Jim Michalak's Boat Designs
1024 Merrill St, Lebanon, IL 62254
A page of boat designs and essays.
(1November 2017) We discuss water ballast details. The 15 November issue will continue the topic with some real capsize tests.
THE BOOK IS OUT!
BOATBUILDING FOR BEGINNERS (AND BEYOND)is out now, written by me and edited by Garth Battista of Breakaway Books. You might find it at your bookstore. If not check it out at the....
ON LINE CATALOG OF MY PLANS...
...which can now be found at Duckworks Magazine. You order with a shopping cart set up and pay with credit cards or by Paypal. Then Duckworks sends me an email about the order and then I send the plans right from me to you.
Bob Holley's new AF4B is headed for its first splash!
1024 Merrill St,
Lebanon, IL 62254
Send $1 for info on 20 boats.
WATER BALLAST DETAILS
WATER BALLAST DETAILS...
SO you've decided to try water ballast. How to do the ballast box? How to flood and drain it? The only boat I've designed with water ballast (so far) was Scram Pram. There were two Scam prototypes built and the first one had the water ballast and second didn't. Here is a letter from the first builder......
.........My sage and good friend, Tim Webber, keeps sending me articles on water ballasting from his homesite. I built a waterballasted boat called Ghostling(design is listed as Scram Pram on Jim Michalak's page).
Of the articles I read I have no real substance of disagreement. However, my experiences with Scram Pram may add these different observations.
First, it is highly impractical to be shifting water ballast from one side to the other unless the boat is: 1) large and 2)on long tacks. Even given these requirements it is still a risky business to make an emergency maneuver with this profile. Before I leave this subject, I would like to point out that of the articles I read I did not find a mention of stress loading on the rigging caused by loading one side and making the other bouyant. Having collapsed two mast supports on previous crafts, this is a phenomenon that I've had some time to contemplate.
Next I want to approach the recurrent subject of water ballast taking up too much space in the craft. If one is going to water ballast they should choose a boat with not only the right shape, mainly wide and fairly flat bottom, but also a design that could integrate the tanks into the structure. For example, Scram Pram easily takes on 300 lbs of water ballast and it actually improves the interior of the boat by adding a strong internal keel, comfortable seats/beds, and providing foot rests. In this case the tanks were in the design from its' inception and of course, Scram Pram is 100% waterballasted. Also, she moves exceedingly well in light air whether ballasted or not.
On Scram Pram I devised a 3 tank system(the third tank being Jim Michalak's idea to be used as a trim tank). Scram had two saddle tanks forming the beds, seats, foot rests and internal keels.
The two saddle taks accounted for about 250 lbs. of the water and each one had 3 apertures in it. 1) first there was the obvious hole in the bottom at the deepest point of 1/2 inch and it filled it like a water fountain. 2) Next was a port hole directly over it with a see-through cover just large enough to put you hand through to put in a stopper if you cared to. This was not necessarry since the tanks were capable of holding their fluids by sheer force of vacuum. 3) The third apeture was at the front of the tank and had a PVC pipe of 3/4 in. rising a foot or more with a screw-on cap with petroleum jelly kept on it as well as the screw-down port cover to prevent air leakage; remember, a tight seal is necessary if we are going to create a vacuum.
This arangement fills and empties quickly giving one the option of using no ballast at all on those light days when you have a number of passengers that you can shift from side to side catamaran-style and the see-through port allows you to check the status of your tanks to see if they are loosing their water and if your vacuum is working properly.
One thing I did not test with Scram Pram that should work is the addition of a bicycle valve at the top of the PVC cap. This simple addition would allow one while under way to "blow" the tanks submarine style when the wind dropped, you picked up more gear, or for those suicide jockies, just to blow the leeward tank to gain more upright sail area at the cost of some stability on the boat.
The air used to empty the tank could come from a compressed can, an electric pump or a manual foot pump. The last two options are certainly inexpensive enough.........
I've never seen the installation mentioned above, but the Scram tanks look like this:
My idea at the time was to fill the tank by removing the deck plate, reaching into the tank and pulling the drain plug. Then stand by as it fills to replace the plug just as the tank is full. If the top of the tank is above the normal waterline, the tank may not fill all the way and you have to top it off with a bucket and replace the deck plate. If the tank top is below the waterline and you forget to replace the plug, your boat could sink. Anyway, I think he system would work with very cheap stuff and no external plugs to deal with. (I'm not sure how Bolger did it on Martha Jane?)
What the Texas Scram builder did was the above but he added a standing pipe with something like an airtight valve on the top, as I understand it. So he can fill the tank by opening the bottom port and let the water rush in while the air rushes out of the open tube. When full (assuming the tank top is below the waterline) the tube is sealed and the water somewhat trapped in the tank. It's very much worth a try and is a noble experiment in that it is cheap, and that if it works is an improvement, and if it doesn't work it can be returned to the original design very easily.
I don't know how much testing the Texas Scram got, but one thing I would watch out for with the tube system: On a long, long tack with lots of heel, the up side tank may not hold its water by vacuum alone. It may dribble out slowly. Solution would be to just use the plug. But for a fin keel water ballast system designed merely to right the boat in a knockdown, wouldn't this system be perfect?
EFFECTS ON A REAL DESIGN....
Last issue we used the Hullform6S program to look at stability of a simple rectangular "boat". Let's look at a real design. The example here will be Jukebox2, featured later in this issue. And we'll put in some spice by comparing the results with Jewelbox, a very similar boat that used the unballasted Birdwatcher cabin system.
Here are some rough cuts at the weights and CG's:
Jukbox2: Item .Weight(W) .Height above bottom (X) .WX Hull 700 21 14700 Bottom
4 400 Mast 50 100 5000 Yard 12 210 2520 Sail 5 150 750 Boom 16 70 1120 Crew 200 36 7200 Ballast 300 3 600 Totals 1380 23.4" 32300
Jewelbox: Hull 700 21 14700 Bottom 100 4 400 Mast 50 100 5000 Yard 12 210 2520 Sail 5 150 750 Boom 16 70 1120 Crew 200 18 3600 Total 1080 25.9" 28090
Running the above weights and CG's through Hullforms and I get the following righting moment curves:
Both boats have the same basic length, cross section in the cabin, and bottom shape. They have identical sail rigs. In the weights you will see the item "bottom". Both boats have a thick 1" bottom and this separate item is supposed to account for the extra weight there. As for the crew situation, it changes all the time, of course, but the crew on Jukebox is above the overall CG and adding more crew makes it less stable. For Jewelbox the opposite is true. Adding more crew to Jewelbox makes her more stable since the crew sits below the overall CG. Also, in the analysis of Jukebox, only the watertight volumes of the hull were used in the Hullforms file. If you look at the gif of Jukebox below, Craig O'Donnell has presented one that shows the watertight volumes. For the Jewelbox, all the volume is watertight except for the small bow well.
I had hoped this boat would be self right up to 90 degrees but it looks like it goes to 80 degrees in this ballast situation. (What does that mean? Chapelle considered righting from 45 degrees of heel was fine for a sharpie while today's bluewater sailors like to self right quickly from 140 degrees of roll.) I think another 100 or 200 pounds of ballast is needed to get it to 90 degrees. Although this discussion is about water ballast, any ballast material of the same weight mounted inside the hull at the same location will have the same effect. (The Jukebox2 plans show the ballast as steel bars bolted across the bottoms of the bulkheads.)
I didn't have a chance to show a "no ballast" situation for Jukebox but the numbers show that removing the 300 pounds of ballast reduces the weight by 300 pounds and raises the CG almost 6". Maximum righting moment goes from 1170 ft -lbs with 300 pounds of ballast to 820 ft-lbs with no ballast (both at 20 degrees heel). Worse yet, the unballasted boat will capsize at 50 degrees of heel. So here the ballast seems well worth it.
I might add that the 300 pounds of ballast, if done with water, would be about 5 cubic feet. This boat is 5' wide on the bottom so the ballast tank might take the form of a full 5' width box, 6" high and 2' long.
...JEWELBOX... I think the fact that the Jewelbox righting moments are generally less than Jukebox's in the usual sailing range is mostly because she is about 30% lighter. If she were loaded with two more people and brought up to a weight about equal to Jukebox's I'd think she might be even stiffer than Jukebox. But the most valid comparison might be with the unballasted Jukebox which weighs the same as the Jewelbox. The advantage of the Jewelbox is that it won't flood and maintains a small righting moment past 80 degrees of heel.
PICCUP PRAM, SAIL/ROW PRAM, 11' X 4.5', 90 POUNDS EMPTY
Piccup Pram was the first boat of my design to get built, back in 1990, I think. I still have the prototype and use it regularly. I designed it to be the best sail/row boat I could put in the back of my short bed pick up truck. But I found it to be a good cartopper, too. It has capacity and abilities I had previously thought impossible in a 90 pound cartopper. The photo above shows the original 55 square foot sail on Pensacola bay a long time ago. Piccup is a taped seam multichine hull which can take a fair amount of rough water.
Piccup continues to be one of my most popular designs and I get nice photos from builders. Here is one of Richard Donovan hoping for more wind up in Massachusetts.
Richard's Piccup has the larger 70 square foot sail that prefer myself. It's the same as the original but is 2' taller. This balanced lug sail sets on a 12' mast and rolls up easily for storage on its 9' yard and boom. The idea was to be able to store the rig easily in the boat during rowing and it works. There is a pivoting leeboard and kickup rudder on the boat and they can be left in place raised while rowing. Converting to full sail takes a couple of minutes as you step the short mast, clip on the halyard and tack lines, hoist the sail, lower the boards, and off you go. And the balanced lug sail reefs very well although reefing any small boat is best done on shore.
Here is a Piccup by Vince Mansolillo in Rhode Island, a nice father/son project. Piccup will be large enough to hold both of them. You can see the large open frameless cockpit, large enough for sleeping. And you see the buoyancy/storage boxes on the end.
But Piccup will take two adults as seen in the photo of Jim Hudson's boat. Jim's boat has a polytarp sail as does my own Piccup.
These boats have proven to be good for sail rig tinkerers (be sure to read and apply the Sail Area Math essay before starting). Here I am in Piccup with a polytarp sharpie sprit sail. The rig is different from the originals but the hull here is totally unchanged (except for paint) from the original shown on the beach at Pensacola.
I think my own Piccup has had about six rigs of different sorts and was always the test bed for the polytarp sail experiments. But, hey!, that's nothing compared to the tinkering the late and great Reed Smith did with his out in California. Here is his Piccup rigged as a sharpie sprit yawl!
Here is Rob Rhode-Szudy's yawl rig Piccup that was featured in his essays about building Piccup that you can access through the old issue links.
Here is another by Doug Bell:
This one is by Jim Islip:
And this one by Ty Homer:
Piccup Pram uses taped seam construction from five sheets of 1/4" plywood.
Plans for Piccup are still $20.
Some of you may know that in addition to the one buck catalog which now contains 20 "done" boats, I offer another catalog of 20 unbuilt prototypes. The buck catalog has on its last page a list and brief description of the boats currently in the Catalog of Prototypes. That catalog also contains some articles that I wrote for Messing About In Boats and Boatbuilder magazines. The Catalog of Prototypes costs $3. The both together amount to 50 pages for $4, an offer you may have seen in Woodenboat ads. Payment must be in US funds. The banks here won't accept anything else. (I've got a little stash of foreign currency that I can admire but not spend.) I'm way too small for credit cards.
We have a Picara finished by Ken Giles, past Mayfly16 master, and into its trials. The hull was built by Vincent Lavender in Massachusetts. There have been other Picaras finished in the past but I never got a sailing report for them...
And the Vole in New York is Garth Battista's of www.breakawaybooks.com, printer of my book and Max's old outboard book and many other fine sports books. Beautiful job! Garth is using a small lug rig for sail, not the sharpie sprit sail shown on the plans, so I will continue to carry the design as a prototype boat. But he has used it extensively on his Bahamas trip towed behind his Cormorant. Sort of like having a compact car towed behind an RV.
And a Deansbox seen in Texas:
Another prototype Twister is well along:
A brave soul has started a Robbsboat. He has a builder's blog at http://tomsrobbsboat.blogspot.com. (OOPS! He found a mistake in the side bevels of bulkhead5, says 20 degrees but should be 10 degrees.) This boat has been sailed and is being tested. He has found the sail area a bit much for his area and is putting in serious reef points.
AN INDEX OF PAST ISSUES
THE WAY BACK ISSUES RETURN!
MANY THANKS TO CANADIAN READER GAETAN JETTE WHO NOT ONLY SAVED THEM FROM THE 1997 BEGINNING BUT ALSO PUT TOGETHER AN EXCELLENT INDEX PAGE TO SORT THEM OUT....
THE WAY BACK ISSUES
1nov16, D'Arcy Ballast 3, Piccup Pram
1dec16, Sail Area Math, Ladybug
15dec16, D'Arcy Thoughts, Sportdory
1jan17, AF3 Capsize, Normsboat
15jan17, The Weather, Robote
1feb17, Aspect Ratio, Jewelbox Jr
15feb17, Aspect Ratio 2, IMB
1mar17, Normsboat Capsize, AF4Breve
15mar17, Underwater Board Shape, Harmonica
1apr17, Capsize Lesson, RiverRunner
15apr17, Measuring Leeway, Mayfly16
1may17, Scarfing Lumber, Blobster
15may17, Rigging Lugsails, QT Skiff
1jun17, Rowing1, Mayfly14
15jun17, Rend Lake 2017, Mixer
1jul17, Rowing2, Viola14
15jul17, Rowing3, Vamp
1aug17, RowingSetup, Oracle
15aug17, Taped Seams, Cormorant
1sep17, OliveOly Capsize Test, OliveOly
15sep17, Plywood Butt Joints, Philsboat
1oct17, Sailing OliveOyl, Larsboat
15oct17, Water Ballast, Jonsboat
Mother of All Boat Links
The Boatbuilding Community
Kilburn's Power Skiff
Bruce Builds Roar
Rich builds AF2
JB Builds AF4
JB Builds Sportdory
Puddle Duck Website
Brian builds Roar2
Herb builds AF3
Herb builds RB42
Barry Builds Toto
Table of Contents