New Aluminum CC design

[EddieWeeks]

My father owned a small ship yard till I was 18 and I have been around
boats all my life but I never got a chance to build one.

Now that I am over 40 (haha) I plan on building this boat from 5086 aluminum plate. I have used Solidworks for years and it has taken about a month to get to this point. But before I get to far along I need some advise.

I think All boats are a compromise, and this boat will be around for over 30 years so who knows what it will be used for. I do know, I will not be taking it off shore, off Louisiana Coast, I will use it mostly in a large 10 foot deep bay
that is always to rough for my 18' hull.

Anyway the sides are 3/16 and everything else is 1/4 plate. The motors are
2 x 250hp E-TEC.

As its drawn with motors its 4200 lbs... I would guess it will be 4700 finished.

As I look at other Fiberglass 27-32'.. They are 5000-7000 lbs without motors !!

My father has been an a$$ lately, not wanting anything to do with this project, so any advise would be great, no matter how small...

Also... I have been on lots of forums, so I have very thick skin... I take nothing personal.. Its just advise

Eddie Weeks
Baton Rouge, Louisiana

[kmorin]

EddieWeeks,
I would like to remind you that an old '59 Caddie had 'ride'. It would smooth out a gravel road, a potholed, rutted, old farm road between the corn fields. It did that by being heavy.

It is not the end-all-be-all of boats to be light wt. Please take that from some one who's built a few hundred welded aluminum boats, none of them, even those with a very deep V that rode as well as their 'glass' boat counter parts.

[Please] Don't forget that entry and power are related rates to momentum which is directly proportional to all-up mass [displacement]- so the light wt. boat may go faster with the same power as its heavier cousin, but the heavier boat will deliver less of the changes in movement to the crew. [A change in the movement of boats is often interpreted as impact.]

I wonder if the after sections being concave in Body plan are a gain in any way to the hull's performance? None of the name open class 'cigarette-type' racers have bothered with concave sections aft, what do you propose to gain by that effort of form?

it would help to post the lines as they show more [real] data in less space than 3D perspective views with shadows, which easily mislead. Another valid view that can be informative is a Plan view showing waterlines in 2-3" increments up to the LWL. Then; show that same set of lines with the hull pitched up by the bow in 2deg increments. I find these views helpful to envision the hull's planing surfaces at different angles of pitch and speeds.

cheers,
kmorin

[EddieWeeks]

Originally Posted by kmorin

EddieWeeks,

It is not the end-all-be-all of boats to be light wt. Please take that from some one who's built a few hundred welded aluminum boats, none of them, even those with a very deep V that rode as well as their 'glass' boat counter parts.

I agree 100%... Good point..

Originally Posted by kmorin

I wonder if the after sections being concave in Body plan are a gain in any way to the hull's performance?

My fathers company, LAFCO, Built all their boats this way...The bottom and sides all have 150 inch radius. I was told this increases the stiffness of the plate quite a bit, like a tape measure.

One of the design goals is to run 23" or 24" pitch propellers... If it will run those props it should go 30 mph at 2500 rpm... Also I want to smash all the fiberglass boats miles per gallon. Witch seems to be around 1.9 - 2.1 mpg for the lightest FG boats.

But like you said, it will get bumpy.

Thanks for the input

Eddie Weeks

[EddieWeeks]

Here is my guess at water line while on plane.

Also here is my other boat... 18 foot LAFCO hull... it was a 42 foot
crew boat hull, but it was scaled down then built. It was built in the 70s.
I blasted it and painted it, early 90s. It spent most of its life with a 200hp
merc. A number of them... Did ~57mph... Has gone 62mph with tail wind.

Today it has a 150 4stroke, witch is to heavy for that boat, but at 20 mph
all you hear is spray, its really quiet.

I named it Isobar because I am a meteorologist at LSU.

This dam boat has beat the crap out of me and I am done with it.
That is my fat a$$ father picking up before hurricane Gustav.

Eddie

[mark775]

Eddy, I don't know enough to comment yet but am a good critic as ideas come forth. Good luck with the relationship with your father.

[FishFleet]

hey eddy, I happened to...happen, upon your boat that you've designed up and i was just wondering what the general size of the boat was. Length? Width and the widest point?

Thanks, looks like you've got a nice little project ahead of you!

[EddieWeeks]

The boat is 30 feet long and 8' 4" wide.

Right now I am making the 1/4 scale model of it.

The scale model will be 4 times smaller in every respect. (not motors)
it will be made from 1/16 plywood instead of 1/4" plate and will be 7'6" long.

I plan on putting an electric motor in it and getting it on a plane to see how
it runs. (did the RC thing for 25 years)

1/4 scale version cost so far has been 2 months on the computer and ~$500 for plywood and water jet.

About the full size... Can't decide on engine. I am stuck back and forth from
a Yamaha 350hp 4stroke or
2 x 250hp ETEC

Fuel mileage with the 350 is about 2.7 mpg (for similar size boats)
Fuel mileage with 2 x 250 ETEC is about 2.0 but 7-12 mph faster (guess)

but full size is on hold until my father gets his head out of his a$$....hahaa

Eddie Weeks

[EddieWeeks]

Parts going to water jet this week... This is the 8 foot version
that will be cut from Formica

Eddie Weeks

[sabahcat]

Possibly not an option, but I always liked this vessel if I was ever doing 30 ft ish alloy vessel



Saw down the centreline and open yours up?



http://www.rowellmarine.com.au/broke...hp?boatid=625#

[alidesigner]

Nice boat Eddie.

Concave hull shape might be difficult to plate as you will have to break its back to pull up at the bow. Convex will be easier (try it with a piece of paper).

You can donwload Freeship (its free) at use it to check that the hull shape floats properly for its estimated weight.

What software did you use to flatten the hull bottom? You need to make sure its developable.

[21ftcc]

I think this is what your looking for.
Check them out

http://rocksaltboats.homestead.com/index.html

or on http://www.aluminumalloyboats.com/

[mark775]

Okay, I have enough to comment now...
The aqua cat I like but those little lights forward suck, the cabin is (subjectively) ugly, the word "Aqua", I think symmetric hulls are better, displacement is best for a small cat. That Rocksalt thing is wonderful looking but what are center console boats for - fishing? How do people STAND having an outboard where they need to fish? Forget having a tiny pooper, or whatever, under the console and put the engine there!

[21ftcc]

Well out in New England with a cc like that, it runs to the canyons and is fishing for tuna.

[FishFleet]

hey Eddie one more quick question, what kind of depth you design in?

reason I'm asking sizes by the way is that the boat your looking to build is pretty much identical to the boat that I'm trying to design up to build this winter. About a 32' by 8' cigarette style boat. Dual outboards...basically fast rigid and something that can move 13,000 pounds of fish at 40mph.

[EddieWeeks]

13,000 lbs.. that is a lot... I don't know if this can do it... I guess with the right props and power it could..

What depth are you talking about... how much water it draws or depth of the sides.. ?

Eddie