Formula 16 High Performance Beach cat class

How to add a genaker ; mast setups

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Document data

By                  : Wouter Hijink
Created          : 4 november 2001
Last updated : 12 april 2002
Classification : Construction analysis
Copyright       : restricted shareware

Status            : Being constructed, Grammer check needed.

Comments     : Adviced to be used in conjunction with genaker document, see link under "Related links"

F16HP class Home

The complete how to make genaker setup document

Explanation of classification and copyright

Introduction

Ofcourse the Formula 16 High Performance class encloses designs that are all sailed and raced with genaker setups. Any new pure F16 HP design like the Stealth mk. 2002 will therefor have a genaker setup delivered with the boat. Several other (grandfathered) boats like the Swell Spitfire and BIM F16 are also offered with genaker setupsin their standard mode. Others like the Taipan 4.9 where sold with genakers as an extra option. It is the last type of boats that would require the retrofitting of a genaker setup to be able to fully exploit the F16 HP class potential. This retrofitting can be done by an amateur and it is this retrofitting that this page is aimed at explaining.

This particular page looks at mast setups and we refer to the complete genaker document (Word 97) for the building of your own COMPLETE genaker setup.

All the setups presented on this page allow simple switching between short and long luffed genakers as might be used in the F16 HP weight equalization system. Ofcourse this system is not operational at this time and will only be made operational if inequality between crews of different weights can be proven.

The building

All presented setups are fixed using knotted pieces of high strength line with a tough outer mantel and blind rivest (Stainless steel, Monel, but not aluminium ones). The lines are either tied of to eyestraps riveted to the mast or tied of to the masttrack. The last by running the line though a drilled hole on the masttrack and placing a small (overhand) knot on the other side. You can nearly completely eliminate wear by smoothing the edges of the drilled holes by shortly "post-drilling" them with a much larger diameter drill.

See picture below for the general idea.

Drawings of the setups, and force vector diagrams

Drawing 1

The most simple and cost effective methode. The investment is only about 1 mtr. of high strength and though Dyneema line and a normal single pully block for up to 10 mm diameter line.

The force vector diagram is as follows :

This setup is also often used on the International Tornado. And It has the extra advantage that this setup can be very accurately place right on th maximum allowed gate height for the highest position of the block is easily measured and altered

This setup can be made such that it allows the sailor to easily switch from a long luffed genaker to a shorter luffed genaker. In such a setup the block is fixed to the loop line running from one side of the masttrack to the other side by a shackle. A second line is looped lower on the mast. The verrtical line is than run also throught the shackle and back up the line where it is tied off to the line itself. Now when a lower genaker hound is need the vertical line is slid down itself placing the block in front of the second (lower) loop where the block is reattached via the shackle.

Multiple tie off solution can be dreamed of. Toname a few : sliding Fishers hitch (often used in powerkiting), two small loops in the line where the shackle is attached too, etc.

Above: the no holes in the sealed part of the mast variation. Seen on Intl. Tornado's

Drawing 2

This setup is largely selfexplanatory. This setup is the most simple to make switchable from long luffed genakers to shorter luffed genakers. The hole transition is done by undoing the shackle which functions as the guiding ring from the highest loop line and fixing is again to the lower loop line. This methode is not much more costly than methode 1; the turtle block required for the mast might be just be a fraction more expensive than the simple pully block.

The loop line must be very close to the mast so they shouldn't be made to long.

Only real disadvantage of this methode is that the Turtle block requires drilling two holes for the blind rivet or bolts that could potentially be leak in a sealed mastsection. Methode 1 can be made to avoid this. Methode 4 is an example of how to achieve this

The vector diagram is abit more complex and it is clearly visible that the position of the ring (which is measured for the max. gate height) is somewhat dynamic.

This setup works and I have used it personally for the last two seasons. Sadly I have no picture of it yet.

Drawing 3

This methode is truelly Low Tech for it has a few distinct disadvantages. The origin of this methode are the skiff mono classes, but ofcourse non of these classes have rotating masts as catamarans do.

Disadvantages :

-1- The genaker will interfere with mastrotation and try to under rotate the mast

-2- When the mast is forcefully rotated the eyestrap experiences high sideways loads, very possibly damaging the mast and rivets

-3- You have no less than 4 potential leaks at a high point on the mast on a preferably sealed mast.

The force vector diagram is as follows :

Note that it is no different from methode 1 with respect to the force diagram. We will therefor not analyse this methode further on a individual basis

Drawing 4

Is a variation on methode 1 and is potentially the best methode for a genaker mast setup. It has all the advantages that metode 1 has and a few more.

This methode has an extra advantage for carbon mast owners.

The extra advantages :

- Absolutely no added holes in your sealed part of mast.

- The block makes the most horizontal movement next to a all steel bail hound

- BEST : It tried to underrotate the mast the least next to the all steel bail hound

- It is also the cheapest hound possible

- By far most of the load is transmitted just through the vertical line which can be tied of the the mainsail hook which take such loads easily. Horinzontal loop is hardly loaded up. Great for carbon masts

The force vector diagram is as follows :

This setup was tested and found to work best when :

- You drill through the masttrack to the other side and make the knot on the outside of the mast

- You round of the edges of the hole using a larger diameter drill

- keep the horinzontal loop as short as possible = close to the mast

- Use a round legged shackle without sharp angles or parts.

Ignore the knots In the picture above, we tied them the right way but also tied of the excess of line in stead of cutting it off. We wanted a little bit of extra line to fine-tune the loop, but found that a tight loop is best. The first picture at the top of this page shows how the knots on the outside should look.

Lets calculate the forces of each methode

Force on vertical red line is equal to the tension on the genaker luff. Force on the horinzontal red line is :

Methode 2

Methode 1 and 3

Methode 4

When mast 8,5 mtr. high, genakerboom 3,25 mtr. and hoist height 7,5 mtr. upline to mainsail hook

F block = 192 % * luff genaker
F loop = 38 % * luff genaker

F block = 200 % * luff genaker
F loop = 38 % * luff genaker

F block = 196 % * luff genaker
F loop = 0-3 % * luff genaker

When mast 8,5 mtr. high, genakerboom 3,25 mtr. and hoist height 7,5 mtr. upline to mainsail hook

F block = 196 % * luff genaker
F loop = 2-5 % * luff genaker

F block = 200 % * luff genaker
F loop = 38 % * luff genaker

It will be obvious that the last methode is the methode to use when mast or masttrack can�t take the string genaker tang because of load restrictions or other practical reasons. The upward line will be attached to either the mast hook that is used to fix the mainsail or to the endplate on top of the mast. This hook will be strong enough for it is designed to take the full load of the downhaul system which will be released anyway when the genaker is set. Ocourse there still needs to be a mast tang to let the whole setup function properly but It is proven here that it will take only very limited loads; loads that even weak masts can take.

Don�t get fooled by the appearence of the drawings. All methodes produce the same bending moments and axial loads in the mast section when the genaker hoists (tang) heights are the same. These loads are fully independend of the tang methode used. The methodes presented only differ in the creation of (local) point loads. The last is important for the construction of the setup given a particular gate height, the first wether to fit a genaker (at that given gate height) at all.

All methodes can be quickly adjusted to a different hoist heights by replacing the ring by a shackle and fixing the shackle to the other tang line. Only the methodes with a upline need to device a way of adjusting the length of this line. In the single upline methode the line can be adjusted easily by using an end knot+loop and a knot somewhere halveway the line and sliding up an down a fishers hitch.

Created by : Projectgroup, 4 november 2001

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