Mast setup, pls comment [Archive]

Fanie

07-09-2008, 07:34 PM

rob denney

07-09-2008, 10:11 PM

Hi Everyone,

Pls comment on the advantages or disadvantages of the attached setup.

Some notes on this.

There is a mast on each hull. There is a cross-bar keeping the mast heads at their distance from each other. There are two stays crossing keeping the stays uprightas seen from aft, and one stay from the steps on each mast and the sails stays keep the masts upright from abeam.

Here are some advantages from my point of view -

The aft beam does not carry the weight and down force of the mast (if it was in the centre), hence the beams can be made lighter.

It would be easier to upright the masts, since they cannot swing either way as could be the case with a single mast in the centre.

The mast sits higher on the hulls than it would be on the beam if it was a single mast. I thus score a bit of mast length (height)

Q-
Do I enlarge the sail area effectively on both sails ?

Can one make way ok with one sail ? ie the other is furled ?

Would a setup like this have any disadvantages, other than maybe extra costs ?

Thanks for taking the time out...

G'day,

Couple of drawbacks:

Large unsupported length of mast would mean the masts are bigger than normal.
Additional weight up high
Additional drag
Difficult to get to the cross bar for maintenance
Sail area is in the wrong place(low and forward) for most sailing.
No sheeting angle on the leeward headsail, particularly when reaching
Huge sheeting loads
Huge tension required to keep the forestay straight
All the loads work backwards. That is, as the breeze increases and nothing is changed, the sails get fuller. What you want is a rig that automatically reduces power in an increasing wind, not decreases it.
Will need substantial bulkheads under each mast. The hulls may need beefing up to take the larger fore and aft loads.
Will not sail upwind very well with partially furled headsails.
Hard work lowering them as the crossbar will see high twisting loads if they are not lowered exactly together, You then have the cross bar sitting 20' off the bows and no easy way to disconnect it.

Last, but not least. If it is deck stepped, there is nothing stopping the whole lot falling sideways, either as a collapsing paralellogram, or by lifting the windward rig off the deck. The stays must attach to the boat, adding more loads and another strong point.

This is taking a complex, high effort rig and making it even more complex.

How could it be improved? Make the masts unstayed, move them forward and replace the headsails with mainsails. This would overcome all the above problems.

Regards,

Rob

Fanie

07-10-2008, 07:24 PM

Hi Rob,

Thanks, some valued comments there.

The reason for using this sail setup is I want the sail setup to remain as simple as possible. Ideally a single sail that can be furled away or deployed easy and quickly.

Since it is going on a fishing cat, the sail or sails has to be able to furl away asap if you get a fish on, so I'm trying to stay away from a boom (bermuda-like) setup.

The centre of sail area can be shifted aftward. Ideally the mast should move aftward to about a meter from aft. A second and smaller sail could be used if the wind gets too much ? and could retain the centre of force on the hulls.

The rig is made trailable, so the masts must be taken down, but they do get bolted down, the parallelogram won't topple over sideways.

As for the substantial bulkheads under each mast, it is going to be even worse if the mast sits on a crossbeam between the hulls. By adding a substantial beam where the mast sits on, I either have to sacrifice bridgedeck clearance or have a beam to step over when you enter or exit the cabin. Neither is a sacrefice I want to make. As it is now the aft deck and cabin is at the same level.

What is more desirable - A big sail with lots of area, (would work better when running) or a narrow sail to get more wing (luff) area (less side force when reaching).

On the little trimaran I built just to test the sail setup I first had an 8 sqm sail. I then increased the sail area to 12sqm, both had the same luff length. Big difference in the force if you hold onto the clew rope. I got the impression I didn't really get more speed from the larger sail area, unless I was running (of course). Unfortunately the wind around here is nothing to brag about...

Meanz Beanz

07-10-2008, 07:34 PM

http://www.schionningdesigns.com.au/www/page.cfm?pageID=271

Shorter masts (divided sail area), simpler & lighter handling, unstayed keel stepped but offset, Schionning provides plans/instructions for the amateur to construct, you might be able to buy them separately but you would have to adapt them.

The con here is some question about heavy air handling issues (turning the boat through the wind), yet to be resolved as I understand it.

Fanie

07-10-2008, 07:57 PM

Hi Meanz,

Nice link, thanks, I'm going to check it out now.

The con here is some question about heavy air handling issues (turning the boat through the wind)
Could you pls explain ?

Meanz Beanz

07-10-2008, 08:13 PM

Flat out now, I will find it later... its was on that other cat design thread (JCD?) I think... search Radical Bay 8000

Fanie

07-10-2008, 08:26 PM

Thanks Meanz... just got an idea.

If I make a cavity in each hull where the masts sits in, this could make the masts easier to put up as well. No stays except the one, so the mast is thus free-standing. Will have to be fairly rigit to handle the forces though. Think it will hold ?

rob denney

07-11-2008, 07:10 AM

[QUOTE=Fanie;214512]Hi Rob,

Thanks, some valued comments there.

The reason for using this sail setup is I want the sail setup to remain as simple as possible. Ideally a single sail that can be furled away or deployed easy and quickly.

Since it is going on a fishing cat, the sail or sails has to be able to furl away asap if you get a fish on, so I'm trying to stay away from a boom (bermuda-like) setup.

Rob
Furling such large sails in a breeze will not be quick, nor easy. Releasing the mainsheet(s) on one or two main sails so the rig weathercocks is easier and gives the option to use the sails for drive (including backwards) if required

The centre of sail area can be shifted aftward. Ideally the mast should move aftward to about a meter from aft. A second and smaller sail could be used if the wind gets too much ? and could retain the centre of force on the hulls.

Rob
Very difficult to support. Headsail only rigs need very strong support fore and aft and sideways to prevent the forestay sagging. There may be pitching issues associated with the weight down the back. They may also get in the way of the fishing

The rig is made trailable, so the masts must be taken down, but they do get bolted down, the parallelogram won't topple over sideways.

Good, but that and the attachment of the cross bar and the rigging will add considerably to set up time. An unstayed mast can be removed and laid down on the hull, ready to trail in minutes, using a gin pole.

As for the substantial bulkheads under each mast, it is going to be even worse if the mast sits on a crossbeam between the hulls. By adding a substantial beam where the mast sits on, I either have to sacrifice bridgedeck clearance or have a beam to step over when you enter or exit the cabin. Neither is a sacrefice I want to make. As it is now the aft deck and cabin is at the same level.

Agreed, a stayed mast down the back in the middle of the boat is the worst option. I think two down the back is a near second. A single mast mounted forward in one hull is my preference, one in the middle or one in each hull if symmetry is important to you.

What is more desirable - A big sail with lots of area, (would work better when running) or a narrow sail to get more wing (luff) area (less side force when reaching).

Rob: Area will triumph over aspect ratio until you are overpowered going upwind.

regards,

Rob

Fanie

07-11-2008, 08:09 AM

Thanks Rob !

Give me a bit of time to ponder all this.

Regards
Fanie

Fanie

07-12-2008, 04:50 AM

Butch .H

07-12-2008, 05:22 AM

Fanie I still have that 11m mast if you are interested

rob denney

07-12-2008, 06:03 AM

I like the Radical Bay as per Beanz's link. The 2 masts are smaller and easier to handle, centre of sail force is low, which I also like a lot. I also like the no rigging, it is simple which I also like.

This still leaves me with the problem of how do I get the masts up and down, and when you fish how do you get rid of the sails quickly.

On the jib you pull a rope and the sail is furled. Takes about a second to do...

G'day,

Why get rid of the sails? Presumably you want the boat to stop quietly and without hassle? Releasing the main sheet(s) so the mainsail(s) weathercock(s) and the boat stops will do this much quicker and with no chance of a balls up (furler lines jamming, junping off the furler, needing to be winched in a blow) than furling the jib. Add to this the ease of sailing unstayed main only rigs compared to fighting flogging genoas at each hoist, tack or wind increase and it is a far more sensible solution.

Stepping/unstepping unstayed masts is very simple.

You have a small hatch in the deck next to the mast and a mast step next to the regular mast step. Calculate the height of the mast centre of gravity above the keel and get a piece of alloy or steel tube that is the same length plus the distance between the mast bearings plus 0.3m/1'. Call this a gin pole.

Attach a block and tackle to one end and place the other end through the deck hatch and into the second mast step. Attach the other end of the block and tackle to a strop around the mast at it's centre fo gravity. Hoist on the block and tackle and lift the mast to the top of the gin pole. Grab the heel of the mast and pull it down till the mast is vertical. Lower the mast into the bearing and down to the step. Remove the strop and the gin pole. Unstepping is the reverse. With cradles that sit on the deck, the mast can be lowered into it's traiering position. There are no stayed rigs that can be raised and lowered as quickly, or as safely as this. as this.

Arrange the boom properly and it and the sail are permanently attached to the boat so do not have to be removed for trailering and need no vang so are trimmed solely by the mainsheet..

Radical Bay rigs are a step in the right direction, but bent masts are hard to build (and to trail) and have halyard problems. They also have engineering difficulties, as evidenced by one of the original RB's breaking.

regards,

Rob

Fanie

07-12-2008, 01:57 PM

Hi Rob,

Releasing the main is fine if you catch certain fish. If you get one of the more sporty fish on you want to get rid of the sails and go to the motors, and trust me there is not much time. A nice size saily or a bluefin will quickly rid you of your expensive braid, somehow these fish goes on to the next continent when they're hooked and they are in a hurry. Those booms are going to cause a lot of trouble if there is a sail on it and you try to maneuver after a fish :D

I haven't delt with large jib sails, the sail on the little tri is only 15m^2, but it furls away in a second, and it takes the same time to get it going again. I never had it malfunction in any way. If I can find a way of making the mast for it work then that is what I would like to have. It is a one person operation and really very easy to do.

If you look at Brian Eiland's articles on the aft mast as well as the one on fishing from a catamaran, that is the thing I'm after. He mentions the advantages there, one of them being able to furl the sail in a second and go to the iron sails right away. He also has an understanding of the requirements if you do fishing from a boat.

The reason for going for sails instead of just outboards (which is much easier and simpler ;)) is you can sail all day long or trawl up and down a stretch of water day in and day out and it coesn't cost you an arm and a leg for fuel. I also for some strange reason developed a liking for sailing. Kinda the best of two worlds.

To get back to the unstayed setup. I like it for it's simplicity. Is there a way one can down and up the sails quickly ? I'm thinking in the lines of releasing a line and the sail drops, then pull it up if you want to make way again. Another way could be to pull the boom up against the mast...

rob denney

07-12-2008, 11:20 PM

G'day,
Ball bearing luff cars will allow the sail to drop in seconds with the opening of a clutch. A wide boom, lazy jacks and or a sail bag to catch the sail and it will be completely out of the way before the jib is furled.

Open the main sheet clutch (may not be required in medium air), open the halyard clutch and turn on the engines. The sail will out of the way before you get the engines in gear.

Small furling jibs are pretty easy to furl. Dump the sheet, grab a handful of line and lean back. Even this will be slower than the mainsail. Large ones need the sheet released, then the line winched in while the whole boat is shaken by the flogging sail. It ain't quick, or particularly easy. Get some experience with large furling sails, or talk to someone who has (not someone who is trying to sell them, but someone who has furled a big headsail in a 20 knot breeze). Then talk to someone with ball bearing luff cars and see how quickly and easily the sail comes down when it is pointed into the wind.

How are you going to lower the mast with a furled headsail attached? They are heavy, relatively rigid and easily bent.

You will enjoy sailing far more with mainsails than with jibs. Less work, better performance and the harder it blows, the better they work.

I don't know much about sport fishing (and don't really want to, it seems barbaric to me), but I have done a fair bit of sailing, building and designing. If you want complexity, weight, cost and lousy sailing, then the aft mast/furling headsail rig is definitely the way to go. Brian is a nice guy, who has done a lot for multihulls in his time, but does not believe in the rig sufficiently to build one and I don't think he has managed to sell one in ?? years of trying, so I tend to take his articles with a dose of salt.

regards,

Rob

Fanie

07-13-2008, 06:12 AM

Hi Rob, thank you for your patience.

The attached picture was posted in another thread, it looks like an easy way to get a mast up or down.

The carrs in the mast is something I can do. It seems functional, I will play with the idea a bit, see how and if it can work out on the boat.

As for fishing being barbaric, I agree but I also disagree. Depends on the the angler. Unfortunately some guys kills everything that crosses their path. As for our crowd, we take special precautions not to harm the fish. Almost all our fish goes back, I'm not scared of catching the same one again ;) We keep some fish for the pan, mostly young ones, the big ones goes back, they know how to make more fish :D

It is very difficult for a guy to put a big fish back if he hasn't cought anything decent in years of trying, he he, it's like taking his trophy from him - but it becomes easier once you get used to let the big one get away by letting them go. What are you going to do with all the fish any way, one can eat only so much ;) Besides, chickens, sheep, cows, pigs and some fish are meant for eating.

Fishing for fun is different than fishing for food. I'd rather you don't try, the thrill and excitement of gettig hooked and your skill against the fishes power is very addictive. It's pretty much the same as when you launch the new boat the first time... :D Fishing is like launching the new boat feeling many times a day...

Getting carried away there. Lemme play with some ideas.

Thanks.

Fanie

07-13-2008, 07:36 AM

I have a question pls.

On the aft mast setup it is easy to furl the big sails and use a small one in high wind conditions, how would one do this with a bermuda type rig ?

Meanz Beanz

07-13-2008, 08:23 AM

You have plenty of options, working down head sail sizes, reefing mainsails, inner stay sails, storm mains and head sails. All depends how you want to set it up... Some of the modern boom furling setups are great, Hoods one I have used extensively. Rolling head sails you are familiar with.

Fannie, with that aft mast setup I think you will have trouble with fore stay tension and furling systems working correctly. If you do go that route be sure you can get the tension. Also personally I don't see how the rig will balance correctly, It looks to me like the center of effort will be to far aft... but I am no designer, have you worked all that out?

With this fishing lark you might find that a sailing multi is not as maneuverable as you need, they need speed to turn well because they are light with relatively high windage. They lose speed like no other boat I have sailed. I sail onto and off my mooring all the time, I virtually never use the motor. The speed at which I can turn into the mooring and the distance in which she stops would astound most mono sailors... its like doing a parallel park with a hand brake turn :D

Once you lose speed hull windage tends to become the overriding force, with boards up at slow speed you can lose allot of control, with boards down things are better but even with a single engine running you can still be at the mercy of the wind for periods of time, in certain circumstances. Sailing you will not want to be making a series of direction changes in a short space, (downwind not such and issue), you lose speed quickly and maneuverability goes with it. If you have twin engines and are motoring then you are better off but still not a craft you can spin around chasing fish easily. I have no idea what you need to do what you want in terms of handling for fishing I just thought I mention that slow speed handling issues, more so in a breeze, are a legacy of a light fast craft with high windage....momentum for low speed handling is lacking.

Not wanting to pee on the parade, just something to consider, maybe experience a bit before you finalise the design.... but then maybe you are on top of all that all ready :D

Fanie

07-13-2008, 09:26 AM

Hi Meanzie,

I have just been outside looking at the little tri I built to test the aft mast setup with, and I made a discovery I never thought of before. It is almost exactly half the size of everything I worked out for Cattrine ! The mast is 6m... I want two that is 12M (maybe 13m), the tri hull is 5m5, I'm going to 10m, The tri sail foot is 5m, I'm going to 7m - 8m.

The only single problem I have with the little tri is keeping the forestay stiff enough, the mast only a few allu pipe extrusions sleeved and OD is only 55mm. I can bend it some by pushing down on it while holding the other end in my hand, so it's not that rigit at all.

The beams I made for the tri are 4m long. Their ends supported I can stand with my fat butt (95kg) on them and they give very little. This may be the way to go with an aft mast - a very rigit pole that gives just about nothing.

There is something about the aft mast sail I like very much. The sail makes lift, this is nice since the amas doesn't get pushed under like with the boom setup. The amas hardly gets pushed under, maybe 50mm or so on a reach, while my friend's tri with the bremuda I sail the leeward hull right under the water like in there... it's gone, water and spray everywhere at 22km/hr (11kts).

I haven't been in some hard wind with my little tri yet since the wind dies down when I get to the water every time :D Really ! I did however get the impression that one can go on the plane when running if the wind is up to it.

The little tri points right on a close haul, but since I haven't a daggerboard (or keel) the side drift is significant and I don't reach target. My top speed so far isn't too great, only 12km/hr (6kts)... sucks eh :D I have what you can call no wind syndrome.

The furling of a bigger sail - Since I make my own furling roller I can easily determine the force-to-furl ratio by increasing the rope drum diameter. The larger the diameter the easier it would furl. You have to let the clew rope out to release the tention in any case, but this isn't a problem either, the sail flies up and out of the way.

Haven't told about Cattrine ! yet... female of course ;) Not enough problems so complicating things a bit :D

Fish are funny creatures. When the take the lure they seldom swim in the right direction. It's mostly in the direction of most resistance, away from you. For instance if you trawl you hook it when behind you, they either go sideways or backwards so things happen really quickly. I get land sick just thinking about it :p

Each hull gets an outboard. Manuevering is not that big a problem though. As for a hand brake turn, I'm not there yet.

BWD

07-13-2008, 11:15 AM

If you are willing to rerig your fishing gear when you change tacks, could you do a proa instead?
One unstayed mast with fullbattened sail (or 2 if you like).
Only one motor needed.
When a fish is on, loose the sheet and the boat will lie ahull. To back down, take up the other sheet (=shunting).
If you lose the fish, shunt again and put out your lines again, or rerig them to run out the other way....
Maybe see what Mr. Denney thinks...

Fanie

07-13-2008, 11:29 AM

Hi BWD,

He he... some brilliant drawing there :D Could put you up there with picasso.

I have had a look at proas. I don't like the idea and I don't think it's the thing for me. Looks like a tri that lost a hull :p

Fanie

07-13-2008, 11:30 AM

Is there a specific ratio between mast height and and boom lenth ? Or is it a discression thing.

brian eiland

07-13-2008, 12:54 PM

..more extensive comment in a few days...meantime since you are looking at all kinds of ideas, have a look at a few of these:

Valkyrie catamaran...bi-pod 36" cat
http://boatdesign.net/forums/showpost.php?p=106915&postcount=31
(regrettably link no longer works)
http://boatdesign.net/forums/showpost.php?p=110509&postcount=38

Under "Main-less Rig" (http://boatdesign.net/forums/showthread.php?t=21274)
A-frame rig sailing well
http://boatdesign.net/forums/showpost.php?p=184703&postcount=11
http://boatdesign.net/forums/showpost.php?p=184941&postcount=21
http://boatdesign.net/forums/showpost.php?p=185146&postcount=28
http://boatdesign.net/forums/showpost.php?p=194774&postcount=73

..another A-frame
http://boatdesign.net/forums/showpost.php?p=185402&postcount=33

Fanie

07-13-2008, 02:09 PM

Thanks Brian, looking foreward to it.

I have a question regarding sails.

The sail is cut when made so it creates s curvature theat makes a vacuum to the leeward side of the sail, right, so the boat's sail get sucked into this vacuum which propel it foreward, similar to an aeroplane wing.

Now an aeroplane has a lot of speed going for it, sails on the other hand rely on the brute force of the relative slow wind, hence the larger the sail the more propel power a boat has.

Now if one looks at the curvature of a sail then it seems that only the foreward third is curved, the rest seems to flatten off, so this is where the most efficient force is created.

Also, one sail curving around another ie, a bermuda rig with a jib, it seems the jib enhances the bermuda's performance by channeling and so accellerating the wind moving past behind it, besides that the jib's leading edge also creates a foreward force.

Now if this is true, why haven't sails a few vertical slits in them with spacers connected to vertical battens to control the 'vent' opening ?

Logic tells me this way one could have two, three... four... five leading edges enhancing one another while making foreward propelling forces instead of just trying to rely on one big unenhanced force which is more heeling the boat over instead of propelling it foreward.

Am I missing something here ?

brian eiland

07-13-2008, 02:39 PM

...Now if this is true, why haven't sails a few vertical slits in them with spacers connected to vertical battens to control the 'vent' opening ?

Logic tells me this way one could have two, three... four... five leading edges enhancing one another while making foreward propelling forces instead of just trying to rely on one big unenhanced force which is more heeling the boat over instead of propelling it foreward.

Am I missing something here ?
Presently working on a new posting on this subject that will appear over in "Sail Aerodynamics"....but it is a week away at least:

Has to do with this paper that Tom Speer has referenced so many times. Does anyone have a PDF file of this paper??
http://boatdesign.net/forums/showpost.php?p=9987&postcount=15

http://boatdesign.net/forums/showpost.php?p=9987&postcount=24

http://boatdesign.net/forums/showpost.php?p=9987&postcount=60

Fanie

07-13-2008, 05:03 PM

Here's something on it too. Tom Speer seems to be a very clever chap, don't understand a word he says :D At least it seems his head is screwed on properly. If only one can get him to tell it in plain English :D

http://www.boatdesign.net/forums/showthread.php?t=1253&highlight=Kipling%27s+Just-So+Stories.

Fanie

07-13-2008, 05:06 PM

I had a look at Tom' web site -
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
No, I'm not going to get involved with this
...............

Pls consider the previous two posts by me cancelled

Think MASTS... MASTS

Fanie

07-13-2008, 05:30 PM

Fannie, with that aft mast setup I think .... Also personally I don't see how the rig will balance correctly, It looks to me like the center of effort will be to far aft... but I am no designer, have you worked all that out?
I can only speak drom the little experience I have with it and trying a little bit of common sense.

If the centre of sail is between the rudder and daggerboard the rudder has to help the daggerboard, so more side force would be experienced on the rudders, should not be a big problem if they are designed for it. We South Africans overdo everything :D

Meanz Beanz

07-13-2008, 06:55 PM

You need the center of effort to be just behind the boards from my understanding. I think that a quick way to estimate it is to draw a line from the mid points of the sides of the sail to the opposing corner. (?)

Have you got a backstay planned? Maybe a back stay with spreader, because the angle will be tight (-15 degrees) will provide the stiffness required. Forestay sag will show up alot more in higher winds, if you get sag in low or no wind it will be pronounced in 25knots of it. My rig is quite tight at rest but the flex in the boat makes it sag in a breeze.

Cheers
MBz

chowdan

07-13-2008, 07:41 PM

Hey Fanie,

I also love fishing. Great game fish out here in these waters along with decent size mahi mahi and all types of tuna. I was just in a fishing tournament a few weeks ago and was asked to be a firstmate/photographer onboard a 51' enclosed flybridge Riviera (has a tower on it as well). Was a beautiful yacht! On the second day we decided to go to to an island that usually has good game fish but it was a 2hours and 40minutes run at 20knots. That day we had burned almost 1000L of fuel on that day! The gauges showed we were burning 90+L/hr when we made those two long runs. When we were trolling we were burning 17L/hr. I would love to get my hands on enough money to be able to own and be able to support the fuel and maintenance costs..lol

But from my experiences on fishing cats haven't been so great. They are hard to maneuver when you have a blue, sail, or black on the line. I used to run a small 24' cat with small twin 50hp outboards. A few times we had a blue on the line I couldn't keep up with it due to there speed (as i take it you know). Also you might want to look more into having a boom and having you sail furl into the mast and having your boom pull up to the mast. That way you wont have any problems with it being in the way (haven't read all the posts but im working on it so excuse me if i am saying the same as someother people said).

I also think if you have your mast(s) in the back of your hulls they will get in the way for your angler. What happens when you have a fish on the line and your fish goes from the starboard side across to the port side and keeps going? your line will possibly be rubbing on the mast.

Are you planning on building her or having someone else?

This is just what i think:P

Jordan

rob denney

07-13-2008, 10:35 PM

[QUOTE=Fanie;214994]Hi Rob, thank you for your patience.

The attached picture was posted in another thread, it looks like an easy way to get a mast up or down.

G'day,
Tabernacles work well on small low righting moment boats, they tend to be pretty substantial on bigger boats and you still have to remove the mast and move it forward for traillering. Still easier than lowering and raising stayed masts with furled headsails attached.

The unstayed rig flexes as the wind increases which reduces the power. Your first reef is automatic. This is the opposite of a headsail where, as the wind increases, it gets more powerful. Further reefing is done by releasing the sheet, the boat stops and you take in a slab, as per most boats reefing systems.

Few other points about other posts and references.

John Hitch's boat is fast despite it's rig, not because of it. The long skinny hulls, no rocker and light weight make it a rocket ship. The rig is ok for reaching (as are most rigs), but not upwind.
Foil shaped A frame masts are more windage than round ones, not less, except when the boat is motoring into the wind.
A proa is the best format for racing and cruising sailboats, not sure what you would have to do to make it a good fishing boat.

regards,

Rob

RHough

07-14-2008, 06:09 PM

The sail is cut when made so it creates s curvature theat makes a vacuum to the leeward side of the sail, right, so the boat's sail get sucked into this vacuum which propel it foreward, similar to an aeroplane wing.

Force = Mass x Acceleration

A sail or an aeroplane wing moves air. Measure the mass and acceleration of the air due to the sail or wing and you get the force.

The air "sees" multiple sails as one unit. The number of leading edges is one. A multiple sail rig has one leading edge and a number of slots. The slots allow the multiple elements to bend more wind and produce more force. The problem you will have is getting all the sails to trim correctly. The more sails/slots you have the angle that the boat can sail into the wind gets worse.

When you do not need/want maximum power, you still have all the drag of the slotted wing or multiple sails and lower performance.

Meanz Beanz

07-14-2008, 07:10 PM

The air "sees" multiple sails as one unit.

Yes, but in the case of a bi-plane rig mentioned earlier?

Fanie

07-14-2008, 07:20 PM

Hi Jordan,

The weather (wind) plays a big role if you want to chase a big fish wheeling off to somewhere, meaning if there are high waves you cannot just charge to anywhere without risk of capsizing or burroughing the boat (you may actually see it when you go right through the wave, but you have to look quickly :D) And yes, some fish really knows how to motor. He he... the guys I usually fish with used to laugh at my one big reel... now their thinking is changing slightly ;)

On a motorboat you hook the fish, then if it makes for the other side of the world you have to try and follow it. The idea is not to ride on top of it which is mostly impossible, the idea is to give the angler a chance to turn the fish and to hopefully gain some line back. If you can turn the fish and fight it sideways it tires quicker than when it swims away from you, so you may not always follow after it, you may want to get an angle on it (sure you heard that one before) So if you're in a bay and the fish is going for shore you head on up the coast instead. Anyway, it happens quickly. (and forcefully). He he if you have the right line you can just hold on, the fish will tow the boat to somewhere, hope your arms doesn't stretch too much.

The cat (and tri's) has to be so you can move right around them. Of course there are compromises, if the fish moves around or under the boat you have to go around too. Unless you want to fight it back from under the boat :rolleyes:

So if you are sailing (and saving the pile of money... piling up in your account of course :D) and you do get a fish on, you have to get rid of the sails and go to the petrol motors... if it is a big fish and the right type. This you know really quickly. Mostly you can just cut the sails to stop and wait for the guy to get his fish out, but when the right fish goes on you must be able to keep the boat right for the guy fighting it. You shoud try to hold on to a rig that drags 120lb (50kg) trying to pull you off the boat and going in any direction. When someone grabs you from behind on the belt it's because you look a bit unstable there :D Mayday mayday mayday, Coast Guard we have a MOB traveling under water at about 80km/hr due North to Noth West, could you intercept please I repeat...

A-hand the-hen, if you're untidy with your line and it gets a loop around a finger it can get amputated very quickly... man are we having fun or what :D

Fanie

07-14-2008, 07:52 PM

When you're fishing bottoms you 'park' the boat, may even anchor if you're on the spot. Sails are furled. If you hook something big-ish you just run over everyone els to get to the other side... Sorrry... Sorrreeeee, sorreee.

Oh yes the masts and sails. I'm looking at the options. I have drawed the outline on the paving to size to get a feel for it... again... if I can get the wife to stop watering with sprayers and the customers parking on the boat :D

There is one thing though. I was recently involved in a prop design for a wind power generator.... there is a substantial difference in a design that makes wind ie aeroplane prop and the design for one that uses the wind. The earoplane prop hardly turns in wind blowing into it, the wind gen prop makes almost no thrust when you rev it up... I suspect it is going to be the same thing with sails. The sail that makes lift has to be shaped to fly with wind blowing at it.

I understand that there are a lot of variables during sailing, but the multiple 'half bra' (sorry, good shape though :D) or semi-cone idea keeps coming back to me. If a sail consists of these and each vertical row has a correct angle which depends where in the sail it sits it may well be possible to make more power, for now the whole sail is full of leading edges, each with a vacuum behind it. The shape of each cone, being longer than the slit where it's wind passes through could also increase the sailing area... the vertical row laid flat could extend well beyond the sail height.

I haven't the funds to attempt it, so just speculation on logic... Imagine how dangerous some of us would be if we had a lot of money :D All those bra's to make a sail...

Fanie

07-14-2008, 11:23 PM

Birds wings does not have a smooth surface, how much does those fine turbulences help them to gain extra speed when like the Albatros they glide for days / months on end. Do those fine turbulences create a 'pocket' that gives extra speed and lift ?

chowdan

07-15-2008, 07:04 PM

Hey Fanie

I've never actually fished off a sailboat before so yea that would explain some of my stupid quotes. But yes I understand what you are saying about wearing down the fish. I've had a lot of experiances with being towed:)...its great fun seeing "true power" pulling a boat. I've also had the stern so far under water that the bottom of the fighting chair was under! And of course I've seen the bow under water. After I started replying to your post I have been very interested in sailboats for fishing.

Here is a design that might do you well. Seems to me this would be even better than a furling mast!
Hi/Low reefer reefer furling boom (http://www.johnmast.dk/uk/hi-low/default.asp)

Some photos of a Riviera that was in the tournament. The last photo is when they hooked a 70kg sail fish!:mad:

rayaldridge

07-19-2008, 07:48 PM

We might all be fishing from sailboats, if the cost of fuel continues to rise. Already, many charter boat captains have been driven out of the business, and a lot of private owners are cutting back. As an example, I have a friend with a 28 foot dual outboard who regularly goes out to blue water to fish. He burns 100 gallons of gas on a typical trip.

That said, big game fishing is a different matter, and if sailing becomes the only way to get to the fishing grounds, and there are no auxiliaries, then at a minimum, tackle will change. Now, big fish can be landed on lightweight gear, because the boats can pursue the fish whenever it takes too much line. If pure sailboats were to become the norm for fishing, then much heavier tackle would be required to land big fish.

I fish a lot from my little beachcruising cat Slider-- in fact, I rarely sail anywhere without a couple of lines out, and I'm rarely skunked. Here's a pic:

http://slidercat.com/smlightwinds.jpg

When we get a strike, we can go two ways. If it's a fish of moderate size, I just pinch up until we are going quite slowly, and let my crew land the fish. If it's a big fish, I generally heave to, and that's really the best way to handle it-- except that getting under way again once the fish is landed is a little more complicated than just bearing off.

If I were fishing for marlin, I'd need much heavier tackle than I'd need in a power boat.

Ray

http://slidercat.com

Meanz Beanz

07-20-2008, 04:07 AM

Furling booms... much better than furling masts.

Fanie

07-20-2008, 04:12 AM

Hi Ray,

You are right, switching to a sailing rig does present a couple of chalanges. The idea would be to have a couple of motors on it, hence the idea of getting rid of the sails and switch to motors. You then will burn only fuel when you have to. Getting there and back or when you trawl you sail. Should save considerable fuel.

Nice looking rig. You can leave the wife, but not the fishing rods :D

MAINSTAY

10-05-2008, 12:15 AM

Fanie
I like you original bi-rig. I know I'm coming in late and you may have moved on. But I think the others have lead you far from your rig for your fishing boat.

Robs assumption that a spar is needed between the masts and parallelogram collapse is true only if you accept the rest of his design. I agree that stepping the mast at the center of the crossbeam requires the strongest beam. I also agree that there is high backstay tension in your design to keep jib sag within reasonable limits.

BUT, consider stepping the mast more forward. Since two sheets are already needed, one each side of the mast, to trim the sail, there is no reason to step it so far back. Stepping it to bisect the forestay/backstay angle will result in equal forces, not multiplied. This reduces the mast compression forces.

AND, consider stepping the mast on or near the INNER surface of the hull or a foot or two onto the beam . In this way the forestay/backstay act as to keep each mast head from moving inward, and the static tie between the mastheads keep them from moving outward. Since no sail is on the mast it does not have to be in the plane of the sails.

Others who claim that the sail area (CE) is too far forward or aft, have too little information to make that claim. It depends on where the keel or centerboard (CLR) is. And you may still be able to put it where you need it.
SO, consider moving the backstay to the aft cabin wall or crossbeam (and the mast step to the forward crossbeam). It makes the forestay more vertical and you give up some uplift, but you gain a clear aft deck for fishing. It’s your choice. Your foresail can still stretch aft as you show in the original sketch while trolling and travelling to and from the fishing grounds.
Larry Modes

Fanie

10-05-2008, 06:56 AM

But I think the others have lead you far from your rig
Not in the least. I like the aft mast, there are a lot of advantages.

The main consideration having the masts so far aft is for mounting / demounting purposes, it means the mast foot will be sitting at about knee-hight instead of 2m up, it makes it very difficult to get the masts up there on top of the hulls.

The only obstruction to the fishing would be the two masts, I'm almost sure one can work around that.

Ideally I would prefer to have a neuclear engine in it and have no sails, power and hot water on demand. Indefenate propulsion.