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  1. dtoc

    Canting keel forces

    It is very interesting what the different teams have shared about their keel systems. Movistar has definitely been the most open, with the Greg Waters piece on The Daily Sail, Bouwe on SA and the pictures that are out there. POC has been the most secretive, there still seems to be a little...
  2. dtoc

    Canting keel forces

    Very Interesting! They appear to have gotten the engineering of the PRV's right, as their boats have not broken. I still believe there is a lot of room for optimization that will add performance to these systems and adding an "accumulator" to the system should be part of this. The other...
  3. dtoc

    Canting keel forces

    The rams are double acting, so when one ram is pushig the other is pulling. The rod on the pulling ram is in tension and I believe this is the rod that has failed every time. Seals have also failed, or similar over pressure failures.
  4. dtoc

    Canting keel forces

    Accumulators are like a spring but have built in damping. The damping comes from having to flow the fluid through the connection to system which is a restriction. If the restriction is too great it won't control the peaks and if it is too small you can get oscillations. Considering how long...
  5. dtoc

    Canting keel forces

    A pressure relief valve will not always work as desired / in the manner described, which is way these systems are failing even though they all have prv's. A prv is a spring backed valve that as the pressure rises, the force opens the valve against the spring and any back pressure. (there are...
  6. dtoc

    Canting keel forces

    Heavy extra mechanism Difficult to lock in place without slack, which causes impact loads Hard/impossible to adjust trim quickly No shock absorbation in system (not sure current systems are taking full advantage of this) Any other thoughts?
  7. dtoc

    Canting keel forces

    Steve, I have just been reading that article and I agree with you on the FOS margin. What is interesting is that I have done my calcs based on the Cariboni system, which as the article states is used by ABN1&2 and Brasil, which have not failed. He also states that the load on each ram...
  8. dtoc

    Canting keel forces

    With the keel fully canted and the boat heeled 5 degrees, the bulb is still 3+ meters below the waterline. So the boat would really have to be launched. Even then when the strut re-enters the water it will be at a 45 degree angle and with significant forward speed. Angle of attack for the...
  9. dtoc

    Canting keel forces

    Good point about the carbon daggerboards and designing the strut to have minimal drag. I don't think the analysis will show any significant forces possible from flow induced vibration on the keel strut. However the analysis is interesting and we'll see what it says. What I'm more interested...
  10. dtoc

    Canting keel forces

    I have been thinking a lot about the transient forces, both resonance and shock loads. The biggest issue for me is not having good analytical tools, because doing the analysis by hand is slow, very error prone and sometimes basically impossible. The one tool that I have used is Working Model...
  11. dtoc

    Canting keel forces

    Where is their website in English? link?
  12. dtoc

    Canting keel forces

    No worries mate. I have chosen to use kg force as my force unit, so it appears that I haven't accounted for 'g', but its in there. So everywhere you see kg, just read kgf. There are a few errors in some of the calcs I posted, mainly in how the loads are spread between the 2 rams, and I am...
  13. dtoc

    Canting keel forces

    Let's not get ahead of ourselves. The analysis has probably been done by others, but I will do what I can and post it all.
  14. dtoc

    Canting keel forces

    My initial calculation for the resonance of the hydraulic fluid in the cylinder is 1300Hz. Too close to ignor, but we are still a long way from showing that the hydraulics are involved in the vibration and that the vibrations are causing damage to the system. Very interesting.
  15. dtoc

    Canting keel forces

    Vibroman, (great name for this subject) If you've got the capabilities to get the frequencies, I would love to see the data. One of times that I have seen pump induced resonance cause significant issues has been with a pressure relief valve on an oil lubrication system. Usually the ripples on...
  16. dtoc

    Canting keel forces

    Very interesting paper, but will take some time to get through and understand what can be taken from it. I had forgotten about Sill and Bonduelle. I never read a clear description of what went wrong. My thinking last night was that keel flutter was neither enhanced nor retarted by the...
  17. dtoc

    Canting keel forces

    Thanks B2S... Some similarities here I think, "The first Tacoma Narrows Bridge was revolutionary in its design and historic in its collapse. The failure on November 7, 1940 marked the end of a trend in bridge engineering towards a maximum of lightness, grace and flexibility. Since the turn of...
  18. dtoc

    Canting keel forces

    I don't think that the use of a self contained unit rules out the issues brought up by Don Jones. The structure used to hold the rams and the keel has still been optimized for weight and is still subject to torsion when the boat rapidly decelerates. At the pulling ram, with 40 deg cant, any...
  19. dtoc

    Canting keel forces

    Three items on my previous calcs: 1. Add an optimization for the offset angle for the internal lever arm. Simple method, but it gave me 12 degrees rather than the 20 I assumed. 2. In doing so I found an error in my calcs which I corrected. Unfortunately this may the results worse, i.e. a...
  20. dtoc

    Canting keel forces

    Much discussion has been put up in boards on why the canting keel systems are failing, including support structure, ram pistons and hydraulics. I thought it might be interesting to look at the forces involved and the equipment used to exert them. The canting keel works in a lever mechanism...
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