Are snuffers the work of the devil?

[Daydream believer]

Iain, LW395, Daydream, DJE...I'm very grateful for your insights here. I do wish that I could point at the dates of earlier posts and shriek with laughter, remarking that my last entry in this thread (above)
was very nearly two years ago,
and that I have long since sorted out the spinnaker and chute,???????????????
and that I now need no guidance..WE think that you do
I am now slightly closer
, I am getting there.

Dan
Apologies Point taken- should really have looked at the date :ambivalence:
However, in defence you do admit that after TWO YEARS you are still faffing. So the work is still in progress so the job is not done, & if the fat lady (I heard she got fed up waiting & went on a diet) & is still waiting to sing, then we should be given the chance to hop in & adjust the programme ; & do not say that we cannot, because you put it out to public debate & we DEMAND ( yes!! we demand) the right to lob our ideas into the ring. We forumites have helped design this boat so half of it belongs to the forum anyway !!!

 

[DJE]

But you've got to admit that it looks a bit like the big ugly ring on the front of a Hawk 20.

 

[Iain C]

I’m sorry, and I might get flamed for this, and I know I sail a dinghy (Fireball) which looks like a cross between a Halfords roof box and a coffin, but for me, for no reason I can possibly explain, the Hawk 20 is probably the most aesthetically challenged boat I know. That ring is the least of its problems!!

 

[dancrane]

But you've got to admit that it looks a bit like the big ugly ring on the front of a Hawk 20.

It does, I was going for that exactly...or rather, the version Rogershaw showed photos of earlier here; but ahead of the forestay.

Daydream, what a rant! I never claimed to be above assistance. I said, "I do wish that I could [say] I now need no guidance...but you gentlemen know me better than that."

So, advice is still welcome, although I really thought I'd made some progress. Probably best if I let this thread go back to sleep until I've finished and tested it. See you in 2023. :encouragement:

 

[EuanMcKenzie]

odd one Dan you must be unlucky. Both my ospreys had chutes in front of the forestay!

 

[dancrane]

I wonder if yours were early 1970s GRP Mk2 Ospreys, Euan?

The closeness of my Osp's forestay foot to the very point of her bow, makes me doubt that any examples from this early GRP construction period could have had a chute-mouth up-front.

 

[ex-Gladys]

I wonder if yours were early 1970s GRP Mk2 Ospreys, Euan?

The closeness of my Osp's forestay foot to the very point of her bow, makes me doubt that any examples from this early GRP construction period could have had a chute-mouth up-front.

The first GRP Ospreys pre dated spinny chutes (and I think were built by Moore's of Wroxham) and some retrofitted them. They weren't serious racers though as they were much slower than a Westerly wooden Osprey...

PS, in Penzance SC, we had one of the original Ospreys, which was fully clinker, as opposed to 4 plank...

 

[dancrane]

Sounds a nice boat, Gladys.

A sailing club acquaintence with a diplomatic turn of phrase, looked closely at my Mk2 when she was standing on her gunwale for maintenance, and observed, "Looks quite over-engineered, doesn't she?"

Ospreys which race, mustn't weigh-in below 134kg. I doubt mine is much less than 150kg, even without oars and the curious miscellany of junk which occupies the foredeck compartment.

I'll never race, by choice; but if I was concerned about the boat's sailing weight, I believe the fact that I tend to singlehand, probably makes her higher (rather than deeper) in the water than the slickest, newest fully-crewed Hartley examples.

 

[Iain C]

I'll never race, by choice; but if I was concerned about the boat's sailing weight, I believe the fact that I tend to singlehand, probably makes her higher (rather than deeper) in the water than the slickest, newest fully-crewed Hartley examples.

...and also out of class!

However, assuming Osprey rules are like Fireball rules, no minimum crew weight is stated. Here's my light wind crew (although he's a year older now with more hair so I might have to put him on a diet...

 

[dancrane]

Nice pic, Iain.

As to being in or out of class, I could scarcely care less...

...my point is that while my boat itself may be ancient, overweight and eccentrically modified, I doubt she's much slower in my light airs use, than a new version with 150kg of human ballast aboard.

Not that I'm very likely to encounter another Osp for comparative purposes.

 

[dragonvc]

Dan
For a really efficient conventional spinnaker set up the Twin pole Merlin Rocket arrangement works well and can be done singlehanded in sensible breeze with preparation.But the fastest way to learn is with a quiet racing helm who can explain the sequences and also the hazards such as when overpressed bear away but always leave enough room to manoeuvre.The reason for acquiring racing skills is to do it better ,all the easy ways evolved on race boats.I have used snuffers a few times and did not find it any easier ,troubles with spinnakers arise from tension in all 3 corners of the sail and the ability to let go the right corner a sufficient amount to bring things under control.However we will hear the joy when Dan gets a kite up planes away into the distance and pulls the sail back into the boat with all under control.

 

[dancrane]

Thank you for that, DragonVC. Not only will there be the sound of joy, but of sheer amazement, because I have as limited an idea of how to control the asymmetric in use, as I have about setting the boat up to carry it.

I'm going for a carbon bowsprit, pulled into working position by a rope attached to its inside end; when I haul on the low-stretch line and cam-cleat it, the rear end of the sprit will be pulled tight to an off-centre fairlead on the foredeck, located such that the outside, foremost point of the sprit will be exactly on the centreline...

...while the front end (holding the tack of the sail) will be a good six feet forward of the bow. I guess the tack-line will be fixed rather than adjustable, once I have established how close to the sprit the tack should be held...

...so, launching the sprit will pull the first six feet of the asymmetric's foot out of the chute.

The exaggerated length of the bowsprit is my attempt to get the right shape in the long-luffed RS400 asymmetric, without hoisting its head high above the hounds. I had previously created quite a useable spinnaker halyard height-adjuster, mainly in order to enable hoisting a tall flat 'screecher' type asymm...

...but the danger to the unstayed upper mast was much in my mind when I paid for the larger RS400 asymmetric. So if possible, I hope to hoist the top of its 21ft luff to the Osprey's standard spinnaker head height (only 15ft 6 inches above the deck)...

...hence, I needed the tack as far ahead of the bow as possible, to allow a healthy but not too-full curve in the luff.

I'm aware that a big A-sail on a long bowsprit is likely to create unwelcome lee-helm. I haven't encountered that before, so anything anyone can tell me about it, will profit me.

I realise that nothing will be as instructive as trying it out, but some cock-ups can be eliminated by foresight.

Having (hopefully) created the means to carry two quite different shapes of asymmetric (one for close reaching, the other for sailing deeper), it's tempting to make a double-chute, such that I can deploy whichever kite suits the circumstances.

All a bit ambitious considering I've never yet hoisted either while afloat, and especially when the screecher only sets properly if it's hoisted high enough to endanger the upper mast...

...so, don't expect any immediate photographic proof of my success, or even of spectacular disaster...but I'm working on it.

 

[lw395]

The luff of an RS400 kite should be quite curved, if it's 21ft along the tape, I would guess only 19ft straight line from tack to head. Which suggests putting the tack roughly 11ft in front the mast.
Do not worry about the lee helm, boats like the 400 are fine downwind, you just leave the plate fully down rather than pivoting it up and back as you would with a sym kite boat.

 

[Iain C]

Dan...be aware 6 foot of unsupported bowsprit is a lot, and you will need a proper piece of tube for that...don't faff around with windsurfer masts etc as they won't be up to it. As an aside, I have a piece of C-Tech tube that was destined for exactly that purpose for sale...PM me if interested.

The issue with lee helm on a big assy boat, when trapezing, is that you get pushed off the side of the boat. I used to race 12' skiffs, which in the size of assy to size of boat ratio, win hands down. On these boats, you need to throw away the mantra of "flat is fast" which is drummed into every dinghy racer from day one, and actually let the boat heel until you get an acceptable level of lee/weather helm balance. Obviously you are doing this by going up/down on your heading...don't be sheeting in/out, just steer the boat.

Wow...this first shot was 12 years ago now!

The boats have 4 rigs, this below shot is the big rig and heel is even more pronounced...

 

[dancrane]

The luff of an RS400 kite should be quite curved, if it's 21ft along the tape, I would guess only 19ft straight line from tack to head. Which suggests putting the tack roughly 11ft in front the mast.

I've tried to draw it on paper with fairly accurate measurements, and I think you're right. The photo below (with the head hoisted about 2ft above the Osprey's standard spinnaker halyard sheave, and about 4ft of oar holding out the tack) seems to me to show the sail in pretty good shape...

...but if I want to avoid significant stresses to the mast above the hounds, the halyard ought to be led through the standard spinn sheave. Lowering the head that far will alter the sail's rather tall profile as intended on the RS400; I'm only hoping that 2ft added to the sprit, will counter the 2ft drop in head-height, maintaining a usable profile overall.

Dan...be aware 6 foot of unsupported bowsprit is a lot, and you will need a proper piece of tube for that...don't faff around with windsurfer masts etc as they won't be up to it.

I have to laugh...the idea of the windsurfer mast (like the 100% carbon fibre example I'm using) came purely from this forum, when people were keen to warn me that an aluminium spar wouldn't be up to the job.

The fact that the sprit must emerge from the boat somewhere, seems inevitably to raise stresses at that point. My exceedingly simple inverted U-bolt is sure to localise those pressures. Initially I concluded that I ought to build-up the thickness of the sprit where it will pass the U-bolt, and I did so with epoxy/fibre layers...

...all of which is probably still inadequate for the stresses, as well as making the sprit almost too fat to fit through the U-bolt.

By the end of last year I had reached a new level of Heath Robinson inspiration, and at present I still think this solution will enable the lightweight carbon pole to be strong enough for my light-wind purposes: dyneema bobstay and port & starboard sprit-stays.

Yes, it sounds like a fast-track to a hideous tangle, but I found a way to attach the outer ends of the stays, to the sprit-retractor line...

...so after stiffening the sprit in use, when I lower the asymm, the stays won't drag in the water but will retract taut along the sprit.

So in theory at least, the light weight of the sprit (around 2.5kg) needn't be disastrous. Of course, if you're selling your C-tech tube cheaply, I'll very happily consider it...but if it's strong enough not to need stays, isn't it also too heavy to be ideal?

(Great skiff photos, by the way! :encouragement

 

[lw395]

In that photo, the RS400 kite looks too stretched from tack to head. There are plenty of photos on the web showing what they should look like.
Regarding the strength of the pole, ultimately the forces on it depend on how hard you pull on the sheet, in how much wind.
A carbon pole will bend a long way before breaking.
Have a look at the B14 picture here:
http://dynamicsails.com/gallery.html
It's the one with the pole bent up a foot or more.
Those B14 poles are a couple of metres long and weigh very little. They survive 30 knots of wind, with two blokes hiked out on racks that make the boat 10ft wide. The kite area is about twice that of the 400.
If you want to make your Osprey rig take that kind of loading, then you have bigger problems than the pole. Your mast does not have the kind of support needed for those loads, so I would suggest you are better off with a pole which will firstly bend and depower the kite in gusts, and secondly break before the mast.
If you start beefing up the pole, then the mast, then you will find the next weakest link, probably the bow structure where the leverage of the pole is significant.
To some extent, the forces from sails are also related to the mass of boat hanging on the bottom, with the weight of an Osprey you are not starting from the right place for high performance.
If you want a skiff, you should sell the Osprey and buy one.
If you just want a kite for making progress in F3 and below, you'll be fine.

 

[dancrane]

If you want a skiff, you should sell the Osprey and buy one.

Thanks LW, but that's specifically not what I want. We're working back closer to the original theme of this thread...I've always been a dinghy sailor who'd like a yacht, and my keenness to increase the dinghy's sail area is simply in order to see the boat sail at her best in the gentle winds I go out in - the kite would invariably be for pretty tame conditions.

If you just want a kite for making progress in F3 and below, you'll be fine.

Thanks, that's the plan, although the bending bowsprit photo in the link you sent, was well worth a look! :encouragement:

As Iain said earlier, I'm likely to have lots to learn regarding controlling 300sq ft of sail with only my 70kg as ballast, including letting the boat heel, and I may be steering pretty wild to prevent capsize in any gusts over 8 knots. Re-creating the thrilling and rather terrifying photogenic demonstrations of what is possible under a cloud of sail in a moderate or strong breeze, isn't my aim...

...I just want the Osprey to make good speed on days when even my minimal weight and 150sq ft main/genoa don't come close to getting the boat planing. When there's enough wind to endanger the spinnaker set-up, I'm very unlikely to dare to hoist it!

On that basis, I may or may not need bobstay, etc to reinforce the bowsprit...but I'm inclined to make it stronger than required, because while I may not have the testicular fortitude to go out in search of high speed thrills, I can't discount unpredictable gusts.