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Old 12-03-2007, 10:16 AM   #1
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Confession....road rage on the water...

We had taken the boat out since it was fairly warm out.* A couple(frends of ours) came along with us.* The rain was coming at some point though.* We rafted up with some other friends and had a nice visit.* Dark was coming and the rain had mostly come and gone so we were ready to get moving.* Due to the rainy grey weather that was now upon us, there was only one other boat out on the whole lake(Clear Lake) other than Troy who we were rafted up to and was pretty far behind us.* We were headed down a channel that "T"s into another channel.* Of course, the only other boat on the whole body of water is converging on that intersection perfectly at the point where we will meet them(I think God does this just to mess with us).* SO I back off the speed and let the guy go ahead.* It is a 40 something sportfish doing about 10-11kts....nice wake.* SO I hang back for abit but am getting impatient so I push the power up to pass the guy.* What does he do....he pushes the power up as well just like the dumbazz in the car that does the same thing when you try to pass them.* So I figure I will come off the power and let him go to allow some spacing between us and then it won't be an issue.* But what does this dude do....he slows down also.* SO I get on the radio and try to coordinate a pass.* Of course, like about 95% of pleasure boaters in this area they don't have their radio on.* So I push the power up to go around and damned if this dude doesn't do the same and at this point I am pizzed.* So I just firewall it.* He is probably doing about 16-18kts and we are doing about 21kts(fast as my boat will go) and end up overtaking him.* Would not have been that big of a deal except when we "fell off" his wake on the pass, my boat lurched to one side and caused one of my crew to slide off her seat and fall to the deck.* She is fine and we still had a good time but will most likely have a bruise to show for it.

I will admit, it did get personal.* I was going to pass this dude....period.* And that is not good judgement.* I could not have gone outside the channel to the South since there was not enough water.* I most likely could have gone to the North but the water is skinny at that point(bout 4ft) but I could still get by in it.* I should have just stopped and reassessed but I was agitated.* Anyway, no big deal but I am pretty down on myself that I allowed this situation to get under my skin so badly.

FYI, semi-displacement hulls do not do that well at more than "semi-displacement" speeds.* The flat aftersections start producing too much lift and causes the bow to lower to the point where it starts trying to steer the boat.*** The boat actually starts trying to plane on the forward*SIDES(any lifting surface)*of the*boat and it*is usually the side that favors the torque of the prop.*Mainship options a bigger engine in this boat and it is somewhat of a waste of power and money and fuel since there is no need/desire to cruise at apeeds above 17-18kts which is where this phenomenon starts to show up.* Mainship has started to go to truer planing hulls on some of their newer boats because of this(as has Grand Banks if ya didn't know).* But a semi-dispalcement hull is magical*in the chop......and the Pilots are still Semi...
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Old 12-03-2007, 10:20 AM   #2
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Confession....road rage on the water...

No I gotta go back to the boat to clean all of the foot grease off of her!!!!!!
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Old 12-03-2007, 03:02 PM   #3
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RE: Confession....road rage on the water...

I do get very up set with semi displacement boats that have to pass within 50 to 100 ft at a speed just over hull speed so they throw out a huge wake, and then wave as they are pass by.* Grrrr. **I mean we can be just out side the shipping lane, one mile out and they still have to pass with in 50 to 100 ft.* Its got to be a secret semi displacement code/club or something?**
*
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Old 12-03-2007, 03:03 PM   #4
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RE: Confession....road rage on the water...

This is why we need the water balloon launcher.......
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Old 12-03-2007, 03:16 PM   #5
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Confession....road rage on the water...

Phil/fill, I have always said they do that to get a better look at your women!!!

And my women had to take off their platform hoochie shoes and track their foot grease all over..... I just got back from the boat and it rinsed off like a teflon pan!!!
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Old 12-03-2007, 04:49 PM   #6
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RE: Confession....road rage on the water...

John,
You expressed an interest in semi-displacement hulls. There are very very few that really are. Most are like GB or Nordic that are planing hulls that are underpowered so they are forced to operate at semi-displacement speeds. I like both GBs and Nordics aqnd would like to see them build a true semi-displacement hull or a full displacement hull. What I belive to be the perfect S.D. hull is found in the boats called " Handy Billy ". These boats were originally designed by William Hand at or near the turn of the century. Unlike almost any other boat these hulls are at thier best at 12 knots. Search Handy Billy or Southport Island Marine. Sorry I'm out of rage.

Eric Henning
30'Willard
Thorne Bay AK
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Old 12-03-2007, 05:09 PM   #7
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Confession....road rage on the water...

Willy,

If you saw the bottom of my boat you would realize there is no flat/lifting area ahead of about midship....it is extememly deep and fine which is what makes it so magical in choppy conditions. There are two disadvantages of SD hulls....one I mentioned above. The other is the fact that a SD hull is less efficient than a planing hull because of the fact that the front half of the boat is not generating any lift.....IOW, it is being pushed thru the water and cutting thru the chop which provides a great ride but a little more drag. You can't have it all!!!!
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Old 12-03-2007, 05:46 PM   #8
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Confession....road rage on the water...

The term "semi-displacement" is not really correct anyway. The better term, and the one I've heard used by boat designers like Tom Fexas (sp?) is "semi-planing" because that's what GB, Taiwan trawler, Nordic, etc. hulls really are. They are in essence planing hulls but with a deeper, finer entry forward, a prominent keel, progressively flatter, shallow-V shape for the aft 2/3 of the boat (more or less), and hard chines. This hull shape can be pushed pretty fast through the water and they in fact do plane--- just not very efficiently.

A boat is either displacement or it's not. However there can be infinite degrees of planing, from very efficient like unlimited hydroplanes to really inefficient like Grand Banks. Take the keel off a GB and either lighten the boat a lot or put a hell of a lot of power in it, and you'll have a fully planing boat. Not a particularly efficient plane, but a full plane nevertheless.

That's why I think the term semi-displacement is bogus, and why I don't use it. I think it was created to give buyers the impression that they're buying into the world of full-displacement, super-seaworthy working boats from which the recreational trawler is (very) loosely derived. In other words, semi-displacement is a marketing term.

In my opinion, semi-planing is a legitimate hydrodynamic term. And if it isn't then boats like GBs should simply be called "really lousy planing boats."


-- Edited by Marin at 18:46, 2007-12-03
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Old 12-03-2007, 06:37 PM   #9
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Confession....road rage on the water...

Marin, I will totally agree although it is all just semantics. Ultimately, a boat like mine or boats like it, there goal is to plane.....which you could call a semi-planing hull. It is not all about eficiency. It is about seaworthiness which is why the semi-planing/displacement hulls were born. Here on Galveston Bay like many bays behind barrier isalnds, the depth is shallow which makes the chop very short and very steep. A SD/P hull slices right thru it with absolutely no pounding....EVER.....because there are no flat spots in the hull.
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Old 12-03-2007, 07:30 PM   #10
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Confession....road rage on the water...

I dunno about the seaworthy business. A semi-planing hull with its hard chines has less of a roll than a displacement boat. However, the sharp-chined hull has a snap-back and the end of a roll that some people prefer to the long roll of a displacement hull and some people hate.

But from what I've been told by the GB folks, the purpose of the semi-planing hull they used is a compromise between a go-real-slow displacement hull and a go-real-fast planing hull. The reason this hull was selected was to provide near-displacement stability and efficiency while allowing the boat to go faster than hull speed for the folks who might be in more of a hurry.

I've been on fully planing boats in the short, steep wind chop we get in our inland waters here, and if the boat has sufficient motor tilt or trim tabs, the bow can be lowered to cut through the water and still be fully on the plane with very little to no pounding, depending on the hull design.

Our GB will pound pretty good, not in the sense of pounding forward through the waves but side to side. On a windy day on Bellingham Bay when the high-frequency,*steep-sided*wind waves can be three to four feet, if the boat is running abeam or quartering, as it rolls back and forth, that flat afterbody can come down with a resounding boom that shakes the boat. It can be rather disconcerting until you figure out what it is.

-- Edited by Marin at 20:31, 2007-12-03
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Old 12-03-2007, 07:43 PM   #11
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RE: Confession....road rage on the water...

I'm not even going to consider getting into the Semi Displacement/Semi Planing discussion, because I don't know, but I do have a great "Wet Road Rage" story. I'll keep it brief.
It was a dark and stormy night. No, that's a different story. It was a beautiful day in Fossil Bay. We were tied to the dock, enjoying all that mother nature and boating have to offer, when this teenager began running the one hundred foot gap between dad's anchored Carver and the dock at about thirty knots. Back and forth, forth and back. On his third round trip, I was forced to point out the 3.5 knot speed limit in the anchorage. I did this with only a slight frustration in my voice, but enough volume to reach him at his 100' distance. Without a word, he went below, and almost immediately was followed by dad, and they began to load the inflatable and thirty horse aboard. In about five minutes they were loaded up and engines running. At this point, a small celebration of sorts had begun on the dock, as we envisioned no more annoyance from them. However, as soon as the anchor was up, the father proceeded to hit the throttle and head right for the head of the dock (where I happened to be standing), and came at us at about twelve knots, then turned sharply right next to my boat, leaving about ten feet between us, and proceeded down the full length of the dock, waking no less than ten boats on each side of our dock, and continued out of the harbor waking another thirty or so boats anchored and bouyed throughout the bay. Not so much as a "Have a nice day." Like father, like son!

-- Edited by Carey at 20:44, 2007-12-03
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Old 12-03-2007, 09:21 PM   #12
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RE: Confession....road rage on the water...

<<I dunno about the seaworthy business. A semi-planing hull with its hard chines has less of a roll than a displacement boat. However, the sharp-chined hull has a snap-back and the end of a roll that some people prefer to the long roll of a displacement hull and some people hate.>>

Marin, you are making an assumption here....and that is everyone is using their semi-whatever hull to do displacement speeds.* Once you get up on plane in a S/D hull, those hard chine flat after sections provide exactly what they were designed to provide.....stability.* At displacement speeds, you will wallow around and snap around and have all of your stuff thrown across the cabin.* But once you get up into the planing range, the boat gets into a groove of stability.* It can be a beam sea or whatever.* I have found that a following sea is the most challenging for the reasons I stated in the first post.* Obviously, you should have the trim tabs trimmed for nose up so it doesn't dig in.

<<I've been on fully planing boats in the short, steep wind chop we get in our inland waters here, and if the boat has sufficient motor tilt or trim tabs, the bow can be lowered to cut through the water and still be fully on the plane with very little to no pounding, depending on the hull design.>>



Another assumption you are making is that chop is uniform and rythmic.* A true planing hull most likely will not pound in short steep stuff if it is perfectly rhythmic.* But knock it out of rhythm(which happens 100% of the time) and you get hammered by that wave that is not in step with the rest and the boat comes down with a bang if it has something to bang on(flatter lifting surfaces).
There was a great article in PMM that describes the difference between hullforms.....the difference is vary vague and that is why we are discussing it here.* But a planing hull carries a lot of "volume" forward that is subject to pounding which could lead to a not so comfortable ride.
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Old 12-03-2007, 09:54 PM   #13
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Confession....road rage on the water...

Of course this is assuming a semi-planing hull has the power to get onto some semblance of a plane. Many of them do not. The best they can do is exceed hull speed by a few knots. This can be helpful in terms of getting there a little faster, but it's not enough speed to really take advantage of the planing capabilities--- such as they are-- of the hull. I'm talking about full-bore, heavy "trawlers" here, like GBs, CHBs, Island Gypsys, etc. that were built with relatively low power engines, not the lighter weight "trawler-cruisers" for want of a better name that have large engines and relatively light construction.

And of course, even with larger engines the price of making a semi-planing hull trawler go faster is pretty staggering. Grand Banks own literature for the GB42--- until they discontinued it--- with the stock Cat 400-something engines called out about 9 knots at about 8 gph total. However, these engines could push the boat at 15-16 knots...... at a fuel consumption of over 25 gph. So you get less that twice the speed at more than three times the fuel burn. No big deal ten years ago, more of a big deal today.

-- Edited by Marin at 22:54, 2007-12-03
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Old 12-04-2007, 09:05 AM   #14
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RE: Confession....road rage on the water...

This one is for Carey, Marin, John, Doc, etc.....

This is a speed/distance chart that I made, very carefully, on a very calm day and in two directions of travel (180 degrees apart) It was also slack tide in San Diego Bay.

The boat is a 2005 Halvorsen 32 Gourmet Cruiser that was advertised at 12/15 knots. The load is half tanks and water, and one person, me. One of the reasons the PO sold was that he said he had tried everything and could not get the boat on plane. He even pulled the prop and had "Prop Scan" redo it. The engine is a Cummins 330B which is rated at 2800 RPM's. The boat at WOT achieves this spec.

<u>I'm in love with this boat</u>, even with the speeds indicated, but I thought I'd throw this out to the forum for their analysis.
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Old 12-04-2007, 09:44 AM   #15
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RE: Confession....road rage on the water...

Ah, Ha, so there IS a secret club/code that you semi displacement/planing hulls have.* Thats exactly what I am talking about putting out a huge wake because the hull can not truly get on plane. I mean if you want a go fast planing boat then buy a go fast planing boat. *Right now you just a PAIN! **Just remember when you see a big ugly old trawler bearing down on you, you probable deserved It. GRRRR.* Sorry, for the little rage there. *(-;
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Old 12-04-2007, 10:16 AM   #16
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RE: Confession....road rage on the water...

Walt
*** I did the same thing for my boat, running a marked half mile, both directions at 100 rpm intervals from 1600-2500rpm. It's good information to have handy.
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Old 12-04-2007, 10:59 AM   #17
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RE: Confession....road rage on the water...

Quote:
Phil Fill wrote:

Ah, Ha, so there IS a secret club/code that you semi displacement/planing hulls have.* Thats exactly what I am talking about putting out a huge wake because the hull can not truly get on plane. I mean if you want a go fast planing boat then buy a go fast planing boat. *Right now you just a PAIN! **Just remember when you see a big ugly old trawler bearing down on you, you probable deserved It. GRRRR.* Sorry, for the little rage there. *(-;
Phil, I have about a 26ft waterline and cruise at 16kts.* I am pretty sure that is planing.* I will admit, even at that speed I do throw a decent wake but any boat of this size at that speed would.* Pic below of me on plane!!!
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Old 12-04-2007, 11:03 AM   #18
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Confession....road rage on the water...

Seahrse, what is the displacement and beam of your boat. That seems a little slow for that power. Many times, builders try to squeeze alot of interior room into their boats at the expense of an efficient hull. The Mainship 35/39s are a good example of that. Mainship got it right on the pilot.....the obvious downfll is that it is a TINY boat for a 30 footer
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Old 12-04-2007, 11:11 AM   #19
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Confession....road rage on the water...

Phil---

The biggest offenders in my observation are not the true "trawler" types like GB, CHB, etc. but the Bayliners and other similar makes. Usually fitted with pretty powerful engines, the owners of these things get them up on a partial plane which parts the waters like Moses at the Red Sea and puts out a gigantic wake.

We ran our boat up to max rpm two weekends ago to get the data for the prop shop that's going to provide the new props we're going to install early next year. To be honest neither my wife or I looked at the knotmeter while we were at full throttle because I wanted to keep the time at that setting to the absolute minimum. So I was back looking at the exhausts while Ruth was driving. The boat did pick up its bow and move out faster than normal, but the wake was not much larger than it is at our normal cruise speed of about 8 knots. It was NOTHING like what the Bayliners in the 32 to 50 foot range put out at the speeds their owners cruise at.

So not all semi-planing boats are running around putting out huge wakes.
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Old 12-04-2007, 12:18 PM   #20
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RE: Confession....road rage on the water...

Ah, Marin, don't you know that all of those go fast wakers come with a manual that talks about running the boat at MWA.* You get the best efficiency, the best comments and the best one finger waves when utilizing the MWA.* I suspect that the manual also suggests that when in big water it is better to pass with something like MSDO or to overtake using the overtakens course line.* Never deviate, never communicate and never, no never make eye contact!* (see page 2 of manual)

FYI:* MWA = maximum wake angle
*** *** MSDO = minimum safe distance off (generally less than 10')

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