A possible 65M class multihull?

I thought I would start a new thread where ideas and plans could be posted for a potetial small 65cm/25-1/2 inch multihull class.

Given the interest in the RG-65 monohull class and it’s size making for easy transportation, I thought I would take a shot at a down-sized GHOST TRAIN in similar size to see what problems I might face.

The attached is an Acrobat file of the general lines of the GHOST TRAIN trimaran, which could be built using balsa-over-stations tempates; or it could be built using foam, and covered with epoxy/glass and the foam removed. It may require more displacement, and possibly a bit of weight for inertia when tacking in stronger winds, but I need to get one on the water to see.

If you decide to try, you will need to enlarge and print the drawing to 100% and it will need to be printed on a wide-format printer if you want it on a single piece of paper. My full size is approximatly 17 inches high by about 30 inches wide. If your printer has “tile printing” capability, you can probably print directly to normal size paper and tape together.

I would make one change when building - instead of splitting the hull/floats vertically with a left/right side - I’d split it horizontally and build a lower adn upper half hull. Makes installing radio gear and internals much easier.

Please post if you decide to try one and how well it sailed when done.

Hi Dick,

good thinking, I’m sure you know that it already has been realized by Peter Gernert from Germany…he designed a very easy to build trimaran made of Depron foam and some other simple parts…rumors on the net say that it is sailing quite well, flying on one hull included…Peter just released a drawing on the german RG65 board, which is currently being reworked by Joachim (nick on this board: haegar) to add some details…not sure what the status is, but I am sure that haegar will answer here…

I will build one myself when my big boat is finished and afloat…



Hi Cord -

yes, I’m familiar with the lines of Peters boat. I have been sharing lines and building information with Haegar/Achim and also have another fellow from France who is also thinking.

Peter’s boat may exhibit some pointing difficulty - but I say that only because of drawings and information from Achim - and the flat bottom of Peter’s hulls. I see there is a board (or two) somewhere, but photos would help to realize the layout. With the lines from Achim, I plan to try a similar build, but glue some foam to the bottom, and shape to a circular cross-section. From the side … I like the lines/looks.

I had heard Peter’s boat sailed well - but would like to see it against a “purpose-built” boat. I recall some Australian Mini40 sailors who converted their Marblehead boats to trimarans, and thought they sailed fast and well - until they sailed against another club and found the true trimarans outsailed their converted ones. We just had snow again this morning so I think I may have some building days left before Spring finally arrives - and stays. Perhaps it will give me time to begin some work on the little multihull - as well as complete my unfinished RG-65 monohull too.

Please keep us informed of any small multihull projects taking place over there. Post any photos you might find of Peter’s experiment.

Regards, Dick

Wiesels tri65 at USheim in 2008



pics by myself

Arjan -

thank you for posting the photos of Wiesel’s trimaran. It certainly looks like the size will work out and at least sail. I’ve been following the German M40 forum, and can generally get through most of the German posts - but speaking is worse and writing is terrible! [grin]

If he - or you - would comment about the sailing characteristics of this RG sized boat on this forum, it would be great. Of immediate interest would be the total weight of his boat - and does he think it needs any more - or less? Also the keel really seems deep - what is it’s length if you know? Would he consider posting the lines to the trimaran here so others interested in a small multihull could give building one a try? It looks to be fairly straight forward balsa sheet in a “box” design.

Thanks again, Dick

I just checked the old postings of Peter

The DEPRONI is really lightweight - 390g

Here is another picture of keel and rudder.

I will ask Peter for more infos

Thats my Problem with english

The Multi is very light, was relativ fast at that Moment in USheim.
Every Tack the boat lost speed but tacking was no Problem.
She was turning very well and after she took speed very fast.

It was nice to sail, it was my first experience with tri-sailing.

in the mean time I have got an answer from Peter.

No comparison - today the DEPRONI is the only RG-65 MH in Germany.
An RG-65 rig is too big and only usefull for lightwind conditions. Normaly a B-sized rig or the MM-rig fits better.
The keel fin ist 30x5 cm, The rudder is the same size as for an RG-65.
The exact size is not important. The most important thing is the correct position oft the mast.

The DEPRONI turns on a point, but needs fast reaction in a breeze. May be that Arjan can tell a little more?

Concerning the weight, Peter said, that most of the Tris today are too heavy. For example, he recommends less than 2000g for a Mini40. His own Mini 40 is only 1650g. When building he saves weight wherever possible. 390g for the DEPRONI is a good example.

I think a 65M class might catch on, I’ve been looking into building a Mini40 or 2M here in the UK but the costs are a bit off putting.

Would movable ballast be allowed in a potential 65M class?

While I like the idea of a 65cm to 75cm platform, I have given thought to any further restrictions. Since by it’s actual type (a multihull) I am not sure I would like to see a one-design - prefer to leave it open for development. That said, in addition to length, some kind of windward sail area size - or mast height as in the RG-65 monohull class would keep things actually “looking” like a traditional boat, yet alowing a vast ability to “develop”.

On the other hand, if owners wanted to stay with a somewhat “scale” appearance, additional rules would begin to creep in.

Personally, I am all for length and maybe a sail area limit “upwind” and those who want to play/experiment with spinnakers for offwind sailing could, just like foils, moveable ballast, multiple rigs, unrestricted beam, etc. I just would like to see ideas expressed here, so a majority could agree - or offer alternatives. The big question is developmental or one-design - and with these kind of boats, one-design is not likely to happen (in my opinion) or if it did, it would require a lot of rules (uggh).

Like the FOOTY Class did before us, an on-line/internet course could be built/sailed and reported on, as the class develops with enough members in each country to warrant national on-water, side-by-side competition. A lot of members fall by the wayside when having completed their boats, they have no one to race. The FOOTY idea might offer independant competition until there are enough boats to hold a true race.

Just my thoughts. To answer your question, my personal answer would be “Sure - why not?” If you can do it within cost, size and weight constraints for this size of multihull - more power to you. I think the idea of development will create some true “monsters” but until raced, they may remain a fear factor until proven - or disproven. I do know of a German boat under development that (I think) will emulate the new world water speed record holder - something with probably a wing and some small pods for hulls… but this would be the price we pay if we play with development. Always have to consider the unknow future and what it might hold. Development can also be partial, but again, nasty rules required.

Good idea - thoughts anyone else?

Hi, Dick,
I fully agree with you. Let’s have an agreement on some basic “box type” rules.

For example:
Length 65 cm (including/excluding rudder?)
Mast hight 110cm above deck
Sail area upwind 0,225 cm²

Then it can be called RG-65 MH or RG-65 M

I think everything should be allowed beside this simple set of box rules. To be honest, many possible things will make no sense with a 65cm tri for my opinion. Movable ballast, for example, will require too much additional weight for moving the ballast …

The DEPRONI weighs below 400g. Peter’s new 65cm tri will come with foils and I am sure, it will not be heavier …

Hi Guys
Thought you might be interested in some of the commercial efforts to market boats to more or less this specification.

HFM Trimaran
This was produced over 25 years ago to go alongside their 575 and 590 monohulls. It used the same rig and was moulded in styrene. The look was semiscale with solid decks between the main hull and floats. Only recently withdrawn from distribution.

Equipage Fidji
When FAI Vietnam first started about five years ago they marketed a 650mm tri in ARTS format. Designed assisted by Pierre Gonnet the noted French mulithull skipper, it has tube spacers holding the floats and benefitted as there was less windage than on a semiscale type boat configuration.Might be available but I think withdrawn from sale while they make mahogany runaboats which sell much better!

Monteleone Tristar
This is a 710 length tri, with shorter floats in the manner of the latest Irens/ Cadanet 100ft tris being built for Abu Dhabi!! rig height is 1150mm, much in line with proposed RG65m rule.

Gemini 600
Similar to a cruising cat in style with dummy cabin , 600mm legth als I thkn made by Monteleone. Bermuda rig as for all the above.

The Monteleone brand name has changed since they launched and may now be named CBM, based in Trieste, Italy. All might be on offer via Ebay!!

Chris Jackson


A developmental class seems like the only way to go. I would really favor a very loose box rule. Max overall length, width, and mast height.

Perhaps a sail area, but I would favor no sail area restriction. It seems that tends to be self-limiting for the most part. It seems to me that any difference between up and downwind sail area would complicate the rule more than needed.

That said, with the F48 mid-way through construction and the RG65 planned after that, I don’t know if I need to build another new boat for a while! :smiley:


I would also wish for no restriction on the number of servos. :slight_smile:

Thanks for the information Chris, I had no idea there were commercial multihulls similar in size however I’ve had no luck in tracking any of them down on the internet.

I have an idea for an R65M multihull which I’ll knock together over the next couple of weeks and document the build. No idea if it’ll work out but that’s the beauty of this small size, nothing much lost.

I would think that the best way to approach this is with a loose box rule, as stated above. The boat, minus rig, must fit in a box 65 cm by 65 cm by 65 cm. As the footies do, a slit, 4mm wide, located in the center of the box, can be used to allow for rudder projections. That surface must be movable. Other than that, no restrictions. I think restricting the sail area or mast height, or number of controls, sail type, ect. will take much of the fun out of this. Can we reach a consensus on this? I would like to start working on one soon.
So what do we say? Keep it simple, with the above box rule? Or do we slightly complicate it with sail restrictions, no movable ballast, mast height, 2 channel, ect?

I might start a poll!

If the boat minus rig has a 65cm cube to fit in, should that not allow plenty of room for rudder and other appendages? I don’t follow what the 4mm slit is.


Hi -

Didn’t vote yet as I think some additional discussion may be needed.

  1. I really don’t want to follow the basics of the “FOOTY” rule with regards to the rudder, slot-in-the-box or diagonal measurement issues. Those, along with their battery rule seemed senseless and didn’t contribute to the idea of development.

Let’s face it, guys spent more time trying to “outfox” the rules, than innovative designs. Eventually they got there - but a lot of keyboard time wasted.

  1. MicroSAIL, back in early 2000’s proved that their foiler was more effective with beam almost twice as wide and the length. Thus, I would suggest no maximum beam width. Some may elect to run a Yellow Pages Endeavor/Macquarie type platform … three pods connected with wing sail in middle.

  2. Sail area and mast length will seem to be self-limiting within the basics of “development”. Those with huge rigs/sail areas “may” be competitive in light air - but there will be a quick learning curve change when wind picks up.

  3. I support a “minimalist” set of rules, and let’s see where “Development” takes us.

  4. Rule thoughts:
    LENGTH: I like the 65 cm length, but am aware of a few 75 cm already sailing - or on drawing boards. And yes, it could go on up in 10 cm increments with every proposal. There already is a 1 Meter class so I see very little difference in 75 cm and 1 meter, yet hate to see the current 75 cm boats excluded.
    RUDDERS: Included within the 65cm LOA
    SAIL AREA / RIG HEIGHT: We had at one time thought about the RG-65 rig/sail combination - however sails may be too full cut for faster multihull speeds - then again maybe not. As I noted above - the size will tend to be self-limiting BUT a mast height restriction (if we must) makes a lot easier measuring for compliance than square inches/centimeters of sail area.
    BEAM: Unlimited
    RADIO: Unlimited
    RIG: No restrictions on mast circumferences, rotation, etc. - but like the F-48 Class, I suppose you could eliminate kite sails as there are no sail racing rules that deal with free-flying kites on a physical “platform”.
    FOILS: No limit on number or location - with exception of rudder T-Foil which cannot exceed the overall length of the boat restriction.
    BATTERY: Open
    SERVO: Number and Type open
    NUMBER OF RIGS: Open - but totals cannot exceed total limited mast height (if we electe to set one) .
    SAIL AREA: Open (both upwind and down) - no limits
    SAIL NUMBER: One number issued to owner, regardless of number of boats owned. All boats will have same sail number.
    BOW SPRIT: Ok but must remain wihin LOA of the rule. (Want a 1 inch sprit, boat hull is one inch less in length)
    CLASS: open to any owner with a boat that meets rules. No mandatory memberships required or suggested. Will be a Class “OWNERS” Association made up of owners only, and run by owners and their elected directors.

Basically - overall length is measured - and rig/mast height (if we have to) is measured as maximums. No other measurement issues at regatta registration time.

I toss if back to the interested parties for opinions and suggested changes/modifications.

The rules above are pretty much what I already had in mind, I would be happy to work within them, pleased to see movable ballast allowed, no restriction on foils and sail area. This would produce some very interesting boats at low cost.

Regarding the central 4mm slot idea, I don’t like the sound of this because I cannot see how it would work on a cat or a proa.

Kind regards,


I think that no width rule might discourage some people based on lack of experience and also transportation. Plus the engineering and materials to produce a boat 65 cm long and 130cm wide, that is stiff enough to perform well might be a turn off. However, since we are adressing this as a potential new class, I think that we should go with the majority viewpoint. Given the poll already, most people want a mast height of 110 cm, and the box rule. This is not set in stone, if you want to do away with the beam of 65cm max, just throw that in in a response in the poll. I for one would like to keep this relatively simple. I didn’t think of kite sails, but we could just say any sail that is not contained within the normal operating sphere of the boat is banned.

One mast of 110 cm - two masts (like the Phillips catamaran or Hobie trifoiler) of 55 cm each or …???

Please see my “Number of Rigs” comment, previous post.

ADDED: Photos - and also note the F-3 Foiler (courtesy of Doug Lord, MicroSAIL Inc.) has only one carbon tube running width of beam. It is probably around 1/2 to 3/4 inch diameter. Just to point out a single cross beam worked on his foiler.