Thinner Footy?

Footy Class General Discussion (Footy)
81

Andrew wrote:

“Do you think I am sailing VT too light - and losing momentum, or too heavy so the immersed hull stops quickly, or badly (change the nut behind the sticks)”

Andrew my experience so far would lean towards your first assumption, sailing too light. My first attempts were lightly ballasted and they would occasionally go very well but too much of the time they didn’t go at all. Any mistake, windshift, puff or chop meant trouble. Obviously just adding ballast to a hull that was designed to sail light may create more problems than it solves.

I look forward to someone cracking this and coming up with a lightweight Footy that will sail well on all points and conditions encountered during racing. Lighter should be faster but I haven’t come up with the right combo to make it happen for me.

I laugh when I think my current boats scaled up to a one meter would have a reasonable 6"-8"/150mm-210mm beam and weigh a whopping 27lbs/12.4kg. Of course they would also carry 1620 square inches/10,450 square centimeters of sail.

Take care,

Brent

82

Angus,

Regarding your third point. I like the idea very much. My last designs have a static and a dynamic waterline. All the Footy’s I’ve seen dip the bow as soon as the rig starts working.

In fat boats the degree of dip is less than with finer entry boats. The fat boat has low and wide reserve bouyancy while the thin boat has tall and thin reserve bouyancy. Thus the fat boat generates the same resistance to pitch while rotating less on the pitch axis.

All that to say I ballast my boats so the static waterline has much bow out of the water possible and the stern can have just enough freeboard aft to keep my rudder servo from getting swamped. My current practice keeps the full 3"/76mm of stem above the water and about 3/4"/19mm of stern out. Given a choice I move the internal ballast (batteries) as far aft as physically possible and adjust the keel bulb accordingly.

Dynamically the boat sails with about 1-1/2"/38mm of the stem submerged and the stern rises by about 1/2"/13mm. My stern is quite deep on these boats so it leaves a fair amount submerged.

What finally dawned on me is that only bouyancy that does me any good is the part that hasn’t been used yet. Anything that is already in the water can’t do any more to resist roll or more importantly pitch.

In this sense a long bow overhang is all reserve bouyancy. I say build it. :slight_smile:

Take care,

Brent

83

Patience Mr.Carter, Sir!

It’s Chris Dicks Trohy time! We have other things at least as outrageous as Xmas stocking fillers!

:zbeer::zbeer:

84

If extending bouyancy ahead of the forward end of the static waterline is the new topic on this thread then perhaps a few views of “Brujo” at play will be helpful. These photos were taken in trials, before the sail markings and the final configuration was worked out.

You all may recall my article in the AMYA Quarterly (which now is reprinted on the Footy website in the articles section) about the unusual placement of Brujo in the measurement box, both diagonally and on an angle with the stern waterline 6" below the box rim. One of the reason’s for placing the boat in this orientation (other than the extended waterline length) was to incorporate a bow that extends beyond the static waterline. The cut-water deck design is also integral to the design. During a nose dive it functions to keep water from loading up on the deck, making the dive controllable. I also use it to raise the mast up so the rig can clear the top of the box without any strange cutouts in the sail profile.

After sailing Brujo I think that this is the way I am going to design footies. I am currently developing a version of my new hard chine design, “Tanto”, with the Brujo configuration, although Tanto II will only sit stern down in the box by 5".

85

One more pic!

86

Hi Brent, with reference to hull weights and different construction techniques I thought you might be interested in how my foam core method is working out on a narrow hull. I am using a hybrid construction where a 5mm ‘Cellfoam’ bottom is added to a hot wire cut foam core. This is allowing me some sanding room to create a soft chine. Sides are skinned in 1/32" balsa and the deck is 1/32 ply but could be 1/32 balsa to save weight. As pictured the hull with RC plate installed is 34g, with the ply deck this rises to 43g but I do like the hard surface of a ply deck for taping covers etc. This is a 90mm max beam 320mm long diagonal hull.

I really enjoyed and absorbed your explanation Flavio, thank you. You and Angus always give me lots to think about. Inspiring thread Brent and Neil your footy looks excellent on the water. I as always have lots to learn.

Graham

87

Interesting, Angus…the foam hull I posted here is designed with rather circular sections intended to keep wetted surface down, rather fine ends, and was designed to maintain a nice shape through 45 degrees of heel. In fact, that’s why I wanted to do a round hull shape. I think it’s in your lead-sled category, though, because I’m keeping displacement between 500-600 grams because of the momentum issues we’ve seen with the lightweights.

It always disturbs me when we seem to be thinking along similar lines…:wink:

I might have to go to Florida to test it though…water will be hard here soon.

Thanks to all for the contributions to this thread…it’s become very interesting.

Bill H

88

fwiw…my “melted” v-12 in racing trim. batteries, rig, ect 565g which turns out to be 40 grams lighter than the same model v-12 with identical rig and batteries. but that boat has a treaded rod through the keel and un painted hull

she floats with about 1/3" of her transom under water. but I have a feeling that it wil rise up since there is not much bouancy at the bow…

I ended up going with a double purchase system for the sheets using my “patented” fishing guides as turning blocks…and small antenna tube for my fairlead.

hi aspect swing rig, all carbon
nicads
8oz bulb(before minor shaping)
futabe 3115 servo (sail)
spectrum micro servo (rudder)

89

Marc,

Your boat and rig are looking very good. I look forward to hearing how it sails. Keep in mind you could lose 20 grams in the hull by going to standard AA’s and nearly 60 grams using the non rechargeable lithium AA’s. As others on the site have posted they are expensive but they seem to last forever.

How is the graphic on your jib done?

Take care,

Brent

90

i could save even more weight by going LIPO…:slight_smile:

I could save weight by omiting the paint as well, but I had to cover the bondo with something…:slight_smile:

The batties are what they are…its what I have, so I use em…

The sails are courtesy of Hank Buchannon from New York. I saw his at the Region 3 Vic championship (he put his v-12 in the water. I liked the sails so much I had him make me suit in exchange for some lead bulbs. I fear though in a real breeze they would be a bit overpowering…

Graphic is Sharpie traced…printed from the internet…Every boat of mine has a gator on it somewhere…

I figure if I was real careful with the heating/bending and not having to use bondo I could get down to 500 and below rather easy…

I’m waiting for all the paint/lacquer to dry before I drop it int he water later today…maybe in an hour or so…

91

it works…kind of…

my sails are not sheeting out…I’m going to try to put new line in before I start surgery. I’m hoping that I got some glue or something on the sheet causing it to hang up…she has a bit of weather helm…not sure there is much I can do about it though…

92

I’ve been thinking about the post by my Italian friend, Flavio.

I have the greatest respect for his design expertise, and the boat he built for last year’s race at Birkenhead was a thing of beauty…Ferrari vs. Shelby.

But it seems to me there’s a missing piece to his analysis of skinny vs. wide hulls…and that’s sail power.

I’ve built and sailed both wide and skinny…in fact, I may have been one of the first to do so with MiniMe and Halfpint…and I just don’t see a real difference either way. I like things about both. Skinny hulls are pretty and look more like real boats, and wide hulls are blunt, powerful instruments.

I believe, based on experience rather than theory, that wide hulls can carry enough more sail to reach hull speed, thereby overcoming differences in drag and so on that may seem to give skinnys an advantage. If that weren’t true, I think we’d see more dominance of one vs. the other in regatta results.

So at the end of the day, I think it comes down to getting whatever boat you have right…to have a well-designed hull, regardless of beam, and a well balanced rig, and a good pair of thumbs.

That’s a winning combination…and isn’t it fun to try to find it?

Bill H

93

To Bill,

you are right, all boats are good provided that they are well built and skippered - as you a have clearly shown us with your nice cobra : an “average” boat , far from radical but alway heading the fleet

Few words more about my “scientific” analisys of footy hydrodinamic:
in a comparison between two boats of same sail carrying ability , the slim hull seems to have less drag in comparison to a beamier one

To Andrew ( about strange behaviour of light displacement boats “angus style” ) :

Yes you are right, the sudden change of gear -from slow to fast- of this kind of boats was clearly remarkable during birkenhead contest.

I have thinked a lot about this point and these are my reflections :

1 - due to the fact that this “strange” behaviour was the same on different similar boats with different builders/skippers, it seems to me that this is not a “problem” with your boat only but a common characteristic of this type.

2 - sudden change of speed was remarkable with reference to the average speed of other models

3 - it seems to me that light displacement boats were faster during wind gusts, and slower in light conditions.

4 - during birkenhead contest, weather was very irregular with wind strengh continuosly changing from zero up to almost 30 kts

This is my explanation ( not an ultimate truth, only another technical reflection )

basically there are two performance parameters that can express a boat speed potential :
a) sail area / wetted surface ratio : an index of light wind performances
b) sail area / displacement : an index of stronger wind sailing

due to the fact that hull wetted surface is not decreasing as fast as displacement is,on light displacement boat :

a ) SA/ WS is more than the average ( slower )
b ) SA/ displ is more than average ( faster )

I have not the real figure of this kind of boats,( may be these are confidential informations in angus secret locker ) but average data for normal boats are :
a ) sail area is about double than wetted surface ( hull + keel + rudder )
b ) there are 200 - 300 sq cm of sail for 100 gr of displacement

Conclusions :

Based on my reflections a “weight watcher” boat -low displacement, small sails-
seems to be suited for:

  • not light wind conditon
  • quite regular weather days
  • no waves race field ( lack of momentum would kill these model when tacking against wind and waves )

In any case a boat that his quite different from other competitors is always a risky options : may be you are much faster, but may be also that you are quite slower than the rest of the fleet.

As discussed with Bill sipping a good british beer, conservative boats have a wider “use specrum” and over a long time they are more regular performers

In any case I am happy too that there are so big differences among our small footys, and in the next future I will try to build my own light narrow slim boat “angus style” to test “hand on” what happens.

My own way, obviously :wink:

Flavio

Folgore ITA 5
Presto ITA 13 ( coming soon )

PS this a model ( not a sailing one ) showing my interpretation of “angus style”

94

Flavio,

Thank you very much for thinking about, and writing down, your thoughts on the question about VT and “stopping”

Much of what you say fits neatly with what I would expect by observation as well - for example fast catamarans with very low inertia are going to be difficult to “keep moving” in rough conditions.

This is a terrible disappointment:confused: to me because I had hoped that just replacing me with a sailor would turn VT into the world-beater:D

I will try and make some simple calculations about sail area/displacement/wetted area and see what we can conclude

I look forward with very great interest to seeing your Italian Narrow footy
btw - what does Footy translate to in Italian?
regards
andrew

95

To Andrew…

may be that a better than average skipper is required for best performance of VT, but if my records are good one of their sistership was belonging to Gary, - a very skilled guy - isn’t it ?

aiming to a less sensitive model, solutions to be investigated are :

  • a thicker keel, with a rounded leading edge to avoid abrupt stalls
  • a smaller rudder ( in comparison to the keel ) to reduce sensitivity to helm setting
  • fuller sails

in any case, all these options are worsening upwind ( and downwind ) top speed

you can try to make a trial to see “what if”

flavio

96

On Flavio’s commebts, I agree with the first. Since nobody seems to go much further with the ‘designer’ in this game tha some roigh approximation of the hull lines, I’ve no idea what you’ve got as a keel but my drawing if I can find it is for either a 9% or 10% thickness ratio.

On the second - better to use some sort of steering mechanism that allows the nut on the stick to do what he likes in the general area of helm centered without actually having much effect on the boat,

On the third, a think a better route might be a bigger rig and softer (or adjustable Z-bar. This should power the boat up better in the lulls but flex faster and dump more lift in the puffs.

Just a thought

:graduate::zbeer::zbeer:

97

You never know where a good idea will come from. My wife had come down to the local pond to visit while I was testing the new Slat Rig on BC3 one evening. She is a sailor but has no interest in the Footy other than the occasional comment on their appearance. (She thinks there should be concours judging at regattas.) BC3 has never been a favorite in this category. The successful experimental white anti-dive extensions only brought more derision. Her idea was to make the extensions from a clear material. Then you could mark deck rails on them so from any distance they might enhance rather than detract from the looks of the hull.

The extensions do help keep the bow above the surface. When a gust hits the bow will dip for a moment while the hull accelerates but then it pops up, sheds the water and stays up better than it did without them. Try a set on your favorite hull, you can always just tape them on with scotch tape for a test.

Take care,

Brent

98

Wonder how a single sponson would work, now that the "AA"s have been relaxed…

99

Nigel,

I say give it a shot. I’m sailing a 50mm beam 470gr boat (280g ballast, 70g battery pack) with good results, especially in chop. I was going to go down to 38mm beam with the old battery rule just to see the results but with the new rule that may not be extreme enough. WL to beam ratios of 9 to 1 or even greater should be possible now. My old standby may have to be reclassified as a fat boat at 100mm. :wink:

Take care,

Brent

100

Is a sponson considered to also be a hull, or would it be restricted from containing any batteries?

Regards,
Bill Nielsen
Oakland Park, FL USA