Rabl Kittiwake. High or low chine at bow?

[LarixMaximus]

Hello eveyone.

I found this thread from 2004. http://forum.woodenboat.com/showthre...tiwake-by-Rabl

and although that thread was interested mostly in material and engine change, my search was for information regarding the bow options.

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The above frame sektion clear to show the difference between the low chine and high, a difference of 9 3/4in.

Sams description of the high chine. " it will produce a slightly better seaboat and takes away the blunt appearence"

I understand reducing the fullness of the bow at the waterline should make an easier boat to power, perhaps be more economical. Sam seemed to be a straight talker with his meanings, but he is not here to ask. Why would a boat with a less full bow (bouyancy) be a better seaboat?

[LarixMaximus]

Unlike some Atkin boats of a similar vintage, does not find any photos of a complete boat. These from the book.

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Certainly see where the "blunt" comment was made. But no different to Martha Green by Atkin with regards to bow.



Have not heard any bad stories about Martha Green being "un-seakindly".

[Peerie Maa]

À high chine reduces slamming anmd makes for an iesier motion in a chop

[LarixMaximus]

À high chine reduces slamming anmd makes for an iesier motion in a chop

Thank you. That would possibly indicate " a better seaboat".

Not familiar with the design history, but understand the construction was Chesapeake bay style, which i read is known for short choppy seas, which makes me more curious about why the low chine was used. Hard to believe the time and material saving over the high chine was as such that builders didnt build "a better seaboat" every time.

[Peerie Maa]

Thank you. That would possibly indicate " a better seaboat".

Not familiar with the design history, but understand the construction was Chesapeake bay style, which i read is known for short choppy seas, which makes me more curious about why the low chine was used. Hard to believe the time and material saving over the high chine was as such that builders didnt build "a better seaboat" every time.

The Chesapeake boats of that hull form were built with a diagonal staved bottom with the forefoot chopped out of a solid lump. Only the topsides were framed to support the planking.
So raising the chine forward would have required a lot more twist in the bottom staves and a larger forefoot lump to be shaped, all requiring more wasted wood and labour. You have to ask yourself why would they make the experiment?

[LarixMaximus]

. You have to ask yourself why would they make the experiment?

Yes indeed, that is the question i ask. Sams comment about the high chine construction was " will be a bit more tedious to construct and takes a bit better carpentary"......compared to a round hull, this is still easy and low wastage.

I noticed many of Sams early sailing V bottom boats also have a submerged chine line or at the waterline, and some later designs with a higher chine forward.

With regard to the Atkin boat, i read that the builder and owner says she does not pound, with no excessive pitching. I guess any boat if caught in the right wave set might possibly meet conditions that pounding happens, and i would ponder that a boat that can keep its way on, by being more easily driven will have an advantage over a blunt boat that could be possibly slowed. Given the original builders design brief and with Atkin himself writing that no boat is simple to build, i do still question why he would have used the low chine example if the high chine was known to be better. The builder commented the first 2 feet at the bow was "difficult", and also considered her 7.38 knots speed, "slow", which i do not.

[Peerie Maa]

Yes indeed, that is the question i ask. Sams comment about the high chine construction was " will be a bit more tedious to construct and takes a bit better carpentary"......compared to a round hull, this is still easy and low wastage.

Most working fishermen were conservative. They could not afford to make changes that might not turn out well, so they stuck to what they and the builders knew.
Change the purpose of the boat, change the construction methods and materials, and you are only constrained by what the new materials will allow.

[LarixMaximus]

Most working fishermen were conservative. They could not afford to make changes that might not turn out well, so they stuck to what they and the builders knew.

That i certainly understand and agree with, yet both these boats were drawn maybe half a century after the first boats were built, so it must have been apparent by then a high chine had benefits.

There is much difference between building a square box that will work on flat water, and a round bilge model, so i guess the option was just to allow for peoples work ethic.

Many working boats here on the West coast with full bow sections, but interesting that some early power vessels had
concave sections in the bow. I suppose the high chine can be viewed as a cross between the two, all boats being a compromise. Apart from chined Doris, not much in the way of history here with chine boats.

[Peerie Maa]

Apart from chined Doris, not much in the way of history here with chine boats.

We are discussing designs derived from US working boats. Reference to Chappelle shows that the us had more flat-bottomed and v bottomed work boats than you could shake a stick at. Some had the chine end at the bottom of the stem, others were like this http://forum.woodenboat.com/showthre...ville-Deadrise

[LarixMaximus]

Thank you for the link, I am still finding my way around, and a lot of information and nice boats to look at.



Even though that is a low chine, the depth of the fore foot make that quite a fine entry, even if it flats off rapidly going aft.

I wonder if the Atkin boat, under sail, might better present a better angle, much like a flat bottom dory? Though the sections look pretty stiff and the area low, hard to imagine the boat sailing at much heel angle.

Atkin drew several skipjack types, none of which had a raised chine forward, that might be because this was his definition of a skipjack, and anything with a raised chine forward just become a V bottom style?

[LarixMaximus]

Are there any members here who have experinse with both types?

After some more searching, i find a builder in Ireland who offer to build the Atkin boat. Hard to understand that a builder today would build something if it was known to have issues. Maybe i get a little hooked on Sams word of "better" and pay more attention on "slightly".
The Atkin boat has ballast where Kittiwake does not, maybe the ballast and heavier displacent keeps the forfoot under water except in very choppy water.

[thecheappages]

You can check out the so-called "Sinepuxent Skiff" Chapelle drew up. This had a sharp entry and a shallow V bottom. These were used for running the inlets on the Eastern Shore of Virginia. The stem area was shaped from a block of wood. There is one (Bessie Lee) at the Ches Bay Maritime Museum but I never succeeded in getting good pix of the interior at the bow.

If you sail a sharpie with a flat bottom heeled, you get a sharper entry (think New Haven sharpie). Workboats like a Chesapeake skipjack weren't sailed heeled.

[LarixMaximus]

Thank you.

I see the Chesapeake oyster type skipjacks are very beamy, so stiff, comparitively. I think the Sharpies are another sort entirely, but my knowledge on such types is very limited. I have read the bottoms can be cross planked in a similar way.

[LarixMaximus]

From just looking, i would have called this a V bottom. I suppose the high-chine Kittiwake could be called the same, despite the construction used?

[thecheappages]

That's the "13-foot" seaside bateau (length of keel) and is smaller than Bessie Lee. It's a deadrise skiff. I'm not sure why it would be important to label the Rabl boat one way or another. I'm just trying to point out that, at least around the Chesapeake, different boats mixed and matched features and were all basically cross-planked hulls.

My assumption has always been, with these, that the deadrise aft and the high transom were meant to cope with waves from aft while running the inlets and give the boat some lateral stability if thrust down a wave. Commodore Ralph Monroe gave sharpies a "pink" stern (pointed, "pink" is the old term for a pointed stern) for the same reason. Chapelle also said deadrise aft allowed heavier loads without dragging the transom. I've never seen one of these in the water so I can't say of that's true of this model, but there are Chesapeake boats that have the deadrise aft without having it forward.

The seaside bateaus were very common along the Delaware, Maryland and Virginia Atlantic beaches for a long time. I know a few still exist but I don't think any are sailing. Years ago I did se a fiberglass version at Cape Charles City.

From just looking, i would have called this a V bottom. I suppose the high-chine Kittiwake could be called the same, despite the construction used?

[Breakaway]

The higher chine/ finer entry comes more into play the faster the boat goes. Theres only so much slamming that can possibly happen at five knots, or seven knots. So, a builder would think, why spend the time and materials for the so-called better boat?

Once you get into or approach the planing regime, things change. Small differences in shape will result in exponentially more change in the ride and handling, basically because resistance increases as an exponent of speed.

Kevin


Sent from my iPhone using Tapatalk Pro

[LarixMaximus]

Thank you both.

With deadrise aft and a non drag transom, the hull that is in the water is to all purposes the same as a double ended boat, but with the advantage of extra bouyancy when heeled. A good thing i think.

I dont know if Kittiwake would be fast, the designer never specified any speed. Power from 20-60hp, but in the plans a 25hp which he suggested was all that would ever be needed. I dont know if the transom is flat enough or has enough area to semi-plane?

I know the owner of the Atkin boat wrote that it never slammed. The low chine model must have some increased bouyancy forward , i dont think that would be an issue in a boat that would never make double figures under power. Its no worse than some sailing dory at the waterline. I did notice the transom has way more deadrise than Kittiwake, so would sail at a small angle without transom dragging.

With a chine low at the bow rising aft, the water flow only has to go in one direction. I dont know enough, but maybe a high rise chine has to forces the water down under the chine before it can go aft, i do not know if it is measurable or would make enough difference to counter act the finer bow shape?

The Atkin boat came quite late into his long career, he did state ease of build did take priority. I can only speculate if ease of build was not a requirement, if he would have drawn in a high chine at the bow?

[LarixMaximus]

I am sure many of you experienced people have seen this. But for those who might like, i found some pictures on another forum of construction, with high chine.

[amish rob]

What is that? Some rack o’ eye beauty, or something from a plan?

Looks lovely.

[LarixMaximus]

What is that? Some rack o’ eye beauty, or something from a plan?

Looks lovely.

I am sorry, i do not know. I found it here. https://www.moyermarineforum.com/for...ead.php?t=5824

Its seems to be for faster speed with a flat chine aft? The sailing examples seem to raise much more.

[amish rob]

Wow. Cool thread.

Dude said in there somewhere he just built it “rack o eye”, which means he must live wherever that expression is used. I only read the term, and I like it.

Thanks for the link. I have a fondness for chine boats.

[LarixMaximus]

It looks, even to me. like an easier way to build a boat. I have not seen a boat built in this way in Sweden. I do not posses the skills for clinker. Apart from the Keel and side planks, it looks like it can use short straight bits of wood, so something a bit easier for an old man to contemplate achieving if focused.

Can we say a clinker boat is one with many chines?

[Bill Perkins]

Howard Chapelle made a study of the cross planked v bottomed boats , measured and wrote about them . One article turned booklet is his "notes on Chesapeake Bay Skipjack's" . This was in the 40's and he was able to interview baymen who had built and used a variety of v bottoms .They felt the low chine models were faster under sail . Chapelle wrote that tank testing had recently confirmed this .He wrote also that the low chine allowed a wider foredeck which made a better work platform . So that's 2 reasons the low chine was preferred on work boats in the age of sail .The yachts were typicaly high chine , according to Chapelle , and powerboats now seem to be high chine , as you show , to prevent pounding at speed .

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[LarixMaximus]

.The yachts were typicaly high chine , according to Chapelle , and powerboats now seem to be high chine , as you show , to prevent pounding at speed .

Thank you. I understand Chappele was quite the historian. Is your sentence above correct? You stated that low chine was faster in sailing boats?

I do not think Atkin would have drawn the Martha Green as it is, if it was seriously lacking. I can only conjecture his opinion of a high chine making "a slightly better seaboat" (according to Rabl), was not worth the extra gain in work. I do not find it unattractive from the bow.It looks quite shippy.

[Bill Perkins]

No . Chapple stated that the Bay builders he interviewed in the 40's thought so ,and that later tank testing ,according to Chapelle , corroborated that . That's what I wrote .

[LarixMaximus]

So that's 2 reasons the low chine was preferred on work boats in the age of sail .The yachts were typicaly high chine , according to Chapelle , and powerboats now seem to be high chine , as you show , to prevent pounding at speed .

Im sorry, maybe a simple misunderstanding. Is there a difference in a "sailing workboat" compared to a "yacht"? If the lower chine proved to be efficient on sailing hulls, why did the "yachts" have a typically high chine?

I can understand there may have been a cross over period, and that some builders may have preffered one over the other. I do not see anything in the link.

[LarixMaximus]

I was reading some articles at Kasten marine website. I think after some thought, and seeing how some boats are shaped today, that the low chine option has some benefits with lower wave making.

I may attempt to work out the prismatic coefficient of both, out of curiosity, though im still stumped on the bow half angle.

The Atkin boat has more of a square waterline plane (correct term?) than the Rabl boat. I do not know how to do a heeled waterline curve, It probably does not sail at a great angle of heel, but would the extra bouyancy aft tend to cause the bow the change course? I have heard of the term "pig headed" but unsure if it is relevant hard steering.