Questions about rocker

[Mr Efficiency]

8000 lbs total weight ?

 

[Bullshipper]

Ok. Thanks anyways

 

[Bullshipper]

8000 dry

 

[Bullshipper]

+275 gal gas, 6-8 passengers, gear, 500 lbs in fish and ice,+ 50 gal of water. If future hull is 10 mm thick, it will weigh 1600 lbs less than this one

 

[Mr Efficiency]

So hull alone is how much, excluding engines ?

 

[Mr Efficiency]

I would think with the dimensions quoted, you would get away with 8000 lbs hull, using outboard power

 

[Mr Efficiency]

They can feel like a slug, if heavy, but getting into a flighty lightweight one, has you pining for the old "slug"

 

[Bullshipper]

In good sea conditions she is fine, but the idea is to make her good in 30 it winds. Thanks for helping with the rocker question

 

[Mr Efficiency]

Rocker is just a very bad idea, don't entertain it for a second. Very few such boats are "good" in 30 knot winds, or the type of seas they create. I can't imagine what a pleasure fishing boat would be doing in those conditions, it is too rough for fishing. What heading relative to the seas is the most problematic ? I notice the "wavebreaker" is a short affair well forward, maybe that could have been taken further back

 

[kapnD]

Rocker is just a very bad idea, don't entertain it for a second. Very few such boats are "good" in 30 knot winds, or the type of seas they create. I can't imagine what a pleasure fishing boat would be doing in those conditions, it is too rough for fishing. What heading relative to the seas is the most problematic ? I notice the "wavebreaker" is a short affair well forward, maybe that could have been taken further back

“Too rough for fishing” is a nebulous term!
Fishing time and ideal weather conditions often do not always fall in perfect alignment, and many fishermen are prone to brave bad conditions in order to catch fish. The boat needs to be capable.
How about some assist foils?
Or how about slicing the bottom off at the chine/spray rail thing and sectioning in a 6-8” flat panel ?
The possibility of modifications like this really points up the beauty of FRP !
Some stability calculations would help determine just how much height is needed to float the boat higher for more bridge clearance.

 

[kapnD]

The red marks indicate the location of the forward foils.
Not a very good markup, but maybe you can get the idea.
Same at the stern, or possibly one foil spanning between the hulls.

 

[Bullshipper]

View attachment 169015 The red marks indicate the location of the forward foils.
Not a very good markup, but maybe you can get the idea.
Same at the stern, or possibly one foil spanning between the hulls.

Thanks for sticking with me on this.

I looked at some technical stuff on the center foil and rear fins and thought about it as fixing a heavy hull is probably the foils best application. The Hysucat foil cats and RIBS well designed but are also being built very light with their 25 footer CC coming in rigged around 4700 lbs, and their sponson design and highly canted motors are also a lot more stable at speed with a wider tunnel bottom than mine. And all their videos are on glassy water, and I have found that the foils tend to hold the bows down in large following seas producing bow steer

So stability concerns me and throwing more money at a bad hull are not prudent at this point, as she will underperform the competition because she will still be overweight with or w/o foils.

I calculated last night that I can reduce the 8120 lb rigged hull to 6050 using my existing molds if I go to 1.5+.75 oz mat+2 mm coremat+1710+3610 for the sides and one more 3610 for the bottom versus using the extra heavy rovings available here in Mexico, where I also applied way too many layers of this thick knotty roving. The thick roving also sucks a lot more resin to wet out and the 1710, so I have made the decision to strip this one, make another hull to assemble again, but weigh the materials prior to application.

I have owned 4 cats and this is by far the best of the bunch in conditions to 3 feet, but I do not want to compromise the design after 3 years plugging away during retirement. It will take me less than 4 months to build the new one, and labor is inexpensive where I am.

Thanks again for your valuable input.

 

[Bullshipper]

Rocker is just a very bad idea, don't entertain it for a second. Very few such boats are "good" in 30 knot winds, or the type of seas they create. I can't imagine what a pleasure fishing boat would be doing in those conditions, it is too rough for fishing. What heading relative to the seas is the most problematic ? I notice the "wavebreaker" is a short affair well forward, maybe that could have been taken further back

You seem to be focusing on tunnel slap and that is not a problem.

But you again confirming the rocker is not needed makes perfect sense to me as I had a 22 Seacat that had rocker and although I was able to fix her bow happy ride, it took 2 Permatims and 5 degree motor wedges to do so. So your help allows me to plow forward with my existing molds, and I really thank you for that.

This hull feels overloaded with fiberglass running "light" on fuel. I have decided I am not going to send someone 100 miles offshore with more fuel weight where conditions often worse than expected, just to save a dime. Her daughter will be a short ton lighter, or 24% lighter than this one as tested and still be stronger than needed.

 

[Mr Efficiency]

You made no mention of the installed power on this boat, the problem as I understand it, is that you have to run faster than you want to, in rough water, to keep the boat planing cleanly, so what is the problem with running fast in the rough water, is there some handling or ride problem ? Are you forced to push the installed engines too hard to keep the boat up and running, sending fuel use too high ? You have not made it clear what the actual deal-breaker is, other than to say it is "too heavy"

 

[Bullshipper]

You made no mention of the installed power on this boat, the problem as I understand it, is that you have to run faster than you want to, in rough water, to keep the boat planing cleanly, so what is the problem with running fast in the rough water, is there some handling or ride problem ? Are you forced to push the installed engines too hard to keep the boat up and running, sending fuel use too high ? You have not made it clear what the actual deal-breaker is, other than to say it is "too heavy"

I have twin 225 hp 4 stroke Mercs on her.
Boat rides too low in the water at 25. needs a lot of speed to stay on top and find her sweet spot.
Planning at 20 versus 12 mph
Can run 40 mph into 1-2 chop sitting with hands off of wheel
But I don't feel safe running 38 mph into or with following seas when they are 4-6 and if boat falls off plane if also feels unsafe .
Hull is currently drafting 20" with light fuel when 17" should be max full
Cats are sensitive to weight and this hull is overloaded.