MacGregor 26 not good? Water-ballast in general??

GTO,

The problem with water ballast really center on the same issue as why we use lead in keels instead of helium filled gas chambers (ok a little extreme but you get the point.

If you want to have a water ballasted keel for instance, you must create a hollow in that keel equal to the amount of water you want it to hold. So if you want to add 100kg of water to the keel it must have a volume of 100L (did I do my metric conversions right?) now here's the kicker though, since the boat if floating in water the volume displaced by the void is exacally equal to the volume of water added. Thus no actual gain in righting moment (discounting any possible gain from a better foil shapes) since the keel now displaces exactly as much water as it holds.

Instead lets take that same volume of water and replace it with lead... Now since lead weighs in at 11.4kg/liter for the same volume of keel displacment you have gained 10.4kg in righting moment relative to the amount of water you have displaced.

As for water ballast... Yes it is better to have the water on the high side to reduce heeling, but this assumes you have to have the water in the first place (which is true for ocean going). But the better solution is to get rid of the water completely if you can and use the same amount of displacement (weight) in a form that allows you the maximum righting force for that weight ( A larger keel bulb).

 

Mas - you need to do a bit of research on this boat. at least check out the web site http://www.macgregor26.com before making silly statements.

How you interpreted having water ballast - POOR DESIGN is beyond me.

The water ballast is for sailing, or motoring in really heavy conditions. The beauty of WATER BALLAST is that you can dump it for extended high speed motoring , and re-ballast for a stint of sailing.

Nor is the motor overpowered, Its only 50 hp, for a comfortable speed of around 18 knots, hardly rocket engine stuff.

STUMBLE -

Your analysis of how water ballast works is incorrect.

I remember one benighted soul thinking that water ballast only works when the ballast is higher than the outside waterline in a post a while back.

It works exactly the same was as 500 kilos of rocks, feathers, talcum powder, lead or any other element you care to name ..... and it doesnt need to be higher than the waterline before it works. True, lead will sit lower than a lot of other things and improve the righting moment (then you would only need 300 kilos in a MacGregor), but water is free, and doesnt take up that much room. And you can dump it for the tow back home.

Next time you watch a 200,000 ton supertanker head off in to the big blue ocean, remeber - if it doesnt have a full load of cargo - it makes it up with WATER BALLAST . thats how all these unwanted sealife get transported around the world.

 

On a 26 ft sail boat??? pish posh... poor design if not for "rule bending" advantage in racing... You would carry a battery, pumping and distribution and "dumping" systems as well as all the mast/sail shaping devices that normally are expected on a keen racing (around the buoys)? stuff ???

There was one advertised for sale a while ago - and I was curious as it had a 50hp outboard (**** of a sailboat at 26ft to need that as an auxiliary???) or is the version I saw just really confused... (It must have had a swing keel too - but I was not interested enough to check it out)... http://www.thecoastalpassage.com/macgregor.html - - A really confused design... neither power or sail... - sort of half and half... does neither comfortably...

Perhaps, based in Childers, and the long tow to water, an acceptable compromise to that owner... with a 1hr 30 minute drive? to the Hervey Bay boat harbour launching ramp...

As another suggested LEAD bulb in the swing keel? or placed alongside the keel box?

 

Rwatson,

I wasn't really saying that water can't act as ballast, but you are right I didn't make that very clear. My point really was that water is a poor choice to use as ballast generally. However there are certainly justifications for it, such as trailoring ability.

Use of water ballast in a keel however I still don't think adds anything to the righting moment of the boat since the keel must have a void exacally the same size as volume of water it displaces. Just like a baloon filled with water floating in water would only have the weight (not mass) of the baloon itself since the water inside exacally equals the weight of the water it diplaces.

Your example of the super tanker is a bit missleading though Rwatson. Since a supertanker has a static hull volume, the addition of water in ballast form acts to increase the displacement of the vessel. However when designing a keel where volume is variable things change.

 

Fair enough - but think about all the benefits, especially for a trailered boat. Price, versatility (dumping for downwind planing, uptake for beating). In my version, the water ballast will incorparate fresh water bladders for really fantastic fresh water storage.

Not so, it is exactly the same principle. Macs do not have a *keel* - they have a form very much like the tankers. have a look at the hull sections in their website. The water provides a lot of righting moment. They have nearly 200 lbs of positve bouyancy at 90 degrees heel for example.

As a point of interest, I have an NA developing a hull that is a variation of the Mac, and I have a full set of righting moments calculated, which are very impressive.

Mas - "A really confused design... neither power or sail... - sort of half and half... does neither comfortably..."

Well, as every owner or ex owner (like me) attests, these attributes are very sincere positives. This is the most popular 26ft production boat in the world, so something must work. Its does both things very well in fact.

Consider - a long lovely day sailing, and you see 4 other trailer sailer boats heading for your launching ramp - down sails, 18 knots in 5 minutes, and you are at the head the ramp queue - also for a sudden storm heading your way, an onboard emergency etc etc.

The sailing technique varies from keeled boats, eg maximimum of 6 degrees heel for optimum performance (keeld boats usually operate at higher degree of heel of course)

You both might like to re-read a few posts from "hard core" users earlier in this thread to get an appreciation of the Macs characteristics.

 

I concede - horses for courses...

 

Thanks for taking the time to reply to my inquiry.

I've a new job that is already requiring overtime, so my visits here have be curtailed.

What prompted my posts was my confusion about general comments about water ballast that, although they sounded correct, just didn't sit right for some reason.

I had an aha! moment about the concept that rwatson supports while stumble doesn't.
I'll go with the guy that agrees with me.

Masalai is obviously a mad-dog racer type, (humorous jab ), so his dismissal of water ballast is understandable.

Thanks again.

 

Hi GTO,
I feel more of a "purist", and a good and pure design does not need to be "f*%#ed with... Trying to make a sleek racing boat out of a bath-tub is disgusting...

 

I guess there are many types of purists. A fan of ancient wooden boats would scoff at wasting lead as ballast - thats what waterworn stones are for, and can be disposed of when you reach your cargo pickupup point, for a usefull load - probably of lead!

I suppose a true racing purist would not settle for anything less than spent uranium as ballast. Goodness knows, with the amount they spend on other gear, its not out of the question. Radiation ? Hell, put a kettle on it!

And as for the shape of boats - we have had a truckload of discussion in the "traditional boats" thread about form follows function. I dont think that Roger MacGregor as "Trying to make a sleek racing boat out of a bath-tub ". He designed this bathtub to be purely *not* a racer, but an efficient sailboat, a competant motorized performer, and he copied no other design to do it.

Now, as a 6 footer, I get really ticked off about having to soak in short baths and spas in hotels. The same goes for boats. When you duck your head into a Mac, even as a six footer, you get the roomiest accomodation on any 26 footer I have ever seen. I have crewed on longer boats that were more cramped, with a centreboard taking up most of the saloon, and a low windage cabin that gave me a backache.

If I wanted mazimum sailing performance, I suppose I would go for one of the small catamarans, with heaps of floor space, and sacrifice load carrying capacity. However, my priorities are, are the ability to spend days, or weeks in remote and pristine waterways, without having to spend a fortune on yacht stuff, with all my gear (food, diving gear, decent head and shower,usable kitchen etc)

The priority is cheap, roomy, cheerful family safe accomodation on the water. I can store the boat on its trailer during the cold unsailable days, and my grandkids will still want to use the boat as a playhouse - its that comfortable. I can tow it to inland lakes for fishing (its small enough) and live on it comfortably for days at a time.

As Mas so aptly put it "horses for courses"

There is no such thing as a perfect boat - the best design is the one that suits you, errrrr me!

Look into my eyes ... you are becoming convinced ... look deeper, deeper (evil laugh)

 

More benefits of water ballast ....

Check out the thread on lead/steel ballasting on small yachts

I think we can all remember this sort of headache. Thankfully, water wont rust or corrode or bend on impact

 

Oh heck, since this has got "legs" why not...
In consideration of the maritime thought police here in Queensland & possibly Australia, do not get caught with old water in your ballast tanks as the clean-up costs could be very VERY expensive if certain non-desired wild-life were to be detected residing within the tanks/pipes etc... Removal of tanks at your expense, clean up of environmental contamination at your expense... farkin scary... Minimal suggestion would be an RO watermaker and to put only PURE water in tanks and fresh flush all pipes/pumps and systems and bio-cide treat to ensure no international hitch-hikers were innocently brought into harbour... (pun intended)...

Who said anything about the Macgregor being a bathtub? your quote, not my assertion... You may have to duck in my boat, or reduce your height at about eye-level, nothing above that level anyway so no loss

 

Hmmm - I'm confused - maybe you meant somethng different than what I inferred. Thread = Macs and water ballast, I presumed you must be referring to the subject.

Re the cleaning out of bilge tanks - thats a really important "downer" for many water ballasted boats - as I mentioned in relation to Tankers spreading their obnoxious pests all around the world.

Mac users, and fishing boats with wet wells are under the gun around the Great Lakes Area with zebra striped mussels, and I seem to remember some other species mentioned.

The other problems with the Mac tanks, is that they are not lined - they are still rough fibreglass - and tend to snag things like hoses and marine life. I wouldnt want to try to import a secondhand Mac from Canada to Australia.

 

I feel a RL26 would be a sweeter choice, and the Court 650 and 750 were a nice trailer sized sailboat... I had lots of fun on all three LONG ago, now I have grown up (old) there is nothing to equal the advantages of a cat...

http://boats-n-stuff.com.au/forum/index.php/topic,2.150.html for my happiness....

 

I agree with FastFred on fresh water bladders.

What MacGregor should do is build-in whatever it would take to install optional bladders, most likely for fresh water, and run a hose to the cockpit.

He should also keep the 300lbs of lead, but in the form of 6 big auto/marine batteries that should be enough to power an electric outboard long enough for docking and trolling in no-gas-motor-allowed waters.

In an emergency the batteries could be tossed overboard, unlike the built in lead he has now.

Family outings in the great outdoors are a lot nicer with a few hundred lbs of fresh water for constantly washing up BEFORE you enter the inside of the boat.

Two bladders, port and starboard, inside the seawater ballast tanks.

On a long tack I'd like to be able to have 400lbs of water on one side, 0 on the other. Even in worst case I'd imagine the MacGregor might heel over way past 45% if you got the water ballast all on the wrong side, but it would survive and you would still have his Positive Buoyancy plus the 400lbs of buoyancy of the half-empty water ballast.

 

Hi, stumbled on a picture in an Oz sailing magazine yesterday of an Imexus 28. Has anyone heard of these, or have any comments etc.?
Pierre