Keel-Forward Footy

Footy Class General Discussion (Footy)
1

The long winter, with ice on the pond, has allowed a lot of time to cogitate on various Footy design possibilities. I have come up with a combination of several techniques to get possibly a very fast boat (or possibly an embarassing disaster).

The design starts with a 3-D hull, much like Chris Staiger’s Pool Shark. It is a little lighter, built from depron foam sheet (14 oz total, including 8 oz bulb).

Then it gets weird.

The keel is mounted up front, to move the CLR as far forward as possible. The chines are rounded off as much as possible, so the keel area dominates the hull area (but this didn’t help much).

The forward CLR allows the sail area to move forward, away from the liomitations of the rule box. A long bowsprit waas added, with the intention of having only a jib, and no mainsail, with an aft-mounted mast.

The boat was built, with a large jib as far forward as I dared, and tested in the bathtub. It obviously had too much lee helm. So a second sail was tried, with a less ambitious forward protrusion, and appeard OK in the bathtub.

Today the ice was gone from the pond, so the boat was sailed. The wind was fairly strong.

SURPRISE - it works. It sails to windward without a noticeable helm. The sail shape needs some work, but that was expected. The mast needs to move further astern to allow a longer sail foot and further forward protrusion, to take advantage of the bowsprit, and reduce the sail height. This will also allow the jib to provide some lift downwind, to reduce submarining.

I had been concerned that the forward CLR would interact with the CG to make the boat directionally unstable (it is like putting the feathers at the front of the arrow), but it didn’t happen.

A picture of the boat is also shown below. It will be named “Slightly Unconventional”

2

That’s some real creative thinking, Walt. I can’t wait to hear how it looks against other boats…you may have a breakthrough!

Bill

3

Walt, an interesting idea.

Keep us appraised of developments.

Is this thinking out of the box or in it?

4

looks like my deltra rigged footy… with the keel in the “wrong” spot…

being that I have not been paying much attention to footydom recently i know th e boats can go on the diagonal but since the bow sprit is attached to the boat is it allowed to extend beyond th e box?

5

Marc, your success with the rig on your RG65 bodes well for Walt’s Footy…should be interesting to see how both develop. Come on back to Footys…we’re finding that things we learn in Footys are useful on RGs and vice-versa.

The bowsprit is defined in the ERS as a “spar.” Since the Footy rule says spars can extend above the box, that applies to the bowsprit…it’s legal. Of course, the hull still needs to be within the box, so some care needs tobe taken to engineer the bow so that it all works.

Bill

6

Walt, will you be able to move the mast farther back and still clear the box?

Bill

7

The mast location clears the box by about 2", so it can move aft by that amount. The original intent was to leave some room for a backstay, to tighten the jibstay and prevent jib sag. However, I soon realized that there wasn’t enough room to get a decent angle on the backstay. Consequently I was worried about the mast being driven through the bottom, or forcing the seams open, because of the very high force generated by the tight backstay angle. Someone on this forum, a few years ago, had mentioned the idea of using a carbon tube for the jibstay. So I tried that, and moved the backstay down on the mast to get a better angle (you can see it in the picture). So now the backstay and the mast stiffness are both used to support the jib. It requires some additional playing with the jib, because there is less tension on the jib leech. But this arrangement allows moving the mast aft, while keeping a semblance of a backstay.

Any time you do something different, there is an additional set of problems to solve, which makes life interesting. I also tried an electronic servo expander on the sail servo. Unfortunately, it has a greater range than the mechanical stops in the servo, so the battery died after about 15 minutes of putting out 1.5 amperes into the servo (trying to overcome the mechanical stop), limiting the duration of the maiden voyage.

A question for Marc or Bill - what sort of RG65 rig are you talking about?

8

walt, I did a skinny V12 with a delta rig, and a round ranger hul rg65 with a delta rig…Ihave a couple threads talking about it… here some pics… one thing I did on the footy is I put 1/2 of a diamond stay which allowed me to bend the mast aft to add fore stay tension its not pictured, but I can get a pic if you like

9

Marc,

I had been thinking of adding a diamond stay above the box limit, with the backstay entirely below tyhe box limit. This would put a bending stress on the mast only at yhe junction of the two stays. But I am waiting to see if the really stiff jib stay is sufficient. It worked OK yesterday regarding jibstay sag, in a strong wind. But I wasn’t happy with the overall sail shape. How well did your V-12 work?

10

it worked well at the local level. never had a chance to try it against any of the pool sharks. my v-12 was a skinny version that Victor never went into production with. I had an immersed transom I could have gone diagonal with it an made a canoe stern to reduce the turbulence. did real well in light air and in the puffs it woudl lift the bow to help reduce sumbmarining down wind.

essentially you have a unarig but its more tunable… I had a second smaller sail which just had a longer forestay so all I had to do was unhook the forestay from the crane, and un hook the sheet and the sail came off. new sail had the fore stay and jib club on it. so it was a pretty easy swap. maybe 60 seconds… I can take some closeups of the footy if you like let me know… we stopped sailing the footy class so i ransacked all the servos, now its just an empty shell hangin on the wall…

11

Marc,

I agree with your comment that it is similar to a Una-Rig. In fact, this hull design could just as easily take a Una-Rig, which would also benfit from the forward keel, to put the sail area where it is less restricted by the rule box.

Looking at the picture of your V-12, it looks like you may be using a carbon tube as a jibstay. Is that correct? The mast also looks very robust, and I was wondering if you needed the diamond stays for additional stiffness, or to substitute a thinner mast?

Any further information (or links) on your delta rig would be greatly appreciated.

Thank you for your interesting and helpful comments

Today I sailed the boat with the original rig which had looked bad in bathtub testing. It looked equally bad on the water.

12

forestay was 65llb spiderwire thats dark green in color. the mast is robust. its actually a 2 peice mast, its what I had laying around… I felt that if I went thinner id get too much deflection. with no shrouds or back stay, wanted to keep it as s tiff as possible…

with such a long forstay even in moderate winds it would fold over. so the extra tension did bend the mast…

when I get home form work I’ll take detailed measurements for you.

13

walt…

mast 74cm
jib boom 34 cm
pivot 9cm from fore most point.
jib luff 74cm
jib head 3cm
foot 31.5cm
leech 66cm
jib boom dia 3mm
mast dia 5mm
mast crane 4cm
rear spreader 45 cm from deck

walt also remember I only used 1/2 of a diamond to put aft bend in the mast to counter the forestay. With the 5mm mast I was not worried about side deflection…

also do a search on rcsail.net for the delta rig… claudio has alot of info…

14

Marc,

Thank you for all the good information. It gives me a starting point for a successful sail.

A question about your picture - it looks like the jib is sheeted at the forward end (like some McRigs), but it might just be a defect in the floor under the boat. There is also a fitting further aft that might be for the jibsheet, but I don’t see a line (it might be too thin to see).

15

walt,

that is just leftover extra string after I tied my knots…i took t he pic before I trimmed. just in front of the mast is my thrudeck fairlead which goes to a fishing pole guide that is attached to the deck. just forward of the keel…

16

Marc,

Thank you again. I also took your advice and looked up Caudio’s thread on the delta rig. It contains more information than I could have imagined, including a bunch of your own experiments on the v-12.

17

Progress Report

I have spent the last 2 voyages experimenting with a very different sail. The mast has been moved aft as far as possible within the rule box, and a storm jib with a 16" foot and a 16" leech has been tested. obviously, it has a 45 degree sweep angle, which is quite extreme. Claudio’s thread on these rigs recommended a much more vertical luff, but I had to try it. There is no room for a decent backstay, but the carbon tube on the forestay works very well. The helm is OK, and it will tack through 90 degrees. But the sail is too full, resulting in extreme tenderness. I will probably revert to a taller sail, or perhaps revert to a McRig. But so far I have seen no reason to abandon the keel-forward concept, since it should still be advantageous even if I switch to the McRig.

I am probably not taking the most direct path to a successful boat, but there are some things that I want to try with the rig.

18

More testing

I have reverted to the red sail shown in the picture at the start of this thread. It is actually not much different from the sail that Marc had been using in his delta rig. After some adjustments, its shape now looks very good when sailing, despite lack of backstay.

I have noticed that the boat appears very tender, despite the relatively small sail (11" x 27"). This is caused by tthe relatively shallow keel, which in turn is caused by the tilted position in the rule box. So I have added an ounce to the keel, using lead tape (the bulb is now 9 oz, and still floats on its designed water line). The boat handled reasonably well today in a moderate but shifty NW breeze, although not entirely to my satisfaction.

The rudder is relatively small, because I thought a smaller rudder would be feasible due to the large distance behind the keel. I willl try a bigger rudder next.

A caveat:

It is possible that some of the behavior I saw today was caused by directional instability, not the variable wind. So I would not advise anyone to copy this design until that possibility has been eliminated by further testing.

19

Hi Walt,

Going to a larger rudder is a good idea but it may mean that the rudder tube has to move forward to get full throw in the confines of the box. Going with a larger area rudder will also move the Center of Lateral Resistance a bit aft and create a more balanced relationship between the foils. This may help with the handling and performance issues.

I would use a minimum area keel fin, something along the lines of the helicopter main rotor blades that have become popular on new Footies.

Fitting your experimental configuration onto a slimmer hull like the Bill Hagerup’s Ranger or one of his later Cobras would give you a proven hull platform. The Ranger would actually be too light a displacement for this experiment until the internal structure to support the keel and mast was worked out to be as light as possible but still robust enough for the loads. Maybe Bill can come up with something specific to this project?

I recommend a slimmer hull because some of the current Footy thinking is that slimmer, sleeker, more M Class type designs will offset loss of righting moment with reduced wetted surface and wave making, simply transferring more power into forward motion and less into excessive heeling.

I think that you have taken an interesting tack, and you certainly are the man to undertake the experiment. You should give yourself half a chance to really succeed by building the best platform to mount your new configurations on. We will all keep watching to see how you do.

20

Neill,

Thank you for your comments. It is very helpful that some knowledgable people are reading this stuff and commenting.

The current hull is quite slim and light (2.9" beam, 1" draft). The shape is essentially a stretched and narrowed Bob-About 2, with rounded chines. At this point I am not too concerned about maximizing speed. But I obviously made a mistake in allowing too much length for the bulb in the rule box, which gives me about 1" less keel depth than Bill’s Ranger. I probably should have made the bulb shorter and fatter, and perhaps put some lead on the bottom of the rudder to balance the boat. The fat tapered keel is a result of trying to keep a reasonable area with a shorter depth, and minimize tip loss caused by the necessary rake angle. But it is also detracting somewhat from the righting moment, as it puts displacement far below the water line. The large taper tries to keep most of it as high as possible. I am reluctant to build an entirely new keel, as it was a major undertaking, and would probably need a new hull as well, so will muddle through until the basic concept is proven or deemed unwise, at which time a bunch of improvemnts will be implemented.

The present rudder is taken from Bill’s Ranger, but reduced 75% in size, to approximately halve the area. The placement of the rudder pivot was chosen to allow a much bigger rudder if needed.