A 65cm CAT (Flyer)

Almost added this to the trimaran thread - but thought better to keep separate. This thread is the basic foam build of my “FLYER” catamaran which I hope to compare sailing qualities against the trimaran.

  1. Ran out of glass for the tri and remembered to order today - so will give me time to cut/shape foam for the catamaran. Using photos from various web pages, I was able to get a decent side-hull photo and using Adobe I was able to “tile print” and paste together a full size (65cm long) outline of the hull profile. [photo 1-1]

  2. Laid out the lines of side and top view and using my bandsaw quickly cut both blanks of foam to rough shape.

  3. Laid out the top view and also proposed beam locations, and proceded to cut one blank to both top and side general shape. [photo 1-2 and photo 1-3]

  4. Using 80 grit paper, I began to shape one side of one block, with deck and below-waterline curvature. Completed all rough cuts and started shaping to give me an idea of what I wanted hull to look like as I began to shape and round over all the sharp corners. [photo 1-4] - the other side of this hull remains to be shaped.

Update: Hull shaping completed
What started late yesterday evening was completed tonight. The first prototype hull for the “FLYER” catamaran was finished and a few photos taken. Following the lead suggested by Siri in his 65M trimaran build/thread, I elected to shape two foam blocks and will cover with a single layer of glass cloth - more for dent resistance than anything else.

Last night I had one side of the hull completed, and tonight I finished off the opposite side, as well as locating the cross-beam “saddles”. I still need to bevel them a bit in order to allow the hulls to cant a bit when sitting flat on water. Also, while I know where I want my boards located, those also will be canted slightly to match the hull angle. This “should” ??? provide me with a nearly vertical board when the boat is sailing on one hull (if I can keep it there). :scared:

I still need to select the sail winch servo and am trying to find one small enough to fit within the hull without the arm (or drum) sticking above the hull deck (if possible). Because the boat will not be sailed dead-down-wind, I don’t need a lot of sheet travel, and it will probably be uni-rig main only so torque demands will also be minimal. Hoping a micro or park type servo will work.

Photos below show hull ready for the coat of glass.

Photo 2-1: This is a bow/front-quarter side view.
Photo 2-2: Front 3/4 view
Photo 2-3: A full side view of hull with maximum rocker just forward of front beam location.
Photo 2-4: Another view of the shaped reverse angle bow. I left the blue marker on to be able to see the actual front - but before glassing I will probably sand this down to a sharp edge.

A lot of home projects this weekend, so probably won’t get to the other hull foam block until late in the weekend or early next week.

Update 2:
Well, fortunately the weather provided some “rain delays” on household projects this weekend, so I headed for garage and finished up hull #2.

I cut some 3/8 wooden dowels for spacing the hulls, and I think the current hulls are still a bit to far apart. I think I will have to move them together until I find a pleasing look. At the distance in the photos, (16 inch BOA) the platform would resist sideways tipping, but the added width will also interact (negatively) on the ability of both bows to quickly cross the wind when tacking. I believe I will give up “tipping” stability for easier tacking.

Cat looks bow high in photo on carpet floor, but bows should come down closer to water once the middle of the hulls sink “into” the water.

Photos are pretty much self-explaining - with exception of cross beams. I am using 3/8 wood dowel for this prototype - mainly because I have to wait to order 3/8 carbon tubes, and for the time being the added weight isn’t critical. Been engineering a way to set up a mast step to move/adjust mast forward or backwards. Also now need to locate the positions for my boards. Was originally going to cant both boards AND hulls slightly, and decided to install board vertically in hulls, and then adjust/cant the entire hull slightly so top of hull is inwards of bottom of hull. Maybe 7-10 degrees?

Boards will be narrow and thin, but deep and rudders will be a bit oversize to allow for light wind steering and I’ll have to “eat” the added drag. Tonight I want to layout a rough draft on tracing vellum for my sail area. It will mimic the current “A” Class sail profile, high aspect ration, part flat-top and very little (if any) roach. A uni rig, but will set up boat to be able to add a fractional jib if needed, but want to try it as a mainsail only.


FINALLY - pulled it out from storage, blew off the dust, and started in on the solid wing “powerplant”. While I didn’t intend to let it set this long, it is amazing how much time grandchildren can take up. The solid wing will be much as the hulls - hand shaped by eye to “general” dimensions and form. I want to try the wing concept before building a hollow wing from scratch. I am hoping this foam wing will provide me the opportunity to develop hinges, and a method for setting camber depth. Will probably do that similar to a monohull - using outhaul to preset the camber based on general wind conditions. Again, if it works I can always add radio control to that function.

For those wondering - this wing is only 24 inches in total height. The RG65 Class allows a mast height of almost 44 inches - so this “could” be nearly twice as high. A future thought since solid wings are allowed for the monohull RG65 version. This is going to be on a catamaran, considerably lighter in weight and I don’t think I will need much sail area to push it along. Less wing height also means less tipping and more stability.

The wing pivot point is currently located above front cross beam, but I am going to make a plate on which the wing can be moved fore/aft since the Mini40 boats have their rigs slightly further back. Once I find optimum location, I can decide how to best make a permanent location for pivot.

Wing design is courtesy of Steve Clark (USA C Class)

Photo 1 - general fore/aft wing location (anticipated)
Photo 2 - wing location at possible pivot point
Photo 3 - general wing shape (photo taken at angle - wing looks short)
added 2 more photos. They better show wing and hull in the same visual plane

Hi Dick,
great you finally pulled your cool looking Cat out from your storage - I hope this time you manage to get it in the water. I’m keen on your first sailing experiences with the wing.


Thanks - hard to stay excited with such a small interest group and spread out so far. My son is pushing me a bit now and he has done some pre-engineering to see if he can control camber using an off-set connect to a single servo arm.

As much as I hate to do it, this one won’t be a “pretty” as I would like it to be. Thus there will be a few “warts” on it that willl have to come off on boat number 2 (yup - already planning for one).

Best regards


Have you thought about hot wiring the wing? You can get a really good shaped airfoil this way. Guys making sailplanes have been doing this for years.

I have a “home-made” wire that has been used for cutting hull sections for my MultiONE (1 Meter) trimarans from foam for a plug from which glass hulls were laid up. I had put it away, but pulled it out last night and proabably will give it a try for the trailing edge portions of the wing elements. Easier to do a free-hand for leading edge. Will be doing different process if wing actually works and can be controlled.


Have you make any progress on the wing sail (as in got it on the water yet)? I am (after a similar 2 year pause) finishing up my GhostTrain, and seriously thinking about a wing for it rather than soft sails. Any useful learnings so far?


David -

wife has has me on a cleaning “project” of my work area. The forward element has been shaped, and this past weekend I thinned the second (trailing) element to make it a bit thinner than leading element. Just ordered a few hinges for aircraft ailerons that I will embed in leading and trailing edges. Since the current wing is on the small side, I’m thinking 4 should be enough for now. No - still not on the water. Useful learnings ? - yup - don’t tick off" the wife ! [smile] Oh, if you sand foam - do it outside. If you do it inside - see my “bold” comment .

Hi Dick,
just got some pictures of one of my RC65 Adrenaline’s - here is a picture as a small incentive to get your Flyer onto the water.


Hi Dick,
finally I made some video clips of my son’s 65cm ‘Adrenaline’ this week. Have a look:




Very nice and looks quit stable for a hollow-hull boat. Did you add any weight to the centerboard ? Looks like I will have to get back to my boats. Been a busy two years for me. Wife is babysitting our two youngest of our 4 grand children, and at the end of April, I managed to make the decision to retire. Of course, there are a lot of “homework” projects lined up waiting for me, so to keep wife happy I must attack those first. Was at the pond where there were a few monohulls out on the water the other day and I was already thinking of restarting the multihulls once more. Thanks for the videos.

Cheers, Dick

Hi Dick,
there is no ballast in the fins. The servos and the receiver are in one hull, the battery is in the other hull.
Here is a picture where you can see the boat out of the water:

The boat sails even better when I sail with both hands - on the clips I only control the rudder while filming with the other hand - very shaky clips but YouTube’s stabilize option does wonders.
I hope you will find the time to restart your catamaran project soon - this boats are much more fun than monohulls.
Time wise I have the same trouble as you. I had shelved the Adrenaline waiting for a time slot to adapt the mast tube to use my standard RG65 rigs and sailed it only on a small pond nearby - this time my son persuaded me to take it to the lake with real wind. The clips are the first few minutes on the lake with a standard RG65 A rig, I thought the ‘Adrenaline’ would capsize when it was hit by the first gusts but amazingly it always managed to get back on the floats. It is very stable sailing and cannot be compared to my F48 ‘Inferno’ I built and sailed yesterday - this boat needs both hands and capsizes in on the slightest mistake.

Here is a clip of the ‘Inferno’ :



Well done Rolando !!! To film and sail in gusty winds at the same time is a skill well learned - and quickly too.

The hulls of the big cat looked like they worked very well considering they don’t have much buoyancy up front. I always felt that by using correct rig placement and and some hull rocker, the tall bows really are needed. The clip you posted seems to confirm my guess.

Thank you, Dick

Hi Dick,
the slim hulls look much better than fat ones and work well piercing through the waves as intended. I have dried my receiver from the last dive and will go for another day sailing as soon as time and weather allows.