Dear fellow homebuilders ;
Naturally the "Tech Corner" on our F16 webpage is your domain !
To bad that is less easy to fill it with content quickly than it is with general interest topics such as regatta pictures.
But here is one of the first trully handy peices of content :
After the "How to make a genaker setup" document; the online Texel / ISAF handicap calculation sheets and the weighting of the spi setup I present to you :
http://www.geocities.com/f16hpclass/tech_main_beam_calculations.htmlThe BETA version of the online excel sheet that calculates the deflections and stresses of the main beam at given platform dimensions.
It calculates three scenarios :
-1- A dolphinstrikerless beam
-2- A main beam with dolphinstriker where all the load is taking up by the striker and not be the beam. Here the beam itself functions purely as a compression bar.
-3- A combination of the two above here the beam functions mainly as a compression bar but also takes a portion of the maststep load.
This is a BETA version for now, but it did accurately model a few test situations.
A few early conclusions can already be drawn :
-1- a round tube will give the highest stiffness for the lowest weight. It also experiences the highest stresses.
-2- with the combined model # 3 ; A larger diameter beam will cause higher stresses in the main beam. However the reduced deflection at mid beam is only some 8 % or 0,3 mm (3 tenths of a millimeter)
-3- Any extra weight is better off being put in the striker strap. The stiffness will remain about the same, resulting in equal deflections but the stresses will be lower in BOTH the strap and beam. In this case the bolts transfering
This leads to the remarkable conclusion that the a strong Stainless steel dolphin striker with a relative weak round main beam (small diameter) is the lightest and lowest stressed setup that you can get. It's stiffness will be equal or more depending on how strong you make the dolphinstriker.
So the irony is that as long as the d-striker is strong that a weak main beam is actually more robust and better suited to abuse than a strong big beam section.
This setup shows that a F16 main beam which is equal to a Taipan main beam in deflection can be as lighter as 5 kg's including the 4 bolts.
And that the Taipan setup can be entlarged from 2,34 to 2,5 mtr. resulting at 1,5 mm extra defelction at midbeam and 9 % higher loads in the striker and beam. These are all well withing the safety margins.
I will make a full page out of these conclusions shortly.
Ohh model 1 shows that a dolphinstrikerless setup is possible but that is will be about twice as heavy as a beam with dolphin striker and it's frontal area will at least be 1,5 times as large. Something like 0,12 mtr diameter against 0,08 mtr. diameter.
And in our lightweight class we don't just throw out some 4 to 5 kg's like that.
Hope the excel is largely self explanatory.
You can find the page at :
http://www.geocities.com/f16hpclass/tech_main_beam_calculations.htmlWouter
