Minuet Yachts: a 2m fun boat-can the design be improved?

One of the biggest advantages of such a small boat is that material cost is pretty irrelevant because it uses so little. For this reason you may as well splurge. SOF would be interesting. There are very few SOF sailboats and no SOF keel boats that I have seen. For that reason I would encourage you but I think that the design is worth 'doing right'. By that I mean doing a good multi-chine single sheet marine ply design that others could reproduce fleets of.

 

I agree, although I think that a cedar-strip boat would be better than plywood, and it could look nicer. The biggest thing I don't like is the weight. Mine weighs 60 lbs without the keel. It's all I can do to get the thing on top of the car by myself.

 

Cedar strip would be a great way to make the hull and you are right that it would be better looking than chines. Standard practice would be to make the hull strip plank and use it as a plug to make a mold for subsequent hulls. Speaking of looks I wonder if your gaff rig with topsail would be better suited to a more traditional style boat deck -square or horseshoe deckhouse. Your deck matches the original Minuet Yacht which is very 'contemporary cruiser'.

Another build possibility would be to make a flat bottom ply upper structure, put a couple inches of foam on the bottom (one surfboard blank would do) and shape the bottom like they do for surfboards, then a layer of glass. The trick on this would be to keep your butt as low a possible. The positive is that you would not need to add buoyancy -it's in the hull adding structure.

Light weight is very desirable in a car-top boat. 60# is not too bad but you should be able to cut that in half with a well designed marine ply or SOF which would make getting to the water that much easier. One note about SOF roof top -it can chafe. This seems pretty obvious but over long distances at high speed it can be surprisingly damaging and out west water can be a long drive.

Congrats on being the first on the thread to get to the water.

 

If you are worried about weight, strip build with glass on both sides can be very light.

Find some light weight 2x4 wood. Cedar is great, but the readily available big box bulk lumber (the S-P-F marking means Spruce, Pine or Fir) has potential. I have found scrap S-P-F that is very light white pine.

Cut strips and power plane one surface. I find I do better to power plane the 2x4 before I cut each strip. For this boat, I would target a one side planed thickness of 1/4" to 5/16".

Focus on the inside surface first as noted in my previous post. For this bottom, I would not worry about any small gaps on the outside surface along the edges of the strips, you will fill them later. Apply a layer of thin fiberglass to the inside surface. Attach any inside structural members, seal everything good and install on boat.

Do final finishing (power planning and sanding) on outside surface. For this boat, I would target a final wood thickness of 3/16" to 1/4". Fill any gaps with lightweight bog (epoxy / microspheres). Glass the outside.

For a small rounded rigid bottom, this will get you about as light as possible and still allow use of "average joe" materials. Plywood of similar thickness can also work, but rounded is tricky and you really do need to get the "good stuff" that may not be available locally.

Carbon cloth on foam is about the only thing significantly better for strength/weight.

I am not sure how you would be able to do a good SOF with the need for your lead keel.

 

Yes. For those of you who have not started, I would recommend wood strip construction. SOF could work, but it needs the bugs worked out first. I may be making another one or two after this, depending on interest and if people will pay me to make boats for them. I have a good source of marine plywood, but I don't really want to get into the stitch-and-glue or tortured ply business.

How does Kevlar play in the game with fiberglass and carbon?

Has anyone played with balsa strip and glass?
This page has a 12 lb canoe someone made. He also mentions several punctures in the outer skin he had, so it would probably be a good idea to beef up the outer skin...
http://www.storerboatplans.com/Balsacanoe/Balsacanoe.html

 

rcnesneg,

Impressive, really impressive. You're a chap with the courage of your convictions. You now have proof of concept & you could use your hull as a mould for laying up another boat, in a similar manner that youngsters paste paper onto a balloon in order to make puppet heads or face masks.

However, rather than using paper & paste, you could try using 6 mm cork sheet cut into lengths & build a triple diagonal planked hull using polyester or vinyl ester resin as the adhesive & internal & external finish coats.

It may seem bizarre, but cork is flexible, non flammable, impermeable & buoyant & it is low cost. Furthermore, I think that at 18 mm thick, it would be tough enough for the size of a boat that was originally built using cardboard. I wonder if the traditionalists at Wooden Boat forum would accept a boat constructed using cork from trees as being an authentic wood boat:?::idea:

http://www.ebay.co.uk/itm/like/1913...3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108

It works for decks as well.

http://www.marinedeck.net/science/techn-university-of-delft

In years to come, when cork boats are on the briny, bobbing buoyantly, please remember you first saw the idea here.

I am not insane. My mother had me tested. (Sheldon Cooper).

 

Interesting idea! I like the cork idea! That might be worth looking into. How well would it handle compound curves? I doubt very well, so it would need to be specially cut into strips, but the strips could be much larger than wood strips, so it would be easier to do. And your right, it is pretty light. I'll have to keep that in mind.

 

rcnesneg

As the 6 mm cork is delivered in rolls, you can certainly cut the widths of the strips to match the contours of the hull, even cutting curved strips where necessary. Cork is very flexible and narrow strips will follow the shape of compound curves of the hull. Once the hull is laid up with two diagonal layers the final layer is laid on the horizontal.

For the interior areas that require greater reinforcement, such as the keel fastenings, build up strength with multiple layers of thin ply to follow the curves of the hull, in order to spread the point loads. The same applies to the mast tabernacle, standing rigging, cleats rudder etc. You could also mould yourself a comfortable seat incorporating a neck rest.

If you were looking for a suitable name for such a quirky vessel, Quercus springs to mind. Casparian would also work.

http://en.wikipedia.org/wiki/Suberin

Good luck,

Perry

 

To be a good 'core' material must have good stiffness in compression and strength in shear. Cork is not used for obvious reasons.

About chine or no chine -from what I can see all the chines would be below the surface of the water so the boat would look the same while sailing. Another strong point for chines is that achieving and maintaining a smooth surface is MUCH easier. If you plan to produce boats for sale you will need high quality 'A' surface. BTW there have been successful fiberglass SOF boats. The frame is just the fastest way to make the mold. You could make many chines and the result would look like lapstrake -which would fit perfectly with a classical boat and your gaff rig. Like a mini Folk boat.

If you still want the round hull strip is the way to go, but as PF said, there is a lot of milling to do -expensive dangerous machines. Once again the small size comes to the rescue -6ft is considered an offcut -scrap- which many would be happy to sell you dirt cheap. Cedar is very pleasant to sand, and you will be doing an unpleasant amount of sanding. Redwood is even better.

Nobody mentioned foam core but it is the primary core used for boat building. You could buy one sheet and slice off strips with a hot wire then build a stripper. For the size of your boat I still think you should just use the materials and technique that surfboard makers use. A professional boatbuilder would just CNC cut the plug out of foam. Thanks to the builder movement there are lots of 4X8 CNC gantries willing to work cheap.

 

Skyak,

Cork is very strong in compression. It's used for flooring & champagne corks & it's also resistant to shear as it's used in certain types of sandwich construction. It's also been used as fishing net floats which is a pretty abrasive environment for them & it is certainly stronger than the cardboard prototype.

http://en.wikipedia.org/wiki/Cork_(material)#Other_uses

As for stiffness in compression, that is ascertained by creating a test panel by using vinyl ester resin to laminate two diagonal layers & one horizontal layer of 6 mm cork strips with the resin forming both sides of the panel. This is a very small boat & the compound curves will also add stiffness. A substantial improvement would be to use epoxy resin & glass cloth, but this is supposed to be a light, inexpensive boat in the tradition of the fibreglass original.

https://www.youtube.com/watch?v=D3QE01xWrAQ

 

Somewhat switching topics, I've done some design work on the rig. The old rig is severely under powered. I cannot bury the lee rail in 15 mph of wind even with everything hoisted, and it is dead slow in any other conditions. Here is a revised plan.




The mast is a 15 foot fiberglass mast, probably about 13 lbs or so.
The main's luff is 12.5 ft, and the boom is 4 ft.

The jib is self-tacking, a change I would make after the sailing I've done on mine.

The main's full area is 37.2 sq ft.
First reef is 24.5 sq ft.
Second reef is 13.9 sq ft.

self-tacking jib area is 18.3 sq ft

Total working area as shown in the picture would be 55.5 sq ft.

It also has provisions for a 53 sq ft masthead drifter/code 0 set on a 3 foot removable bowsprit, for a total of 90.7 sq ft.

Old sail area was around 25 sq. ft. This would basically double it.
What do you guys think? How does it all sound? I realize weather helm is going to get a little bit worse, but I plan to leave the Hobie rudder on, as it does a good job of dealing with all that.

 

I hope you have taken a little time to learn how to calculate heeling moment and righting moment. It doesn't take that long and you can do the numbers for your previous rig and for your new rig and have the numbers to compare with the actual performance and for other boats you may do down the line.
You may have doubled sail area but you have also increased the height of the center of effort dramatically. I strongly urge you to day a few days and use something like Skenes or Principles of Yacht Design and learn how to figure this out the old fashioned way. It will be an asset to you down the line...
Good luck you've done well so far!

 

Some quick calculations, maximum righting moment from keel alone at 90 degrees of heel is about 150 ft-lbs.
Max heeling moment from old rig at .25 lbs/sq ft is about 25 ft-lbs.
Max heeling moment of new rig at .25 lbs/sq ft is about 87.5 ft-lbs.

So going off of that, at 30 degrees of heel, they would both be around 75 ft-lbs and it would be balanced at .25 lbs/sq ft.


And calculations for reefed sails at .25 lbs/sq ft.
Single reef and working jib: 63 ft-lbs.
Double reef and smaller jib: 23 ft-lbs. A little below current sail moment.

 

rcnesneg

The centre board in the Minuet does not weigh as much as the keel you fitted.

https://www.youtube.com/watch?v=D3QE01xWrAQ

Sensible move to raise the boom above your head. Have you considered using a sailboard rig with wishbone boom & a battened head for more lift & predictable CoE?

http://www.actionsportsmaui.com/students/asm_kids_camp_summer.jpg ......... BTW, the kid should be balancing the rig to windward.

Good luck,

Perry

 

That is correct. I believe I heard it was 30 lbs on the Minuet. Mine is more like 55. I was considering the full 70 I bought, but I decided 50 lbs of lead would be a wiser choice. I am quite happy with the amount and how it handles with that amount of lead. I did move the boom up about 3 inches on the plan. I am also going to be sitting about 2 inches lower. I have considered trying it out with the sail that came with the windsurfer, but I don't think I'll do much with that, except maybe look at the luff curve and try to match it on the sails I make.