How do you think these would go? They're for sale on ebay for $900.

waste of good battens and sail cloth! With that much sail way up top you wouldt have a hope of controling the twist . the sail would only become effective when you took it off and put on a 4.0 m. perhaps the sailmaker needs to take a really good look at how a blokart sails

what i am waiting to see is a blokart sail where the boom extends forward of the mast and a small jib is attached that moves with the main.

this swing boom idea was used and still is used in rigless remote control yacht racing, not the IOM class nut the marbleheads used then extensively.

they were simply called a swing rig, and amazing ly easy to get the hang of.

hills said...

Yeah, that's how the RC yacht I build is set up although the jib boom is completely seperate to the main boom. You can even goose wing them down wind and it only requires one winch servo to trim both sails. It would work but I don't know what it would do to your COE.

hills, you into remote yachting? check out these two little rippers i have on ebay
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&rd=1&item=280208719382&ssPageName=STRK:MESE:IT&ih=018

landyacht said...

waste of good battens and sail cloth! With that much sail way up top you wouldt have a hope of controling the twist . the sail would only become effective when you took it off and put on a 4.0 m. perhaps the sailmaker needs to take a really good look at how a blokart sails

Hi Landyacht,

Why do you say this? Modern windsurfer sails have a similar shape to the sail above, and for them it's all about twist.

How are blokarts and windsurfers different in that they need a differently shaped sail?

Not having a go, just curious

hills said...

Hey, they look great. It would be good to have a few others to race against. Knowing how much time and effort goes into building them, someones going to get a good deal there!

This is a picture of one of the ones a mate and I made from the "One Australia" plans. I built the balsa strip plank hull below and we used that as a plug to make 2 yachts. Unfortunately they don't conform to any class so we could only race each other.

very nice hills.
the two i have for sale on ebay, started as four boats that i ordered to my specs, from a guy, brett mccormick, in new zealand, he was making the footy class, which is 300mm LOA, i wanted something slightly bigger, and we came up with the 'fun430' which is 430mm LOA.
the sails are fantastic, professionally made, by a sail maker in NZ, i did know who, but cant remember now.
i got the four boats, at $400 each without radio gear, plus freight and GST, all up it was around $2200, if my memory is right. The intended use was to hire them out at Hamilton Island race week, after much debate, i was allowed to show them to the organisers of HIRW, at airlie beach sailing club on an open day weekend they had. the boats, two of them, were used by over 70 people over about 12 hours on that weekend, they went down a treat, got rave reviews, but alas, i could not get insurance to hire them out, its different if you are going to use them your self, but as a hire business, it was a big flop. the two that were used, sold almost instantly, and now reside on hamilton island, and can still be seen in the marina on hamo.
that was around 4 years ago, these two have sat on my mantle ever since then, and i'm now selling them to help fund my first blokart. at $200 including the radio gear, is an absolute steal. they sail just like a marblehead or an international one metre, both of which i have sailed for quite a few years.
you can get them to gull wing very easily, and compared to a marblehead which is 1400mm LOA (or is it 1200mm) they are about 1/4 of the speed, so their scale speed is actually quite fast. i used to sail them against the others at the Mackay Model Mariners, and they would do 4 laps to my one. so i always had a huge handicap!!
if anyone is interested, i am more than happy to answer any questions.

I found this Lift vs Drag diagram.
This shows that a low apect ratio sail has more lift mainly in the 30-40deg region BUT it has LOTS more drag.
Where as the higher aspect ratio sail has LOTS more lift in the 15 deg region.

i was quite impressed by the blokart 5.5 at gillies they sailed well the really light winds/softer surface. the examples seen on this thread had a "big head" that theblokart original doesnt have.
im told by the blokart sailors that they have a set top speed and that was apparent in that they didnt always win and could be caught when a slight gust came in .
i'm quite impressed that blokart pulled off such a big sail on a small light yacht.

gizmo1160 said...
The reason that sailboard guys WANT twist is that they pull the sail INTO the wind and this gives them LIFT much like an aeroplane wing giving UPWARD LIFT and reduces the resistance and drag of the board in the water and with little or minimal resistance they go MUCH faster...and we all know "Speed is King".....

Here is a quote from a previous posting in this thread..
And as you can see in the previous pic of the world record holder the angle back to windward..giving him lift (similar to an aero wing) and therefor less drag in the water.I am thinking at at least the bottom 1/3 is giving upward lift.
The high top sails are used to clear above the disturbed air caused by the waves..
But a point to note though is have a look at how flat in profile the sail is on this sailboard... set up for high speed..

G'day Brian,

I felt I should comment on twist here, as I have changed my views on it after racing 5s in US & Standart in Belgium.

That sail twist is actually very effective if done without flutter (problem in the old days) and also becomes part of the "energy storage / return" process of the yacht itself. This works in conjunction with (using a blokart as example) axle flex, mast and chassis flex. It's not as bad aerodynamically as you might think and is a way of making some sail area "disappear" at higher speeds.

Even Vindicators wing works better with a twist at 140 kmh.