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Nov 10, 2018, 01:59 AM
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Wow she looks great. That extra jib is really nice. 0.75 gives about 0.42 on the displacement. What does the whole boat weigh?
I have printed out using 80% with Adobe Reader and started to transfer to plywood. 0.8 gives a displacement scale of 0.51.
I have also scaled the alu fin. Did you scale the fin 75%.
I think Irene has 5.5kg lead. Your scale factor would give 2.3 kg. Seems about right what you have.
Hope to sail my Emma today.
A bit cool now 5C in the morning, but sunny.
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Nov 10, 2018, 08:49 AM
Registered User

flying jib

Originally Posted by Shaggy_From_NZ
Hi irandar

I built Irene to a Scale of 75% of the Plans so she is 3'8' long from stern to tip of bowsprit. I did not adjust anything just printed the plans to 75 % of their original size.( actually got my partner to Scale the PDF down and then got that printed , there are advantages to knowing a Graphic designer) i Then Scaled all the measurements on the Mast plans as well . i made up an excell spreadsheet to do these calculations as i also needed to convert to metric as well.

Having just taken Ketty Jay for her Maiden voyage I can report that everything worked out fine Probably the only thing i would do differently is the winch system as i am a bit tight to the Keel pins. obviously while the externals are scaled down the winches, servos and batteries all stay the same so some Playing around needs to be done with those.

As Gary said you want to make her as light as possible so you can maximize the Ballast to give a High Righting moment, Mines a bit heavy so only has 2.5 kilos of lead , got the rails underwater a couple of times today but she is still dry inside so no biggie, could fix it with a linger keel but then might end up grounding in the shallow end of the lake .

Her are some Pics of Maiden voyage, As you can see i also decided to make it slightly more challenging by adding a flying Jib, its controlled off a second winch and seperate Radio Channel.

Enjoy the Build

I love the way she looks with the flying gib, IŽll try to have a flying gib in my schooner, but seems some difficult to get the right trim of this sail. Congratulations, I think you did a great work,
Nov 10, 2018, 10:13 AM
Registered User

Calculating the size of a 80% bulb for Irene

Hi folks,

The keel bulb for Irene is sort of a streamlined ellipsoid and I wanted to try to learn
about the shape and size required for my 80% Irene.
An ellipsoid is an egg form defined by half the length a and by radii b and c, as seen
in photo from the Internet.
The volume is given by

V = 4/3 * pi * a * b * c

The shape is defined by the three radii, (1/2 the length a, and 1/2 the diameters, b, and c)

From Gary's Irene plans the size of a tapered egg can be seen.
Here the taper is neglected to make it simple.
From the plans the ratio of the radii c/b can be seen to be about 1.25.
For the 10 inch length the radius a in cm = 12.7
Radius b is 1 inch =2.5 cm
and radius c is 3.1
then calculated from the formula, V=412 cm3
Calculating with lead density 11.3 g/cm3, gives 4656 g
Gary has said that Irene has 12 lb of lead or 5.45 kg.
So I need about 20% more for Irene.
Increasing both radii by 10% (b=2.8, c=3.4)
gives V=506 cm3 or 5720g, more than enough and the increase
was just a few mm.

Scaling down to 80% of linear gives 12.7x0.8=10,
2.5x0.8=2.0, 3.1x0.8=2.5 which gives V=209cm3 or 2365g.
This is about one half of the original weight of 4656g.
This calculation demonstrates that the 80% scaling is about correct
for 1/2 displacement, as expected since 0.8x0.8x0.8=0.51

This can be brought up to 1/2 of Irene with a 10% increase in b and c.
So the ellipsoid needed about 20.4 cm long, with 4.4 cm and 5.2 cm diameters.

I will try to make a tapered ellipsoid as shown in the plans with styropore
to give 1/2 of the Irene volume.
The fin will be reduced by 20% to 46.7cm.
Gary gives the advice that I should wait and see how the hull weight works out
and then simply add enough weight to come up to 1/2 total displacement.
Or should the lead be added to bring the waterline to the correct level?
It will be interesting to see how all this works out.
Good building and sailing, Irving
Nov 10, 2018, 04:46 PM
Recent Convert
cheers for that.
The whole boat weighs 5.3 Kilos all up. it was a bit breezy yesterday but she seemed to handle it quite well,
I'll hopefully get another sail in today in calmer waters.
Nov 10, 2018, 10:05 PM
Registered User
Thread OP

Huzzah Ketty Jay!

Originally Posted by Shaggy_From_NZ

Here are some Pics of Maiden voyage, As you can see i also decided to make it slightly more challenging by adding a flying Jib, it's controlled off a second winch and separate Radio Channel.

Enjoy the Build

Thanks so much, Shaggy, for sharing your lovely Ketty Jay! So interesting. Please tell the story of her name. Her size looks quite attractive as a smaller and lighter alternative.
I'm sure many of us also have considered multiple jibs and are eagerly hoping you'll share details of her winch gear below deck.
Your sails appear to be made from strips of fabric simulating the full size yards of sailcloth. True?
I'm very much hoping for some video!
Nov 11, 2018, 03:53 AM
Registered User
Here are some youtubes on using magic or kinetic sand for making metal molds. Here for aluminum.
I have ordered kinetic sand and plan to use it for my keel lead by making two halves. Seems simpler than other methods. I will make the positive plug out of styrofoam and cover it with tape.

Kinetic sand vs aluminium-Hot video (2 min 40 sec)

Surprisingly Easy Way to Cast Aluminum (6 min 50 sec)

Regards, Irving
Nov 11, 2018, 06:46 PM
Recent Convert
Thank for that Paul
Ketty Jay was Named after the Airship in the Book Series"The tales of the Ketty Jay" by Chris Wooding which Linda ( My better half)and I both Enjoy reading.

to answer your other questions. The Sails are all one piece but Linda sewed rows of stitching to mimic seperate panels rather than drawing them on, This gives the slightly rumpled Appearance . image of this below

as for the Flying jib sheeting I spent a while surfing the web and discovered many wonderful things in the process , I think l'll save the spinnaker for another build though

I got most of my inspiration from looking at builds of the Robbe Schooner Valdivia which has two Flying jibs

there is a seperate multi turn drum winch beside the Keel box which controls a line similar to to the Main sheet controls except this one is routed through copper tubing to run above deck either side of the Cargo and Main Cabins , this has two attachment for the Sheets that go up to the flying jib in front of the main Jib Have put in some pictures and a diagram below to show how it all goes together. . The only issue i had on the maiden voyage was that the Loop line stretched enough to fall off the bottom of the winch drum and got tangled up in the shaft, Hopefully now i have prestretched it and that wont happen again.
if it does I might need to put a guide in just in front to the drum to hold them up.
Nov 12, 2018, 02:42 AM
Recent Convert
Hi Again

Well i took Ketty Jay out for a sail again today, sorry no photos or video as its just me on weekdays so a bit tricky. will hopefully get some this weekend

She sailed well again for a while then the Flying jib sheets got tangled up in the winch drum again so I will have to look in to that, It may be that the 1mm braid i am using for the Loop is too stretchy so I may try some slightly thicker braid. the timing of the tangle up makes me think i may have caused it by winching it the wrong way during a tack as it was working fine for about half an hour and many tacks before failing and it happened when I was going around in Loops with tacks and Gybes while talking to some passers by , get a lot more of them stopping to chat than when i sailed my DF65 still need to try and make it idiot proof though, fortunately she can still maneuver ok even with a stuck Jib

Nov 12, 2018, 03:46 AM
Registered User
Hi Shaggy
I have found that a small pulley with a rubber band in the bow does well to keep the winch line tight. I am thinking that adding a bow sprit and flying jib on my Emma would be nice.
Have fun, Irving
Nov 12, 2018, 10:04 AM
Registered User
Thread OP

Pretty boats

Originally Posted by Shaggy_From_NZ
Hi Again

Well i took Ketty Jay out for a sail again today... talking to some passers by , get a lot more of them stopping to chat than when i sailed my DF65

Isn't that the charming appearance of these Schooners?! It usually feels like putting on a show at our pond. Paul
Last edited by Paul~; Nov 18, 2018 at 01:38 AM.
Nov 17, 2018, 10:35 PM
Mad on modding
robcrusoe's Avatar

Easy As RCG Index

The companion site to this forum] is nearing the end of the 12 months I have for that domain and is being replaced in full with simply as a matter of economics.

Both sites are currently up but the earlier one will go down with all bytes on Dec 6th.

Since the site is purely for the newcomer in mind it will be of little interest to those who have at least completed one build and have achieved at least a satisfying level of skill in doing so.
The original concept was to make it easier for the new chum to find concise articles of importance, in one place and easy to locate.

It has turned out to be a real job of work for the editor and if it wasn’t for Gary’s help it would probably have floundered on the rocks of failure.
But the problem persists in how to sieve out the enormous content of both threads to finish up with prime information.
It will be no news to regulars to know how difficult the RCG search function is for someone unfamiliar with the terminology, or patience to find just what they are seeking.
With the replacement site now in place it seems there is a way to achieve this, and do it well, with just a heavy task to begin with, then relatively easy going thereafter. Bit like a build.
Like a lot of tasks, simple is often also successful.

Check the Easy As RCG Index now
Last edited by robcrusoe; Nov 18, 2018 at 02:21 AM.
Nov 18, 2018, 04:09 AM
Registered User

winch control for Irene

Hi Folks,
My 80% scaled down Irene is coming along much faster than my Emma build went. She will be half the displacement of the original Irene and about 1m length. Already all the parts are drawn out on plywood. The lead bulb form has been done in styrofoam ready to be placed in magic sand for the molding. I have a scaled aluminum keel and the necessary lead to be melted outside on a camp stove in a steel pot.
I am thinking ahead about my winch control. My less expensive servo-transmitter system will give me only 18cm travel, not the 18 inch travel that Gary uses for Irene. If I rig it 1:1 on the sheets, instead of 2:1 as in the plans, will the 18cm be enough? It is OK for Emma, so I imagine it will work out on my smaller Emma-sized Irene.
Thanks for any suggestions.
Regards, Irving
Nov 18, 2018, 03:33 PM
Mad on modding
robcrusoe's Avatar
Are you trying to use an arm winch? It should have a drum winch to get maximum boom travel.

The 18" target is meant for the full scale version so this one will be somewhat less.
The only way I know to ascertain these things is to jury rig it up, either in the hull or even on the bench, to the dimensions the modified hull will be and play around with it. you'll need to knock up a simple mast and boom to try out various sheet to boom locations.

Good idea would be to provide a photo or two so we can see the setup clearly. Photos should always accompany requests such as this to achieve top results.
Nov 18, 2018, 03:43 PM
Registered User
Remember too that that the rigging will limit movement of the booms.
Nov 19, 2018, 12:46 AM
Recent Convert

Video Of Ketty Jay tacking around


here is a short video of Ketty Jay doing a Few Tacks to show her flying jib in action, Excuse the shaky camera work, it was done on a phone and as you can see its a bit windy,

RC Schooner Ketty Jay Tacking and Gybing (1 min 21 sec)



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