65- by 32-foot catamaran 3200sqft of living space

Binnacle Bat

New member
It seems we are reduced to checking in to see which lee shore has claimed the FH, and have to wade through deep piles of troll poop to find out it ain't happened yet. Maybe we should all give it a break, and wait for real news.

 

jerryj2me

Super Anarchist
1,758
1
It seems we are reduced to checking in to see which lee shore has claimed the FH, and have to wade through deep piles of troll poop to find out it ain't happened yet. Maybe we should all give it a break, and wait for real news.
A betting pool of what the windspeed is when it breaks loose and ends up either grounded in mud or on the rocks?

$5 each?

I want 25 knots. Make that 40 knots.

 
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Timo42

Super Anarchist
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It's still a big circle jerk. The size (and shape) of the rudder determines the amount of force it CAN generate - that's the water tank measurement. The size and shape of the boat (plus other stuff like waves and windage) determine how much force is NEEDED to initiate a turn. If the rudder can generate more than this force, that excess is unused - you just don't push the tiller as hard or as far, and you center it sooner - and the hardware doesn't see the full load. I'd like to think my cruiser's rudder has some excess capacity all of the time, for race boats like an I-14... well, to paraphrase: 'if you aren't stalling sometimes, your rudder is too big'. And if you don't blow up the occasional gudgeon, it's too heavy.

The examples earlier in the thread are based on putting the 'wrong' sized rudder on a boat. A laser rudder on the FH will be at it's 'max force' most of the time, on a laser, that max force is only occasionally seen. The FH rudder on a laser would only use 1/100 of it's maximum potential force cause it's so big and the boat is so easy to turn - you would simply be unable to get to it's maximum force. However if you made the hardware for attaching the FH rudder to the FH based on measurements taken with the FH rudder on a laser (like my example)... it would be severely underbuilt.

Then there's the whole issue of dynamics. It's an entirely different situation for an overpowered I-14 leaping off waves and pounding into chop with trapeze crew dancing on gunn'l than for an O-day 14 puttering along at 4 knots (even if they weighed the same, ha!), and different still for the rudder on a 20,000 pound catamaran getting pooped by a big following sea. None of which will show up in your towing tank.

 

Timo42

Super Anarchist
Gary Busey? He doesn't hold a candle to Patrick Swayze in drag. :blink:

patrick-swayzejpg-71b9356e6ae76114_medium.jpg
gary+busey+drag.jpg


 
Thank god all that America's Cup bullshit is over so that this site can go back to focusing all of its attention on the Bay Area multihull that really matters.

 
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silent bob

Super Anarchist
8,705
1,285
New Jersey
It's only worth picking out specific details to criticise if it entertains you. This "boat" is a fractal mistake--it is wrong at every level of resolution, from the specific to the global. It wouldn't matter if he got the rudders right because the boat and the rig are so wrong. It wouldn't matter if he'd gotten the hull shape right because the materials selection was so godawful. It wouldn't matter if he'd gotten the right materials because his craftsmanship and engineering are so poor. It wouldn't matter if he'd engineered it right because he has zero offshore experience and no clue how to handle a giant catamaran at sea. . .and so on.
On some level James McMullen is exactly right here. There is basically no plausible set of changes that would turn the FH into a boat that most of us would consider remotely acceptable. But it really doesn't matter if James or I see this as acceptable, or even safe, since it isn't our boat.

While I see a million things wrong with the boat, they are not all equally important. Some of them might kill HR or his son, but many of the mistakes will just make the boat slow, ugly, and prone to rot. Hot Rod should prioritize -- the classic emergency management list is "buoyancy, then steerage, then propulsion." It seems that there is a lot that HR could and should do to make it less likely that the FH sinks. Maintaining buoyancy takes them a long way toward surviving. Here are my suggestions:

1) Install several (4?) transverse bulkheads per hull. They can be temporary, i.e., removed when not sailing the boat, but they should extent from the bilge to at least 2' above resting waterline and be watertight. These could each be built for $20 a pop... cut a 4x8 sheet of cheap plywood to fit the cross-section of the hull, screw it to the frames, then add a 2x4 as a cross member. Such bulkheads would dramatically strengthen the ring frames to reduce the chance that a structural failure propagates down the hull. They also limit the extent and rate of flooding in the event of a hull failure or serious leak. This is just about the cheapest insurance you can get, short of running the boat into the mud and walking away.

2) Tape the inside of all plywood joints below the waterline with fiberglass/epoxy. I know HR taped the exterior joints, but the interior joints did not appear to be taped. Every joint is a likely leak and it is much easier to tape all of the underwater seams while the boat is relatively dry, than to patch a single seam when water starts gushing in. It would not take much material to strengthen and waterproof those plywood butt joints.

3) Add blocking between the frames near the bilge of the hull to take longitudinal compression loads. Plywood is extremely strong in tension but can collapse in compression, particularly if the plywood bottom is already flexed by water pressure. When the middle of a hull is lifted by a wave (the "hogging" condition, which might occur when a wave overtakes the boat from behind), the middle sections of the hull support the entire weight of the boat, with the bow and stern out of the water. This puts the bottom of the hull in longitudinal compression (the hull deck is in tension) while the hydrostatic pressure bends the plywood panels inward at the same location. This introduces one of the most common catastrophic hull failure modes in which the hull buckles below the waterline near midships. Many wooden boats would have a structural keel to take these compression loads but yours appears to rely on the plywood and (wafer-thin) stringers to take those loads. Putting sections of 4"x4" between your frames would provide a structure to take these compression loads when the plywood starts to flex. This is most important for the middle 32 feet of each hull. I am not as worried about the deck compression loads when in the "sagging" condition, since a compression failure of the deck is likely survivable.

4) Add intermediate frames. You currently have lightweight frames on 48" centers. You could insert 16 intermediate frames so that the frames would be on 24" centers. Material costs are low but these would take a bit of labor. You could glue + tape them into place so you would not need to screw through the hull.

If HR makes these changes the FH, it will still be ugly, slow, and have no ability to go to sail to windward... but it will be quite a bit less likely to fill with cold water 100 miles off the California coast. "Not filling with water" should probably be your primary goal at this point. Just about everything else is optional.
Step 1 - Jack up Windex.

Step 2 - Replace boat under said Windex.

Step 3 - Replace Windex.

 

silent bob

Super Anarchist
8,705
1,285
New Jersey
We promise not to make fun if you switch to Junk, HR.
The Rod is going to change his junk???
Oh, great. Now the thread changes to transvestites and drag queens...argh.
I thought that the Julie Newmar references were where it changed...

How about Patrick Swayze to play the Rod?
Well, Swayze is dead, and Rod will probably be dead soon after the boat slips beneath the Gate.

 

JohnMB

Super Anarchist
2,837
609
Evanston
Beacuse everything you're saying is irrelevant. It's like saying 'well would gravity work different if you called it Muriel?'. The MAXIMUM force the rudder can possibly see is easily calculable. What it sees AFTER the boat starts to turn is completely irrelevant as it's less than the maximum.

You didn't really understand what I said did you.

Sorry, but if you think that the maximum force the rudder can see is easily calculable you may need to review your calculation wrt newtons second and third laws, and make sure you are not neglecting the change of momentum of the rudder. In some cases you can, in some cases you cannot. How does this affect your calculation for the reaction loads at the rudders attachment points?

 
We promise not to make fun if you switch to Junk, HR.
The Rod is going to change his junk???
Oh, great. Now the thread changes to transvestites and drag queens...argh.
I thought that the Julie Newmar references were where it changed...

How about Patrick Swayze to play the Rod?
Well, Swayze is dead, and Rod will probably be dead soon after the boat slips beneath the Gate.
Wait.... Swayze's dead?

 

Remodel

Super Anarchist
10,232
880
None
For all you whiz kids who seem to love getting it on with rudders, you want to read this:

http://dome.mit.edu/bitstream/handle/1721.3/51251/DTMB_1938_T052.pdf?sequence=1

Written, 1938, "Calculation of Rudder Force" US Experimental Model Basin, Navy Yard, Washington D.C.

For the more normal people in the room:

https://www.facebook.com/pages/Beautiful-Booby-Girl/177528162349174

Where you will find works of art such as this:

970061_384761518292503_1512664689_n.jpg
That should kick off quite the discussion of rutting.

 

Boston1

Super Anarchist
3,653
0
BF colorado
Still floating Rod ?

For all you whiz kids who seem to love getting it on with rudders, you want to read this:

http://dome.mit.edu/bitstream/handle/1721.3/51251/DTMB_1938_T052.pdf?sequence=1

Written, 1938, "Calculation of Rudder Force" US Experimental Model Basin, Navy Yard, Washington D.C.

For the more normal people in the room:

https://www.facebook.com/pages/Beautiful-Booby-Girl/177528162349174

Where you will find works of art such as this:

970061_384761518292503_1512664689_n.jpg
Yummy looking rutters ;-)

 

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