Watch me build my autonomous solar 20-footer...

[amaurer]

I've been asking questions in the design forum, but since no one yelled at me for not using Okume plywood, I figured I must be in the wrong place

I've been posting high speed videos of the entirety of each step of my build. This is my first time with stitch-and-glue, or building a boat at all, so be gentle - I'm narrating for the non-boat-building crowd so be nice and don't call me on my BS. Anyway, thats all at www.lonelybot.com

Here is the plan:


And the progress:

[Rick Willoughby]

Great stuff Andrew. My only request is to balance the music and voice volume on the clips.

I personally think building a strong back is easier than the full stitch you have done. That is what you do with the leftovers from the bulkheads. Use them as formers to hold the panels together.

After Hawaii send it to Melbourne so I can have a closer look.

The legality of sending a craft of this size unmanned into the ocean might be worth a thought - have you looked into this? I expect with your background you could develop some very interesting collision avoidance systems. Might have commercial potential for light handed sailors. I for one do not cope well with broken sleep. It would be nice to sleep in peace knowing there was something taking care of your welfare.

You could set up a lonelybot friends network for meet and greet sessions in far away ports. Over a few years it would be a huge network.

Rick

[amaurer]

You're a sharp cookie Rick, you're always reading my mind!

Collision detection is a stinker, it'll probably wind up being my largest control system challenge, as the sensors are more complex that a GPS or a compass, say. The plan is to have a laser sensor for keeping from running into things, and a pair of side-facing optical sensors (cameras) for avoiding things running into me.

And your meetup idea is exactly what I had in mind. I actually envisioned a contest, perhaps, something like Where In the World Is LonelyBot? - some sort of daily prize for intrepid souls who can manage to position themselves in front of the craft's camera at a specified time of day. Vandalism concerns exist, obviously, but this project wouldn't be possible if I wasn't willing to lose the money I'm putting into it...

For the nerds among us I intend to dump all the telemetry directly to website for public use. Performance data, sea conditions, etc, will all be monitored and uploaded.

[amaurer]

Oh, and FANTASTIC idea re the plywood - now I can build a cradle without pulling out the trailer to cut more wood!! THANKS!

[amaurer]

Ok, question-time:

Im about to glass the inside of the hull, but taping the seams really taught me a lesson about not having bumps underneath the glass. I'm going to fillet the edges of my butt joints, then, and sand down the one or two errant lumps of thickened epoxy laying about, but what about the edges of the fiberglass tape? Should I sand them down? That might be tough today without damaging the wood...

[Rick Willoughby]

Smooth them down or bog then up so they are smooth. Have you got micro-bubble filler? Actually I was going to tell you that you would need long tapers on your backing boards. The easy way to join the ply is to make a shallow skive and tape over the butt joint with some decent weight triaxial tape. But that was a few clips ago now.


Also do you know about amine blush:
http://www.epoxyproducts.com/blush4u.html
Something you need to look out for if you are glassing over cured epoxy.


Rick W

[bntii]

Is it just me or does this look a little top heavy/tippy?
Panels are heavy, etc..
Are you using outriggers?

[Petros]

Andrew,

looks like a fun experiment. I am also an engineer with lot of Aerospace experience in my past, and love building things (nine boats so far, old cars and lots of other fun stuff). I can not help but notice that Long EZ model on your garage wall. Some day I want to build my own homebuilt aircraft as well, one of my own design, just for fun (I do not even like flying that much, I just building things to experiment with ideas).

A couple of considerations for your boat-bot. As bntii pointed out, it looks tippy to me, unless you have a lot of ballast low in the hull. You might see if there is a navel architect or knowledgeable amateur on this site that will help you with developing a CG location that will be self righting. Sooner or later some condition might come along that will capsize the craft, if it was inherently self-righting you still have a chance to have it recover without a rescue. I probably would have started with a hull with more beam, but with the CG low enough, or perhaps a weighted keel, it can be made to stay upright.

You also do not want it to have a stable inverted condition either, out riggers might make it more stable, but if inverted it can not right itself either. All the equipment should of course be weather tight and able to operate inverted as well.

You might also consider altering your solar panel arrays so it is recessed or built-in to the upper deck. The size and height of the panels show would catch wind or waves and make it hard to control, or worse, keep flipping it over. Even if self-righting, you will not make any progress if rollers, or a strong quartering wind keep flipping it over. It will founder around for days until the seas calm.

When working on the hull, if you raise it up on saw horses you will not have to bend over so much to work on it. It will save a lot wear and tear on you back. Just watching your video clips made my back hurt! Trust me, you will be able to work for more hours with less discomfort if you can raise the hull up to hand level. It is also light enough so you can roll it on its side, or flip it, to give you the best access as you work your way around the hull.

Also, why sand the fillets if it will not be occupied by humans? So what if it is not very attractive on the inside, it just needs to be strong, not pretty. Save the sanding and nice finish effort for the outside.

You might consider a short and lightweight mast with a beacon on it so other ships can avoid it, especially at night. The mast can also carry a radar reflector so larger ships will see it and avoid it (better that than have it run down by a tanker). Check the regulations for lighting requirements, I suspect if you meet that you would be okay for an unmanned boat-bot/RPV. You would not be considered a navigation hazard if it is lighted at night and has a radar reflector.

you may have started a new hobby that could lead to remote maritime combat! Way better than War-craft, requires both skill and building knowledge.

Good luck with the project. Keep us posted.

[Rick Willoughby]

For those who have not seen the development threads for the design:

10 foot SWATH

trolling motor prop rpm?

My solar drone project...

Rick W

[bntii]

Thanks Rick

[amaurer]

I'm still trying to figure out exactly when the forum will notify me of new posts via email and when it wont... sorry I've missed these.

Anyway, yes, I realize it looks tippy - I made it tall on purpose because the solar panels need to be kept cool. Most specifications require them to be mounted 3" off the mounting surface to allow ample airflow beneath them. I figured it was good to get them into free air and may out of any spray.

However, looks can be deceiving, as there will be lots of empty space in the hull, so the density is very nonuniform. The ~700lbs of batteries along the keel help quite a bit.

Still, it remains a concern - I'm not a boat builder, so I don't have a feel for stability margins are acceptable. Silicon Valley isn't exactly the boat building capital of the world, so you guys are functioning as my naval architect consultants Tell me what you think:

I wrote a script that simulates the hull with voxels (volumetric "pixels") and rolls it through various angles while calculating the resulting waterline. The deck is shown in red voxels and the keel in blue. Green voxels fill the area that lies beneath the waterline:




The script, then, gives me the height of the CG over the waterline and intuitively then we can say that the craft will roll to a local minima.



That is essentially a potential energy function, so the derivative of it can be converted to a force, or in this case a moment:



So, reading that, by 5 degrees of roll I have 100ftlbs of restoring moment... which to my untrained eye seems like a lot... but what do I know. Moreover since all the moments are positive, the design is self righting from any angle.

[rwatson]

Hmmm - 20 ft unmanned boat with losts of batteries on board. Will probably go close to some financially disadavantaged sea travelling folk in its travels.

What is the current price for scrap lead and low usage solar panels these days ? :-)

[Ad Hoc]

amaurer
Do you not have access to a stability program?

Anyway, just fill the hull with non-hygroscopic foam (so you have always have positive buoyancy) and ensure you have a positive resorting moment by carefully placing your weights, in the vertical plane.

[amaurer]

Originally Posted by Ad Hoc

amaurer
Do you not have access to a stability program?

Anyway, just fill the hull with non-hygroscopic foam (so you have always have positive buoyancy) and ensure you have a positive resorting moment by carefully placing your weights, in the vertical plane.

I have Freeship, but I don't know how to use it [well]. I played around by dragging nodes until I have something that looked like my hull, and ran the stability job - I see it gives me the metacenter but I'm not adept enough with the definition to actually use that info. If I recall correctly, the KM value was something like 1.4' - my CG is ~9" up from the bottom, so the separation between the two is about 8".

Its clear to me that thats "stable" in the technical sense, but its still not clear if that means its going to roll at the slightest breeze or if roll excitation by wave action is going to outweigh the damping available... thus my attempt to find restoring moment.

[Ad Hoc]

If you can 'roughly' model the hull, that you think looks about right, print off a set of hydrostatics. Check this against your own little macro, the two should be very close...if not, there is an error. Keep doing until the two values are very close.

Once you ahve done that, use metric!!...sorry don't understand imperial units.

The CoG...is that a guess or a calculation?

Once you ahve the CoG, plug it into the program, and run from 0 to 90 degrees. Then post the output on here.

One step at a time.