Thursday, February 28, 2013

This is the aluminum I cut for my first custom paravane yesterday.  I cleaned off the edges and took them by the welder today.  He thinks he can have it welded Monday.  Can't wait to try it out.

These pieces are sort of in position with it coming toward us and the string going to the right.  Two square pieces are 1 foot on a side and will go below as keels.   There will be several holes on the right so I can try different string positions.  The keels will be angled at a 2:1 slope so they are at 90 degrees to string. The longer small pieces below are at the front and will be angled up so as to push water down and keep the center piece at a good angle to lift. The back two small pieces will be angled up a little bit so they only push if body starts to angle too much. Styrofoam pieces will be like two hulls of catamaran on left and right, same width as small pieces. 

Below are 3 views.  Note that the top view below has front up where the pieces of aluminum above had front down.  

The main test I want to do is walking along the pier at 4 or 5 MPH and then suddenly pulling really hard on the string.   This is to simulate the boat moving along and then a wave making the mast pull hard.  I want the paravane to top out around 100 lbs of pull.  If it is too high I could make the area on the 2 keels smaller.

Amoni next to the aluminum before cutting.  He helped me mark out where to cut.  I asked what blade to use at the hardware store and they gave me a blade for cutting steel.  It was horrible.  I then checked with the Internet and found that the blade for cutting wood that I had taken off was fine.  I put that back on and cutting was fast and easy.

Today we also moved the boat next to where we live so it will be easy to fix up.  Lots to do.

Wednesday, February 27, 2013

Naming the idea

If I am the first to try stabilizing a boat by connecting two paravanes to the top of the mast, then I think I get to make up a name for this idea.  So I am going to list some here and welcome any suggestions anyone else comes up with.  Can also comment about which you like best.

Mast stabilizers - stabilizes the boat by stabilizing the mast
Tension trimaran - two extra hulls attached by lines - really wide and stable

Inriggers  - a boat can push down on two outriggers or pull on two inriggers
Mast paravanes -
Training keels - kind of like training wheels for boats
Mast keels - couple extra keels you attach to your mast
Mast fish - trawler paravanes are called fish
Mast floopperstoppers
Dual overhead stabilizers - at least the lines are overhead
water-kite stabilizers

Thursday, February 21, 2013

What could possibly go wrong?

I really like the idea of stabilizing a small solar/electric boat converted from sail using two paravanes attached to the top of the mast.   I think I can make it work.   But it seems prudent to look at what could possibly go wrong.  So here is a list.

If the forces are too great we might snap the rigging on the mast.
I remember in the MacGregor26 sales video that 130 lbs of force was needed at the top of the mast to hold the boat on its side.  So I think that 100 lbs is not going to be too much for the rigging.   Also, I will probably use a string or fishing line that breaks at 100 lbs so that it would snap before the mast was damaged.

The paravane might hit the boat and damage it.
I will probably use a PVC pipe as the float and aluminum as the keel.  If things went bad and somehow the paravane hit my boat I would expect the PVC not do damage it.  The strings will be like 50 feet, so if it is next to the boat is is not being pulled, but just sitting in the water.   A 5 MPH collision between my boat and a PVC pipe with maybe 20 lbs of keel should not be bad.

Getting the paravanes in and out of the boat could be trouble.
I will make a loop on the top that I can grab with the mooring pole.  They should not be to heavy to lift up.  As we drive the big boat toward one it will just be sitting in the water, not pulling.  A regular trawler paravane resists if the boat is moving, but with out long line we will be drive close to it and snag it withe the pole without having to stop. 

If the ropes are too stretchy it might not help too much, but if they are not stretchy they might snap too easy.
I will have to try to see if it really can be made to work.

The drag from the mast, rigging, and paravanes could be too much for a small electric motor.
Will have to see what speed we can get with mast down, mast up, and mast up and paravanes.

Tangled lines or lines in propeller.
Need to be able to wind in lines to pravanes.

If mast tips away from paravane it will increase the speed on that paravane.
So paravane must be design for more than just the 4 or 5 MPH of the boat.   Also needs to be designed so that it does not pull out of the water in a way that messes it up.

Waves making paravane go up/down/left/right could make for peculiar motion on the mast and undesirable ride.
If the paravane is 80 feet to the side the up/down motion should not matter too much.    The left right might.  If you were going straight toward or away from the waves then the paravanes would be experiencing the same wave motion as the main boat.  In this case there would not be a tipping due to waves.   A wave right at the edge of the boat can move the side up some amount.  A wave at the paravane would move the mast a similar amount.   But the long lever of the mast means that the boat is moved much less.   So it seems like it will still be a big improvement.  However, I think we will need experimental results to really answer this one.

If the mast tips toward a paravane the string might go slack and it could be like a kite in the air that stops flying.   
Some stretch in the string could reduce this issue (though making others).  Experimental results needed.

Both paravanes have a downward component to their pull.  When the mast tips this full downward component is on one side and the more it tips the more lever this downward force has.  So there is a instability issue.
If the forces are small compared to the righting force of the boat, and the mast never tips very much, this could be ok.  But it could be a problem.  The longer the lines to the paravanes the less downward component to the force vector.  So longer lines could reduce this problem.

The paravanes pull back a bit and when the mast is on one side they will tend to turn the boat toward that side.
This could make stearing more trouble but my boat has two rudders and the engine so it should be possible to compensate for this.

Tuesday, February 19, 2013

Paravane or Toy Boat?

I bought a piece of aluminum and was about to start making a paravane.  But I don't really know how fast the boat will go with the electric motor or how big the paravane should be to give me 50 or 100 lbs pull at that speed.

As I thought about what the paravane should look like so it would stay near the surface and off to one side I realized that it should look very much like my boy Amoni's toy sailboat.  So I explained to him that I could figure out better how big my paravane should be if I did some tests with his sailboat with the sail off and he agreed.  I put on 3 strings tied together and will do a long string from that to  the scale (in Teryn's hand).   The strings should hold the boat at the right angle, like strings to a kite.   If we can walk at 3, 4, or 5 MPH we can see how much the boat will pull on the string.  Then I can have some idea what size the paravane should be.   Plan is to head to the dock after school gets out.  

We put the model in the water and measured 3 to 6 lbs force on the string with probably 3 or 4 MPH.  It works!

You can see more pictures.

MacGregor26s with Solar

I asked a few questions on and a couple people had mounted solar panels on this type of boat.  Below are two pictures.  I bought two panels yesterday and they are only 35 lbs, not 90 like I thought.  So weight up high is not nearly as bad as I thought.  Ya!

Sunday, February 17, 2013

Stabilize the mast with two paravanes!

Today (Feb 17, 2013) I think I have just about figured out the key part for my first solar boat experiments. I will be converting my Macgregor 26 sailboat to solar/electric. The real trick is how to make a slow boat without sails not roll so badly as to make all the crew sick. My idea today is a water-kite/paravane on each side that is attached to the top of the mast and designed so they stay at the surface maybe 50 feet to each side. 
 The top side of the paravane will have a float.  If this is under the water the drag will cause the paravane to turn up.  The bottom of the paravane will have something to cause drag, but less than the float, so that if the float goes out of the water  the paravane will turn down into the water.  There will be some kind of tail so that it does not turn too fast.
The boat is about 8 feet wide, so 4 foot radius.  The top of the mast is about 35 feet above the water.  So the leverage some force at the top of the mast has, compared to someone standing on the edge of the boat is 35/4 = 8.75.  So 100 lbs of force sideways at the top would balance 875 lbs on the edge of the boat.  Now the rope to the paravane will have an angle on it so it will be less.  The point is that a small force from the paravane can make a big difference because of the long lever from the mast.
I can't find anyone else who has tried exactly this.    It is very similar to the flopperstoppers used by trawlers but these will pull to the sides instead of just down.  Then we don't need special poles on each side and can just use the top of the mast.  As the mast gives me more leverage and my boat is much lighter than a trawler, the forces I will be dealing with are far less.  However, I will be moving slower than a traweler so my paravanes may not be smaller, but they won't have to be so strong.  The military minesweeper paravanes were towed off to each side, and automatically kept to the sides without any poles, but not for stability.  There is a speed sailer that used a paravane from the top of a mast but only on one side and while sailing.  So there are enough similar things that I think I have a good chance of making paravanes  work for stabilizing my solar electric boat.
I am going to use the Minn Kota RT160EM which mounts onto the engine.  This is about 3.5 Hp.  Since the boat is so light I think this will do for moving slowly (I am guessing 4 MPH but will be very interested in real data).
I plan to start with two rugged solar panels from Commet Systems and just let them charge the batteries for  6 days and then play on the weekend.  If this works as well as I think then I will probably get some lightweight solar panels and put up a bunch more.
 The danger is that the paravanes might go bad and cause the boat to tip.  With the electric motor we won't be going fast, so I think even if there is a glitch we will be fine.   Will experiment with caution.  
I think a simple paravane can work well enough, but the idea of adding a computer to control fins on the paravane is another possibility.  A simple paravane going up and down in waves will cause some pulling on the mast.  A smart paravane could do a better job. 
The paravanes could be radio controlled, much like a toy boat really.  Just that a string is pulling it through the water.   If I have one son driving the toy on the right and another driving the one on the left they could compensate for waves and probably keep the mast straight up and down.  It would be a fun game for awhile.  Then would want to get a computer to drive the two paravanes.