Tuesday, April 18, 2017

Model testing 4/2017

We have 3D printed pieces for a catamaran and a swathy design.   We glued the pieces together using gorilla glue and clamps to hold while the glue foams up and hardens.  Then we paint the whole thing with styrospray to make sure it is waterproof.  
Catamaran in clamps while glue dries

Amoni with Catamaran model - printed as 10 pieces 37.5 inches
Swathy design - printed as 8 pieces

Amoni making a test wave

Both the swathy design and the catamaran were weighted down with cups of gravel to 2.56 kg.  The catamaran did not take much weight, about 1/10th kg.   The swathy design was close to 1/2 kg of gravel.

The above video shows the setup.  We make the waves at one end of the pool using a 12 inch diameter PVC pipe.  The tension holding the models in place is just from the weight of a rope to the top of a lounge chair.   The "infinity pool" edge dampened the waves some but we had the pump off because it was making waves and with the pump off the pool soon got below the edge so only large waves went over.   The camera for most of the video was on the tripod in the middle of the infinity overflow.

I think the following videos should be viewed full screen and you can also use youtube to slow them down by a factor of 4 to study interesting parts.

First waves hitting from the side:

Next waves hitting on the bow:

Then two older models.   I did not actually use the best of my older models but it then got windy and so other tests will wait till next week.  The orange model with 4 floats is 8 lbs.  It should have been weighted down to about 12 lbs for optimal stability.  Maybe in a future test.

 In these videos the catamaran really looks good.  It is hard to beat but I still want to try.

This next video the model on the left is 4 lbs with 1.1 lbs of gravel in cups for a total of 5.1 lbs.  The catamaran total is 5.64 lbs.   This one does well against the catamaran.

Sunday, October 30, 2016

Quadmaran model testing 10/16

With the latest 3D printed floats we have a new model and tested it in several different wave conditions.    These videos were shot at 8x and then slowed by 1.5 for a net slowdown of 5.3.  This is about right for the scaling factor of this model.  So how fast you see the model tipping is how fast the full scale boat would tip in full scale waves.

We put either my Tiva shoes or a sandwich bag of sand to get the boat to float at the right trim.

First in small waves.   This design does not move much in small waves.  This is good.

Next in small waves but there was some swell or passing boat that caused some rocking.  This is not ideal and I think if the center part of the float were to smoothly curve from the bottom to the top instead of just going straight up that up down motion would go away as waves more and so the boat would stop rocking faster.   We will experiment with this new float shape in coming models.

Next tested in a pool.

Then what are sort of medium ocean waves for this sized model.  Still looking good.
And the same medium waves but also two large waves coming by.  It handles these 2 large waves very well.
Last some large confused waves.   These are large enough that in real life you would try not to be in them.  Like you would stay in a harbor if the full scale ocean was going to be this rough, or navigate to avoid a storm like this.  But the boat must be able to survive these and probably even worse.  I think it does fine.

Tuesday, September 27, 2016

Quadmaran 3D taking on water

Teryn modified the 3D model so it has more waterline area. These are not as thin in the middle.  These are a little bigger than the last set.  However, we had not fix all the overhangs of more than 45 degrees and so it leaked.  We put on some waterproofing but it was not enough and some still leaked.  The test below was this morning and Teryn has since fixed the design and we started printing on the next set of 4 floats.  These will be even bigger.

Look what is at the end of the rainbow

Taking on water in the front
Slow-mo but since the front edge is touching water it is not really working the way it is supposed to yet.  Next version in a few days (about 1 day to print each float).

Tuesday, September 20, 2016

Starting on Aluminum Quadmaran

Teryn cut the first piece as we started work on our aluminum quadmaran.

I did the first welding on our aluminum quadmaran:

However, it did not go so well.  Our training welds (see below) were much different.  The first boat weld was in a corner unlike any of the training welds.  I was not as prepared as I thought I was.  Probably need some more practice.

Anyway, aluminum is cut and we have started!

Aluminum is cut

Started welding
So earlier key lessons are:
   1) Must clean aluminum surface with stainless steel wire brush to get off aluminum oxide.
   2) Power level to use depends on what exactly you are welding.  Should be an app for this but
         there is a sliding card.
   3) Wind matters.  Want to block as much as you can.

And from this new stuff we learned:
    1) for welding inside a corner you should use different electrodes that can hold a point,
         like red ones.   The grey ones we have melt and ball up.   This does not reach into the
         corner so well.
    2) May want a smaller gas shield to reach into the corner

We have ordered some red TIG electrodes and will start welding again when they get here in 2 or 3 weeks.

Thursday, September 15, 2016

Quadmaran 3D with patch

Amoni and I made some thin pieces of foam with the hot-wire cutter.  Then we attached them to the very thin part of the 3D printed floats with quickties.  This made the model work really well.  All it needed was a bit more flotation near the waterline. We took the SWATH idea too far and had to back off a bit.   See video below.

The batteries were dead on our good slow-mo camera so we had to use my cell phone.  The sun was bouncing off the water to the camera.  So this is not great video but the model worked really well.

Update next morning with slow-mo video:

Sunday, September 11, 2016

Welding delays and rats

So it turns out these "gas shields" on the welder get red hot and break easily.  An experienced welder would know this and have a number of boxes of replacement parts.  We, on the other hand, will be getting boxes of these from Amazon soon.  We can't weld till they come.   On tropical islands Amazon does not have 1 day delivery.  Anyone know why Amazon does not make it easy to pick DHL or FedEx for overnight delivery to anywhere in the world for urgent things like this?  

A rat was in our welder.  Now we have rat poison.

And glue traps.

And mechanical traps.  And new "Rat Zapper" electronic traps on the way from Amazon.  Old Rat Zapper gave up the ghost.

Rats are a problem with having the welder outside that I had not thought of.  There is a water tank and cooling system that a rat could damage to get at the water.   This is troublesome enough I am thinking some of moving to someplace where we could have a nice shop/work area.

3D printing our own hull shapes and testing model

We can now print nice parts on our own printer

This has a lot of plastic in the hollow areas.  It is heavier than it needs to be. We will experiment with the settings for filling in and reduce the weight on future prints.

There are 4 places in the current design that went straight sideways over open space.  This is not something our 3D printer can do well.   Some printers with 2 print heads can make support structures out of a material that you can easily dissolve later.  Because of this these 4 sections on our part are messy and and had holes in them, so they were not waterproof.  It is sort of amazing that they printed at all.   We use gorilla-foaming-glue and then also painted the parts with Styrospray to make them waterproof.  Then we used quick ties to attach the 4 printed floats to a platform.
It can tip to either side and stay there
When the model tipped there was enough more weight on the down side that it would not come back up.  So we need more flotation at the waterline.  This is also very sensitive to the amount of weight.  The next shape we want to try is with the thin part as long as the rest of the float.   This will give more waterline area but no more drag.

We now have the ability to 3D print floats but we do not yet have the perfect float shape.  We can keep trying different shapes easily enough now.   If we do the designs right they should be waterproof without any glue or painting.

Note that this float design did not work well enough to even try in waves.  We will get further along soon.

If we rotate the part 45 degrees in the printer so it is going diagonally across the print bed we can print rather large parts.   We will do this at some point.   The bigger the floats the more weight the model can carry.  So we want bigger floats if we are going to put on batteries, solar, motors etc.

Along with testing float shapes we also want to eventually make 3 models that we make into drones so we can develop software for a train of our boats connected together.   Turning in a train of boats will be different than for a single boat.  The boats need to work together.   We want this software working well before we get to full scale and far more expensive boats.