Don Carron in Wil Gordon's Scram Pram
Contents:
Contact info:
Jim Michalak
118 E Randall,
Lebanon, IL 62254Send $1 for info on 20 boats.
Jim Michalak's Boat Designs
118 E Randall, Lebanon, IL 62254
A page of boat designs and essays.
(1apr01) This issue will present some thoughts about Birdwatcher type hulls. Next issue, 15apr01, will repeat an essay about choosing a design to build.
A WORD ABOUT COLD WATER...
Now is a good time to run the annual warning about boating in cold weather: Every Friday the St. Louis paper gives the fishing report and I read it because it gives the water temperatures of the local waters. Right now they are about 50 degrees F. Now, here is some valuable info that came with my life jacket:
WATER TEMP:...............UNCONSCIOUSNESS................DEATH
32.5.....................................under 15 min.................................15 to 45 min
32.5 to 40...........................15 to 30 min...................................30 to 90 min
40 to 50..............................30 to 60 min...................................1 to 3 hrs
50 to 60..............................1 to 2 hrs........................................1 to 6 hrs
60 to 70...............................2 to 7 hrs.......................................2 to 40 hrs
70 to 80..............................2 to 12 hrs......................................3 hrs to indefinite
Over 80..............................indefinite........................................indefinite
If you wonder how the data was gathered click here, scroll down about 60 percent, and read. Clearly anyone falling into our local waters currently needs saving right away. There may a good chance that you won't save yourself unless you are very close to shore or can get right back into your boat. I've also heard the cold water can be completely incapacitating to the point where you MUST wear a life jacket to even float. It's quite sobering when you think about what can happen.
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Don Carron in Wil Gordon's Scram Pram
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Birdwatcher Hulls
HISTORY...Around 1984 I visited Phil Bolger. I had built his little Teal boat and the prototype of his Jinni design and we chatted for about an hour. I recall now reading an interview of Phil in Woodenboat magazine. The author thought that Phil was feeling him out for how new designs struck him. So it was with me and Phil showed me a sketch of a new boat idea where the crew sits inside the hull, looking out through watertight plastic windows and seated more or less on the floor where their weight would act as ballast. The goal was a cruising boat with light trailer weight because it had no ballast and yet full self righting. It was the first time I had ever seen such a thing and I had no idea what to think of it.
That same design surfaced two years later in the old Small Boat Journal as one of Phil's bimonthly essays, this time he called it "Birdwatcher" because that was one idea behind it. In fact the design was to answer a request for a homemade Dovekie. Dovekie is a 20' fiberglass production boat that Phil had designed in the 70's that feature ultra shallow draft, a small cabin, and the ability to get around without a motor by rowing and sailing (the fuel crises of the '70's being very much in mind at that time). Birdwatcher was relatively large and sleek and simple - a big flat bottomed double ended skiff sort of like a Teal times two. But it had a plexiglass house on top. Access to the inside of the boat was by a 2' wide slot on centerline that ran the full length of the boat, so if the boat was blown on to its side, it would still float without shipping water into the hull. It was supposed to be swamp proof and self righting, even better than Dovekie in that respect. I still didn't really know what to think of it.
Soon after that I found the first Birdwatcher was being built out in Colorado by Ron Mueller. I got in touch with Ron. He went out with his new boat trying to tip it over. It would only go over so far, he reported, about 90 degrees with the windows in the water, and it would self right at the first opportunity. Ron convinced me the idea worked.
I built my Birdwatcher in 1989 and used it quite a bit for the next few years. I've used it less recently as my shed has filled with my own designs but I still have it and it is ready to go.
HOW BIRDWATCHER WORKS....
This figure shows a cross section of a cabin boat hull that has been blown over 90 degrees and is lying sideways in the water. What you see here is the force of buoyancy, deterimined by the shape of the hull in this sideways position, pushing up. Weight is pushing down and acts as if it is all centered at one point, the center of gravity. If those two forces are directly aligned then there will be no tendency for the hull to return upright. But if the buoyancy force acts to the right of the weight as shown in the figure, the boat will try to return to upright. The farther the two forces are apart in that way, the more quickly the boat will return upright. (If the weight were to act to the right of the buoyancy force in this diagram the boat would continue to capsize.)
What is clever about Birdwatcher is that it has both a fairly deep cabin, which moves the buoyancy force to the right, and has crew weight down low, which moves the center of gravity to the left. A more conventional cabin design, where the crew sits in a cockpit looking over the cabin, has these challanges: The crew must sit fairly high to see over the cabin so their weight is not effective as ballast. In fact one of the main reasons for ballast is to counteract the weight of crew. The higher they sit and the more crew you have the more ballast is needed. If you try to lower the cockpit and crew weight you also lower the total recovery buoyancy with negative results. With Birdwatcher, the more crew you have, the more stable the boat!
THE GOOD AND BAD ABOUT BIRDWATCHER...
The righting system really works. My own boat never went over to windows in the water but it did go over about 60 degrees one day when I was solo and up in the bow. I stumbled back to the stern where the sheet was tied, released it, and the boat popped upright instantly. So in this case my weight was not really in the ballast catagory since I was standing in the boat.
So the boat is self righting without ballast and thus is probably no more than 2/3 the weight of a similar sized conventional ballasted boat. I should mention that Birdwatcher has its topsides of 1/4" plywood and its bottom of 1" plywood (two laminations of 1/2") and probably weighs about 700 or 800 pounds empty on the trailer. The thick bottom is important as far as self righting is concerned and does indeed act as about 100# or so of ballast. As we see later a boat built like this without the thick bottom was stable on its side when knock down. (Birwatcher also has a small blob of lead in its centerboard that no doubt acts as ballast when the board is down.)
I found this photo of Bob and Sue Archibald sitting in the bow of my Birdwatcher. You can see the walkway slot above them and see that the mast and centerboard are offset to one side such that you can walk from stem to stern in the center of the slot. These are shady boats. Wind cascades off the sail down through the center slot for ventilation which you need to cover on colder days. I should mention that the windows probably need to be tinted, as you see here, to keep the interior a cool house and not a hot house. In cold or bad weather the centerline slot is best covered with a simple fabric cover.
All of a Birdwatcher type boat is "interior" and thus it has about twice the cabin size of a similar sized boat which has a large cockpit. So there is a lot more living space inside but there is no living space outside. I think that not having an exterior cockpit has been a sticking point with most boaters who would really like to have a place to sit outside. In any normal weather you can stand in the walkway of Birdwatcher and you can usually sit on the aft deck with your feet dangling down into the cabin operating the tiller. But lots of folks want a full cockpit and there is no way to do that in a smaller sized Birdwatcher because the crew weight is important as ballast and must be kept down low.
As to performance, Birdwatcher is sort of interesting. The rig is a single sharpie sprit sail, about 125 square feet as I recall. Very simple and quick to rig in maybe 5 minutes - no longer than a Sunfish. The mast is about 24' long and can't be any longer and still be easy to rig by a mortal man. So the sail area is limited and the boat is sluggish if with wind is less than about 8 knots. It really comes into its own at about 15 knots, popping along at about 5 knots. I've sailed mine reefed up to about 25 knots wind.
So what do you do below 8 knots? Phil's idea was that you would row. In calm flat conditions mine would row at about 2.5 mph. But it is very hard to row a large boat in any wind, especially anything over about 5 mph. So the boat had a bit of a dead spot in its performance at a wind speed that is quite common around here in the summer. Later variants of Birdwatcher had more sail area with the simple sprit sail replaced by a Solent lug sail with a jib.
But the Birdwatchers I know of ended up with motors, including mine. It only takes two hp or so to get it up to 5 or 6 knots. If you try to go it without the motor you won't be able to launch from busy ramps, or ramps at the end of narrow coves. You can't row in the crowd (the motor boats will pester you on purpose) and you can't launch under sail. And in a narrow cove or any shallow lee shore you will have a problem in that you won't have depth to lower the centerboard to sail to windward and you won't be able to row into the wind. You can try to push out to deeper water and anchor and set the sail and hope you can get off on the first tack. If you drag the centerboard you will drift back to the shore and have to try again. So after doing that for a year or two eveyone has mounted a motor.
The boat pounds a bit in rough water as will any light shallow boat. And Birdwatcher is shallow! It may be the shallowest boat I've ever had. It will float off the trailer in about 2" of water!
Well, with a couple of years Birdwatcher experience behind me I set out to "improve" things. Here are the Birdwatcher type boats that I've designed that have been built. None of these are currently in my paper catalog but I still sell the plans to all of them.
JEWELBOX....
This one had an interesting start. Bolger had just introduced the AS19, a 19' foot scow that was mostly a deck boat. It had leeboards, ballast, and a yawl rig with a gaff main. I said, "Hey you could use the similar thing with a Birdwatcher cabin. Do away with the ballast and get a big cabin with a self righting hull."
While I was at it I redid a few things that bothered me with Birdwatcher. I gave it a real motor well in a squared off stern which allowed a simple rudder (Birdwatcher has a pointed stern which required a welded metal linkage to the rudder and makes mounting a motor difficult and takes away a lot of cabin space). I added to the sail area by using the AS 19 sail (about 150 square feet) but mounted it as a balanced lug, much easier to rig than the gaff. And I did away with the mizzen sail since I had found that the single sail Birdwatcher, with its tiller lashed, would self steer better than my old Jinni with its yawl rig. I did away with the Birdwatcher centerboard, which took up a lot of space, was hard to build and had the interesting quality of shooting water out its case top at speed. In fact at full bore the original Birdwatcher would shoot water right out the top of the boat! Later we devised ways to keep the water in the case. I went to a single pivoted leeboard. I also added a small open well in the bow for messy things like the anchor and cut it down it front so you could step into it with no effort.
Karl James built the first one. He brought it to one of our messabouts and I got a chance to sail in it although we had little wind that weekend and spent most of our time with the motor going. It was everything I wanted except beautiful. It was roomier than Birdwatcher even though it is about 5' shorter. It was much easier to get into from the beach. Karl used it for several years, trailering it all over the country. He crossed the Florida peninsula with it by canals and lakes. Yes, it pounded in rough water. He had it self right from a full tilt knock down with the windows in the water. Like most sharpies it was really quick on reaches and runs. He later went to design his own sharpie and I was told the Jewelbox was sold to a man in Florida.
Plans for Jewelbox are $35.
PETESBOAT...
Karl's brother Pete wanted something like Jewelbox but bigger and faster! With Jewelbox experience behind we tried for less pounding by warping the front bottom into a V. The lugsail was kept but in this case we borrowed the main sail of a Bolger Martha Jane, over 200 square feet.
Pete wanted his boat to plane under power. Guessing that the weight of the boat might be at least 2000 pounds we also guessed that 50 or 60 hp would be required. I thought that size motor would need mounting in the center of the transom, not out on the edge. Where to put the rudder. Pete was thinking in terms of two rudders like the MacGregor or a Hobie. I drew the boat with one mounted off to the side, requiring a linkage to a tiller on centerline.
How to treat the stern lines? A boat with a deep powerboat transom won't sail worth a damn, and one with fine lines aft for good sailing won't take any sort of power! I gave it a wide transom with a flat bottom in the stern and I ran the bottom up so that it just touched the waterline in the stern. Adjustable trim tabs might be needed under big power.
Pete built the boat straight away. The only hitch that I recall was in warping the ply in the bottom bow into the V shape. I had called for two layers of 1/2" plywood but they didn't take the warp without such a fight that Pete gave in and used four layers of 1/4" plywood instead.
He found it would plane using a 40 hp motor from a fishing boat he already had, but got a good deal on a new 60 and mounted that. It went about 20 mph with that at full power and planed along happily at 15 mph at a comfortable part thottle. No trim tabs were added but he said he had to stand to see over the bow while operating the motor with its own tiller in the stern.
Pete told me that in a good wind the boat would reach at 8 knots! He confided that the work involved in warping the bow into a V was probably not worth it. Especially under power when the boat squatted aft, the V area was for the most part in the air and not in the water.
So now the two James brothers traveled the country together with their strange boats.
Plans for Petesboat are $50.
IMB...
I have always owned small cars and was thinking that a small Birdwatcher type that would tow behind a small car might be a good thing. About the same time the International Marine Publishing company was having a design contest and I named my idea the IMB for "International Marine Beacher".
I borrowed heavily from my Piccup Pram design which has worked so well. A short wide multichine pram gave lots of volume in a compact hull that was very seaworthy (if wet going to windward). I made IMB 13.5' long and 5.5' wide with a Birdwatcher cabin 8' so I could camp in it. It took a while to find a builder for the IMB. I think one was completed in Ohio early on but I never got a report or photo. The first one on record was this one by Gerry Scott.
Gerry's boat is still quite new and I don't have a test report although the photos look impressive. IMB is light at about 350 pounds and has no thick bottom. There is a good chance that IMB will not self right from 90 degrees, maybe from 70 degrees or something like that. It won't flood but will float on its side. What to do then? Sufficient agitation by the crew clinging to the floor of the sideways boat might bring it upright. Swimming outside and putting weight on the rudder or leeboard will make it pop up but then you must be prepared to get back in the high sided boat.
Plans for IMB are $30.
SCRAM PRAM...
Wil Gordon knew about IMB but wanted something larger. So I enlarged it to 16' x 6', added water ballast, a motor well and a huge rig. Wil built the prototype quickly through a brutally hot summer in Texas. A second was built by UT Roberts in Savannah with a smaller rig and no ballast tanks.
I don't recall if UT is a sailor but he first launched the boat with its sail fully hoisted and sheeted hard and no one low inside and it promptly got blown over at the dock by a big gust! Remember that the crew weight is supposed to be the ballast. A quick grab of the skeg by a swimmer brought the boat back upright. UT uses his boat mostly in tidal rivers under power.
Wil's boat went to Tim Webber in Texas who did some worthwhile testing of the ballast system. There are three tanks which total about 300 pounds of water. With a man inside the boat and no ballast, they pulled the Scram over with a rope tied to the masthead. It would not self right, staying on its side until a light touch of the skeg brought it upright. They filled two of the three ballast tanks and pulled it over again and it self righted quickly. With the third tank full they found it hard to pull over and the man on the rope had to relocate onto dry land for a good angle to pull. It self righted very quickly then and they thought no need to ever fill the third tank.
I think Scram is my be all around Birdwatcher design. The only thing I might change is to add a pointy bow to take on larger waves. But I can assure you that these step through bows that I've used on Jewelbox and Scram are quite nice, especially if you have family members who don't relish the idea of climbing up over the hull from beach to boat.
Plans for Scram are $35.
NEXT TIME...
We'll give some guidance about choosing a boat to suit you.
Jon Jr.
JON JR, POWER SKIFF, 12' X 4', 100 POUNDS EMPTY
Jon Jr. is a small jonboat, sort of a personal sized boat that will take two normal sized adults. It would be a perfect "back of the pickup truck" boat. It could be cartopped. (To me the idea of cartopping a powerboat is a bit strained since you would need to carry the motor, with its smells and drips, and the gasoline inside the car). If you are sure from the start that you will be trailering the boat, you might consider the larger Jonsboat design which has more capacity, but is not so large that it will be expensive to build, use and haul.
As for power, I'd suggest 5hp max. Sometimes you can find low power motors at yard sales since they don't fit the image of modern boating. The usual rule I've seen for power on planing boats is a horse for each 50 pounds and motor salesmen like to quote a horse for each 25 pounds. I've found that in good conditions a simple flat shape will plane with less, so this boat with a normal sized man might plane with 5 hp. Actually, the Coast Guard suggestions for powering boats comes down quite hard on small hard chined boats like this and they might advise even less than 5 hp. A boat like this is unsuited for big waters anyway. So the little motors will cover the little lake quite well.
Construction is of the simplest "instant boat" type from three sheets of 1/4" plywood. All nail and glue construction with a smattering of epoxy and fiberglass to fortify the chine corners and help seal the water out of the bottom joints.
Th prototype Jon Jr was completed by Joe Leinweber and Dan Ellis and tested to a certain degree. Click here to read about the test and the surprize ending! ("The waters are only safe until next time!")
Jon Jr plans are $20.
Prototype News
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.
Here are the prototypes abuilding that I know of:
Caprice: A brave and experienced builder in Texas is making the 25' Caprice water ballasted sailboat. Here it is being born...
Skat: I'm told the prototype Skat project is underway again and very close to being done.
Normsboat: This is an 18' sharpie being built by Cullison Smallcraft in Maryland. You should be able to check on it by clicking through to his web site at Cullison SmallCraft (archived copy, actual site no longer active). He is presenting an excellent photo essay of how to assemble a flattie.
AN INDEX OF PAST ISSUES
Herb builds AF3 (archived copy)
Hullforms Download (archived copy)
Plyboats Demo Download (archived copy)