Questions by Phill, who is unable to post them.

Folks,

I've been trying to post some questions on the F16 Forum but for some reason either my PC or the forum just won't make the leap to recognise my babble.



Assistance in answering the following questions would be apprecated.





1. When you rig a T4.9 with 17m2 kite what is the distance between the top of the pole and the intersection of wires at the bridle.



2. What is the overall addition to the weight of a T4.9 when you add a kite kit. Including all fitting and lines.



3. What does a 17m2 kite typically weigh when it is wet. Actually I'm after the difference in weight between wet and dry.



4. What does the F16 Stealth weigh all up. Has JohnP got it down to 100kg. I think this is a big ask for a manufacturer.



5. If you increased the min weight to 110kg what type of increase in jib area could you get and reach the same texel rating.



I would appreciate help in answering these questions.

If nothing it will give me piece of mind.



Regards,

Phill

Dear Phil,



Maybe I can answer some questions:



Q:2. What is the overall addition to the weight of a T4.9 when you add a kite kit. Including all fitting and lines.

A: The overall weight of my spi setup (with inter17 snuffer+pole) 5.7 kg



Q 4. What does the F16 Stealth weigh all up. Has JohnP got it down to 100kg. I think this is a big ask for a manufacturer.

A: Dont't know yet, but probably it will be measured at texel, in june.



Q 5 If you increased the min weight to 110kg what type of increase in jib area could you get and reach the same texel rating.

A: The "rated" jib size could then grow from 3.33 to 3.62 m2



Remark, last year, when the class had to be formed, I already asked to let the minimum weight be 105 or 110 kg, otherwise it would be quite qostly to transfer a Taipan 4.9 to real F16 specifications. But voted was for 100 kg. min weight, including spi.



Regards,

Geert

Q1: At SF Bill and I rig my spi which was very similar in size to Gregs 17 sq. mtr. spi. (I was only slighly bigger around the edges.) was rigged to the end of the pole which was at the same height above the ground as the bridle intersection.



I don't know how much forward it was with respect to the Bridle intersection. I estimate somewhere about 2.15 mtr in front of the Bridle intersection on a Taipan platform. I've calculated this value.



Another example; I will place the tip of my pole at the same height as the current bridle intersection on a Taipan now. My pole will be 3.55 mtr. long and be 3.55 - (1.37 - 0.11) = 2.29 mtr. in front of my bridle intersection. My spi draw will become 7 to 7.1 mtr. with that. My luff will be over 8 mtr. with that. I expect some 8.5 mtr.



Q2 : I think I remember measuring my setup to 5.3 kg's including everything (manual bag launch system)



Q3 : ?



Q4 : As Geert says, it will come out when it is measured at texel.



Q5 : Again Geert said it best ; however I can add the following considerations to the minimum weight of 100 kg's



A standard Taipan with F16 spi comes out at 0.68 % rating disadvantage. This is within the 1 % margin that we had given ourselfs in the very beginning.



A Taipan 4.9 with F16 spi and F16 mainsail but with standard jib comes out at 0.27 % rating disadvantage.



These points are valid but not the most interesting :



For a while I hear rumours that the shape and size of the Taipan 4.9 jib is discussed. Some sailors want to increase its size and maybe alter its shape. That is what is rumoured, but I have no idea how likely it is that this will happen. However, the 100 kg's and the rating that comes would allow the "new" Taipan jib to have a luff of 5.25 mtr. and and area of 4.3 sq.mtr. and come out at the same rating as the F16 class.



Personally I think that the Stealth without the spi gear will weight in at 95 kg's and not 93 kg's as Texel estimates. I also feel that the Euro Taipan (with carbon mast) that used to be offered would have a spi-less weight of 102 - 4 kg's = 98 kg's (based on measurements and quotes by Pieter Saarberg). All in all a pure F16 and a Taipan F16 can be expected to be only a very few kg's apart.



This was also a reason why some (including myself) may have voted for the 100 kg's limit.



And now some extra info for the Techies among us



As some may know, i'm looking at beams now for my own boat and found that a standard Taipan beam ex dolphin striker



13.5 * 2.34 / 8.5 = 3.72 kg.



3.72 / (1.4 / 8.5 * 2 * 0,002 * 2.34) = weight / volume = density alloy = 2413 kg /cubic mtr.



A stronger and stiffer alloy round beam (ex striker) of 0.075 mtr diameter with a wall thickness of 2 mm (equal to the Taipan beam) and of F16 full 2.5 mtr. length (longer) will weight in at :



0.075 * Pi * 0.002 * 2.5 * 2413 = 2.84 kg



(Bob what do you think ?)



So it should be possible to shave off a few Kg's here and there and end up on mimimum weight with a new boat. But ofcourse this doesn't help the standard Taipan 4.9 owners much. However, they get to use the larger jib to compensate for their 7 kg's extra weight under the grandfather rule.



And ofcourse Bimare pretty much garanteed that their boats would make this minimum weight.



These points need to be considered before opening up the minimum weight discussion again.



With kind regards,



Wouter

Wouter...you have my attention...LOL...what type of alloy were you using to base your beam calculations on?



Bob

I assumed same alloy for both beams, otherwise we couldn't compare them. I did not include the small ribs inside the mast though.



If you look at my calculations you see that I determine the weight of the blank Taipan forebeam by deviding the weight of the mast by it's length and than multiplying it back to 2.34 mtr.= length of beam.



Now the mast has probably a wall thickness of 0,002 mtr. And I know the circumference of the mast by deviding the 1.4 sq. mtr. mast area by the mastlength and multiplying it be 2.



With these values (derived from measured values) I can determine the density of the allow used for the mast = 2413 kg/cubic mtr. Which is a good value for aluminium alloys.



Now I assume I make the round section of the same alloy (hence same density and strength) and that it has a diameter of 0,075 mtr. and a wall thickness of 0,002 mtr. The rest is just mathematics.



From the moment of enertia calculations I made the Round beam section has at least the same stiffness as the ribbed mast section and probably is stiffer by some 15 %.



I also assume that the same but just longer dolphin striker is fitted which only adds less weight (about 6 % more) than the weight difference that I calculated. I';m still looking at optimizing that too.



But I expect that with the approach given above with give you a slightly stiffer beam of full F16 length with better torsion resistance which is at most of equal weight as the shorter Taipan beam and probable is lighter and stiffer.



Wouter

Geert and Wouter,

Seems I can post again.

Thanks for your answers.

I had forgotten the Taipan jib was larger than the F16.

People will have to make sure they keep their Taipan, class legal to the Taipan restrictions, at the time the boat was grandfathered or they will lose the right to carry the bigger jib.



In my mind, I think the jib was the point that allowed the 100kg min weight be voted in instead of the 110kg. Now it will be interesting to see if anyone can get down to it.



Phill

Wouter...do you happen to know what type alloy is typically used for the mast section on the Taipan, or the round beam section on the stealth? What I am asking is it 6061T6? or what?



Bob

Maybe we should ask the maker Goodall ?



Wouter

This time I had enough (joke) and I decided to pack up all the Spi gear that I had at home (my boat is still not on the beach) and walk down to the local supermarket and MEASURE all the stuff on their electronic scales ON SATERDAY AFTERNOON.



I received alot of attention but also alot of good hard data.



These electronic scales are accurate to the gram.



Than I gave it some though of how to spread the information. And since I have to much time on my anyway I decided to make it into some good content for the webpage. Coz, that is where the class organisation and webpage is for right ?



So go to the webpage :



http://www.geocities.com/f16hpclass/Tech_weight_and_cost_spi_setup.html



And find out what a spi setup weights.



Wouter

Any takers to fill in this particular task ? That would really help me out.



Wouter