Tuesday, October 22, 2013

Hook Paravane 2

I made another hook paravane where the aluminum extends forward under the foam.   This lets me attach the string forward more.

Some videos.   The Sun was going down at my wave tank.

Thursday, October 17, 2013

Hook Paravane

I read about a hook paravane some time back but did not fully understand it.   I decided I understood enough to make one that would work so today I made one and tested it.  At first the curve was not tight enough and it could not go fast.  After bending it a bit more it worked well.  It is mostly off to the side, like a good paravane (water kite) but a bit behind.  Because it is a bit behind the lower part acts like a plow pulling the paravane down into the water.  The upper part is positioned to lift if the paravane goes too far down into the water.  So the two balance each other and it does not go down too far or pop out of the water.  This is a very light device.  This makes pulling it out of the water and onto the dock or boat much easier.  It will also take much less space on the boat.  The maximum pull is less, so I am hopefull that it will not break the line when the mast pulls hard.

This was the shape after some more bending and it worked well.
I had to start out slow.
 This last video is with the most curve in the aluminum.  It seems to work the best.  I don't think this will ever jump all the way out of the water, so it will always keep tension on the mast.  This is much better than my pipe prototypes.

Future Plans

This design has great potential.  It is also really easy to make.  I now expect the final paravane design to evolve from this basic design.  In the past I have gone from toy sailboat, aluminum foiling catamaran, to pipe, to this hook.  These are big changes in design.  From now on I expect small changes to the basic hook design.  This is a very efficient design.  Lifting my big pipe paravanes back onto a tipping boat was a bit much.  This will make for a much more practical device.  Also, because it is so light there is far less chance that it would damage the boat in any way when you are pulling it out of the water.   I think the chances of making a product that other people would like went up today.  :-)

I made this design very fast today and did not take the time to make the aluminum resemble an air-foil at all.   Doing this will reduce the drag, so it is well worth doing now that I like the basic design.

I would like to have been able to try attaching the string forward of where it was, but there was no more aluminum under the foam going forward.  In a future design I will extend the aluminum forward another 4 inches under the foam.

I seems like other hook paravanes don't have a surface following thing like my foam.  I was hoping my foam would be out of the water more and only for slow speeds but it was always part of the function.   If the foam were not touching the water there should be less drag.  So if a hook paravane can operate that way it would be better.   

Monday, August 5, 2013

Lowering Mast with Solar Panels

As I was lowering the mast it became clear the spreaders wanted to pass through the solar panels.   This was a problem.

I detached the spreader (one bolt) and lowered some more.  Then the mast was about to hit the solar panels.  So I moved all the solar panels back as far as I could without hitting the mast support.  Then I was able to lower the mast onto the mast support without the mast hitting the panels.  In this picture it looks like I have a good inch to spare, but the mast jack is still lifting on the mast.  After it is removed there was only about a half inch.   That is cutting it close.

Then moved the mast forward onto its stand and reattached the spreader.    This means I will always have to undo the bolt for the spreader, but this is not too bad.   It could have been worse.

Sunday, August 4, 2013

Solar Panels on Boat

One of the drawbacks of living in paradise is that shipping big things here can take a month or more.  So getting the right aluminum takes a long time.  Then when the welder needs more Argon gas, that takes a long time.   So living in paraside requires a certain amount of patience.  But I think it is worth it.  We now have the solar panels mounted on the boat.  Next we have to wire up the panels and the batteries.

Wednesday, July 17, 2013

First Sea Trial With 2 Paravanes

There are 2 paravanes with 2 yellow balls. Inside each ball is a fishing reel that can let the line out for the paravane automatically. This lets me toss in both paravanes at nearly the same time.

This video is the whole experiment. The left side reel let the line out at a slow speed. The right side must have had a higher drag setting on the reel as we had to move a bit faster to get it out. Eventually the fishing line knot on one of the reels came undone. I need to get better at fishing line knots. But the system for letting the lines out is getting reasonable.

One of the paravanes has been filed so that it stays down in the water better. I thought I had done the other but had not. Both of them came out of the water, so they're not the ultimate design.

Here is the view from Ethan's camera:

After a line comes loose we both have to focus on getting things out of the water.   One of us driving and the other grabbing things with the mooring hook.   So far we have always recovered everything.  The side that has not come loose we just wind in with the reel in the ball.   But we still have to get the paravane onboard and then stow things.   Anyway, no video of the recovery work.  :-)

Thursday, May 23, 2013

Testing Direct Attach

Tested the paravane again this morning moving the point that the line attaches to the pipe back and up a bit.   Seems to work very well.   The lines should have less chance of getting tangled.  I doubt I will use the old method of two attachment lines to make a sort of bridle ever again.

Also note that yesterday's mod of making the bottom of the pipe pull down works well.  The paravane does not come out of the water like it used to.

Wednesday, May 22, 2013

Mods to Big Pipe Paravane

I used my powersander on the bottom leading edge of the PVC pipe so that is pulls down as it goes through the water.  I tested this today along the dock and the paravane now stays down in the water much better.

I also tried connecting the line directly to the side of the pipe instead of to two lines on the paravane. This works, even though I don't have the right spot yet. I just happened to have 3 holes on the pipe that were drilled in the wrong place. The right spot is a bit further back (maybe 2 or 3 inches) and a bit higher (maybe 1 or 2 inches). This will reduce the chance of lines getting twisted around something the wrong way. Probably easier to manufacture correctly too.

So maybe the Big Pipe Paravane is still a good way to go.

Tuesday, May 21, 2013

Kid Paravane

So dad was thinking about paravanes and outdoor activities for kids and came up with "Kid Paravane".  The idea is to have the kids use their body like a paravane or water kite.   We attach a rope to their life jacket and then pull.  Their goal is to angle their body so that they are pulling away from the beach enough that as I pull forward and toward the beach they stay out in the water.  My 6, 9, and 11 year olds were all able to do this.  My 4 year old declined dad's experiment.  Video below.  Note that Dad was pulling the rope and holding the camera while going backward down the beach and Youtube can only do so much to remove shake.

Sunday, May 19, 2013

Long Line Troubles

We went out again yesterday.   We had about 80 feet of 125 lb fishing line and 20 feet of line that is attached to the top of the mast, for about 100 feet from the paravane to the mast.  

We tested the line in the office and with 8 feet of line we could stretch it about 1 foot before it snapped, so we should have about 10 feet with the 80 foot piece.   The good news is that we did not snap the line!   The bad news is that we got slack on the line and the paravane turned around in the waves before we got the slack out.  By then the two strings on the paravane had gone under and it would not straighten out.  

I am thinking I will push ahead with the all aluminum catamaran paravane design as it does not have the 2 strings that could get messed up.

I am also thinking of having the line to the paravane on a fishing pole reel.  So I would just attach that to the line on the mast and then toss in the paravane.  The reel would be set to let out the line when there was enough pull.  I think this will be a much simpler procedure than what we have been doing.   It would also make it easier to reel in the line when done.

It is a bit windy this next week so we probably won't be going out again soon.

We had camera trouble so I do not have any pictures or video to show from yesterday.

Thursday, May 16, 2013

First Sea Trials

We have been out on the boat twice testing a paravane.  The first two days we have only tried on one side.  While it was out the boat did seem more stable. 

With the paravane tied near the top of the mast it has a lot of leverage.  It is almost 10 to 1 leverage compared to the cables from the side of the boat to the mast.   For simple arithmatic I will pretend that is it 10 to 1.   If I had 200 lbs of pull from the paravane that would be 2000 lbs of pull on a cable supporting the mast.   Because that might break something, I am trying to limit the paravane to 100 lbs or a bit over.   I am doing this by using a line to the paravane that will break before anything important in keeping the mast up does.  

The first time the spool that I was letting the string out with broke.  The paravanes pulled so hard it snapped the plastic spool.   I had two strong lines and a short 100 lbs test line in the middle and it snapped that.  Decided to risk the mast and use the two strong strings and it snapped an aluminum carabiner.  Eric and all 4 boys are with me on this day.

The second day I used 40 feet of 100 lbs test fishing line, that will stretch,  from the mast line out.   This worked better but still broke.   We only had a paravane on one side and were outside the reef.  Nils, Ethan and Teryn were with me.   When the line breaks you can hear my cameraman Teryn say "grabber grabber grabber", "here daddy take it". He got my "paravane grabber", which most people would call a "mooring pole". :-)   It worked great for getting back the paravane.  Nice to have some boys to help out!

The basic problem is that with only one paravane the mast can tip toward it enough that the line goes slack then move away getting momentum so that when the line gets tight it snaps.

Wednesday, May 1, 2013

Pair of Paravanes

I have a matched pair of paravanes ready for testing.   The boat is in the water.  Sea trials will start as soon as a few stars align just right.  Maybe today, but if not then probably tomorrow or Friday.

Sunday, April 21, 2013

Big Pipe Paravane

This paravane uses a 1 foot long piece of 1 foot diameter pipe, a piece of aluminum bent into the shape of a water ski, and a piece of foam attached with quick ties.   The ski is to follow the surface.  The pipe makes an entraped volume of water that gives good inertia against sudden pulls.  The round shape means that it can tip and not reduce how well it works.  When going fast the foam does not add resistance as it is out of the water.  It was cheap and easy to make and works really well.

It would have trouble with catching seaweed.  With holes on both sides  this could work well as a spare paravane for either the left or right side of the boat.  Once when I was running and it hit a big wave it got out of the water enough to reduce tension but then went back in right away.

Some short pulls got my scale to read about 50 lbs.  So this is in the right size range to try attaching to my sailboat mast.   Getting eager to get the boat in the water and test paravanes attached to the mast.

Thursday, April 18, 2013

Pipe Paravane

Last night I thought up a really simple paravane and then built it this morning and tested it before school!   It is just a pipe and some styrofoam.  It works reasonably well.  The two problems I see so far are that it will catch seaweed and that when the front comes out of the water it gets lighter and does not pull enough.  I will probably try a bigger diameter and shorter pipe next.   If I angle the front and have a notch all the way down the length of the pipe there will be less seaweed trouble.  Seaweed could still catch on the string.  The pipe would always be under water, so I am not sure yet how to keep the string safe from seaweed.

I could jerk on the line hard and as long as there was water in the pipe it resisted well.  The foam would lean away and the pipe would stay underwater.  This really was better than I expected.

The pipe is 3 feet long. The foam 2 inches thick and 2 feet long.


Sunday, April 14, 2013

Tabs to keep paravane down

I have attached two small pieces of aluminum to the bottom of the two keels and angled them so that they pull down.  This keeps the paravane from lifting out of the water, which has been a problem.  I also trimmed the back of the keels so they are like the front.   I can now yank on the line and it does not jump out of the water like it used to.

Wednesday, March 20, 2013

Elecrtic Motors

My electric motors are mounted!   This is the Minn Kota Riptide 160 EM that mounts on the engine.  Together the two motors are 160 lbs thrust.  They have separate wiring and control, so one could keep running even if one breaks.  I like to have options when things fail.

Monday, March 18, 2013

Paravane 2 - thinned down

I made the center body only 4 inches wide instead of 1 foot wide.  This makes the paravane lighter.   It seems to work well.  Tested early in the morning before school and the sun was bouncing off the water into the camera.  So the quality of the video is bad even though the results are good.  :-)

Friday, March 15, 2013

Becoming a hydrofoil expert

I got the book "Hydrofoils design build fly" by Ray Vellinga in the mail today.  It looks like a very good book.  I should be able to learn enough to make paravanes that work well.

There are human powered hydrofoils.  A human is about 1/8th Hp and with the machine is over 200 lbs.   My solar powered boat wants like 25 normal  to 100 lbs peak pull.  So this should be less than 1/16th Hp each, but I have 2 paravanes, so less than 1/8th Hp.  The electric motor I have is about 3.5 Hp.  The drag for the paravanes should be acceptable, if I get a good design.

Thursday, March 14, 2013

Video of Paravane 2 experiments

Here are some videos of Paravane 2 after it was balanced by cutting out part of the front of the 2 keels. 

We had some trouble with seaweed:

More trouble with seaweed

Nice run:

Another nice run:

Using 3 lines to control angle better:

Using 3 lines again:

Just 2 lines, front and back, not bottom of keel.  This can flip if I pull to hard.  Catamarans have two stable positions and one is not good.   Thinking about a monohull design.

The keels are trying to push up on the water a bit but the water off the far keel pushes on the bottom of the main body and lifts it up.  I will probably try cutting down on the width of the center piece next.

Thursday, March 7, 2013

Results for Paravane 2

The front was too heavy and it would make like a submarine.   While in submarine mode I could pull about 40 lbs worth.   We then put a rock on the back so the front went up and then it would plane.  Then we were around 20 lbs force on the string.   My son wants to edit the video and we don't have pictures of the action.   The dock had a boat in the middle so we were running up and down the beach.  Sand flies were bothering the boys so experiments were cut short.   We will try again.

Next time we should bring GPS to get an idea of how fast were are going.

Also more than one camera could be good.  One doing stills and one doing video.

Even with some coconuts it is still nose heavy:

 Tried some small coconut halves for balance.

But still a bit nose heavy:

 Then added some rocks and it was reasonable:

Starting to move and the angle is good:

Every wave tank should have palm trees:

Wednesday, March 6, 2013


One thing a computer guy living on a tropical island has to worry about is redundancy and backups.  There is no Fry's in Anguilla.  Anything you order takes at least a week to come.  When I think about boating I do so with a keen eye to redundancy.  Some of the things we will have are:

  1. Solar/Battery/Electric  - Even if the battery goes dead we can just wait a bit to charge it up.
  2. Outboard - Eric got the 50 Hp outboard engine working.  It was not as bad as I had feared.  This can move me along like 12 knots for 50 miles or so on the two 6 gallon tanks I have.
  3. Sail power - this is a sailboat so wind is an option
  4. Kite - I have a few kites.  I think even a small kite could be fun for steering with rudders and engine up.  If I stand near the front of the boat it will turn downwind, if I stand near the bank the back will go downwind.   Will have to try this just because.
  5. Sea Anchor  - can stop out in the ocean anywhere and take a break
  6. Regular anchor - most of where I go will be shallow water
  7. I have spare rudder and daggerboard.
  8. Initial testing will be done upwind so we could drift back to the harbor if we had too.   
  9. We will also have cell phones and these work further from shore than we will be going for some time.
  10. Installing a VHF radio
  11. We won't be going out unless the weather looks good
  12. The boat has so much foam built into it that it can not sink.
 So we should have lots of redundancy.   

Paravane prototype number 2 is almost ready

I got my aluminum paravane back from the welder today.  I cut some styrofoam to go on it and took some pictures.  I was planning to put the fiberglass and resin but I have a sun cure resin and it was cloudy.  If we get any sun tomorrow I will finish this and try to test it.

With the foam resting on top, this is the view from the front.  It is sort of a toy catamaran with huge keels and no mast.  At slow speeds the foam will also act like a keel.   The string attaches on the right, so I want that one to lift out first if the pull gets to be too high.  This should reduce the pull even though the left keel was still in:

This is the view from the side.  If you look close you can see where the string will attach.  The foam has been cut away a bit:

This a view looking down the way the string will be.  Note how it attaches at the top of the close keel and is in line with the bottom of the far keel.  I think this will reduce the rolling force from the string.

This is a view with the foam set to the side:

I need to be able to lift it out of the water while I am in the boat, without hitting the boat.  I have a pole with a hook on it that I use to grab the mooring for the boat and expect to use that.   The welder made this nice handle but if there is water going over the top it will cause drag, so i might cut it off.  I was thinking to have an aluminum welding rod between the inside of the front tabs and have drilled holes there in case I decide to put a wire there.

The goal for this paravane prototype is to test the stability of this basic design at slow and higher speeds and to get more pull on the line than the 6 lbs we got from the toy sailboat prototype.

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 MacGregorSailers.com 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.