Hi All



Looking at the spi launching options for single handed T 4.9 I've decided that I will probably start with an IO snuffer and work on getting the set-up of the kite (design. sheeting etc) right and then possible review the launch system.



The question I have relates to the angle of the spi pole in front of the boat and which snuffer to use.



The IO snuffer is available here in Australia in two configurations with different angles for the snuffer head. One version has been developed for the Nacra 5.8 with front foil where the spi pole passes under the foil meaning that the pole is pretty low above the water. I've been told by Nacra sailors who use this one that on the 5.8 the low clearance is only a problem when the wind is light and the sea is choppy causing the boat to hobby-horse and the bag sometimes drags through the water. The head of the snuffer is set at a flatter angle on this fitting than the 'standard' snuffer as used by the I 17 etc.



From the photos I've seen the Inter boats have their spi poles, bag and snuffer head way up in the air where it would be affecting airflow over the mainsail up wind.



I'm thinking that the 5.8 snuffer would be the way to go to keep the dirty air down low and reduce the affects up-wind. I guess thi would also enable me to develop a spi with a longer luff which is my aim.



Has anyone got any views on whether there are any advantages of a 'low' pole over a 'high' pole or vice versa. Also what should I be aware of regarding the angle of the snuffer head to the pole (ie which fitting would be better)



While I'm here I'm also intending to rig my boat with a bridle / single forestay rather than twin forestays - is one set-up better than the other when sailing with spis ? My thoughts are that one stay is reduced windage and less likely to get in the way of the spi.



All ideas gratefully received



regards

James



T4.9 AUS 153 "Woof"

keep the pole as low as you can.

the challenge is getting low without the pole digging in upwind..



Luff length is king

James,



Have you considered teh Guck snuffer in relation to the IO snuffer ? Same principle but the loop is halve way down the pole and the bag is more aerodynamic too. There shouldn't be much price difference too.



http://www.guckinc.com/skunk.htm



See picture at attachment. Just an idea.



On the issue of high and low and the double or single stay setup.



The lower you go with your pole the more you'll put the bows under bending stresses. Especially when you you lower your bridle strop too.



Alternatieves are to keep the catrigged stays and make an extra stay of small diameter dyneema line or something for the pole. The reduction is stresses caused by the absence of a bridle strop can then be used to lower the pole.



OR



You go for the bridle strop anyway and fit a pin between the pole and strop a la intl. tornado's. This would also allow fitting a high aspect jib sheeted from the mainbeam if that is of any interest to you.



I'm fitting the last option to my boat.

The last option also has the extra advantage that the pole is alot less likely to buckle and therefor I can get away with a smaller diameter pole with less wallthickness. I think it saves some 0.5 kg's to 0,75 kg's on the setup.



I can look up my calc when needed but that will take time.



A single stay does allow windward drops and hoist but these aer only done when manually handling the spi.



Wouter

.

Thaks for the feedback.



With respect to the Gluck snuffer I'v had a look at it but I have a couple of reservations about getting one for my first configuration. Firstly it appears that the kite has to be hoisted to the end of the pole and I assume this requires another line - I'm trying to keep this as simple as possible because I'm going to be learing in an area where 15 to 25 Knots and 2 metre seas is the norm. Secondly I can get the IO snuffer over here (head fitting) for about $500 AUS ($250 US) which I think is a lot cheaper than the Gluck - and I really think that my first setup will be discarded after a while after I've learnt a few things so cheap is good. I also have concerns about the clearance of the bag under the trampoline in big waves - we often get waves washing over the front beam.



With respect to the bridle I was intending to use the minimum height allowed by the T4.9 rules - AHPC do not recommend any lower - and have a strop from there to the pole under.



If I used a rod as per Wouter's suggestion would that eliminate the need to have wires from that same point (Pole midpoint) to the forestay tangs?



As for the increased loads on the bow from the low pole I hadn't thought of that one although sailing cat rig the loads would be less because I dont have a jib (?) I guess the thing to do is keep an eye on it and adjust as required. Has anyone determined what the luff length on a T 4.9 spi is that doesn't drop the pole too low ? I notice that the I 17's use a short strop between the snuffer and the tack of the spi to get it clear of the pole arrangement - I gues in the first instance I could get a 'safe' luff length and keep extending the strop until I lowered the pole as far as practical and then the next kite luff could be made longer to suit this setup.



James

James-

Comments re the "skunk"-

Yes, it's expensive-

Windage is MUCH less IMO than pole end, can use "stock" pole w/o shortening and whatever size pole you want (IO snuffers here use 2" poles), can mount anywhere along pole desired (and move easily enough)-

No extra line is needed BUT you lose the option (with a single line) of adjusting the tack height underway (uses a double block inside the pole ala "stock" T 4.9 bag launched option w/ single halyard line)-

I now put my "bag" above the tramp (it's offset to one side anyway and cat rigged isn't in way of crew/jib) so "drag" is no longer an issue- Real trick would be to have tramp built to accomodate bag above-

That's VERY cheap for a snuffer head!



Regards-

Kirt

I hear that Yves from Mystere is making his own snuffers and skunks. The snuffer on the M4.3 is glass and looks good. Rumor is $300 for a skunk head (road kill?). If you are interested you might contact Jamie Diamond who was putting together a group buy. He's at:

jamie.diamond@sailocra.com

In relation to developments of the snuffer, I thought I would convey my thoughts and what I am developing for my Taipan.



Making a snuffer out of carbon rods and attaching this to the side of the pole just in front of the bridle (Guck style). Carbon rod is from a kayak oar and was relatively cheap (approx $35 aussie) but also very light and strong. Cut it up and fibreglassed this together in a rectangular/house shape with inserts and fancy little joins to lock the pieces together. Currently needing to sand it down to make all smooth before putting on a final layer of carbon. The spinnaker chute bag will wrap around the rods making a smooth entry for the kite. The chute will then go back underneath the tramp about 50cm and attach to loops sewn into tramp.



The spinnaker retrieval rope will then go through the end of the bag and back to a cheek block attached underneath the tramp (or rear beam have not yet decided). It will then go forward (still underneath the tramp) to an exit block about 2 feet from the front beam in the middle of the tramp. Made a small metal plate to be sewed into the tramp to hold this on. Crew will pull the spinnaker down from this point. The tail of the retrieval is also the halyard (one line for both) so the next point is an upside-down 180 situated on starboard side of mast about 2 foot up where the kite will be pulled up (Tornado style).



I have a seperate line to pull the tack out which I am in control of which is 2:1.



This system should work a lot better than the bag on deck which I am currently using. It is sort of an adaption of what the Tornados are using. Let me know what you think, comments etc.



On another point, using the kite the other weekend in 12 to 18 knots gusting to over 20 was an absolute blast. Lots of control with no load or helm on the rudders. Basically point and shoot stuff. Still working out where skipper and crew need to sit to get best VMG. Can't wait to get it all properly organised and for the new season to start.



Cheers

James