bpyhullgen silver bullet 4.8

This boat is hull number 3 - the previous two hulls were 1:10 scale models laser cut TIG welded aluminum:





2020_Tenth

The first two were built in a highrise building on the 17th floor and I was limited by space and what size I could fit into the elevator.

The basic hull specs for this build are:

Length: 4.8m (15 feet 9 inches)

Width: 1.3m (4 feet 3 inches)

Height: 1.26m (4 feet 2 inches)

Weight: 600lbs (272kg)

Length to beam: 3.7:1

This is the first full size boat I've built. It's big enough to sleep one adult and one or two children or maybe two adults but it would be a little bit tight.

Think of a giant canoe that you can sleep in.

My expectation is to be able to do photography and wildlife watching on a river or lake or short expeditions with my kids.

Propulsion is will be electric thrusters in form of pod drive or trawling motor.

Boat will be based on a farm with frequent high wind storms (Columbia Gorge). Sometimes the gusts get up to 50 or 60 knots. Having something that's heavy and tough and aerodynamic is desirable for strong wind - you can point it into the wind. For a long time I've wanted to have a vessel that I can put out in the middle of a field and watch extreme weather or spend the night with the kids. We have a trailerable sailboat that we do this sometimes but after several trips I have a list of things I wish were different and I've wanted to design my own for a while. This build is an iteration (hull number 3) in that journey. I hope to build a larger hull in the future but realize I have a lot to learn and am approaching this incrementally with larger and larger iterations.

One of the design goals is dual purpose on land and on water use - we can use it as a camper on the land and also go onto the river and do short overnight trips in an enclosed vessel on the water.

The longitudinal structural members are aligned perpendicular to the side plating with the exception of the bottom (keel) which is aligned to a vertical plane. This is not exactly perpendicular to the bottom plates but I would like to have an axle that wheels can be attached to as part of the internal structure in a future revision and thought this would be strongest.

Hull will have insulation foam in the interior in the top half for safety floatation.

It's a displacement hull - not designed for high speed planing. There is 20 degrees deadrise on the bottom chines (10 degrees each side). The center of gravity is low.

The design (hull shape and structural members) were generated automatically based on an XML definition file.

The way it constructs the model all the chines are developable. Rapid construction is one of the design goals. It's self jigging - the frame is the jig.

bpyhullgen is not a fully polished product but an opensource project that is under development. You are welcome to try it and modify it or use it as you wish.

 

This is the first build using the new XML hull definition feature. There is a basic user interface bpyhullgen that allows you alter and modify hull parameters - the underlaying data can be stored and retrieved using XML. This is the XML definition file for this hull:

Code:

<?xml version="1.0" ?>
<hull>
    <size height="3.600" length="4.800" width="1.300"/>
    <materials slicer_overcut_ratio="1.100" slot_gap="0.000" structural_thickness="0.005"/>
    <generate bulkheads="1" hide_hull="0" keels="1" longitudinals="1"/>
    <bulkheads>
        <bulkhead floor_height="-0.400" station="0.000" thickness="0.005" watertight="0"/>
        <bulkhead floor_height="-0.200" station="-1.800" thickness="0.005" watertight="0"/>
        <bulkhead floor_height="-0.400" station="1.800" thickness="0.005" watertight="0"/>
        <bulkhead floor_height="-0.400" station="1.000" thickness="0.005" watertight="0"/>
        <bulkhead floor_height="-0.400" station="-1.000" thickness="0.005" watertight="0"/>
    </bulkheads>
    <keels>
        <keel lateral_offset="0.000" station_end="1.200" station_start="-1.200" top_height="-0.400"/>
        <keel lateral_offset="0.000" station_end="-1.200" station_start="-1.700" top_height="-0.300"/>
        <keel lateral_offset="0.000" station_end="-1.700" station_start="-2.400" top_height="-0.200"/>
        <keel lateral_offset="0.000" station_end="1.600" station_start="1.200" top_height="-0.300"/>
        <keel lateral_offset="0.000" station_end="2.400" station_start="1.600" top_height="-0.200"/>
        <keel lateral_offset="0.300" station_end="1.050" station_start="-1.050" top_height="-0.400"/>
        <keel lateral_offset="-0.300" station_end="1.050" station_start="-1.050" top_height="-0.400"/>
        <keel lateral_offset="0.200" station_end="1.600" station_start="1.200" top_height="-0.300"/>
        <keel lateral_offset="0.200" station_end="1.850" station_start="1.600" top_height="-0.200"/>
        <keel lateral_offset="0.200" station_end="1.200" station_start="0.950" top_height="-0.400"/>
        <keel lateral_offset="-0.200" station_end="1.600" station_start="1.200" top_height="-0.300"/>
        <keel lateral_offset="-0.200" station_end="1.850" station_start="1.600" top_height="-0.200"/>
        <keel lateral_offset="-0.200" station_end="1.200" station_start="0.950" top_height="-0.400"/>
        <keel lateral_offset="-0.200" station_end="-0.950" station_start="-1.200" top_height="-0.400"/>
        <keel lateral_offset="-0.200" station_end="-1.200" station_start="-1.700" top_height="-0.300"/>
        <keel lateral_offset="-0.200" station_end="-1.700" station_start="-1.850" top_height="-0.200"/>
        <keel lateral_offset="0.200" station_end="-0.950" station_start="-1.200" top_height="-0.400"/>
        <keel lateral_offset="0.200" station_end="-1.200" station_start="-1.700" top_height="-0.300"/>
        <keel lateral_offset="0.200" station_end="-1.700" station_start="-1.850" top_height="-0.200"/>
    </keels>
    <modshapes>
        <modshape mod_mode="intersect" mod_shape="trapezoid" mod_type="cube" name="modshape" symmetrical="1">
            <location x="2.300" y="0.000" z="0.000"/>
            <rotation x="0.000" y="0.000" z="0.000"/>
            <size x="0.400" y="-0.800" z="0.005"/>
            <deform p1="0.000" p2="0.000" p3="0.000"/>
        </modshape>
    </modshapes>
    <chines>
        <chine name="side" symmetrical="1">
            <curve extrude_width="10.800" height="3.600" length="5.200" width="0.650"/>
            <offset x="0.000" y="0.000" z="0.000"/>
            <rotation x="0.000" y="0.000" z="0.000"/>
            <asymmetry a0="0.400" a1="0.000"/>
            <longitudinals>
                <longitudinal width="-0.150" x_max="2.200" x_min="-2.400" z_offset="-0.100"/>
            </longitudinals>
        </chine>
        <chine name="bottom" symmetrical="1">
            <curve extrude_width="10.800" height="3.600" length="5.200" width="0.600"/>
            <offset x="0.000" y="0.000" z="0.000"/>
            <rotation x="80.000" y="0.000" z="0.000"/>
            <asymmetry a0="0.400" a1="0.200"/>
            <longitudinals/>
        </chine>
        <chine name="top" symmetrical="0">
            <curve extrude_width="10.800" height="3.600" length="5.400" width="0.650"/>
            <offset x="0.000" y="0.000" z="0.000"/>
            <rotation x="-90.000" y="0.000" z="0.000"/>
            <asymmetry a0="0.400" a1="0.100"/>
            <longitudinals/>
        </chine>
        <chine name="upper_side" symmetrical="1">
            <curve extrude_width="10.800" height="3.600" length="5.400" width="0.650"/>
            <offset x="0.000" y="0.000" z="0.000"/>
            <rotation x="-37.000" y="0.000" z="0.000"/>
            <asymmetry a0="0.400" a1="0.000"/>
            <longitudinals>
                <longitudinal width="-0.100" x_max="2.200" x_min="-2.400" z_offset="0.070"/>
            </longitudinals>
        </chine>
    </chines>
</hull>

 

Inside looking forward showing structural members. There are three keels defined with different lateral offsets. The center keel has lateral offset zero. It would be stronger to have a continuous curved keel instead of a break and shift near the end bulkheads but I decided to break it up so the keel had parallel equal spacing in the tips (bow and stern). I could have designed it as a curved keel so it was one long continuous keel that curved along the longitudinal axis but it would make the interior space hard to utilize - think trying to store batteries containers and other square objects in those spaces if the width is constantly changing. Its a little less strong this way but more functional. Extending the keels parallel all the way to the ends would make it difficult to weld in the tight corner spaces on the tips so this is the design decision I made for this boat.

 

Side profile with model of person to show scale. The intention is to add a small low profile pilothouse in the future high enough to raise your head up and view around you around while remaining protected from the elements. I decided to construct the hull without any openings and cut them out later. The previous models I built hull #1 and #2 I cut out hatches and pilot house holes in the design files - The welds were much more prone to heat warping on the sides around the edge of the pilot house because it was a thin narrow strip and bending the plates was less uniform. The best solution would be to have tabs cut so it's a continuous sheet with dashed edges that can be cut out later after the welding but this is not designed into the software yet. A future software revision should automate this but for this phase of the development cycle this is what it does for now.

 

The design is just big enough to sit up in to read a book or work on a computer.

 

Cutaway profile view looking down from top side.

 

The keel (floor) structural members are level on top to allow placement of a bed or flat surface for sitting on. The floor steps up slightly near the ends like a shelf - this allows a flat floor in the very extreme ends of the hull.

 

Aft view looking forward showing transom. The hull is not exactly a double ender - the aft end is slightly wider than the bow. This is done by creating non Symmetrical chine curves in the bpyhullgen hull definition.

 

The top of the structural members for the keel are stepped to allow easier interior placement of flat surfaces on floor instead of curved floor. This feature is determined by the floor height of the keel structural element definition in bpyhullgen.

 

I sliced the bulkheads into halves so they would nest easier an optimize material usage to minimize waste. The first step of the build process is to weld the halves of the bulkheads together into a single piece.

 

Two bulkheads welded together - side plating behind it.

 

Bulkhead clamped to table for welding. I wasn't sure how much heat I could put into it so I welded edges to half center instead of a continuous weld across the joint. The material is 3/16 thick aluminum (4.8mm) looking back I probably could have welded all the way across the seam but was being extra cautious as this was the start of the build and I didn't want to have any heat induced warping.

 

Fantastic Zukobo. Keep us updated, and you will be amazed by the quality of encouragement and advice you will get from the community. On my own build, some heavy hitters from the forum regularly help me out.

 

This looks insane, I love it. Like it's a submarine or designed to be a survival pod for a tsunami! And in blank aluminum it should look awesome Maybe you could find a large semi sphere / dome window to complete the look.

You probably could shorten the size of the ribs by half once it's welded up. If you want more interior space. Are you going to insulate the interior?

Did you do some stability calculations? Like is the top considerably lighter than the bottom? You really wouldn't want to roll in this. Could be a deathtrap.

With 272kg it's very heavy and slow. It's going to be hard to get it in and out of water or onto a field. Maybe you could add a winch in the nose and add a nose-cone fairing.

I've played around with an idea for an enclosed boat-camper idea myself.

 

I wanted to try 3/16 (4.8mm) plates - The previous two scale models I did were 1/8 (3mm) thickness - never tried the thicker stuff. I had a lot of questions in my head how the thicker stuff bends / welds / handles ect... It's way overbuilt but it will be strong for sure... will be able to climb on the top and jump around while on land or water without denting anything. It was easier to nest it all from the same plate / same thickness...

There are lots of additional structural members in the bottom that are not on the top so the center of gravity is much closer to the bottom.

Planing is not one of the design goals, displacement hull, electric motor is what I had in mind.

The ribs could be thinner - it would create more interior space - that's just what I went with for this build.

As far as the weight - compare the weight of a seedoo, jetski or some other 16 foot boats... it's actually relatively light considering it has an integrated cabin.

I had some eyehook shaped plates cut out in the design files that are welded on - can be used to pull it and maneuver it in and out of water. For on land a tractor or UTV will pull it around, for in and out of water a pickup or SUV, I don't have any expectation to move this "by hand". Building a minimal basic trailer.