I’ve been reading the forum for a while. Yesterday I have finished building my own boat, so I thought that’s a good reason to become a member and post some pictures. I don’t know many of the nautic terms, but I hope you know what I mean anyway.
Its actually my third Catamaran, the first one was made from Balsa 15 years ago. The second one - two years ago - turned out to be a pain to sail.
The new one is promising so far. Its a modified ‘Team Philips’ concept.
It is turning a little bit slow, like all wide Catamarans. To reduce this drawback it features four rudders. Two bigger ones at the stern and two smaller ones right at the attachment point of the forward crossbeam. Still turning sloooowly. The Crossbeams are X-shaped to add more torsional stability. It features two unstayed wingmasts (which are preliminary right now) that stand in 2 big ballbearings each, which are mounted in a special box inside the hulls to take up the loads. The wind resistance of the two wingmast might be one of the reasons for the boat to turn slow. I’ll probably test it with conventional riggs.
I am using 4 Servos for the rudders and one whinch for the two sails.
Everything was buildt in female moulds. Some parts of the Laminate turned out a bit hazy. I guess that is because the temperature in my workshop tends to change and so the Gelcoat maybe didnt’ have enough time to precure in some spots.[:-banghead]
I saw a lot of pictures on this forum of beautiful laminates. I never got it that way. I wonder if there’s a special trick to it that I miss. Do you put your weave on a plastic before you put it in the mould for easier handling? How about cureing time and temperature?
I am currently working on the masts and the sails. The masts are still too heavy. I wasn’t able to find good material for sailmaking so far. The two different sails on the pictures are (horrible) test sails one of heavy mylar the other one of extremly thin mylar. No sail adjustment so far other than the sheeting lines and the compression struts for the booms. Did anyone ever get fully battened sails to work really well?
LOA: 1,3 m, BOA 1,05m, weight 2,3kg
hulls: carbon
rudders: Carbon
masts: Carbon/Nomex/Glass Sandwich
crossbeams: Carbon with reinforments of Carbon/Aramid honeycomb Sandwich
Hey Marcus
Your boat looks great, both in terms of design & construction! When I get around to building another multihull, I’ve long thought that the Team Phillips concept is the way I’ll go. I really liked your experimentation with wingmasts. Don’t give up on them prematurely, as I believe they would work well with multihull models, just as they do on the full size multis. How tall are they & how much do they weigh? The wingmasts I’ve been building (out of glass vacuum bagged over a foam core) are coming in at about 150g for a 1.7m mast. Full battens can be made to work well. I’ve found that inserting them into the luff groove will cause them to “pop” over to the other camber when the mast rotates. However, since I use stayed rigs I’m able to induce positive mast rotation by the side stays acting on a lever arm at the hound.
Please feel free to contribute to a discussion of wingmast rigs at the F-48 Multihull forum ( http://formula48.proboards13.com/index.cgi?board=technology&action=display&num=1091880327 )
I’m building an RC Team Philips myself! though its no where near as complete as yours - Sailing my Taipan and completing a Masters Degree keep getting in the way.
I’ve built a set of hulls and I’m working on the masts at the moment but still have no beams or control pod.
I particularly like the use of the ram vang to control twist in the sails and the rubber band rotation inducers - very nice!
Just a thought on the turning problem - do all the rudders/servos turn to the same angle? On beach cats, the tiller arms are curved inward to connect to the tiller cross-bar. The effect is that when the rudders are turned, the inside one turns more than the outside corresponding to the fact that the inside hull needs to turn around a tighter arc than the outside. I don’t quite know how you accomplish that effect with the four servo setup you have but its something to think about.
Your boat looks fabulous! you should be very proud. How big is it out of context? like on a driveway or in a living room??
cheers,
Andrew.
ABC - Andy
Taipan 4.9 Catamaran
‘Team Philips’ Formula 40 in building phase.
Regarding the wingmasts:
I will keep on trying, but I think there is one simple reason why they will not work:
A big Catamaran or Trimaran weights lets say 2tons. When turning, the inertia of this mass has to drive the bows through the wind against the resistance that the projected front area of the ship offers (beams, masts, hulls seen from the front).
When you scale the ship down, by lets say one tenth, the mass is reduced to 1/1000 but the front area is 1/100. Which means the ratio of the front area versus the inertia of the mass is worse by a factor of ten. When you have a conventional rigg that obviously still works, but when you have a wingmast that doesn’t always aim at the wind before switching sides(for lowest possible resistance) this might be just the bit too much.
I think I will try a smaller mast next. Right now it is 178cm/13cm/2,8cm. weight is 290gr which is way off. I was a bit afraid of the unstayed masts breaking, so I made them way to massive.
On my last ship I also had a glass over foamcore mast with about 200gr. 90gr of that was the foamcore.
For an unstayed mast of this size I think 200 might be the limit that I will go for.
As for the rudders: right now they are still working in parallel, To be honest, the reason why I didn’t angle the lever arms is that the hulls are so narrow, I was more then happy that I made it to tighten the mounting screws without breaking my fingers. When all the cuts on my fingers are healed, I will surely give it a try thou…[B)]
As for the battens:
Bill, do I understand that right, you stick them in the trailing edge of the mast?
Dear Andrew, it doesn’t fit in my living room anymore. Its not so big, but the two wingmasts make it very bulky. I actually did the first complete setup right at the lakeside.
reading through my post I think I have to be more specific:
I think a single Wingmast on a Trimaran will work since Trimarans turn bettter, a single Wingmast on a Cat might be the limit, but two Wingmasts on a Cat is pretty sure just too much.
Normally, a wing mast will follow the wind regardless of how little the shift. Be sure that the masts are pivoted fairly far forward, and that both shrouds or rotation controls are not preventing the mast rotation.
On my big cat, my 4 inch deep aluminum mast easily follows the wind direction without problem. If your mast fails to rotate easily, especially with that much soft sail trailing the mast, I would suspect some adjustment is preventing the mast from rotating.
As I read your post, it seems the mast is not rotating to keep the leading edge pointed into the wind during a tack. Normally, a wing mast will emulate a wind vane and follow almost all wind shifts. By keeping the leading edge into the wind, the wing portion of the mast should rarely lose lift (power) when tacking, as it has a foil shape that doesn’t have to collapse or pop-over to regain it’s camber.
Double-check to see you don’t have too much tension on your shrouds that might be preventing rotation. Just a thought.
Just a thought: Maybe it is your rudders that are stopping your tacks and not your masts. Does your inside rudder turn proportionally more than your outside rudder when tacking? This is important because the radius of the turn that your inside hull is following is much tighter than your outside hull.
On full size twin rudder boats the tillers are pointed inward when the rudders are pointed straight ahead. In this way, the tiebar that connects the two rudders is shorter than the distance between the two rudder posts. Normally the two tillers point at a “focalization” point that is about half a boat length ahead of the bow. But this focallization distance is something you will need to play with to find the best turning radius for the boat. If the tillers are improperly focalized, then one rudder will be either over or under turning and that is just like putting out a sea anchor!
On an RC boat, what this means is that the arm on the servo is not going to be parallel to the arm on the rudder shaft. If the arm on the rudder shaft points to the outside, then it should be angled slightly forward when the rudders are straight (and the horn on the servo will point straight off to the side). You will need to do the same thing for the two forward rudders as well…
When the boat is turning, take a close look at the wake off the two aft rudders. If one rudder is at the wrong angle you will be able to tell by the amount of disturbance in the wake around the rudder. Once you have the focalization adjusted correctly for the aft rudders then you will need to take a look at the two forward rudders. I’m not sure how easy this will be to detect, but you should be able to tell if they are mis-focalized as well.
There is a good chance this is your real problem - not the masts…
there is a simple reason why it is not pivoting freely. The rubber bands keep the mast pivoted to the max. (you can see them on the pictures) I followed Tom Speers research on this.
If I remember right, he writes on his webpage, that the maximum power of a wingmast is achieved when it actually is “overturned” by a few degrees. On (some) Tornados and as far as I remember on the Dart too this is done either by pulling the mast rotator with a line or automatically with a rubber pulling it to the side.
I have choosen the second setup.
I might be wrong on that, butI think that having the mast point exactly to windward might result in a loss of some of the power this kind of riggs have, since you just have more resistance than with a smaller mast, but don’t induce any lift through it when aiming it directly art the wind.
If I understand Tom Speer right there are two ways of using a wingmast that make sense:
If you are sailing with the mast alone and “underturn” it, you induce lift.
If you sail with a sail and “overturn” it, you get a deeper profile with a better flow and thus add more power to the sail.
But anyway, I’ll give it a try.
Just a thought: Maybe it is your rudders that are stopping your tacks and not your masts. Does your inside rudder turn proportionally more than your outside rudder when tacking? This is important because the radius of the turn that your inside hull is following is much tighter than your outside hull.
On full size twin rudder boats the tillers are pointed inward when the rudders are pointed straight ahead. In this way, the tiebar that connects the two rudders is shorter than the distance between the two rudder posts. Normally the two tillers point at a “focalization” point that is about half a boat length ahead of the bow. But this focallization distance is something you will need to play with to find the best turning radius for the boat. If the tillers are improperly focalized, then one rudder will be either over or under turning and that is just like putting out a sea anchor!
On an RC boat, what this means is that the arm on the servo is not going to be parallel to the arm on the rudder shaft. If the arm on the rudder shaft points to the outside, then it should be angled slightly forward when the rudders are straight (and the horn on the servo will point straight off to the side). You will need to do the same thing for the two forward rudders as well…
When the boat is turning, take a close look at the wake off the two aft rudders. If one rudder is at the wrong angle you will be able to tell by the amount of disturbance in the wake around the rudder. Once you have the focalization adjusted correctly for the aft rudders then you will need to take a look at the two forward rudders. I’m not sure how easy this will be to detect, but you should be able to tell if they are mis-focalized as well.
There is a good chance this is your real problem - not the masts…
Will
Will Gorgen
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Good thought Will
This is known as “Ackerman” on cars and can be seen if you crank the wheels hard over and then look at the angle of the wheels. The inside wheel is turned way tighter than the outside.On a boat with dual rudders if you don’t consider the Ackerman the inside rudder will be steering the boat less than the outside which means that both of them will be dragging. On a wide cat in a tight turn I think this would cause a tremendous amout of drag. Four rudders-well! If you want an idea just go look at your car. Maybe this is the reason tri’s work so much better than cat’s.
I followed Tom Speers research on this.
If I remember right, he writes on his webpage, that the maximum power of a wingmast is achieved when it actually is “overturned” by a few degrees. On (some) Tornados and as far as I remember on the Dart too this is done either by pulling the mast rotator with a line or automatically with a rubber pulling it to the side.
I have choosen the second setup.
Over-rotated will tend to flatten the sail and depower it. Under-rotation will leave the sail fuller with more power.
Rotation is applied/removed by the crew and only when on a specific tack. It <u>MUST</u> be removed prior to tacking or gybing. You cannot leave it on all the time or when tacking because your sails and battens will be held in negative camber. Unless you are controlling your rotation by servo - take it completely off and I bet your tacking problem will disappear - or be greatly eliminated. Try it and let me know if NO rotation (positive or negative) helps. Keep in mind that until your mast tacks, you have shut off all power. It is like trying to sail upwind with your jib backwinded and on the weather side of the hull rather than the leeward side. I think you will find that no rotation, tack, let out mainsheets, fall off and then slowly sheet in and begin heading up will provide you with much faster tacks.
Somewhere I have a video clip of Hoj’s boat (NIGHTMARE) tacking in Hawaii. Pretty impressive in those reasonably light winds. Will see if I can locate and will email it to you so you can see. Really don’t think it tacked any slower than a monohull. (personal opinion)
Regarding the mast rotation question, I would tend to agree with Tom Speer’s analysis. One of the advantages to wingmasts is the wide range of airfoil camber which can be obtained thru outhaul adjustment which controls rotation. You might look at your compression vang which will tend to inhibit rotation unless it’s attached along the same axis as the mast pivot.
An easy way to test if the rudders are your problem would be to remove one of the two rear rudders and then try tacking the boat. I would also set the forward rudders so that they don’t turn and are held perfectly parallel. If the boat turns easier with only one rudder than with two, then it is your rudders that are causing you to park up in your tacks. If the boat still stalls out, then the rudders may not be the problem (or may not be the ONLY problem).
Bill brings up a good point about the vang. The compression loading along the boom is going to tend to push the mast and cause it to want to over rotate. You may not need to help it at all and may in fact find that you need to limit the rotation. I seem to recall on the Nacra 5.8s that I used to race that there was an arm off the back of the mast that had a rotation limiter line attached between the arm and the boom. By easing the line, the mast would rotate a bit further. Trimming the line would reduce the rotation. but it was the compression loading along the boom that caused the rotation.
On the Nite iceboats I used to race, we would move the mainsheet blocks forward or aft along the boom to cause more or less compression load along the boom to control the amount of mast rotation. You may want to try this as well. By moving the point where your sheets attach to your boom aft, the sheet will ps the boom forward and cause the mast to rotate more. By moving the sheet attachement forward, you will pull the boom aft and reduce the rotation of the mast.
Either way, you should be able to control the amount of mast rotation without needing to force the mast to rotate with a rubber band.
The key to the whole process is finding the correct angle to the tillers. In cars, the tiller is called the Pitman arm. Normally, the Pitman arms are pointed directly at the center of the rear axle. This is generally agreed to be the optimal focal length for the system. Some drivers like to add a bit more toe out in the turn to create more stability (I’m not sure I understand why, but they do it) so they would have a longer focal length and thus the Pitman arms would be pointed at a location behind the rear axle.
In boats the story is a bit more complex. In the scows I used to race, we tired first setting the focal length to be the distance to the bilgeboards (the tillers would point at a point directly between the boards, or about halfway to the bow). This would be the same idea as setting the Ackerman on a car to point the pitman arms at the rear axle. This turned out to be WAY to much Ackerman. We then tried a point closer to the bow. This was better but still too much. We kept increasing the focal length and examining the wake behind the rudders until we found a point that seemed to work best. It turned out to be about 1/2 boatlength ahead of the bow. The rudders on scows are very close together compared to your catamaran, so you may find that this distance does not work for your boat. It is as good of a starting point as I can give you. But you should be able to figure out which way to go from there. You may find that you need more Ackerman - especially with “4 wheel steering” like you have - so you may want to start with a focal length shorter than that…
One more thought occured to me. You can induce the Ackerman angle at either end of your steering pushrod system. In other words, you could angle the horn on your servo to achieve the same effect as angling the tiller on your rudder shaft. So if it is easier to fiddle with the servo than it is to adjust the angle of the arm on the rudder shaft, then play with it at that end instead.
Angling the horn on the servo aft will produce the same effect as angling the arm on the rudder forward, I believe.
Are you sure Will? I think Ackerman depends on the fact that a straight line pull causes more rotation as you reach the over-center point(sort of). If you just move the arm on the servo it would be the same as changing the steering box on you car,that won’t change the Ackerman. I’m pretty sure I’m right on this one. It doesn’t happen all that often.
Don
One other point that everybody is missing regarding tacking cat’s is that on full size boat’s the jib,headsail or whatever is held to help the bow through the wind.
The rudder setup will assist but if you can set your sails so that you can adjust them independently then you will find that the cat will tack much better.
The other problem with tacking cat’s as compared to tri’s is the fact that both hull’s are “pushing” water through the tack, whereas the tri’s pivot on the main hull so they tack more like a monohull.
Masts at 1.78m! Crikey - the things taller than I am!
Mine is a tiny bit smaller at
LOA 1.2m
Beam .76m
Mast Height 1.35m
I agree with the other guys, perhaps the problem is in the rubber band rotation inducers? I see you’ve got the rotation control line from the boom so that should be all that you need if there is any wind about. That’s the only rotation control that I have on my boat and it seems to work fine - Generally we have a small amount of rotation for upwind and a lot for downwind due to the apparent wind changes. In an RC model you probably don’t need a lot because you’re always sailing pretty fast compared to the true wind speed.
The amount of rotation you have should be ok - you might have to run with a little less vang pressure to let the masts flick over to the new tack? The sheet tension should pull in the twist when close hauled but you might have to ease it off to let the masts flick during the tacks.
The other problem with tacking a twin rig boat is that as you turn, the apparent wind changes differently for each rig and effectively the windward rig is going backwards.
How does it go on the gybes? same turning slow problem? might narrow it down to rudders or masts/rig?
ABC - Andy
Taipan 4.9 Catamaran
‘Team Philips’ Formula 40 in building phase.