Catnewbie

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About Catnewbie

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    München
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    High Tech Catamarans
  1. Catnewbie

    14' Stunt S9 Foiling Cat

    As stable as the S9..... windward https://www.facebook.com/hollandcomposites/videos/966716083382537/ Enjoy
  2. Catnewbie

    Foils

    Regarding the shared lift, I d have one concern: If a sailplane or glider is the reference with >95% of the lift generated by the main wing and the 5% remaining generated by the tail All the moments at work for a glider are very small, the CoG, center of drag, the aero center of the wing and so on...are very close from each other For a flying beach cat, the moment create by the rig, is very far above, the foils aero center, the boat's CoG, .... That's why I wonder if the sailplane "model" is that relevant for our cats? At the same time I noticed the AC72's foil packages are more in the spirit of sailplane, minus the high aspect ratio of the main wing. Same remark for C-Cats the only conclusion I can suss out is that I achieved the limit of analogy reasonning. But intuitively , for an A-Cat, higher surface & higher AR T foil, could make foiling easier, everything else equal To get a 40+ cm T foil span, it would be necessary to fit the rudders parralel, and aligned with the inner gunwhale of each hull. Regarding the arm race if rule 8 are deleted I would make the following remark: AC72 or C-Cat have no rule 8 and as above-mentionned, they do not show great AR for their main foils A-Cat rule-box does not put any limit on mast height, and surprisingly when going graphite from aluminium, mast lenght remains the same. I dont think removing rule 8 will be the can of worms some Cassandras are predicting Even if HM carbone would allow thinner foils, here again, a practical limit will be achieved quickly. Have a good week W
  3. Catnewbie

    Foils

    Thanks a lot Phil, Even with greater AR foils, split tips should improve L/D ratio for Moth too, unless rule-boxe... I feel confident somebody is brainstorming at the moment about it. A-Cat foils with split tips is probably the next to come. Cheers Everybody W
  4. Catnewbie

    Foils

    It's a thread about foils, that's why I would suggest those who are interested with the topic to have a look at the WASZP foils Split tips is not a new idea, it comes from bio-mimetics research and improves the induced drag and the L/D ratio But it's the first time it's done for a large production boat. Probably all foils specialists on this thread could confirm , if it comes from 3D carbon printing ?
  5. Catnewbie

    Foils

    Overall, if we make basic observation 1-The Moth's rig Moment is probably half the A-Cat's rig Moment 2-The "Wheelbases" are not that different between Moth & A-Cat 3-The split between front & rear lifting surfaces is very different Independently from any wand control system, it would be interesting to see if the above-mentionned parameters can have an influence on stability. Very interesting discussion. Happy week-end W
  6. Catnewbie

    Foils

    Yes, as far as I understoood, the Hydros C-Cat crew were ajusting "real-time" their main foil's AoA and less frequently, the"canting". Their lifting surface was quite short for a 21cm chord section and almost perfect L @ 90°. Hydros' had incredible boost of speed but a lack of stability. It's probably very difficult to keep concentration for this kind of real time adjustment As a result, the helm had the tiller + wing main control line I don't know who was adjusting the sail camber & twist when the boat speed was changing a lot.
  7. Catnewbie

    Foils

    Thank you Boink, That's interesting and could trigger interesting discussions too. There's a point I miss with this kind of foil, I though these anti-cavitation sections were relevant for speeds >50 knts? It seems that they are also used for height control/ lift management purposes. Regards W
  8. Catnewbie

    Foils

    Ok that's quite convincing, but why don't you use end-plate for the sails on your models, it will not bother any crew to have no space below footsails
  9. Catnewbie

    Foils

    I can testify, you can find this prose on BoatDesign.net and it's actually Tom Speer who wrote it; his academic writing is easy to recognize because always crystal clear for the concepts he wants to explain, Proasailor it s a no brainer about that. Regarding model boat, I am afraid it will be almost impossible to have stable foiling if you don't have a few gyroscopes like R/C helicopters. How and where to connect the gyros, you should ask a specialist. Stability is also dependent on the moment of inertia which is proportional to the mass and square distance from barycenter It's a bit crude calculation but a model 5 times smaller than a beach cat and 100 times lighter will react (5^2) x (100)=2500 faster than a beach cat for the same gust. That is why I don't believe it's actually possible to achieve very stable flight with boat model, even if you push the stability diedral to the max, I am afraid it won't be enought.