Depending on original size, you will run into “volume” issues of the floats.
I was working witht he original designer of the US1Meter “ZIPPER” and discussing a scale down from 1 meter to 65 cm and his suggestion was to retain the shadow templates sizes of the 1 meter and simply make spaces between templates smaller to retain volume but “shrink” length.
I think if you tried that with a 1.2 mete/48 inch multihull, the floats would be way too fat for the length. Multihulls are known for long, fine entry, thin hulls with length to beam ratios that would never work for a monohull. Thus, trying to build like a monohull, and sail it like a monohull will result in a boat of questionable performance. Then again, if all are the same “bathtub” - who cares?
Dear Marc,
I have emailled you the shadows and will email you the rest of the plans soon.
Good luck with the build, I hope there will be a second 65M soon.
Here you are definitely right!
The lenght : width relation for multihull -hulls are very important - for “seaworthyness” as well as for speed.
But to scale down a 1 meter to a RG65 is only 1 : 2/3 -
while scaling down a Mini40/F48 to a 65cm Multihull would be 1: 1/2.
The first one would still work, the second one would be too blunt.
You could as well turn it around and build Siris RT65 with identical templates, but 1 Meter long and wide. It would work.
It´s all about proportions.
Siris first RT65 has floats with a relation of 1:10 and a mainhull of 1:7,22 - but both with identical bow opening angle, which is very important for low water resistance.
Of interest Ernst, is why the r/c designs you are providing, don’t follow current small boat design, but rather use the bigger, off shore boats as the design basis?
It is a proven that the hottest boats today are the Formula 18’s which seem to out perform many (most) of the 20 foot versions of older designs, and older sail plans. It would suggest, that at minimum, the hull shape would be similar to most F-18’s regardless of in which country they are built - Sweden, Italy, France, USA, Australia, etc. - for floats (and let the middle hull - if you are going the trimaran route) to be as small as practical. With the exception of one less rudder and board, there would seem to be no reason for a middle hull other than to house electronics and lessen rudder and baord fabrication by 1/2. The one view of Siri’s photo of the main hull almost resembles (in the photo) a scaled down monohull shape, and with the wide stern, I’m not sure why ?
Once I see how the 65 cm one I am currently building performs, I am already thinking of revising the hulls to reflect the current “A” Class hulls, where the bows are very low, compared to your (and Siri’s) current float profile. Lower bows would also seem to prevent a lot of cross-windage issues, especially when tacking.
Well- as always - will (and still) looking for your designs to show up in any major r/c multihull event.
I understand your comment about scale factors, but if we take Group IDEC as one of the most recent multihull designs and the sister-ship Sodeb’O, I am simply pointing out the difference in design thought between your designs from perhaps 2002 versus 2007 or more current - that’s all. The photo of IDEC (below) is so radically different in thought/design from yours, I am only wondering why you have not yet embraced current design thinking?
Only trying to open the dialog about multihull design you have so many times in the past requested, that’s all. Mine was a question Ernst, not a criticism.
Eric Gielen, the current owner of the Mk.vII carbon/epoxy prototype visited a french race together with Karl Schmidt (SKAUT 07) last year in november. Karl won - I don`t remember Erics ranking, but he´s not an experienced rc-sailor.
Both have sailed here at Vienna together and exchanged their transmitters several times.
And SKAUT won each time - no matter if he sailed his own design or the Mk.VII -…-
Slight differences in handling, but overall same boat performance - was his comment, when I met him the last time.
Karl (73 or 74 years) is the Austrian President of the sailing section of the NAVIGA - he has been sailing M-boats and TEN-raters in most of the major races for 20-30years, as far as I know.
I´m personally not interested in sailing races at all - I would prefer to sail around the globe alone in a 40ft version of the “NightmareMk.VIII”, but simply cannot affort it. So I´m simply helping others to have fun with their hobby -
and try to avoid the problems for them I had run into, when I checked the internet for reliable datas about trimarandesign.
Well - design criterias -…-
First of all, the thumbs of a rc-sailor need some time to react.
So there needs to be a little designed-in safetyfactor for less experienced sailors - and easy-to-build and easy-to-reproduce are also vital factors.
Simplifications + fast build versus state-of-the-art + building untill winter takes over - what is better?
The windspeed increases (doubles) from 0 m above waterlevel to about
12 m per each meter - then it “may” be considered as steady windspeed.
At 0 above waterlevel it can be considered ZERO windspeed.
Therefore a bow of a RT65 with a height of only 80mm can be ignored as “crosswind issues”.
With the first design for Phanchita (Siri) I stayed on the “save side”,
but a slimmer boat has been calculated allready - with identical bow heights though.
I could do the same linedrawings with wavepiercing bows, but right now there is no need for that from my or Phanchitas side.
I´m looking forward to see a RG65 Multihull like that IDEC or Banque Populaire IV built by you. Can you get it sailing this summer?
I certainly want to give it a try. As you are aware, many “home” projects, plus a few RG-65 monohulls that I’ve taken on and just can’t seem to find summer time to work on them as easily as in the winter. The current boat is of GHOST TRAIN (which I know you consider “old” - as do I) but it has been a past proven design and I want to confirm the past arguments/discussions that a multihull HAS to be big to sail well. (Doug Lord?) - thus the 1.2 meter tri has proven that, and my 1 meter tri also proved that (but I ran into the issue of tall bows on that one) - so the 65 cm is now the target. Should that one sail well (I doubt it will have many issues as evidenced in Siri’s videos in at least light wind) then I do plan to look at the “A” Class hull design - similar to the “FLYER” design, although a good big cat friend has recently built and sailed his own design, of which I may be able to obtain lines.
Basically, my current (future build) thoughts are of a hull with little distance between rudder and boards, a very long and thin extended bow with the wave piercing ability (I’ve driven one and cannot express how smooth they are through waves) and a fairly flat, and wide rear section to improve ability to get hull on top of instead of through the water. Now, without moveable ballast, this may be a complete failure - or it may be wonderful only in light air… not sure, but Yes, I certainly would like a prototype on the water before next fall’s cold weather.
Today I made some clips of my RT65 in winds between 20and 40 km/h. Roland who is promoting the RG65 in Thailand and sailing together with me did sucessfully maiden his RT65R. Clips are uploaded to my web site http://www.rcsails.com/rt65r.htm in this moment and are available soon. I will post links to the clips at YouTube as soon as I have uploaded them here.
Floats appear to have suficient reserve buoyancy to handle the reaches in the stiffer air.
Tri “appears” to have problems tacking in the heavier air - perhaps not enough momentum or weight to carry it through the tack. Looks like skipper resorted to gybing instead of tacking. Sails hauled in too much. Too much weather helm so it tends to “wind vane”. Possible jib too large to effect an good tack.
Also appears to have problems “pointing” (sailing closer to the wind) as it “seems” to stall out when the skipper steered closer to the wind.
As noted - just observations from watching the videos, and I know the wind was strong, and the weight f the boat is still a concern of mine. Too light and it won’t carry through a tack, too heavy and it won’t accelerate and may pitchpole due to slow acceleration.
In all - an informative video to use for attacking the handling issues note. Will give us something to compare to - and any fixes you find would be most welcome.
Thanks again.
ADDED - consider trying to sail as a uni-rig. Granted it makes it even harder to tack, but with main only, you can check on pointing. Just an added thought
I checked last night from home - and all opened OK. Have a feeling here at work there are selective URL’s being blocked - I know I can’t read “ANY” blogs or personal sites ! :mad:
Hi all,
finally got online again. Have been busy working on the female moulds for my 65m tris, here are the first pictures. I’m preparing them for production now.
RT65 moulds
RT65R moulds
Keel and Rudder
I think the first boats off those moulds will hit the water in 3 to 4 weeks.
When production gets going, I think you may see a big interest from those who don’t want to spend time building. Any production multihull that has performance without the usual Southeast Asian “problems” will be welcomed.
Once you are set to go, I may proceed and line up a sailmaker/rig maker for here in the US and Canada, to further reduce the cost of shipping.
Dear Dick,
getting some sailmaker in the US to build the rigs is a good idea. I have checked approximately shipping cost for the hulls and appendage set, it will be about 50 USD by economy airmail.
I’m still working on the moulds, the pics show them when I demoulded the plugs.
I’m building an auxiliary mould to have the joining surfaces moulded to the hull halves already. this will make it easier to assemble the halves.
Don’t forget I’m not going to get into mass production, it is my hobby to build those boats.
I wish you good luck with the maiden of your Tri and your new Cat and hope they will hit the waves soon as well.
