designing a fast rowboat

[Clinton B Chase]

I am reading Pete Culler's Wooden boats right now as I design a pair of oars. This is a great read, from what appears to have been a great man.

I'd love to see Tad's drawing, too.

Nordvind, what you say about making many changes sure makes me remember to build the boat with this in mind. I feel like I can nail the seat fore/aft pretty well by floating the hull. Should I plant my butt directly amidships so that the hull is level on the waterline or should I cheat the thwart fore or aft. I've heard it is important to be slightly stern down. Should I consider making a wide thwart to make any minor adjustments. Seat height can then move as long as fore/aft is same. So there is my first question. Hull turnover is not far in the offing. Interestingly, there may not be any unfrozen water in this part of the world until late April. Hmmmm....what then. An indoor pool perhaps.

Clint

 

[nordvindcrew]

thanks

Tad, thanks for the OK to pass your drawings along, and thanks again for being so interested as to do the drawing and send it to me. I'm constantly looking at it as well as all the other drawings I've accumulated. Your lines will find their way into the skin on frame boat I'll be doing this spring. Jeff

 

[nordvindcrew]

thwart placement

Clint, I've expressed my ideas on thwart placement a couple of times in this thread. I difffer from many in my opinion that you should be as far FORWARD as possible, and that oarlock placement cannot be done by any formula known to me. Your faering, being a double ender, will tend to squat as you reach hull speed, so being a tad forward will counteract that. Look at yor drawings and sketch in a thwart amidships. Then place the oarlocks aft of that a good 18". The oars will be so far aft that holding the bow into a cross wind will get difficult at best. Changes of even a few inches can result in huge improvements. Mock up your station and try to swing the oars and see if you are going to scrape your legs on the catch, if you can get the blades in the water without the handles being too high or low on the catch and pull, and, last and very important, make sure that your stroke has a full amount to swing fore and aft to accomodate a good, long, full, pull. RE the Snow Row I've just loaned out my other boat, the Nordvind, so can't help out there. The race is March 1ST at 1PM at the old life saving station at the tip end of Hull adjacent to Hull High School, Hull Gut And Peddock's Island. I don't know if any one will be looking for crew or not, but it is kind of rare. Drive down anyway and get a look at all the boats and meet the crazies who do this row. The chowder and coffee after the race will warm you up. I was looking at your pictures, and had a thought about the unfairness in the garboard plank. I can see the beautiful hollow you've built in, and suspect that may be the culprit. A traditional wood faering, planked in cedar or pine can't achieve that shape, and the thickness of the planks fairs the edge automatically ( I think ) Looking at pictures of traditional faerings, they don't seem to have that pronounced hollow entry. Keep Building, Jeff I'll copy Tads drawings and mail them to anyone interested

 

[Clinton B Chase]

Learning from doing!

Jeff,

TX for your thoughts on my planking challenges. The HOLLOW you speak of...are you seeing that in the drawing...the hollow in the waterline, or are you seeing it in the construction pics too. I just glued down the middles...everything looks OK, but there is this dang hump right around the first station and it translates into the middle strake. Could be worse though. Yes, it is becoming clearer to me that I needed to not make the bow so fine and when I redraw the boat I will push the widths out a little bit at the ends of the boat...about 1/2" or 3/4" as this is about how far off the molds the plywood sits at ST 1. Aft it is about 1/4" off. A fellow I know who knows faerings claimed that the solid timber boats can be more forgiving at the ends than a plywood boat which struck me as counterintuitive, but upon reflection he is right. Plywood can only follow a developed surface and cannot bend two directions at once. Grown wood can be steamed and worked a bit (or carved in the case of a faering garboard) to conform...plywood wants to only go one way...along a developed surface. So this is interesting.

Your other point about the rowing station leads me to a clarifying question: are you sugggesting I put the locks 18" aft of the thwart!? I am tall and plan to use long oars, but I was thinking 13" or an inch or two more.

Secondly, I am designing some oars and am trying to figure out how long I can go. The beam is 4' with the outrigger oarlocks so the spread between pins is about 4'7. I drew in a 9'8" oar into a section view with the outriggers drawn in and a 36" blade length and assuming I do not want crossed hands on the pull (I like my thumbs to be whisker close). When I did this I estimated I could have a long inner loom of 2'4" with the handles about chest high. But the "formulas" tell me with that length inner loom the oar should be between 8 1/2' and 9'. This would make the handles steeper in that section view and the handles too high...I feel like 9' to 9'8" should work but perhaps would yield too hard-pulling an oar. Could you give me some guidance on this one. I feel like I have to figure out what oar length matches the boat before I go about placing the oarlocks, seat height and doing a mock up in a month or so. Am I on the right track in trying to arrive at a close oar length by drawing it out? (I plan to build these oars)

I sure appreciate the help and will go back to the posts you speak of...wow this thread goes way back!

 

[nordvindcrew]

faerings

Clint, the hollow I thought I saw is in the photos. It looks like a compound curve has been tortured into the plywood. Wooden boat has a book: planking and fastening which shows a traditional fearing being built, maybe that will help you visualize where your problem lies. My 20' boat has a 51" spresd at the locks, the oars are 8'9" long and the distance from the buton to the end of the grip is 27". distance from rear of thwart to center of lock is 20" we have the top of the thwart at 6" above the keel and the bottom of the oarlock is at 16". This works for us. A 24" inboard on an oar of the length you're proposing, the effort to pull it would be pretty daunting. Also, from my point of view, at 13" aft of the thwart, you won't be able to get much of a pull to finish your stroke. Mock all this up with a few pieces of wood and a block to sit on and see what kind of a pull you get. Remember, too, that as your oars dip into the water the open up at the handles so that you can have a bit more inboard than you might think. Horizontal to the water, our oars overlap a bit. When we're pulling there's no overlap at all, in fact there is a substantial spread that feels right to us. Can the formulas, mock it up till it FEELS right to you. Remember that keeping your thwart low helps stabilize the boat and makes it easier to row. Our 19' Jersey skiff had such bad rowing positions when we launched her that we thought we had built an un-rowable boat. many changes later, she is a very capeable and fast boat. good luck Jeff

 

[Clinton B Chase]

Tx Jeff, I think I hav what I need to continue the oar design part. Sheer strakes hopefully go on tomorrow.

Cheers,
Clint

 

[mike1]

Mr

High , I 'm also getting the urge to build another boat. this time i'd like to have input into the design.
Can one of the experts explain CP to me.
and I see from previous posts that the relation ship between speed length and CP .
and How do you calculate the speed / length ratio,, what units are used
I kinda like lapstrake , especialy the athelas.
Regards to all

 

[mike1]

Tads drawings

Hi Nordvinndcrew, havent been arround for awhile , see youre getting on famously.
Any chance I could also get a copy of Tad's lines,, Perhaps over the net.
Caope Town is warm and sunny.
Warm regards
Mike

 

[charmc]

and How do you calculate the speed / length ratio,, what units are used
I kinda like lapstrake , especialy the athelas.
Regards to all

Hi, Mike,

Here's a discussion of hull speed and S/L ratio, with English unit and Metric unit formulae.

http://www.boatdesign.net/forums/showthread.php?p=185557

Scroll down here to Prismatic Coefficient (CP) for a good description.

http://www.selenetrawlers.com/company.php?menu=12&PHPSESSID=6a10bd44fe15b7c63c85553654564e5d

Don't forget pix here as you build her!

 

[mike1]

Thanx, Have had a quick read will do a proper one tomorrow
warm regards
Mike

 

[nordvindcrew]

Snow Row

Racing today. weather:40 degrees F, light rain, winds mostly calm at 9 AM. The course: start at Windmill Point in Hull Ma. to Sheep Island, Clockwise around the island to Harrys' Rock day mark, round the mark and back to Windmill Point. Distance: 3.75MN. Tide will be just starting in at the start of the race, and the final leg of the race will be against an incoming tide. Best idea will be to tuck in near Peddocks' Island on our port side and try to stay out of the current as much as possible. A little further, but less current hopefully. A dry change of clothes at the end of the race will be the order of the day as well a a hot cup of chowder back in the old coast guard boat house while we.wait for the results. ROW HARD, NO EXCUSES

 

[sailing canoe]

snow row

Norvindcrew - Your killing me ! howed it go? Thought about you on and off all day. Nick

 

[nordvindcrew]

seagoing massacre

Well, It was race day last Saturday and the rain stopped just before the start and held off through the race. That is the good news. The bad news is that we got killed. 5th place with a time of 42:49 (3.75NM). Winning time for our class was 37:33. posted by the "Daniel J. Murphy". Two boats that have never beaten us did just that! I'm still not sure what happened. I haven't compared times to past races so I'm not sure if evertone was just fast or what. I do know that we felt that we just couldn't get the power to the water. Oars too long or maybe our stations aren't quite right yet. Can't avoid the thought that maybe it thing most wrong with the boat was us. I felt flat and couldn't dig in and get that strong long pull we like to use. We have decided to go back to square one and re-think everything about our oars and rowing stations until we get it feeling right and we pick up some speed. next on the agenda is a modification to the bow to get a finer entry with a bit of hollow to it. A couple of Sunday mornings should be all it takes. the, it's back to training and analyzing to find out how to row at 5.75 knots at a steady pace. Google Hull Lifesaving Museum to see the race results. We actually did pretty good against the fleet and beat a few coxed fours.

 

[charmc]

I do know that we felt that we just couldn't get the power to the water. Oars too long or maybe our stations aren't quite right yet. Can't avoid the thought that maybe it thing most wrong with the boat was us. I felt flat and couldn't dig in and get that strong long pull we like to use.

Jeff,

If you begin to suspect you are out of shape; you are.

Trust me on this; I know from personal experience.

That being said, fine tuning the rowing stations and oars will help.

Hey, any day you beat a coxed 4 by 20 minutes is a good day!

 

[nordvindcrew]

moan and groan

Charlie, thanks for the kind analysis of our physicaL condition. Yup, I/ we are not in good shape to row fast and it showed. Sounds as if you looked up the race results. It is kind of amazing how fast some of the single and double fixed seat boats are. If you notice, one of the competitors is Piantidosi, he of the drop in sliding seat fame. He is rowing a slick sliding seat double, and its' twin is also in the race. The New Bedford whale boats beat us, but only by a bit. Work hard, get back into shape , tune the boat and go back out there and try to win some. I think our class is getting stronger, and the results over the years prove it out. Against the fleet, we're doing better each year. Thanks, Jeff