Making a new Yacht

If you increase mast height you will more than likely want to decrease sail area or lower the CE. Don’t increase mast height and sail area, or more than likely you will over power the boat. it also becomes very hard to find cheap masts longer than 72 inches.


Heres another off the wall suggestion…If you fancy building a really individual boat rather than a faster one, you could have a go at building a Mari-CHA IV look alike, I know the hull shape is no where near but a scooner would really stick out amongst the usual array of sloops… Bit more to do as you have 2 rigs to build but it could be quite cool, might be able to blag quite a bit more sail area without needing to mess much with the keel. 2 square top rigs! Just a suggestion before anyone flames me…

To calculate sail area just find the area of the 2 main triangles: 1/2 luff X foot lengths for the main, 1/2 leech X foot for the jib. The roach of the main can usually be split into other triangles and added on.
You shoulden’t have to change the rudder if you keep the center of effort in the same place, no matter how much extra sail you add.
Hope that helps!

Luff 'em & leave 'em.

Does the sail area sound about right for a mast that is 2.2m
The current winch on dads boat is a Hitec HS-72588 Ball Bearing whinch

Rob, based on what you said earlier about wanting a spinnaker your number one consideration in how much area you have in the main vs. the jib has to be whether or not you’re going with a spinnaker system. You can’t just pick an area relationship between the two and have the spin work right.
If you add a square top main you should give serious consideration to using the bent back tip that I use on the S50 and F3.The major benefit is that it makes a square top practical by not requiring full battens or a diagonal batten to support the head; the bent back tip wil probably have less drag then a standard square top and MOST important of all using that system you have an UPPER OUTHAUL that facillitates having the twist profile of the sail completely adjustable which can be a problem in models.
Last problem I’m sure you recognize but I’ll mention anyway for those that don’t: if you add SA only to the main you’ll have to move the whole rig forward to maintain proper balance.

Doug Lord
–High Technology Sailing/Racing

Hi all,
Here is what i have to do,

  1. Research & describe 3 different projects, 1 being the rc yacht based on my 10 Rater hull, 2 being a IOM & 3 being some other rc power boat/yacht.
  2. i have to acknowledge the sources of info.
  3. what is the function of each project.
  4. labelled block diagram of each
  5. major parts lists for each
  6. where i would obtain materials from & approximate cost of each
  7. advantage & disadvantage of each
  8. my preferred selection, the rc yacht based on my 10 Rater hull.
  9. reasons for my selection.

this part is due friday the 13th of feb.

Can everyone please help me with this?

thanks everyone who helps me.

For research you might consider going to; there is a huge suppliers listing as well as tons of other information.
You might also consider going to Graham Bantocks website( I think-listed above) . Graham has an information section where he talks about his boats.
Go to Great Basin -also listed under suppliers on have a wide selection of parts with prices listed. You might want to contact Rob Guyatt in Australia designer and builder of the RMG Sailwinch for some guidance and other info(listed in suppliers listing above). Check the Windpower discussion site for some possible IOM information as well as Lester Gilberts invaluable site for IOM and other design info. All these are listed (I think) on
Finally, if I can give you any more information on the spinnaker you originally were interested in just contact me. You can use any of the information I have posted here or on my website including the sketches if they would help.
Contact me with any further questions at:
Good Luck!

Doug Lord
–High Technology Sailing/Racing

doug is right about lesters site. it is packed with techknowlogy that i cant ebven begin to understand. but some how he explains it well. you could learn alot from lester gilbert. i did
<font color=“red”></font id=“red”>edit by mod (me)

How do i make a mould for the rudder?

See the “keel Deflection…” subject on page one of the Technology section; some alternatives are presented there including a system I use to produce high quality matched molds.Alternatives are also mentioned for producing one off foils.
But are you sure you need a mold? Are you going to produce these rudders?

Doug Lord
–High Technology Sailing/Racing

Make one up from laminated balsa, 3 layers is enough usually, put the middle layer with the grain across the across and the outer layers with the grain running down the blade. It should be more than stiff enough for a one off and alot qicker to make than messing about with plugs and moulds.

Luff 'em & leave 'em.

i actually made a flexi top rig for my victoria… aluminum base, graphite top section. As soon as i ease up on my top stay that thing flexs like nuts. just an idea, and it works good for spilling air in puffs…

i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon

Okay everyone,
I have decided to just use dads rig for the moment, no kite, but instead of having a keel have a system where i have a traveler on the deck like the Harken Virtically Curved Track (ends up so they don’t touch the water when heeled over), but for that I need to work out what the force of the sail area is, does anybody know how to workout what the force of the sail area is?
Sail Area is 4367 sq mm, jib is about 2859.5 sq mm
Regards Rob

You can do the conversion but: 10mph wind =.5lb. per sq, ft. pressure. 17mph wind =1 lb.per sq.ft. presure.
These numbers yield a somewhat conservative answer but will get you close.
In my experience you can probably get away with 20 to 30% more SA than would be possible taking these pressures literally.

Doug Lord
–High Technology Sailing/Racing

how much lighter can i make the wieght?

If by weight you mean ballast you can figure somewhere around 40-50% less than whats in there now using a canting keel /Trapeze System combo. Using the combination makes it easy to add or remove weight from the cart.
What is the fin length and ballast in the boat now? Is it stiff ,tender or just right?

Doug Lord
–High Technology Sailing/Racing

fin length is 41cm long, its all up hull weight with radio gear is 7 kg.
if i just use a canting keel, i think it would be easier to use than the canting keel/trapeze system. as the saying goes Keep It Simple Stupid. I am gonna just use the canting keel with another fixed board for LR, minus 40-50% bulb weight, that makes the all up hull weight between 3.5 kg & 4.2 kg.
What does everyone think, does anyone else apart from Matthew Lingley & Doug have any ideas, canting keel designs or any other queries?

hahahah you lazy boy getting every one else to do your sack’s for you let me guess its for tdd? ahhhhhhhh know all to well about tdd in year 12
what fun

When the Apprentice knows more than the Mentor its time to quit!

whats tdd?

techongolical design and development (shop as the usa calls it)
materials tec wood work/metalwork

that is the subject that your are doing isnt it??

When the Apprentice knows more than the Mentor its time to quit!

what school are you going too??

No, im doing Systems Technology Electronics & Mechanics (intergrated course)
Im going to Karingal Park SC