a better tiki 21

Discussion in 'Multihulls' started by guzzis3, May 7, 2019.

  1. Angélique
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    Angélique aka Angel (only by name)

    At least everyone should wear some flowers in their hair . . .

    Harmony Day 2013 in QLD

    — Edit June 5, 2019: I thought the thread could do without the pic, was just kidding, but for whoever is interested it's still linked.

     
    Last edited: Jun 5, 2019
  2. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    Here's some inspiration to add ‘‘Tiki style’’ to pretty much anything, maybe take a desirable design, and rework the topsides plus the cabin . . .

    — Edit June 5, 2019: I thought the thread could do without the pic, was just kidding, but for whoever is interested it's still linked.

    ‘‘ Postcard view of Bali Ha'i Restaurant in the 1950s. This was a restaurant serving Cantonese and Polynesian food decorated in "Tiki" style, located adjacent to Pontchartrain Beach near the Lakefront end of Elysian Fields Avenue in New Orleans, Louisiana, USA. It closed down about the start of the 1980s and the building was demolished. The postcard is not dated, this copy was mailed with a postmark of 1959. ’’
     
    Last edited: Jun 5, 2019
  3. guzzis3
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    guzzis3 Senior Member

    Yeah I always found the naked woman thing off putting, but I guess it's better than naked men...but so very unnecessary...

    I guess my origional idea when I started this was not so much to build a "better" sailboat. I think there are some improvements that could be made without radical redesign like more efficient build and shifting the maximum beam aft a bit maybe 5% or 10% of mid warterline, which shouldn't require any torturing, but not complicated or intimidating hulls or massive rigs. If you want an efficient sailboat build Acorn or any number of other cats. I was thinking something simple cheap and fun, stylish, but nicer to build and use than a Wharram that's all.

    I was thinking the other night that something similar to Acorn but which is specifically designed to use as much or a tornado would be interesting. There aren't as many cheap 20' beach cats around as 14' and 16' boats but a lot aren't race able anymore and are virtually worthless. If you could replace the hulls with ones with more clearance and basic accommodation but use the rig, boards, maybe tramp, rigging, so all you have to do is make hulls and probably beams as I don't think beach cat beams would be strong enough or wide enough. Set the beam so the original tramp can be used and extra beam through wider hulls. I know a lot of tramps are shot. I guess acorn is already close to that idea....
     
  4. waterbear
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    waterbear Junior Member

    It sounds like you're well aware of the tradeoffs! I made the diagram out of curiosity more than anything.

    That being said, I'm not convinced it would be easier or much easier to build. One thing about the Tiki 21 is the "floor" (bed?) is about half way up the side of the hull and acts as reinforcement for the hullside panel. If you lower the floor and use full width panels for the sides, then maybe you will need stringers or some other method of reinforcement, and that probably means moving to strongback contruction. It looks like the Tiki 26/31 addresses this by splitting the side panel and adding a stringer at the seam. So the lower half is built like a T21, then the stringer is added and then the upper half is added, or something like that. Definitely not as simple as it should be.

    Anyway, this gives me an idea: Phil Bolger used external chine logs, so why not use external stringers? You could build the hull like the Tiki 21, then add stringers to the outside afterward. The floor could add stiffness below the waterline. See below.

    Interesting, I didn't know that. The mana looks like it's 90 deg or so amidships, so that means wharram has gone from ~45 to ~60 to ~90 over the years. I would think it's not just a matter of drag due to surface area, but other issues as well, like pitching and being able to turn/tack. I'm guessing there will be more rocker which could mean more volume amidships (?), and the waterplane is definitely narrower.

    Also, yes, I don't think 10 inches is necessary for the floor. All that is really needed is the width of a shoe.


    [​IMG]
     
  5. redreuben
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    redreuben redreuben

    The thing about flat panels is they are weak and need the stringers.
    The other option is laps in the ply, this might give you some interesting styling options with the lines and materials usage without need for chines and stringers.
    But pulling even a little shape into the hull makes it stiffer.
    Crowther used this on the Buccaneers, those single chine hulls have a slight curve in the panels which makes them stiffer.
    I think you could cull a lot of weight from a small “Wharram” by using Paulownia framing and a thinner but stressed ply skin.
     
  6. guzzis3
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    guzzis3 Senior Member

    Hence my comment previously about torturing a 4mm ply skin. Once you add chines the work increases a lot because you have to plane them to match the 2 skins, then fit, fillet and tape. That is why I wondered if torturing would work better. The other upside to me is reasonably heavy glass skins make the hull more rugged possibly less prone to water ingress, and maybe reduces the ply requirement from marine to exterior since it is now basically a core. I guess tortured ply scares people as much or more than dory hulls and strip plank. ?

    It's all swings and roundabouts, there are tradeoffs which ever way you jump. I did a really rough calc earlier and I think at 300mm/1' depth the tiki 21 is about 14:1 on the waterline. The 45 degree hull would be even slimmer. It would be interesting to explore the performance trade off between higher wetted surface and slimmer hull form.

    V hulls hobbyhorse. Hulls symmetric bow to stern hobbyhorse. Boats with small simple rigs not optimised for windward performance, big overhangs heavily built bits and low aspect boards/keels/hulls don't win races. My origional thought wasn't to make a great sail boat, that's been done. My thought was someone somewhere might have designed a boat that people could actually dive into confidently, finish quickly and cheaply, that looks pretty and sails reasonably. That's what the tiki 21 should be but it just falls so far short in so many areas, IMO.

    Anyway until I get some time to make a model it's probably moot. Drowning in appointments at the moment.
     
  7. Manfred.pech
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    Manfred.pech Senior Member

    "V hulls hobbyhorse. Hulls symmetric bow to stern hobbyhorse. "

    This caused me to make a 1/1 model with bendable plywood (4,5mm), which was no problem at all. The plywood was to be formed very easy without any torture or stress. I didn`t need wire only a little tape and some clamps.
    The only concern is that you need a jig to avoid too much flexibility. The shape of the hull can be formed by cut out wedges at bow and stern. Models can be made of very thin aircraft ply (0,6 mm). If you want to avoid too much flexibility you can use bendable ply only for the bottom and combine it with normal stiffer ply for the sides.

    [​IMG] [​IMG]

    [​IMG]
     
  8. 23feet
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    23feet Junior Member

    Hobby horsing, like windward ability, is another myth about Wharrams and vee hulls. When the rig is powered up, there is no hobby horsing, or certainly no worse than most other sail boats. When the rig and sails are not powered up, Wharrams are prone to hobby horsing, but again to a much lesser degree than pundits think. The only time I have been really bothered by hobby horsing on my Tiki is motoring to windward in a short chop. Note well that all the other boats in the same conditions were also hobby horsing pretty badly as well. I have never had hobby horsing issues when well powered-up, and have also enjoyed the big ADVANTAGE of veed hulls which is that they are relatively smooth when powering into rough seas. This huge advantage to the vee-hull shape is often down-played or ignored in discussions about hull shapes.

    Waterbear note that your drawings of the Wharram hull cross sections are off. The waterline as designed is never deeper than the floor level, and you are showing the floors as well under the waterline.

    And finally (promise) the Wharram Tiki hull designs are not "flat panel". They are tortured into a curve just like most other "modern" designs.
     
  9. redreuben
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    redreuben redreuben

    23feet thanks for the “real”world feedback.
    So if you put a straight edge vertically against the Tiki hull say midships, how much curve is in each panel ?
     
  10. 23feet
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    23feet Junior Member

    About 1" over 2 feet (0.5 inch per foot)
     
  11. guzzis3
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    guzzis3 Senior Member

    23feet:

    You are mostly correct. If you read back over my ancient posts on this and other forums I have been defending V hulls for decades, BUT...

    Hulls which are symmetric from to rear do pitch more, no doubt about it. That's why I was looking at shoving the beamiest bulkhead aft of center a bit. It's not a big deal but may help dampen the rocking a bit. One thing you don't have to worry about with a Wharram is it dragging it's tail :D

    I am glad you are happy with your boat, but I do not share your experience with V hulled boats. Maybe our shallow water and strong winds present a different problem to where you sail. I have not owned a Wharram but I know quite a few people who have, albeit not tiki 21's.

    You are correct that tiki hulls have a bit of curve in them, they are what you might call mildly tortured. I was careless with my language. There is a previous post in this thread where someone suggested shifting that maximum beam aft would require impossible torturing of the hull. I contend it would not. The "classic" designs like hinemoa don't have tortured skins at all and rely on a lot more framing for stiffness. My thinking was to start with straight hull sides and then see what could be achieved. Unfortunately in trying to respond to various comments I did not make myself clear.

    Manfred.pech's hull above is very pretty but it is probably too intimidating for a first time builder to try. If we take on board the previous comments about the perceived ease of construction I think you need to be careful not to make it look hard.

    So again I'll try to be clear:

    I like V hulls. Everything is a trade off. V hulls ride softer in a seaway but they have higher wetted area.

    The boat would need to be cheap quick and easy to build, it probably also needs to not be intimidating. I'm not sure how you quantify that. Strip plank in a small boat with gentle curves is easy. Tortured ply is easy when it's developed (no pun) properly. The problem is if someone who has little experience with building things looks at the plans are they going to be scared off trying it ?

    It should have some style about it.

    It doesn't have to be a great sail boat but it should sail ok and have usable accommodations.

    This is my thinking anyway. I'm always wrong though, ask any woman who knows me :D
     
  12. redreuben
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    redreuben redreuben

    Just thinking aloud but another way to minimise pitching is T foil rudders, yes it has unwanted complexity but thats minimal compared to reshaping hulls.
    The foils could actually attach to the bottom of the rudder skeg parallel to the waterline, even simpler. Solid glass/carbon would make them bashable enough.
    Sizing could be estimated from racing cats.
     
    Manfred.pech likes this.
  13. Manfred.pech
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    Manfred.pech Senior Member

    A very good idea. You can find a lot more ideas in The Sea People Magazine of the Polynesian Catamaran Association Polynesian Catamaran Association http://pca.colegarner.com/sea.people.html .
    The download is for free.
    And: Rudder T-foils http://forums.sailinganarchy.com/index.php?/topic/96366-rudder-t-foils/
    Rudder T Foil - Google Search https://www.google.com/search?q=Rudder+T+Foil&client=firefox-b-d&tbm=isch&source=iu&ictx=1&fir=JhjKOB0eEnTiSM%253A%252CecBMRfmKgRNMHM%252C_&vet=1&usg=AI4_-kTLC6qxdTwi7cYN9SBXFU05QYB2BQ&sa=X&ved=2ahUKEwis86mH8M_iAhXtkYsKHWtuBoUQ9QEwAnoECAAQCA#imgdii=JeTnRCQXDS3qmM:&imgrc=z7PznqWTAK6YEM:&vet=1
     
    Last edited: Jun 4, 2019
  14. guzzis3
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    guzzis3 Senior Member

    Good idea. I don't know if I was clear. I wasn't going to go to great lengths to dampen pitching I just thought if you could shove maximum beam back 5 - 10% from the mid point that might help a bit.
     

  15. redreuben
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    redreuben redreuben

    It might but it might also just shift the centre about which the boat rocks ?
     
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