Construction Photos - "Illusion"

[MultiFast Is MultiFun]

I have been documenting the basic construction of ILLUSION, my MultiONE trimaran. While it doesn't show every step, I think I am capturing enough of the process to allow someone to follow the "concept" and build their own. Hopefully water tests will take place Spring of 2004 once water gets a bit "softer"

The boat was built using shaped foam, with a glass covering. After starting, I decided to use the foam as a mold, and remove the glass/epoxy hulls to make a hollow set of floats and hull. One BIG change I would recommend, is to split the main hull horizontal rather than vertical - in order to make installation of bulkheads, radio gear, rudder and daggerboard box easier (locating them).

For others wanting less work, just glue up the foam shapes, fair with wallboard joint compound (easy sanding) and after covering foam with glass - leave the foam inside. Need to pre-plan for all your equipment installation and hollow out foam accordingly, but while a bit heavier, makes for faster construction, since you don't have to go back inside to add bulkheads, and fastening points. Just cut out foam and replace with wood for any needed "hard" attachments.

On-going construction photos at:
public.fotki.com/rcsailor/multione/

[Doug Lord]

Just curious how you intend to prevent pitchpole with your model? Can you describe the beam to length ratio of the individual hulls? Will you use the maximum beam allowed in the multiONE Class(48")? Will you use a t-foil, movable ballast? Will you carry the maximum sail area?

[MultiFast Is MultiFun]

The main hull and float dimensions could be scaled by printing out the cross section drawings and measuring. Just print to 100% scale from the PDF file.

Approximate dimensions are:

MAIN HULL
38.5 inches long w/o bumper
4 inches wide - max. hull beam at front cross beam
5.5 inches tall at bow stem
6.25 inches tall maximum

FLOAT
33 inches long w/o bumper
2.75 inches wide
3.75 tall maximum

TOTAL BEAM
39.5 inches wide (outside float to outside float)
.5 inch diameter carbon tube

MAST
61.75 onches - height from deck on main hull
.5 inch diameter taper to .375 inches over total height
13 degrees aft mast rake

BOARD
12 inches draft
3 inches maximum chord
1/4 inch maximum thickness

RUDDER
7.5 inches draft
3 inch wide fixed "T-Foil"

SAILS
Cannot access the sail design program at the time of this posting, but the "pink/white" sail set was a calculated 1089 square inches as I recall. Can verify later.

There is no moveable ballast being considered at this time, however a daggerboard with some lead at the bottom may be used for testing in extremely light or heavy winds to determine if more mass is required to carry the boat through gusts or holes and during tacks. Lead will not be in the form of a bulb, but will be faired in at the bottom of the board.

The original rudder has a "T" Foil end plate with 0 degrees angle of attack. As the bow presses down, a negative angle of attack is created. A second rudder has been built but without the "T" foil end plate, as local sailing venues up this way tend to become weedy as summer progresses. Thus the reason why no foils being contemplated either.

Until it is sailed, I am unable to answer the pitchpole issue, other than "Stick time" and becoming familiar with how the boat handles - and probably any shortcomings expected to be found in the first design iteration. Design considerations for this first effort includes a very fine - but extremely tall main hull bow of just over 5 inches in height from waterline to top of hull, along with a very rounded deck to shed water. Add in the "T" foil on the rudder, and the 13 degrees of mast rake which must move forward to induce pitchpole, unlike vertical masts which begin to take on a negative angle as soon as the bow goes down, and I am hoping that in combination, these features will aid in reducing pitchpoles. Only time and actual on-water sailing experience will tell.


Edits in GREEN noted above !

[MultiFast Is MultiFun]

SAILS - Update to above

Main = ,47m² or 728.5 in²
Jib = ,22m² or 341 in²

for a total sail area of ,69m² or 1069 in²

Since the sails still haven't had a final fitting to the mast and spars yet, it is possible I may shave off a few inches on the foot - which will shorten the luff a bit. For now, the sail dimensions are *approximately* the following dimensions:

MAIN
LUFF: 1524 mm
FOOT: 355 mm
GAFF: 150 mm
LEECH: 1479 mm

and the JIB
LUFF: 1371 mm
FOOT: 406 mm
LEECH: 1101 mm

So in reality, design size is a maximum of 1069 square inches or .69 square meters. I have also done a few different jib sizes, and as the jib gets smaller, it will have a shorter luff and if needed, a shorter foot length - all depending on the total sail area I am trying to meet. Worst case would be total elimination of the jib and sail with main only as a uni-rig of about 728 square inches. I would also have to bring the rig more vertical from the 13 degree design rake. Again - a lot depends on sailing characteristics when it hits the water.

[peter]

After reading through this post, two questions spring to mind .
Firstly the mast rake being at 13 degrees has to be counted by the angle of the daggerboard, as the rake may leave you with a tacking problem.
This was encounted when one of our members built a boat off original plans from the UK. It had mast rake similar to what you are talking here, but the daggerboard was vertical on the plan. Moving the mast forward or back did nothing to alleviate the problem, it was over come by raking the daggerboard back.

Secondly I am not sure if you are aware but with multihull sailing the way to assist with the pitchpole problem is with sail size. Most sailors come from monohull background where the idea is when reducing the main sail size you also reduce the headsail size. This doesn't work in multihulls. The pitchpole effect is created by the main driving the leeward bow deep in to the water. To help to alleviate this problem on multi's the idea is to balance out the sails so that the lift created by the jib counteracts the main sail.

T-foil rudders help in heavy airs also.

I.E light air ...............full main , small headsail
Power comes from the main and the headsail is really only there to asssist in tacking and pointing.

Medium air...............reduce main size to reduce the drive effect and increase headsail size to assist lift

Heavy air.................small main large headsail for reasons already stated.

This information has come via a multihull sailor in the UK with more years experience than most people I can think of.

It was published publicly and the entire acticle was extremely interesting to read.

Peter

[MultiFast Is MultiFun]

Peter - something just doesn't "sound" right.

If you add sail area forward of CLR, the jib will tend to induce lee helm, and push the bow to leeward. If you remove the jib and sail with main only, the CE will be behind CLR and induce weather helm.

Sailing my uni big cat, I never had pitchpole or bow down issues upwind or even reaching. Downwind, the tall mast (31 feet) wanted to push forward and downward and invite a pitchpole. Sailing beach cats since 1974, I have never suffered a pitchpole, and only tipped sideways once due to sailing parallel to waves in heavy air along the start line before the race.

If one could allow the foot of the jib to rise, then I think there would be some inherent "upward lift" generated, much like a spinnaker when it is allowed to "float up". With the jib strapped in tight and much bigger in foot than at head, it would "seem" that there is little possibility of the jib offering "lift" whereas I could see a bit of additional downward push of the bows. In essence - a kite (real) flown from the bows would have a much better chance of "lifting" bows than a jib. (again - in my opinion and vision) Since it is pulling upwards. The other factor - is keeping the bows up so that they are able to shed water and waves, and remain as horizontal to the water as possible.

If you look at a DN Class iceboat, they have a tremendous amount of mast rake, but even with that, if something stops the front runner downwind, they too will have a spectacular forward crash (speaking form observed experience!)

The daggerboard in place right now is vertical, but significantly aft the mast. Unlike a monohull, the board is well behind the mast, not directly under it. This moves the CLR further back which is what a angled board would also do. IF you take a look at some of the newest "A"Class boats, there is little room between the boards and the rudders (fore/aft) and the IMPULSE design was based on those trends.
I can easily make an angled board with vertical trunk extension if there is a need. A lot of speculation right now. Once on the water, the many overlooked flaws and errors will make themselves known. Just anxious to see how well it does sail. Have two more guys here in town interested, and wanting to build, but have held them off until I know the boat is at least able to sail, tack and gybe. ;D

[Matt L]

Sailing beach cats since 1974, I have never suffered a pitchpole, and only tipped sideways once due to sailing parallel to waves in heavy air along the start line before the race.

If you dont crash and burn somtimes, you ain't pushing hard enough! ;D

The jib on your boat does look a bit on the big side, In my experience of cat sailing you let off the jib when the leward bow goes down, surely if its a bigger jib and you can't do that having only one winch? could be messy...

I must say though that is one smart looking boat, a hell of alot better looking than mine anyway!

[MultiFast Is MultiFun]

Matt -

I "never" said there were no "WHITE KNUCKLE" ;D moments in that many years - just that the boat was carefully sailed. At 11 feet wide once on it's side it requires outside assistance to get back on it's feet! (3 Michigan State Championships and 4th. place North Americans are among my better accomplishments)

Thanks for comment about looks of "IMPULSE" - I appreciate it.

The rig pictured is the lite-air one with maximum sail area. Several smaller jibs are at hand, and I also want to experiment with sailing it as a uni-rig even if there are tacking problems. Experience has shown that a uni-rig outpoints a jib/main every time - but downwind the added sail area is missed. We usually sail a triangular course, so windward and reaching legs HAVE to provide enough of a lead to hold off on down-wind leg. I view it that I need to win/hold my own on 2/3 of the course! If sailed windward/leeward, then I need to rethink and the jib would become a necessity.

[Matt L]

Squares sound like a good course to me, you have the tactical upwind leg, a blast of a beam reach, a tactical downwind leg and another blast of a beam reach, Thats 1/4 of the course favouring una rigs! ;D Windward lewards are only really fun in boats with assy spins, IMHO. Like I'm ever gonna have the chance to race you guys anyway!

[peter]

Hi
Over here we sail a diamond configuration course. From windward mark(a) to bottom mark (c) is approx. 150 metres. Wing mark (b) is approx. 50 metres from start mark (d) . The racing is then start-a-b-c-d-b-c-d-a-b-c-finish at (d).

Peter

[peter]

My apolgies for the post concerning mainsail and jib relations is wrong. The article that I read the information on has been posted on another forum. It makes for interesting reading I think.
Peter

[MultiFast Is MultiFun]

Matt -

when the Aussie skiffs were here one summer to race our Squares out in Washington (West - left-Coast), they set a "bow-tie" course layout.

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If this helps. By varying the lengths between the marks vertically and on the diagonals, the race leaders were constantly changing. Upwind the Squares were ahead, off-wind the skiffs would catch up, downwind the skiffs were ahead, and so forth. It got to the point after about 4 races, they had the course set so that lead changes took place on almost every leg. Being close to shore was an added plus for spectators. Only did it one year as cost of transportation was prohibitive.

[MultiFast Is MultiFun]

The topic of rudder and board sizes are being discussed in the F-48 Class discussion, and while I had previously posted the dimensions, here are a few photos during construction which may help in understanding sizes and shapes:

The Daggerboard:
12 inches draft
3 inches maximum chord
1/4 inch maximum thickness


The Rudder WITH T-Foil:
7.5 inches draft
3 inch wide fixed "T-Foil"

Both are from 1/4 inch (4mm) plywood, shaped and tapered and then epoxy coated. The trailing edge can be easily seen on the daggerboard. I continued to use the "trunk" concept for the board, since I have several different boards and keels of the same size which can all fit the trunk and are interchangeable. Not yet installed was the 1/4 inch stainless bolt that attaches to the top of the keel trunk.

The rudder log is visible and is incased in a slot filled with epoxy. I have since added an epoxy fillet to each side of the rudder blade where it joins the "T-Foil" for added strength in our weedy pond.

[MultiFast Is MultiFun]

Bridle Wire Side Shroud Attachment

Here is close up of how I attached my side shrouds to the cross beam ends at each float. I created a wire "bridle" with one piece coming off the forward beam and the second piece coming off the stern beam. These meet and the side shroud attached there. The bridles are wire, the shroud is dacron which has bowsies for tension adjustment.

The cross beams are "untapered" carbon tubes (about 1/2" diameter) and I turned down a wooden dowel and epoxied it into the end. A small brass screw holds the triangle shaped ring in place, but is left loose enough to allow the connection to swivel. The connection is nothing more than a mirror hanger and can be found in most home improvement stores. Cost is about $ .50 US