Aluminum Offshore Fishing Catamaran CNC Cost?

[jwells11]

We always used 5086 H32. on the sides and bottom, 5052 for stringers as we they were a bit more ductile for bending. Upper decks etc were 5052 I think H112

There is a difference of opinion on using hardened alloys. The discussion being is why choose a hardened alloy that when welded the aluminum becomes almost a Zero hardened alloy due to the property changes in the Heat Affected Zone
My own view was that while the weld zone hardness and hence strength will be reduced in the HAZ, there are areas away from the HAZ that may become under a high level of stress, say due to impact. As our almost all of our boats were meant to run boulder strewn waters and impacts were expected, and the price between the hardened alloys were not significant when compared to the price of a completed boat, we wanted any factor of safety that we believed that we gained.
Our area of concern was mainly between stringers where permanent bending could occur upon impact. You will not have this issue.
If you google the aluminum boat builders, the manufacturers often will include the allow that they use.

I am not sure what the cost of 5086 is these days and certainly not at a one shot buy price. You really want to buy sheets as large as you can handle and as wide so you do not have to spend time joining sheets. Additionally, using large single sheets reduce the chance of inflections in the hull at joints. Say you take 3 12 foot pieces to make 36, but install each 12 foot ends on the framing. You can ruin the fair curve and if you end the sheets on a frame, you cannot properly weld the inside of the joint. . It is extremely difficult in curved sections of the hull, developable bend, to carry the same curve with joints on frames or welded in position. The best procedure
is to pre-join the sheets on a flat area, and install a large section at a time.

In an earlier post you mentioned a 4 x 12 sheet. Often smaller aluminum suppliers
will offer stock sizes as it is easier for them to handle. For a 21 foot hull, we bought 20 feet by 5 foot in 1/4 and 3/16. We had to join just a bit on the front, tack one side, 1/2 inch tacks, flip it, tack the other side, , sand the tacks smooth, flip it, sand the tacks smooth, make up the weld on one side. Back cutting every start and stop, to eliminate the potential voids due to crater cracks or cold bead stoppages, Flip it, back cut the weld to the first weld, weld the side, grind and sand the weld, flip it grind and sand. Then on a perfectly flat
surface, use a body hammer and tap out any discontinuity

If your aluminum source distributor has a coil line, ie they by hundreds of feet on a coil, and unroll, straighten and cut to length, they you are buying some a large aluminum distributor. I would make up a list of what you need and email it around for a one time quote, and you may find different prices varying significantly

The $40 that you suggest to finish seems a little light. By the time you buy and anchoring system, head components, fuel tanks, lighting, hatches, dipped wired,
batteries, cleats, and a good quality Radar, gps, a couple of vhf's, fish finder, and the list seems never to end, you will easily burn through this.

You should also discuss with a marine insurer as your boat will be "home built"
Some insurers will require a complete survey and if the vessel is large, they may want a surveyor to do periodic inspections during construction. Something to keep in mind

Good info....

I heard some crazy numbers on CNC costs........Numbers that will put CNC costs higher than the sheets of aluminum themselves. Is this true or should I expect much much lower costs than that?

I imagine a 30ft sheet gets heavy though.

I have a 50hp tractor w/front end loader.

If that dosent do good enough, I will build a I beam winch that slides(dont know what they are call).

40k after thinking and looking up what I wanted is a low.

Thought about it with some research this morning, and for 24inch simrad and radar, Im at 10k plus already. 5k in stereo to do right at least, 5k in good llebroc seats, $3500 in Dometic AC, and then you got general hardawre, auto pilot, good bottom scanner, upholstry, and possibly a windless(I want a flat deck up front for now toe stubs so still debating on windless)

Then glass although I have a good friend that will cut me a deal on that. No labor no mark up most likely. But still......

Will be simple as possible though. Im a utility person.

 

[jwells11]

I am looking at those numbers and wondering.
5 000$ for a custom design of a high speed boat and at least two building licenses (yours and the one you want to trade with your buddy for work)? Absolute bargain.

15 000$ for Al I can not comment about, it depends on how much you actually need (total surface, nesting), local prices plus transport and discounts available to you. As had been said a high volume customer dealing with a producer has different prices. A specialised Al fab shop could possibly deliver the already cut plates on your doorstep for less then you can buy the raw materials and still make a profit. Only quoting helps here, but you need the plans for that.

10 000$ for CNC cutting the boat? Crazy. You could own the machine for less. Remember you don't actually need CNC cutting. Print the plans on adhesive backed vinyl, buy a good jigsaw with new blades and spend some quality time cutting. A small angle grinder and a dremel for fine tuning and beveling. Under 1000$ and some elbow grease all in. The saved 9000$ you can spend on things you actually need like renting a professional welding machine, buying supplies for said machine and paying a pro to weld the thing up after you tack it together.

40 000$ for a complete fitout? I suppose you will not paint the boat, do the wiring yourself, and be spartan everywhere else.

Time and I grew up in a sign shop and just down imagine the lines being accurate. I did think of this though

If I do another boat, it will be a hybrid bay catamaran. and will probably use this and make a cardboard model. be free and make sure I have the demensions right for I dont havent found a CAD for one.

Only one manufacturer making a catamaran hybrid bay worth doing(aka CAYO)

@Barry As far as cnc costs I heard some crazy numbers flying around on CNCzone.

Thats why Im concerned that CNC work will cost 20k alone on this. Doesnt seem like it should cost more than the metal though

 

[Barry]

As far as cnc costs I heard some crazy numbers flying around on CNCzone.

Thats why Im concerned that CNC work will cost 20k alone on this. Doesnt seem like it should cost more than the metal though

It is unlikely that the cost for CNC work will be that much. We had our own plasma table so I cannot comment on current costs. As per my earlier email, contact Specmar or those companies that they recommend as they will have experience with pricing etc.

A good quality table will do about 80 inches of cut per minute in 1/4 inch with an AIR-AIR gas mix. So to make a 20 foot cut would take about 3 minutes. As most of your cuts will be slow curved cuts the machine can pretty much set up to
run at a high rate of speed. If you have a lot of tight corners, and there will be some in the frames, you might need to turn it down 40 ipm.
I would expect that it should not take more than 3 -4 hours of cut time and even that seems high. But positioning each sheet does take time.

There a couple of things to consider
1) If you have someone design the boat that would be one cost.
2) making the dxf file, ie the cut file can be another.
3) almost all good CNC machine programs will have a nesting feature where you can enter the data, ie the shapes and the quantity and then enter the size of sheets and the number of sheets.
The program will then nest all the parts to minimize sheet usage. This is such a huge savings as compared to starting with pattern and trying to get the best bang for your buck. Another good feature is that for aluminum you can use
air for both the cut and plasma functions, which does not cost anything

Cutting of aluminum
The best way for larger pieces is a 7 1/4 inch circular saw with a 60 tpi carbide blade, Freud or Diablo, cross cut grind ( don't try to skimp here and buy offshore junk) You might need 2 to do a 40 foot boat, maybe 3.
Buy a good saw, Milwaukee was our choice. We had tried Makita and Dewalt but they did not last as long.
Do not use wax or oil or anything during the cut as it will impact the integrity of the weld. Clamp everything well. AND ALWAYS WEAR TWO LEVELS OF EYE PROTECTION Safety glasses and a face shield. The chips coming of these cuts
are HOT and I am convinced that they can turn 90 degrees within 2 inches to get underneath a single barrier. (they probably are bouncing at 90) And the cut process is loud, extremely loud, buy a top level set of muffs.
As aluminum is tougher than wood, you need to ensure that if the saw bucks back at you, that the blade path does not cross a member of your body.

You will need a circ saw to back cut butt welds on sheets and to cut back any welds that are continuous or where they meet each other to get rid of any craters cracks which sometimes you do not see easily

 

[Rumars]

CNC costs are determined primarily by the time on the machine, then machine size and type (asuming nesting is already done by the NA). Your basic need is a 3-axis router as is commonly used for plywood, the problem is most of those have 4x8 beds. A 5-axis machine can already put in all the bevels, but only if your NA draws them in, which is a lot of work for what you are paying. Waterjet is faster then router, but usually more expensive. You will not know the needed machine size until you know how you buy the material.
Finding someone with a 12ft long 3-axis router and a good price should not be difficult, if not you can build one yourself there are kits for them.
Cutting by hand is accurate enough. The full size plans stay glued to the plates and you can cut wide and adjust by sanding.

 

[jwells11]

I see a ton of people using square tubing stingers on the more straight part of the hull and then using plate on the curved parts.

Whats the purpose of this? Why not run the entire length with cnc plate as stringers?

From what I plate read is that square tubing is not that much stronger and more expensive to use than plate. considering that you dont have lateral/side force.

 

[Barry]

I see a ton of people using square tubing stingers on the more straight part of the hull and then using plate on the curved parts.

Whats the purpose of this? Why not run the entire length with cnc plate as stringers?

From what I plate read is that square tubing is not that much stronger and more expensive to use than plate. considering that you dont have lateral/side force.

A general statement that square tubing is not that much stronger than plate requires many more parameters as height, width, area distribution around the neutral axis OF JUST THE TUBING compared to JUST THE PLATE.

When you weld/attach the tubing to the plate, if you have enough weld to carry the shear flow stresses, the outside skin becomes part of the cross section. Ie the bending strength is stronger
than just the square tubing or plate plus say the bending strength of the plate. When welded the components act as a single cross section which can increase the strength of the pair significantly.
Normally, (with some other considerations ) say your stringer spacing is 12 inches. ( and for the discussion, the hull plate is at the bottom) It is a generally accepted design practice to take half the distance to the next stringer in each direction
and that will be the lower cross sectional area/flange of welded profile. Then the upright section can be the web, ( for this example say the height of the web is 4 inches) either singular plate or double tubing, and then the upper flange ( for this example say the width of the upper flange is 2 inches) will be the third component.
So when welded together then you have a plate formed into the web and upper flange as an angle then you have 12 inches of bottom plate forming the lower part of the cross section.
As the lower flange length is 12 inches you do not need more material in this area to add strength to the stringer.
If you weld in a square tubing though, the lower part of the tubing will be welded to the 12 inch wide flange (hull bottom) so you are providing and paying for this redundant material. If you need to bolt something through a piece of tubing
which normally would be then half the equivalent thickness of say the formed angle, it can become a bit of an issue as the bolt can deform the often thinner tubing side wall.
Additionally, you really don't want a lot of surface to surface contact of aluminum in a salt environment due to crevice corrosion. It may not be a big problem but why introduce this into your boat when the scribed/fitted plate option can be stronger for the same weight, allow better bolting ability and reduce chances of corrosion.

We always used formed angle. Formed because due to our deadrise, the vertical webs could be formed so that the tops of the angle would form a flat to bolt the floor onto. If you do it with say 2 or 3 inch tubing, the only way then to make a flat
attachment point for a floor is to add more material onto the tubing. Seems to me you would be going backwards.

( some very loose assumptions were made here, as you more than likely would not use a 12 inch measurement for calculations for the bottom hull flange, 6 inches either side of the vertical web if the top flange is only 2 inches)

The main summary is that if you use square tubing welded to the hull bottom, you are spending more money with the extra weight for material that is not significantly contributing to the strength of the floor,web and upper flange combination
With an angle ( some people use T's) for less weight you can get more strength

 

[Mr Efficiency]

Being paranoid about poultice corrosion, I'd be leery about box tubing in contact with the skin, seems like a potential hidden problem.

 

[jwells11]

@Barry

Talking Corrosion, how do y'all better ensure that the boat doesn't experience electrolysis?

I dont plan to leave in water but is there any common practices to prevent this.

Insulated cable trays and other solutions to help prevent it.............

Working in HVAC for a bit taught me one thing. If its loose and there is vibration, it will eventually wear a hole in it. Maybe 2 months, maybe 6 years.

 

[Barry]

@Barry

Talking Corrosion, how do y'all better ensure that the boat doesn't experience electrolysis?

I dont plan to leave in water but is there any common practices to prevent this.

Insulated cable trays and other solutions to help prevent it.............

Working in HVAC for a bit taught me one thing. If its loose and there is vibration, it will eventually wear a hole in it. Maybe 2 months, maybe 6 years.

A galvanic protection system like Mercathode but there are many more that impress an appropriate charge on your hull to prevent metal transfer powered by your boat battery, an adequately designed anode bolt on system and
as important a device that checks the polarity of the shorepower coming into your boat when at the dock.

 

[jwells11]

A galvanic protection system like Mercathode but there are many more that impress an appropriate charge on your hull to prevent metal transfer powered by your boat battery, an adequately designed anode bolt on system and
as important a device that checks the polarity of the shorepower coming into your boat when at the dock.

Now to paint

How much is it to have someone do it?

Can it be done adequately by myself?


****No anti foulant needed

 

[jwells11]

@Barry

Also considering painting below chine, tunnel, and above rub rail.

And wrapping the "Slab". For two tone paint job

 

[jwells11]

also considering white slab wrap, polished aluminum look, and seadek

 

[Mr Efficiency]

You should be busy till 2025 building this thing, Do you really have to travel 150 miles to get to fishing grounds ? That is really an enormous distance for a day boat, the fuel bill would be "catastrophic", and even in a relatively soft riding boat, gunned along to ensure a longer period of fishing time, than travelling time, one would be thoroughly shaken up, if not stirred, at the end of the day. Whatever happened to the simple life !

 

[Mr Efficiency]

When power cats became popular in Australia back in the 70's, most were glass, but inevitably alloy was experimented with, the limitations of shaping with developable surfaces were not really an issue as much as with monohulls, performance wise, but many of the early alloy boats experiences structural problems, a cat not being a natural "shell" like a monohull. I would say structural design errors will show more readily in stressed areas of a cat, as the two hulls are sometimes working at cross purposes, so to speak. I would go with what is known to work, not experiment.

 

[jwells11]

140 miles each way. Venice, La is about 120.

Hence the reason charter captains in Venice have 42ft catamarans that will do 80+ mph.

World Class fishing all be it.

if I CNC and have someone help me weld I don’t think it will take that long.

But if it takes that long it beats spending 400k for a used contender or 750k-1 million used on the a similar setup.

yes I imagine a custom pilot house would be closer to 1 million