Ninigret Flare

Hi, I am new to the forum. I have built a number of boats and am starting a new one. I have a question. If I add a bit more flare to the aft sections, would I make the design more seaworthy in rough water conditions, or would I add too much buoyancy to the stern? Thanks larry

 

Hi, I am new to the forum. I have built a number of boats and am starting a new one. I have a question. If I add a bit more flare to the aft sections, of the Atkin "Ninigret" would I make the design more seaworthy in rough water conditions, or would I add too much buoyancy to the stern and wreck an otherwise great design? Thanks larry

 

My advanced amateur opinion says absolutely not. She has plenty of flare as it is axman why would you want any more? More flare anywhere would add a little more seaworthyness I would think. Very little though. I would think the only downside would be that fenders may be slightly more difficult to use. I lust after the Atkin "Tang". And think his flat bottomed boats like Wader and Marcia would benefit from more flare so they were more Dory like. Where in Canada are you located?

 

Thanks for the input Easy Rider. I am located on Vancouver Island in British Colombia.
The boat will see some fairly rough stuff I expect. I will probably do another circumnavigation of the Island and further trips to the Queen Charlotte Islands and possibly up to Alaska. One of the problems we have here is the Currents even in Georgia Straights 1- 1 1/2 knots is common. running against the waves it can be a bit nasty. Most well known rough weather boats tend to hav a bit more flair twords the stern (Tolman skiff, Bartender, Simmons skiff,) I am trying to run on low power (20hp) and Ninigret pushes fairly easy as a semi displacement boat

 

Axeman,
I'm 50 mi NW of Ketchikan. I have a 2011 copy of Small Boats, an annual magazine by Wooden Boat Magazine. There is on page 32 a 4 page article on Ninigret. Have you seen it ..have it? I like Ninigret a lot. Wonderful lines, sea worthy and very efficient ... perfect for your needs. I prefer the deeper heavier hull of Tang. If you come this way please stop in Thorne Bay and visit.

Easy Rider

 

Ninigret would have no stability benefit or off shore advantage, from additional flare in her stern quarters. She wouldn't make a very good rough water boat, but would be a fine protected waters craft.

She has a classic pre 63 series warped bottom hull form (typical of the 1950's), with an especially sharp entry. This shape was popular before the early 1960's planning hull model tests were published and similar shapes where adopted by several manufactures; Lyman and Thompson where of note. Most of these manufactures upgraded these hull shapes after the form tests were published and better riding boats resulted. As an example the last wooden Lymans still used the warped bottom form, but with the revised shapes, from that learned in testing and these are some of the softest riding boats in protected waters I've been in, less of course, some modern craft with considerably more hull form development.

With Ninigret's dead flat deadrise at her transom and her chine run, I'd say she isn't a very sea worth craft, if the sea state was rough. She would cut through short, moderate chop, but you'd have to throttle her way down once off shore or she pound pretty good.

Tang is a different animal all together, being speed limited by her shape and weight. She'd be much more comfortable in a nasty, off shore sea, but she'd adopt a pretty nose high attitude if she was driven over say 25 knots. At 18 knots, her forefoot is still "engaged" with several degrees of bow up trim, but at 25, she'd have to pull it clear and this would be a pretty uncomfortable way to drive her. I can see why Eric likes her and she'd make a good cold water boat, in moderate to rough conditions, with her speed limitations in mind. I'd venture 22 knots would be the max you'd want to drive this boat it, which isn't anything to sneer at in serious off shore work, especially considering you could do so with less then 100 HP.

The specifically answer Axman's question about making Ninigret a better sea boat; well, cut the bottom off and give her a monohedron form. She can keep the chine where it is and her sharp forefoot, but carry an appropriate amount of deadrise aft, say 10 degrees for low powering options, 15 to 20 for serious off shore work, with the understanding you'll need more power and you can easily venture too far out on the deadrise limb, making for a "roller" in a nasty seaway. Naturally, this makes her a completely different design and you're better suited with a different set of plans.

If what you love about Ninigret is aesthetic, then any good hull form could be "modeled" to look like her, above the LWL. She'd ride and handle like a modern craft, yet retain the classic styling cues of the Atkins design.

 

Thanks guys, I hadn't seen the article in Wooden Boat Magazine. I downloaded it last night and read it the writer was definitely a fan. Interesting. There are probably designs better suited to my needs, but they tend to fall into the displacement category. Where as I am trying to achieve 10-12 knots (in flat calm , two aboard & a bit of camping gear) with a 20hp outboard.
I am fine with going hull speed or slower in the rough stuff ,or when loaded heavier (longer trips) The reasoning for more flare was too bring it more in line with the dory's (designs with proven seaworthiness, narrow bottoms & lots of flair) I guess I'm talking about seaworthiness in the sense of withstanding the sea conditions rather than how comfortably,or how fast I can beat through the waves, the price for doing that is huge engines and large volumes of high priced (soon to get higher) fuel. There seem to be a shortage of these types of designs, I guess as long as the public expects to drive there boats like their on the express way we will have deep V hulls with mega HP. If you know of any plans out there for the type of boat i'm describing please let me know and I'll change my plans. I basically want a semi-displacement George Calkins"Bartender" that will cruise at 10 knots with 20hp. Is this reasonable? Thx

 

Seaworthiness is 90% skipper and crew and 10% boat. The dory isn't inherently seaworthy, but half full of fish and in the hands of a skilled crew, they do quite well.

 

Axeman,
Also by Atkin is Little Effort 6'x23'10" and the very similar Russell R at 5'11" x 21'10". In plywood they'd both meet your 20hp performance requirements if kept light. With 30hp on Little Effort you could probably build medium heavy and be more comfortable in rough stuff. Several Russell R's have been built. Do you know about the Atkin Yahoo Group? http://groups.yahoo.com/group/AtkinBoats/messages

 

Thx Easy Rider. I considered the Russell R and I like the Ninigret better. Little Effort is too long for my building space. There is nothing wrong with Ninigret I am sure the design as it is will do what I need. I didn't know about the Atkin Yahoo Group, I'll check it out.

 

OK good. I agree w PAR to a great extent but any light boat with a flattish bottom is going to be at a disadvantage in most head seas in our area. Especially when tide and wind oppose. My philosophy to minimize the pounding and porpoising is to have a long footprint on the bottom and as straight as is practical. For your type of boat that would mean a plum stem instead of the typical highly raked dory stem and some but limited rocker. And to minimize wave making resistance the double chinned sampan form should be considered to retain acceptable stability and minimize chine width where the water meets the hull. Ninigret with no rocker (as I recall) so should be quite to very level riding and have minimal wave making resistance. Six or 7' seas, at least the ones we have here in Clarence Strait, could be a bit difficult to deal with. PAR's concept of dropping the keel to increase deadrise is excellent (I think) but to have much effect it may require more deadrise than a shorter boat. Me thinks deep V boats tend to be short and wide for good reasons and any deep V boat will probably require more disp than is required for your other requirements. If I were you I would build Ninegret as designed and be a bit more cautious w your seamanship. Two books I think should be in your library are:
Skiffs and Schooners - by R D Culler. He presents a chapter on file bottoms. These boats are quite similar to Ninigret and indeed may have been the inspiration for Atkin to design Ninigret. As a result of his short chapter on finishing I now mix my own natural "teak oil" ect.
The Dory Book - by John Gardner. It's hard to read this book without the strong urge to grab some wood start bending and fastening. A great deal of the book is about "Semi Dorys" and an interesting extension of this is his "Flat Iron Skiff" whose bottom is not only flat crossways but fore and aft as well. His 19' Semi Dory may be more seaworthy and more easily driven than Ninigret. Perhaps a slight scale up (over-all not just length) would create the mother of all boats for you and would be real easy compared to increasing the deadrise on Ninegret. A more distinctive appearance. But the 2 books are great.

 

All the offshore racing motor mono hulls have very deep V hull forms of very narrow configuration. The deep V doesn't need to be a fat boat and in fact is better if it isn't. I'd also not got to the deadrise extremes seen in current production craft. These boats tend to be rollers in a heavy slosh. I keep deadrise under 20 degrees and below 15 for craft not designed to motor in the high 40's. Because of the low HP requirement, you'd want to keep the deadrise in the 5 to 10 degree range.

 

So what I am looking for is a Tolman skiff - Dead rise at transom, 8 degrees, dead rise amidships, 12 degrees. Only narrower and a finer entry on the bow too accommodate my 20hp & 10-12 knot requirement. I am not a designer obviously, what would happen if I married a Toman bottom too a Ninigret top (from the chine up)? would that improve it for my purposes. Would a 20 ft boat with only 5 to 10 degrees be all that much better a rough water boat than say John Gardners 19' Semi Dory that Easy Rider speaks of? Or would it just be theoretically better? I guess it would handle better under power, less chance of the chine hooking.

 

Axeman,

"less chance of the chine hooking."

Yes I see that element of the design of considerable importance in the waters you intend on going but will only play an important part when things get really nasty. Such a design element saved my skin once and I hav'nt forgotten it. But the Gardner Semi-Dory has a reduced power requirement because of the narrower bottom but a full double chine design like the Diablo 15 and 18' skiffs offer a better chine for sliding sideways down the face of waves and an even narrower bottom. Aesthetically you will probably prefer the Semi Dory. But the Dynamite Payson Diablo is an excellent boat. See pictures ...Sorry about the fuzzy one. Don't know how easy either design would be to scale up over-all as in beam, depth and length but I'm sure that will be much easier than adding dead-rise to Ninigret.
I think deep deadrise is a bit over rated for soft riding qualities. I have a deep V that I don't think rides as soft as it should and less than 10 degrees DR seems to ride very similar to a flat bottom. And I think the difference will be even less with a light boat such as you desire. Pick a boat up w a crane 20' and drop it .....most any boat will hit hard. I suspect you'll not get 20' in the air but w fwd speed and the wave speed the effect may be about the same. I'd like to hear some other opinions on this. I think it matters more how far aft you are in the boat than how much deadrise you've got. I don't see any flat bottomed racing boats. However one must consider that a planing hull dos'nt ride on it's bow but on the center (roughly) of it's bottom. Ninigret is close to flat at amidships but the directional stability offered by some deadrise probably is of value but most flat bottomed boats have a small keel or at least skegs.
Easy Rider

 

I have been considering Bolgars Diablo Grande but was unsure of it's rough water ability
, or how it might perform @ 20HP. How efficient would it be at semi-displacement speeds or displacement speed?