My Cherub Design

[JP233]

true, could be i have just got used to the self tacker.

What are the thoughts on an inverted jib track?

[BenR]

Ah, I didn't get that you were just doing a model of the boat. Is the model supposed to sail? or is it purely a design exercise?

[JP233]

just an exercise, as much i would love to build it, i have no budget

[phil_kirk]

W-tracks have been tried to get the clew of the jib further back but if the W shape is too extreme you end up with the car not getting to the end of the track as the sail fills.  A straight track with curved ends will give you nearly the same benifit. 

Some of the jibs have a bit of roach to add area meaning that they do twist like a square top. 

Bethwait identified that for a given sail area the ratio of main to jib should be something like 73/27 which gives you a much smaller jib than the current 05 rules rigs. This was practical research done on 18's in the early 90's and is described in his second book.   Perhaps the Square top allows the jib area to be increased without changing the parameters that gave them the performance they measured.

[JP233]

Finaly printed my hull, or at least on section of it, it took 30 hours to print.

All it needs is a rub down, sticking to the other sections then a bit of paint.

Pictures to follow

[JP233]

so here are the pictures of the rear third of my final model

the first is while it was being printed
the second is pre rub down
and the third is post rub down

All i have to do now is print the other two sections, rub them down, glue it all together, make some foils and stick them on. i have 3 weeks to do this, if by a miracle i have some spare time, i will make some sails.

[roland_trim]

These bits emerged from the bed of our printer this weekend. Replica of crash test dummy parts. The elbow will follow later in the week.

Like being back at school I have the new work printer in the sitting room (except I was never trusted with the pets following an incident involving my little sister freezing the school Siberian Gerbils). Bought it home so I can free some space on the queue during the week to print off some more rack end fittings when I have finished drawing them.

[JP233]

Unfortunately I have will have to miss this weekends cherub sailing.

Reason being that I have printed my bow, I have a fair bit of sanding to go as well as a couple of layers of filler primer.

The bow section took about 25 hours.


Next questions are, what colour should the finished model be? single tone or two tone?

[roland_trim]

Not suprisingly I'd say paint it red, white internals.

If you paint it white it will hide more of the defects though.

[JP233]

How dare you suggest there are defects in my work!

i agree the red does look good!

[Clive Everest]

I agree that white does hide more

[JP233]

I have gone for 'Ford Electric Orange'

I didn't have enough time to make the rudder a t-foil, and i still have a jib track to make.

If you a have any questions/thoughts/comments please fire away!

[JP233]

Can someone tell me what the diameter of a cherub mast is at the bottom, and the kite pole.
Also the length and chord of the rudder

a ball park figure will do!!

[Tim Noyce]

Hi Jamie, I have just noticed that your scale 'cherub' seems to be a solid mass, no wonder it is taking so long to print! If you are ever in the position that you are having to pay for your materials you will be a lot better off that you put in some sort of internal structure to support the shell (a lot like a real boat) as it will be a lot cheaper and faster to print.

[JP233]

Hi Tim,
There are two skins in my model to bring up the wall thinkness.
The ends are colosed off, but the sections are hollow.