Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(1September 2015) This issue will try another look at box boat stablilty. The 15 September issue will continue the topic.
TIME FOR THE INDIANA MESSABOUT!
July 4th is behind us and mid-September is closing fast. We just wanted to send a short reminder that the 24th occurrence of the Lake Monroe Midwest Messabout will be September 18, 19, & 20 -- mark your calendars.
Go to https://sites.google.com/site/lakemonroemidwestmessabout/home for additional information and feel free to drop us a line if you have any questions. If you're planning to attend, and want us to add your name/boat/homeport to the website's "Who's Coming" list just send us an email.
Hope to see all of you in just a few weeks. We have the ice cream maker standing by!! Pass the word to all your boating friends. Regards, John & Susan McDaniel
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.
JIm Young drifts along in his Mikesboat under Montana skies.
118 E Randall,
Lebanon, IL 62254
Send $1 for info on 20 boats.
Phil Bolger, who taught me about everything I know about boats, wrote a column in each issue of the great paper magazine Messing About In Boats. A few years ago, I recall seeing the first of a new type of cabin on his boats. It was an add-on to a modified Micro design that he called called the Navigator. So I'm going to call it the Navigator cabin. At first glance it appears to be pilot house shell. But there is more to it than that.
I didn't pay much attention to the idea until I saw Richard Spelling's Bolger designed Chebacco Light Cruiser which had the Navigator cabin at a messabout in Houston last September. Nothing like seeing the real thing. The original Chebacco has been around for a good while being invented as a large daysailer with a small cuddy cabin. I think the first were cold molded in a professional's shop but since then the plans have been reworked more times than a WW2 fighter airplane's and there are lapstrake and taped seam plywood versions, some with nearly full houses.
Here is a photo of the original daysailer cuddy version, this one by Jamie Orr.
Here is a photo of Richard's Light Cruiser version:
The volume of the added Navigator cabin is obvious. Where the original has a cuddy that you might be able to crawl into, here is the inside of Richard's boat:
Quite a change!
Looking from cabin to the cockpit is like this:
Looking back at the photos you can see that the Navigator cabin has an aft bulkhead about where the original cuddy bulkhead was, and then the cabin sides and roof run aft to form a protected nook. So the cockpit is about half open and half sheltered. Very nice.
So as a living space you can see the great advantages of such a cabin.
I think there are some disadvantages, very similar to my experiences with the Birdwatcher. You must have curtains for all those big windows for real privacy. The skipper has to see ahead through two sets of windows. So the optical qualitity must be good. The windows usually must be tinted to keep the cabin cool. So sailing at night, looking through two sets of tinted windows, will be more difficult. No shades or curtains allowed either during sailing, so cabin privacy is none then. Also, the window plastic is expensive. I made my Birdwatcher windows out of 1/4" Plexiglass as shown in the plans and I think the cost in 1988 was over $500 which was about 40% of the cost of the hull. Most guys seem to be using Lexan now. Lexan is harmed instantly and permanently by some common bug sprays as Richard and others have found. Although it is more impact and crack resistant than Plexiglass I think it is softer so more prone to scratching and impossible to polish out.
A FUNNY LITTLE STORY...
Back when my Birdwatcher was brand new I had it out on Carlyle Lake on a day with very light winds. A fellow in a Flying Scott chased me down, a very easy thing to do for a Flying Scott. He thought the design was quite clever but for an entirely different reason than why it really is clever. From a distance he mistook the tinted glass for screens and he thought the boat was totally screened in, I suppose it might be renamed Bugproof! Of course the screened in Birdwatcher would swamp and capsize in a knockdown, unlike the real thing where the solid windows do the work of keeping it dry and upright.
And so it is with Navigator cabins. The windows must be watertight and strong enough to float the boat. The only opening windows or doors allowed would be on centerline.
The effect on self righting is quite powerful even for a short cabin, as long as the Navigator section is tall.
Here is a drawing of Jukebox2, a design I did about ten years ago. None were built that I know of. It is a 19' flat bottomed scow hull with ballast and a raised cockpit deck. It has a private cabin and a small raised deck in the bow with a step through bow transom for easy boarding after beaching.
Here is chart of Jukebox2's righting moment curve as calculated by the Hullforms demo program (there is a link to the Hullforms site at the bottom of this web page) for a center of gravity location of 24" above the hull bottom. A word of caution here. I think Hullforms does a very exact job of these calculations but the calculations of weight and cg location can be really nebulous, in fact just varying the crew can change things a lot. Just having the crew move around in the boat can change things a lot.
So it looks like Jukebox2 is very marginal at righting from 90 degrees of heel.
Next I took Jukebox2 to make Jukebox3 by adding a small Navigator cabin. Looks a bit like an old fashioned telephone booth but it goes full width of the hull. This one is only 30" long and doesn't have the "nook" in the cockpit as Richard's Chebacco has, but the nook could easily be added. Also I rearranged the cabin slightly to maintain the privacy in the forward part.
Here are the righting moment calculations of the Jukebox3 hull using the same weight and 24" cg location:
So you see the effect of this short Navigator cabin is to give the hull a boost as soon as its windows get into the water. The effect is quite powerful. In the final Jukebox3 design the effect allowed me to get by with water ballast instead of iron ballast (iron ballast is a lot denser and can be set lower in the hull making it more effective).
VIREO, LIGHT ROWBOAT, 12' X 45", 60 POUNDS EMPTY
Vireo is a very light and simple boat with lines that make for very surprizing performance. A while back I built a dink called WeeVee which was the usual 7-1/2' long. It had a V bottom full length and had to be quite deep in the V to get enough capacity (displacement) to carry anything. I've always thought is was one of the fastest rowing dinks ever built as it would go 4 mph with medium effort, unheard of for such a short boat. But the deep V made for problems, the worst being that it made beaching a challenge. The bottom of the V was 9" below the waterline in usual trim so as you approached the beach the center of the V would ground first usually well before you made the shore. And there you balanced precariously until you threw a foot over the side and got wet. It was OK when launching from a dock, of course, but I seldom do that. Later I found I could heel the boat over when approaching shore and get in a lot closer but it was always tricky. She was a bit tippy but that was no problem once you were seated.
So that's how you learn and things evolved quickly into Vireo. Vireo is over 50% longer than WeeVee but is still only 12' long. She has a long lean bow for splitting waves. The V of her bottom is a lot shallower than with WeeVee and although she still needs heeling when beaching, the angle of the heeling is greatly reduced.
I think this shape has great potential, perhaps is the fastest of of any simple plywood shape. Here is why I say that. I try to draw these such that at normal weights the chines will not push through the water, that is to say they are normally above the waterline. Only the two bottom panels flow through the water. Those two panels join only at the centerline and in straight motion no water would cross that joint. So the flow is smoothly down two gently curving panels with no joints or complications. In addition, the shape makes for a boat that cuts chop and likes to go straight. But the V bottom means it won't beach as well or be as easy to move around in as a boat with a flat bottom panel.
The first Vireo was built by Charles McMahan in Ohio. He used lauan underlayment and lumber salvaged from motorcycle crates or from the Ohio River. The Vireo in the photo was a delux version built by Frank Kahr of Providence, RI. Frank wrote me:
"Yesterday I accomplished a long term goat by rowing from Providence to Newport in a Vireo I built from your plans. This was trip of approximately 26 statute miles which took 6 hours, 12 minutes. I had a little help from a fair tide, but this was still a good time for a long trip made without great physical effort."
"I think the Vireo is a good balance of light weight, seaworthiness, and speed. A longer narrower boat would be faster, but would also be less stable and would have less spread at the oarlocks. I built mine from 6mm Okoume plywood with a permanent center rowing thwart. It weighs only 57 pounds and is very easily managed out of the water. I have built several other small boats and this one went together easily in about 30 hous. The plans were very clear."
Vireo plans are $15. Taped seam construction from three sheets of 1/4" plywood. No jigs or lofting required.
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:
And the first D'arcy Bryn is to the point the builder can sit and relax in it and imagine boating. You can follow the builder's progress at http://moffitt1.wordpress.com/ ....
The first Jukebox3 is on the (cold) water. The mast is a bit too short - always make your mast too long. A bit more testing will be nice...
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.) Double layer bottom on and glassed, hull returned to upright. On to the interior and superstructure...
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
15sep14, Rowing 2, Philsboat
1oct14, Guessing Weight, Larsboat
15oct14, SailOK2014, Jonsboat
1nov14, Chine Runners, Piccup Pram
15nov14, Lugsail Rigging, Caprice
1dec14, Sail Area Math, Ladybug
15dec14, Poly Laminates, Sportdory
1jan15, Sharpie Spritsail, OliveOyl
15jan15, Knockdown Recovery, Dockbox
1feb15, Mike Monies, Laguna
15feb15, Cartopping, IMB
1mar15, WeeVee Lessons, Vole
15mar15, Bulkhead Bevels, Frolic2
1apr15, Capsize Lessons, Riverrunner
15apr15, Hollow Spars, Slam Dink
1may15, Boat Costs, Blobster
15may15, Small Boat Rudders, Roar2
1jun15, Emergency Flotation, RB42
15jun15, Thailand Mixer Cruise, Mixer
1jul15, Rend Lake 2015, Musicbox3
15jul15, Box Boat Stability, Mikesboat
1aug15, Taped Joints, Cormorant
15aug15, Plywood Butt Joints, Paulsboat
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