

Is it my imagination or would a 21’ mast dampen the rolling due to the moments of inertia ignoring the steadying effects of have the actual sails set.

I have to add that between the two Seafairers I owned a 31’ Westerly Pentland so it perhaps I just became used to the motion of a bigger and heavier boat and that my first Seafairer rolled just as bad as the present one.

JC

The short answer is yes. I have been in a sailing yacht which lost its mast. It rolled so badly and so quickly that crew had to hang on for grim death. You can experiment by putting up a pole and hanging a heavy weight (an anchor, say) at different heights. Just don't overdo it! It's all about metacentric height if you want to look into it further.

 

[Strathglass]

Hi John,

Adding a mast is pretty well bound to introduce some damping to the movement.
It is quite amazing how much a bare hull rolls about without a mast.

I have been demasted once in the Forth (nothing serious just I was too slow in sorting the runners - wooden mast broke at the deck)

The boat (25ft) was rolling all over the place.

Adding any sail as well as a mast would certainly make your boat more comfortable in a swell or wash.

Iain

 

[Seajet]

Yes it will help.

I launch my 22' sailing boat mast down every year to allow going under a bridge, and raise the mast afloat.

Although she is beamy at 7'7" and very well ballasted, moving on deck is awkward as she rolls to the slightest input with the mast down.

With the mast up, she's very stable; as previously mentioned, this is a well known problem with dismasted boats.

A mast & half-decent rig would make a good Plan B for WHEN the engine fails too !

 

[Jcorstorphine]

It works

Well, I bit the bullet and found a second hand mast, albeit a bit lighter in section than I would have liked together with a SH Rotostay courtesy of Marinaskip.

Set it up with new rigging and with new sails from Crusader. As soon as I stepped aboard the boat after it had been launched I could feel the difference right away. Everything felt more natural and relaxed. The boat did not courtesy in the same manner when one stepped aboard and when I took it out in the ogin the boat felt so much more steady in every way. I should say that the boat always had the correct amount of balast for a MS.

Passing by the gap in the Cumbries’ on the way up from Troon, the wind went to the west so set the Genny, total bliss, extra knot on the log and boat as steady as a rock.

Worth every penny. Here is a wee pic of my project boat sporting its new mast and sailcover.

 

[rich]

I think you will need a sail, this sail makes a big diffrence to Hermees.

.

 

[Jcorstorphine]

I think you will need a sail, this sail makes a big diffrence to Hermees.

.

Nice boat, got a main and a furing genny from Crusader.

 

[pampas]

Does it seem to roll very fast, if so, try two equal weights (2-20ltr cans) tied securely just above deck level at the max beam and see what happens .

If this slows the roll the you have too much ballast low down.

worth a try.

 

[onesea]

Does it seem to roll very fast, if so, try two equal weights (2-20ltr cans) tied securely just above deck level at the max beam and see what happens .

If this slows the roll the you have too much ballast low down.

worth a try.

What your trying to do here is reduce stability

This would help but the other big reducer of stability is slack tanks. IE tanks that are not full, water in bilges can have same effect.

Ore Carriers suffer from this with to much stability fast rolling over short periods.

Car carriers on the other hand have less stability and can roll significantly long slow rolls. Which can be just as uncomfortable/ dangerous.

 

[Jcorstorphine]

Too much ballast perhaps

What your trying to do here is reduce stability

This would help but the other big reducer of stability is slack tanks. IE tanks that are not full, water in bilges can have same effect.

Ore Carriers suffer from this with to much stability fast rolling over short periods.

Car carriers on the other hand have less stability and can roll significantly long slow rolls. Which can be just as uncomfortable/ dangerous.

I think my problem was that I had too much ballast for use as a motorcruiser which made it feel cranky. However adding the mast has damped the rolling but not to the point where the boat feels unsafe. It actually feels like a bigger boat and I now have the benefit of a very well balanced rig. All in all, I am pleased with the result.

 

[Ben Dockrell 22]

Id be weary of a mast for the problem in case it added to the problem though getting more weight and size on the keels would be my first choice.

 

[Jcorstorphine]

Too much ballast.

Id be weary of a mast for the problem in case it added to the problem though getting more weight and size on the keels would be my first choice.

I don’t think that would be right. My problem was I had too much ballast for use as a motor cruiser. The problem was that the boat rolled quickly (I think due to the high mass of ballast trying to correct the roll)

The spec for the hull is to have 300 to 500 lbs of ballast when fitted out as a motor cruiser (depending on engine fitted) and a 1000 lbs for the same hull when fitted out as a Motorsailor. During the refurbishment of my boat, I removed all of the internal ballast and the Bilge Keels so it could be weighed and redistributed it as I had installed a heavy (400 lbs) engine and topped up the ballast to 1000 lbs as there was a plan that someday, I would add a mast and sails.

I had already built one of these boats in the 70s as a Motorsailor and used 1000 lbs of ballast in that boat. The problem was that my identical refurbished project boat (which had been a Motorsailor at one time but was missing its mast) did not behave the same in terms of comfort in rough conditions and all I could think of was that as I had fitted the same amount of ballast, it was that the lack of masts that caused it to be cranky.

As other have stated, they have seen this on other boats either through being dismantled or not having the mast on when launched.

I am happy and its nice to have a bit of "rag and stick" again

 

[Ben Dockrell 22]

Fair enough

I wish you continued contented and trouble free sailing

 

[Bobobolinsky]

It's a major job cleaning and painting the billet ballast in my motor sailer bilges. I reckon about half a tonne in the bilges and another tonne in the long keel, which is formed from steel billets

 

[Lakesailor]

Anyone noticed this is an old post with an update?

Job's done.

 

[pampas]

What I meant was that his GM and Cg were to close together and raising the Gm might help.

 

[Jcorstorphine]

Thanks to all

Anyone noticed this is an old post with an update?

Job's done.

Yes, you are right, it is an old post however, it took me a long time to get my act in gear and take the plunge to fit the mast. Having got a good result, I felt it only right and proper to report back with my findings and thank everyone for their input.

Thanks