I sure there are many of us that are aware of wiebel sail systems, as they have been in the fore-front of speed sail record breaking attempts. A wiebel rig leans the sail aft to provide dual axis thrust, thus the hull has less wetted surface in most points of sail while still maintaining forward thrust. A standard wiebel rig has a aft mast and a spar that runs down the luff of the sail, these rigs have the tack of the sail furthest away from the mast and a pivot to maintain dual axis thrust. I have tried to incorporate this concept to a footy hull for moderate to strong winds.A hike bar is attached to the swing pivot and adjustable weights can be applied to simulate a crew hiking out for a strong gust or at the very least provide some sail regulation , this would return to centerline via tension in aft mast that is adjustable. I know that there are experienced sailors out there and this may only be a pipe dream, but it is my hope that with your comments a feasible system is born.
An interesting concept, and it will probably work. There are some drawbacks:
A. The moveable weight is probably illegal, and it will need to be large (several ounces) to have much effect.
B. It will require a more powerful sail servo for 2 reasons:
The unbalanced wind force on the sail.
The force required to move the balance weight against gravity when heeled
FORGET THE ABOVE COMMENT
I just realized that the force of the weight will help balance thr force on the sail, which will actually reduce the force needed by the servo.
It looks like an interesting adaptaion of the Wiebel rig. How about using carbon rods instead of the tubes? How did you attach the tops of the mast & spar?
thx
The balance weight could be removed and the hike bar shortened if not legal, you would still reap the benefit of having the sail present itself to the wind and would solve some sail control rigging problems. solid carbon rod could be used for stronger tension, by adjusting hike bar fore or aft you can pre-load or reduce tension to aft mast which keeps the hike bar on centerline without sail input. the mast and luff spar are connected via silicone fuel tubing and a stainless wire internal bent at 90 degrees , by bending the wire up or down produces even more or less tension to hike bar . this could be an alternative adjustment if a larger sail required the hike bar to be fixed. the restrictions of this rig style would be sail area as it must fit within mast and luff spar, I guess a longer bar would allow a somewhat bigger sheet but I think a tall slim sail profile would produce good results in strong wind. a foot note to this concept would be that even if the hike bar was shortened and the counter weight removed, there would still be some sail regulation in gusts due to the luff spar and boom rotating towards the aft mast. this would relax the sheet slightly as a gust hit the sail
Sorry to interrupt the discussion, but how are these ring-like parts called the weight and sails and so on are fixed with and you can see on the fotos? And where can you get them? I was searching for them but couldn’t find a name, thus my search was pretty unsuccessful.
Thanks in advance,
Julian
The ring like things that you are referring to are rubber grommets, they are used to protect wiring in electrical panels. a local auto parts store may have them as well as an electrical supply outlet.
Jim,
Is your hull fitted with a fin keel and bulb balance, or are you relying entirely on the weight on the hike bar ?
If you have no fin and ballast then I’m sure the rules mafia will sting you with the moveable ballast rule as mentioned by Walt. However, if you do have a fin and ballast then could I suggest that you stop mentioning that your hike bar weight simulates the crew movement because this too will probably be declared illegal as moving ballast. Just say something like it is there to facilitate free movement of the sail in the same way that balance weights are attached to the front end of some Sloop Rig jib booms to facilitate gull winging.
I chose to call this Rules Avoidance rather than Rules Evasion.
Cheers,
firstfooty
Thank you Firstfooty for the comment and I see your point, in fact the counter weight has quite an effect on the swing travel. moving it inward towards the pivot produces faster swing movement and vice versa at the end of the hike bar. sail reaction adjustment is what we will call it. and yes the hull has a removable keel and bulb.
This rig might solve some interesting problems…
How tall is the vertical spar? If it’s 12 inches to the top, then you could use this as your B- rig, and still have a somewhat large sail area- maybe even as much as a 20+ inch rig?
The drawback is that you may need to have those extra holes on the deck to accomodate two different kinds of rigs, like a stayless and a Wiebel.
The aft mast is just over 22" from top to step, I am working on two other versions ,a shorter version that has a two piece luff spar that will resemble a lug style sail and be under the 12" limit for b rig, and one version with a 16" aft mast. the 22" version will have a very slender sail similar to the foils that sail boarders use for speed runs . there will be only one extra hole in the deck if planning to use the wiebel rig and a small length of solid carbon rod will fill the grommet when using the light wind MCcormick rig.
I have been looking at something similar, but slightly more conventional. It is also a stern mast, but with a conventional jib, on a conventional jib club, with a long bowsprit. The initial objective was to get the projection of the thrust vector to pass through the pitch axis (LCF) of the hull. If this could be done, the submarining would be eliminated. Unfortunately, there are a number of other constraints that prevent the full realization of this objective. I have found that a simple scheme, without a bowsprit (so it could be used on a diagonal hull) could give a 15% improvement in submarining moment, with a reasonable sail size and shape, on a 13" hull. But my analysis may be too simplistic, and did not consider things like the variation of wind speed near the water surface. So results may differ, and it is probably worth a try.
It would work much better on a 12" hull, with bowsprit, and possibly a small mainsail for balancing (which would then need a boomkin). It appears that an improvement of nearly 50% is achievable.
It is important that the jib not be blanketed by a large main when going downwind, since the jib is providing the lift.
Walt,
I’d been thinking along the same lines as you … started sketching some things to see how the physics and all would come into play. As I am very new to RC sailing in general and footys in particular, the numbers fascinate me.
The one item that I have not yet worked out is what happens in a crosswind (sorry, my sailing vernacular is not so acute)?
In my rather limited experience, with the keel more midship, boats by-in-large tend to blow directly sideways unless the wind is spilled from the sails. With an “engine” mounted more to the aft of the boat, it seems the boat would want to do more of a pirouette about the centerline of the boat in a crosswind. I was thinking that moving the keel toward the stern might counteract this. Also, the CG with sail and/or keel moved aft will also move aft. Is is possible to get the bow too light?
Gotta love it. Will let you know once it starts going from paper to building board.
To explain how the sail is balanced with the keel position on the Bob-About, the jib club projects well beyond the prow, and the mast is a little forward of the stern, which allows the boat to have a normal helm with a normal keel position when beating. When running, the jib rotates to a position where it is about 30 degrees off vertical, and the reduction of submarining moment is about 15% (the cosine of 30 degres). It can be reduced further by increasing the angle (reducing mast height, which also helps in other ways, but reduces sail area), or by moving the sail forward, which would require a bowsprit and a forward keel.
On a 12" Footy, the bowsprit can be used, and the whole arrangement moved forward. Then an additional stern mast can mount a small mainsail to balance the helm without moving the keel too far forward. This is starting to look like a regular sloop, except that the 2 sails are far apart. The aft-mounted mainsail will also have its thrust vector pointing in a helpful direction, as was pointed out by Angus on another thread.
Now that you have me pondering about CE and CLP relationships,is it not true to state that a slight weather helm is desirable ? and what would an induced weather helm do to control at a stiff blow ? we all know that the lead of a sail plan moves around while the boat is in motion and heel , pitch ,wind strength and other factors are the cause but, my concern is that on the Wiebel rig , the CE shifts aft as the hike bar pivots, would this produce excessive rudder input ? I guess what I’m trying to say is it better to set the CE slightly towards the leeward side and have it transition to weather for all round control ?
I have since tested the the little boat and rig with both disastrous and promising results, and I have learned a great deal in the process. first lesson is to use a controlled environment when testing a new rig / boat, I chose a small lake not to far from home for the first test, it was a lightly wooded area and I thought the trees would provide some wind break. the wind was moderate with a few gusts thrown in for good measure and blowing at my back ( second lesson), with my camera ready I performed a quick test of the controls and placed the little boat in the water. I started off on a broad reach and pulled the sail in to get some forward speed, but she quickly turned leeward and took off like a rocket. after many attempts to round her to the wind ,all she would do is turn away and scoot down wind. this was about the time I started to worry as there was not much area around the lake for foot access (third lesson)and it looked as though I would be doing a rescue to recover the boat. she had come to rest in a weed bed ten feet from shore ,and after slogging thru mud and weeds( forth lesson) wearing only sneakers,I walked out in knee high water and the rescue was completed . Cold, wet, and a whole lot discouraged I called it a day. it would appear that the CE was to far forward and after many checks and CLR confirmation , I reduced the aft mast’s length to 19", this moved the CE aft 3/8" behind the CLR. I not sure if the angled sail has an effect on the CE location, as this measurement is quite a bit aft of calculated.lthe second test was performed at a local park with a small wading pool and light breeze coming towards me, she was far more controllable and I could even run close hauled after a bit of tightening on the foot of the sail.she sailed flat in the light breeze with no heel to speak of and release of the sheet would slowly turn her into the wind,further tests at same location will follow with more wind , cameraman,rubber boots,etc.
Tests performed this morning in 11 knot winds gusting to 14 knots, the same results as first test prevailed in that she would turn leeward,even with sails let out completely and rudder control proved disappointing. using a rubber band,I locked the swing arm and found it far more controllable , there was more heel mind you but not as bad as the light wind MCcormick rig at these wind speeds.with the swing arm locked ,I was able to shift sail forward to original calculated mark with better tracking qualities as a result. these little boats are a handful and it’s something I have to get use to. she sailed well in most points ,but I was a little disappointed with her down wind performance, I guess sail area is the cause there.I reefed in the sail similar to that of a roller furling jib and almost eliminated any heel at the expense of any down wind power, I found myself tacking slightly down wind to move at any reasonable speed. If anyone has ideas, please feel free to comment.
I just found this aft mast concept sailing rig, this might solve down wind performance issues. http://www.transitionrig.com/progress_in_2005.htm
Perhaps, but it probably won’t go upwind too well. Notice all the photos are on off wind points of sail, none show it pointing. Sometimes what’s not shown tells you more than what is.
Dont most boats tack downwind anyway because its faster to the mark than straight downwind?
Nick
I’m not sure if this will work ,and maybe the sail designers will find flaws with having two sails side by each, but it does open nicely without any assistance . I used a small home fan for wind and note the shape of sail looking down from top. I thought it would cause the non windward sail to luff, but it expands at the luff and tucks in at the leach. note pics 1 thru 3 wind is coming off the port bow ( if you look at pic 3 ,you will note fan stand on floor )