* The non-lifting strake ( photos )

* The non-lifting strake ( photos )

Paul
Paul

March 1st, 2009, 6:10 pm #1

I keep parking in front of this hull and looking at these strakes. They are a puzzle to me, obviously intended to cushion the ride I guess, but they sure don't appear to do anything to help lift the boat at speed, or do anything for speed at all. Not that I would do it, but filling them in to make them lifting may add a little speed, except for the fact that back where it really counts they taper off into a flat hull section. Strange? This is the 1966 20' fiberglass Sea Skiff hull, and the Corsair Sea-V hulls were from the same mold, different gelcoat color and badges.









The Lancers and small Commanders use the deep V hull, but include the patented Wynne lifting strake. I guess this particular model was never thought of as a fast boat, and these "strakes" that mimic the shiplap siding of the wood Sea Skiff may have been a styling feature as well as a bit of a cushion too.

Regards,

Paul



(one thing about it, I can't wait to get this thing back on the water, and since it's going to be 70 degrees this coming weekend, I may well do just that)

















Last edited by FEfinaticP on May 15th, 2012, 8:37 pm, edited 1 time in total.
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Joined: October 17th, 2008, 6:09 am

March 1st, 2009, 6:29 pm #2

I'll bet they help with performance and economy by disturbing the water and lessening it's grip on the hull as it moves through the water. Looking at the larger Commander hulls, I can't help but wonder if that wouldn't have been a nice feature for those hulls as well.

Do you think your old 35' Sea Skiff would have been as quick with a slick bottom as it was with the lapstrake hull?

Kevin Bray
'06 CC Launch 22
'69 31' Commander Express
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Paul
Paul

March 1st, 2009, 6:46 pm #3

I'm not sure about the Sea Skiff hull comment, it was one fast boat partially because the power to weight ratio was way up there at around 28 pounds per horsepower, while my 38' Commander with nearly two hundred more horses aboard is around 30 pounds per horsepwoer if it does, in fact weigh in around 18,000 pounds, and 33 if it's at 20,000 pounds.

The strakes on the Sea Skiff extend the entire length of the hull too, as they must be shiplapped all the way to work. She sure was a fast one!











Regards,

Paul
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Joined: October 17th, 2008, 6:09 am

March 4th, 2009, 3:43 am #4

I only know as good as I've been told a bunch of times. Power to weight ratio has to be key to the 35' Sea Skiff performance vs. your '38 Commander, but I've had enough people that supposedly 'know' what they're talking about say that having something that disturbs the water a bit helps lessen the drag (wetted area?) Once upon a time, in between riding on my Dad's '60's Cavalier, and my own new and old Chris Crafts, I owned a '79 Hammond. Don Hammond was one of the fellows that brought Glastron boats into our world. Austin, Where I live, was the home of Glastron boats back in the day. I met Don Hammond and was talking about the boat that I had, and what I was doing to fix it up, which included a bunch of polishing and waxing. He told me to NOT wax the bottom of the hull, as that would hurt the boat's performance. A perfectly slick hull for a power boat/planing hull was not something that was wanted. For a displacement hull...yes, but not a planing hull.

As for power to weight, I also remember reading my 'Legend of Chris Craft about Chris Smith adding a small step to one of the Gar Wood racing hulls that just wouldn't get up on plane and run. After adding the step, the boat performed as designed and hoped for. Same boat, same power, but after loosening the water's grip on the hull, the boat took off.

I think I got that all that right.

Anyway, long story short, it's a boat, it's a Chris Craft, so it's cool stuff! I'm glad the weather's turning for the better and I can start playing with this old '69.

Kevin Bray
'06 CC Launch 22
'69 3`' Commander Express
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Paul
Paul

March 4th, 2009, 3:53 pm #5

I hear what youre saying loud and clear, but I am not (yet) in agreement. The steps you mention are perpendicular to the centerline and keel of the boat. They are intended to create turbulence under the hull, and in some cases air bubbles, and even get the entire hull up on the step (out of the water as far as possible) for reduced friction.

Longitudinal lapstrakes run the entire length of the hull and it looks to me that they just create one long additional surface where friction is added logarithmically to the overall speed of the boat in a linear manner. A lapstrake hull has quite a bit more exposed surface area than a smooth hull would, and I've seen a heck of a lot of smooth hull race boats and very few (only the Jersey Speed Skiff) lapstrake racing hulls.

I can easily see how the step promotes speed, but dont see how the lapstrake does UNLESS it is turned in a manner that also creates lift, as Jim Wynne did (and patented). The whole deal with his lifting strakes was to help get the hull farther out of the water, again to reduce friction and thereby increase speed. The Lancers and small Commanders use this to great advantage, but virtually never see what I think is a useless lapstrake on a fast boat hull bottom, unless it may be for stability reasons. Most of them are lifting strakes to do double duty.
As for a cushion ride, yes indeed. Thats my opinion, sure am interested in the subject. I wonder what the Lyman guys think, theyre bigtime lapstrakers.



First of all, we must first recognize that people will race ANYTHING, from lawnmowers, motor homes, cruisers, cars, trucks, boats, virtually any kind of machinery that is self propelled and some that isn't. Naturally boats have been raced for eons.

There is a category of hull called the "fast planing hull". Here is an example below, virtually "the" formula for all smooth water runabouts since the onset of the motor boat. Naturally this hull is not good in rough water, but for speed it's hard to beat. When a step is added to break friction under the hull, these hulls became faster but more difficult to control too, therefore the step had some stability issues (and features added) to help.



When the "gentlemans racer" category or "limo" style boats came on the scene, including the big Hacker Crafts and Gar Woods, and some big Chris Craft models, the hulls started conforming to the very sharp entry and somewhat deeper v sections, because these wealthy customers wanted a smooth ride. I have been absolutely ASTOUNDED at how a Hacker Craft can approach a big swell and it looks like you're about to bury the nose or pound hard, and the hull just SLICES the wave in half. Those John Hacker designs are superb, and of course everyone else picked up on the idea and used it too. Those boats, including the entire "gentlemans racer" category used a deeper v simply because if you were racing, the water would be choppy due to the other boats, and if you were going to win you had to maintain speed in the chop. Here are a couple nice sharp hulls doing the slice thing. These boats would be faster on smooth water with flat bottoms, but there is a lot of satisfaction being able to go fast in the chop (as the Lancer and small Commander owners know!)












Believe it or not the one below has an Italian V-12 motor and the hull also has a step. It was "very fast" for being an "in the water hull", naturally it could have gone faster if it had sponsons, but the step and power on this thing pushed it over 60-mph. Thsi thing was also swinging a surface drive prop, ha, looks vintage, but is new and state of the art interpretation.















This one is a true Gold Cup design, also with a stepped hull. That's Mark Mason at the wheel with collector vintage racer Peter Kreissle as the passenger (Peter owns JUNO, the 3-point Ventnor tail dragger of 1937 design). See JUNO below!











Here is Peters JUNO, sponsons in the water and filled with water too. They drain out as the boat gains speed. I really want to build one of these 80-mph boats. All it takes with one of these to get to 80 is 175 hp, so little friction skipping across the water.






And now, the lapstrake hulls, these are Jersey Speed Skiffs, and yes, they race them too! These light weight but strong hulls have so much power they're often out of the water. Great fun to watch. Fun to drive, but terrifying to be a passenger.








The true wood lapstrakes naturally have the strakes all the way, because they're real.
But as you can see with the newer adaptation of the Skiff hull, the fiberglass versions are going with flat bottoms.






Here is the fastest boat I've ever been on, DANCING BEAR, owned, built, and driven by Curt Brayer, APBA 2-time World Record Holder, and high point man for SEVEN (7) years in a row with this full race hemi powered boat. His records will never be broken because the F-Service Runabout class has been discontinued. What a wonderful man, generous to give Janet and me both rides, and I'll never forget hearing the Casale V-drive singing and that big hemi bellowing as he gave it the gas straight down the center of the St. Lawrence river. ha! What a thrill. I have it on video, will have to transfer it to digital.






In any case, it's not my intention to argue or start an argument, I'm just sharing photos I have and trying to promote more good discussion! You are right, indeed, warm weather is on the way and I'm going to be running my cheap little Skiff and having a ball. I'll be increasing my carbon footprint too, in that big 427 powered 38 every chance I get too




Regards, all the best,

Paul












































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Kevin
Kevin

March 4th, 2009, 4:19 pm #6

In my U-22,the boat sure does slice the waves. As some of you have heard before, I drove my Sportsman from NYC to Annapolis, out side in the ocean on a 250 mile "adventure". I had out of date charts, an alcholic for a passenger, and a GPS programed to take us in circles and into a Nuclear power plant (makes for a better story). My boat cruises at tach speed, in other words, what the tach says in our speed. So at 1800 (18 mph), she just kind of goes along nicely without pounding. When things got dicey, I throttled down to 1100-1200 and she just sliced through the big waves. However, without any reserve boyancy (sp)in the bow, she does not go over them and hence they go over her. Which means that in big waves they come over the bow, over the windshield, and into the boat. This is where the second bilge pump in the stern helps

In really steep big waves she barly makes headway because she will fall off of them onto her flat section and BOOM. I hit so hard one time, with hardly any headway at all, when she slammed down it split two DECK PLANKS! We survived, although the alcholic (tuff guy from NJ who races ninja bikes)was begging to get to shore! So we pulled in and slept in an abondoned camper trailer in a field.

So, the limits of the boat are better then the limits of wanting to get wet and go slow. The crew gives up first.

In the flat though, she will go 45 mph with the big V-8 and is a hoot.

I agree about the Jersey Speed Skiffs. I rode in one at the St Micheals show and it was the most fun I have ever had in a boat with my clothes on (since I do not varnish nude like some people do ) They are scary!!!

So now I need speed in a deep V. Lancer anyone?

Kevin
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Ned Lloyd
Ned Lloyd

April 12th, 2012, 5:14 pm #7

As a commentary on the Jersey speed skiffs. - Both glass and wood hulls have the same flat bottom. the glass hulls are derived directly from the wood speed skiffs of the early 1960's. They have been 'tweeked' over the generations, but are still the same in appearance (flat bottom lapstrake sides). That way since the first one in 1922.
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Ned Lloyd
Ned Lloyd

April 12th, 2012, 5:18 pm #8

I meant to add that in the picture of the three speed skiffs, the green one and 'JS44' are glass hulls, and the one in the middle with the stylized bird on her side (falcon) is a 1950's wood hulled Foresberg skiff.
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Paul
Paul

April 12th, 2012, 6:18 pm #9

Hi Ned,

Thanks for the comments, always good to learn something here. I took the photos of the skiffs, and you can see just how close they were to the photo boat, what a hoot. Somewhere I have a video stashed away of that even too, and it was like being in a swarm of angry hornets when they came by. What fun !


regards,

Paul
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Joined: February 25th, 2012, 12:49 pm

April 12th, 2012, 10:41 pm #10

I keep parking in front of this hull and looking at these strakes. They are a puzzle to me, obviously intended to cushion the ride I guess, but they sure don't appear to do anything to help lift the boat at speed, or do anything for speed at all. Not that I would do it, but filling them in to make them lifting may add a little speed, except for the fact that back where it really counts they taper off into a flat hull section. Strange? This is the 1966 20' fiberglass Sea Skiff hull, and the Corsair Sea-V hulls were from the same mold, different gelcoat color and badges.









The Lancers and small Commanders use the deep V hull, but include the patented Wynne lifting strake. I guess this particular model was never thought of as a fast boat, and these "strakes" that mimic the shiplap siding of the wood Sea Skiff may have been a styling feature as well as a bit of a cushion too.

Regards,

Paul



(one thing about it, I can't wait to get this thing back on the water, and since it's going to be 70 degrees this coming weekend, I may well do just that)
















Paul,

Given the shallow transom deadrise of that hull, those strakes probably perform a function similar to the "skid fins" you see under some inboard ski boats.. They probably help the hull "bite" in order to reduce the amount of sideways skidding when turning at high speed...

My 1978 251 Catalina has a shallow skeg keel that stops just ahead of the shaft log, it's about 6" deep at that point.. It makes a huge difference in how that hull handles a turn at speed.. 251's built prior to 1977 didn't have the skeg..

I drove a 1975 model before I bought the one I have now, I threw it into a hard turn at 20 kts and it slid sideways for a few hundred feet before finally getting a grip and heading into the turn.. My 1978 with the skeg responds immediately to a hard over turn at speed.. It will bank into a hard turn so deep it will almost dip the rubrail on the inside of the turn..

On Edit:

You can see the skeg in this shot taken on the trailer... It gave the trailer builder fits..

Last edited by CC-John on April 13th, 2012, 1:14 pm, edited 1 time in total.
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