Hull modifications....See it to Believe it

brian eiland said:

Just one example. Quite a few years ago, the US Coast Guard was looking for a replacement vessel for their 82' patrol boats. Several things they wanted:
1) Good turn of speed
2) Economical to operate
3) Helo pad
4) Fast launching RIB capability

This design by Lock Crowther would have fit the bill VERY nicely. I tried to get the option to submit the proposal. I was even allowed to submit.

BUT it was before catamaran forms became 'acceptable', and it was designed by a foreigner (Australian).

Shortsightedness

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Sorry but your story doesn't fly..literally about the helo pad for sure.

I was a fairly senior officer when the USCG was looking for replacement patrol boats...the helo pad wasn't part of the realistic approach even if it was thrown in there...because of the helo's the USCG used at the time were way too heavy for that class vessel....

There are many reasons why a "cat" may or may not have fit the bill...first and foremost they are usually more expensive than monos for a given length...plus berthing a cat can be a disaster in small places the USCG has to moor.

I'm sure the design could live up to the parameters you listed but that's just a short list...not all the requirements that ultimately didn't meet the USCG's satisfaction.

To blame the refusal sounds more like sour grapes than blaming it on old "gov't" fogeys.

brian eiland said:

Perhaps you should write Passagemaker mag and/or Dave Gerr and ask them to explain these numbers?

I don't know Tad, I just quoted the article.

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magazine articles are always correct...just ask them.

brian eiland said:

BUT it was before catamaran forms became 'acceptable', and it was designed by a foreigner (Australian).
Shortsightedness

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Or ever so slightly unkind.
Incat, located in Tasmania (the southern island state of Australia) built a range of wave piercing fast catamarans they call a SWATH (Small Waterplane Area Twin Hull) which were sold worldwide,including to the Australian Navy, probably others, and can be quite large.
A passenger/vehicular ferry version operates on the notoriously rough Backstairs Passage crossing between Cape Jervis on the South Australian mainland and Penneshaw on beautiful Kangaroo Island. You get good espresso coffee and pastries onboard for breakfast, but it`s not entirely advisable.

BruceK said:

Or ever so slightly unkind.

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Not sure how you are interpreting what I said about the designer Lock Crowther??

I meant only that as a foreign design that made it unacceptable to the US powers that be. Lock Crowther was a friend of mine from the early days of multihulls. I respected his designs immensely.

psneeld said:

Sorry but your story doesn't fly..literally about the helo pad for sure.

I was a fairly senior officer when the USCG was looking for replacement patrol boats...the helo pad wasn't part of the realistic approach even if it was thrown in there...because of the helo's the USCG used at the time were way too heavy for that class vessel....

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I think you are correct there....the helo pad was not a 'requirement'. its been a long time ago, and I've forgotten a lot of the details of that transaction.

I was really disappointed that they didn't look seriously at more possible multihull designs.

Its a shame that new Navy littoral ship tri-hull vessel is plagued with corrosion problems as its performance is not lacking in comparison.

brian eiland said:

I think you are correct there....the helo pad was not a 'requirement'. its been a long time ago, and I've forgotten a lot of the details of that transaction.

I was really disappointed that they didn't look seriously at more possible multihull designs.

Its a shame that new Navy littoral ship tri-hull vessel is plagued with corrosion problems as its performance is not lacking in comparison.

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maybe to make multihulls competitive...too many corners have to be cut.

wouldn't think so but that has plagued multihulls from the beginning...

I bought it

Greetings from this new member. I've enjoyed reading the comments on this heavily modified IG 32. I bought/stole her last month in a complicated estate situation. I'll be keeping her in Greenport, LI this season.

All her modifications are reversible. I will decide what if anything to do after a full season on the water. As a diver, I will probably keep the stern extension.

I'm thrilled with her all-new electronics, new fuel tanks, the layout, and her overall condition.

Feel free to stop by and see her this season.

Dave

satfly said:

Greetings from this new member. I've enjoyed reading the comments on this heavily modified IG 32. I bought/stole her last month in a complicated estate situation. I'll be keeping her in Greenport, LI this season.

All her modifications are reversible. I will decide what if anything to do after a full season on the water. As a diver, I will probably keep the stern extension.

I'm thrilled with her all-new electronics, new fuel tanks, the layout, and her overall condition.

Feel free to stop by and see her this season.

Dave

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Frequented Greenport in 1960's. Be well... have fun! - Art

Congratulations, I would be interested know how she handles. Sounds like you got a lot of boat for the money.

A question though, is the running gear as per the original spec's.

Basic question when it come to dead rise. Positive dead rise, transom leans forward?

OldDan1943 said:

Basic question when it come to dead rise. Positive dead rise, transom leans forward?

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Deadrise isn't about transom lean, it's about the angle of the V of the hull bottom. Typically the quoted figure for a hull is deadrise at the transom. In the case of my hull in the picture below, it's easy to visualize, as there's just a constant angle, no strakes, tunnels or chine flats to cause a visual interruption. The hull in the picture has 10 degrees of deadrise at the transom.

In the case of a hull with reverse deadrise, the angle would go the other way, as in higher in the center, lower at the chines.

rslifkin said:

Deadrise isn't about transom lean, it's about the angle of the V of the hull bottom. Typically the quoted figure for a hull is deadrise at the transom. In the case of my hull in the picture below, it's easy to visualize, as there's just a constant angle, no strakes, tunnels or chine flats to cause a visual interruption. The hull in the picture has 10 degrees of deadrise at the transom.

In the case of a hull with reverse deadrise, the angle would go the other way, as in higher in the center, lower at the chines.

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I am still confused
Perhaps a side view would help explain the difference.

OldDan1943 said:

I am still confused
Perhaps a side view would help explain the difference.

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Basically, the transom angle is irrelevant to deadrise. Deadrise is just the angle of the V bottom on the hull. Typically measured at the point where the bottom meets the transom. I think this might explain it better than I can: Deadrise Defined - Weldcraft Marine

OldDan1943 said:

I am still confused
Perhaps a side view would help explain the difference.

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Dan, it is a very "elegant" way of saying something very simple. Deadrise is simply the angle of the "V" at the transom. It you were to put your boat on the cement and balance it evenly, deadrise would be the angle from the middle of the boat(the part touching the cement) out to the chine. It is as simple as that.

The reason some boat manufacturers brag about deadrise angle is that it does somewhat indicate the seakeeping ability....OF A PLANING BOAT! Deadrise doesn't mean much on a boat that does not plane. Actually the less deadrise, the more initial(static) stability a boat will have since it will have more level flotation. Deadrise is also the reason why planing hulls do not do so well at displacement speeds....stabilitywise. They have a tendency to wallow around because they do not have that initial stability that a hard chine with minimal deadrise provides. To put it another way....a flat bottom skiff has no deadrise. It will ride very poorly(but technically better performance since more lifting area). The more deadrise, the better the ride but you do sacrifice performance since you are sacrificing lift. Look at a big sportfish....they have tremendous amounts of deadrise because they need it to cut through the seas while at planing speeds.

Positive "use" items about a full planing hull:

- Can go slow [with relatively good fuel economy]
- Can go fast [for getting someplace quickly with relatively poor fuel economy]
- Under power at at any speed; hard chines enable rapid vertical return from a limited roll angle
- At anchor hard chines make considerably less roll occur due to wave, wake or wind conditions
- Shallow draft for being in reduced depth waters
- Flatter interior bilge areas that work well for equipment placements and product storage needs
- Efficient for localized and coastal cruising uses

Positive "use" items about a full displacement hull:

- Goes slow, for relatively good fuel economy [usually some 15% +/- better than a planing hull fuel economy at slow speed]
- Full keel for much better protected prop and rudder
- Somewhat efficient for localized use, considerably efficient for coastal cruising and long range uses

Semi displacement hulls have some of the pluses and minuses of hulls described above.

Photo is profile of our boat's full planing hull

You make the call... as to what hull features you desire!

Even on a planing hull, deadrise is a compromise. In general, more deadrise leads to a better ride in a head sea with less pounding, but as Baker said, it's worse performing at low speeds. High deadrise hulls like a deep-V sport fish also don't plane as efficiently as a lower deadrise hull, so minimum planing speed is often higher, they require more power, burn more fuel and often throw more wake as well compared to a fairly low deadrise hull.

Here you go...don't mind the commentary at the bottom...it is from a very elementary boat shopping site.

rslifkin said:

Even on a planing hull, deadrise is a compromise. In general, more deadrise leads to a better ride in a head sea with less pounding, but as Baker said, it's worse performing at low speeds. High deadrise hulls like a deep-V sport fish also don't plane as efficiently as a lower deadrise hull, so minimum planing speed is often higher, they require more power, burn more fuel and often throw more wake as well compared to a fairly low deadrise hull.

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I have been on a 72 Viking doing 42kts....the hole that the boat is tearing in the water at that speed is absolutely mind boggling....so is the fuel burn as you would imagine....I think it was somewhere around 240gph

Baker said:

I have been on a 72 Viking doing 42kts....the hole that the boat is tearing in the water at that speed is absolutely mind boggling....so is the fuel burn as you would imagine....I think it was somewhere around 240gph

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I can only imagine. There's a reason I'm very ok with my low deadrise hull that planes cleanly and without a massive wake. Yeah, I have to be a bit careful with speed and trim to get a decent ride in a head sea, but for everything else, it's a worthwhile tradeoff.

Art said:

- Under power at at any speed; hard chines enable rapid vertical return from a limited roll angle

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I think this is more descriptive of a semi displacement hull. SD hulls have a tendency to have a very deep forefoot similar to an FD hull. And then flatten significantly as you go aft...many to almost zero deadrise. A zero deadrise hull will most certainly act in the way you mention above....INITIALLY. But it will have a tendency to snap back which is why they suck in a beam and following sea. A hull with significant deadrise does not have as much flotation...or at least the "lever" of the force is different or "delayed". The boat will roll initiall until the lift of the angled hull can react....if that makes any since. My last boat was a planing boat with no autopilot. It was horrible to steer at low speeds.

Another positive for planing hulls is that they do provide dynmaic force(lift) for stability. IOW, being up on plane is much more stable than not being on plane...and can be more stable than a non planing boat. I cruise with non planing boats. And there are certain conditions I can handle better simply because I can plane. A beam sea(shorter chop is what I am referring to) would be a perfect example. A planing boat in a beam sea generally does not roll...it just goes up and down while remaining level. A short choppy beam sea generally does not bother me. It is horrible in an SD boat.

Hmmmm, thanks for the info. It is becoming clearer.
Now, on the boat with a squared transom.... full displacement, no dead rise, soft chine, measured to the bottom of the skag (protecting the prop and rudder.)
A planning hull, is where the dead rise measured from the hard chine to the lowest part of the keel
Now, the fun part. A semi-displacement hull design...... measured almost the same as a planning hull, realizing the chine can be hard or semi-hard.
NOW, a canoe stern..... ???? The advantage or disadvantage ????
Finally, a reverse dead rise would imply a negative angle?
With a follow sea, the advantage would be, the canoe stern would split the waves and the stern would rise less?

Correct, a canoe stern does better in a following sea, as it gets pushed around less. When you've got a flat transom and small rudders, the best defense in a following sea is speed / power. Running with or ahead of the waves greatly reduces getting pushed around, as the waves aren't overtaking. When that's not an option, powering up a little pushes more water over the small rudders, making them somewhat more effective.

Baker said:

My last boat was a planing boat with no autopilot. It was horrible to steer at low speeds.

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No AP on our Tolly. She is a joy to steer at any speed.

Having been around boats for many decades... many persons in TF realize the sheer individuality that each hull design provides regarding handling.

We do luv our Tolly!

I do wish for autopilot on my boat. In calm water, she steers nicely at low speed and downright beautifully up on plane. But when it gets rougher, it starts to take a bit more work to keep a good course on a long run, so autopilot would be nice for workload reduction. Especially on long, straight runs down the lake.

rslifkin said:

I do wish for autopilot on my boat. In calm water, she steers nicely at low speed and downright beautifully up on plane. But when it gets rougher, it starts to take a bit more work to keep a good course on a long run, so autopilot would be nice for workload reduction. Especially on long, straight runs down the lake.

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Yes - For long straight runs AP would be nice!

rslifkin said:

I do wish for autopilot on my boat. In calm water, she steers nicely at low speed and downright beautifully up on plane. But when it gets rougher, it starts to take a bit more work to keep a good course on a long run, so autopilot would be nice for workload reduction. Especially on long, straight runs down the lake.

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The destroyer I was on,(DD881) no AP. The duty helmsman and his reliefs would hand steer all the way across the ocean using a magnetic compass.

OldDan1943 said:

The destroyer I was on,(DD881) no AP. The duty helmsman and his reliefs would hand steer all the way across the ocean using a magnetic compass.

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Same on the USS Constellation...but the shifts at the helm were 4 hours, so no AP was really needed...

I served hand-steered helm watches on the 700' guided missile cruiser USS Chicago CG-11 in WESPAC '79. Upon returning to our cramped, windowless, below the waterline berthing space my shipmates consistently yelled at me for zig-zagging all over the South China Sea.

Now, there is a lot less yelling and I really enjoy the autopilot...

Don't even ask me about the yelling during a Navy shower. I still have emotional scars from that.

Five years ago seeing an outboard or two on the back of a boat designed and built for an inboard was basically unheard of. Oh sure there was always a hacker who rigged an old forty horse Johnson to the back of a 23 foot wooden boat. But a quality job involving big dollars and respectable glass work ? Never.

Nowadays, they are everywhere. Purpose built 4, 5 and even 6 huge outboards totaling thousands of horsepower. From the factory or from a respectable conversion shop.

Paging through a new boating magazine will show you how much design has changed in the past 20 years. Not so much for the good in my opinion, but what do I know.

The big outboard powered rigs are here to stay, not just center counsel but all shapes and sizes.

IMHO the only thing which will bump the big outboards out of prominence will be electric power. It is on the horizon but will be a while in getting here.

pete

When I was a kid, we used to take an old Grumman canoe out in the surf. If you got it "right" and could keep the canoe perpendicular to the wave, get sufficient paddling to match (or over take) the wave speed, you would get a great ride into the beach (or sometimes the rocks!)

My point here is that when you were NOT 90 degrees to a wave, it would twist you parallel to the wave, you'd roll and deposit the whole load up onto the beach.....and getting sideways would happen very quickly!

So it gets me wondering if a canoe like stern would fair in following seas. Of course there's a lot more mass to push sideways, but bigger waves....not sure. I would think a fantail might do better, as waves couldn't get a purchase on the exposed port/starboard aft area....

Just my thoughts on my experience. I've entered/exited rivers in the Northeast that required "timing" or surfing in with a planning hull.....very exciting (pucker).