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Nov 27, 2013, 03:05 PM
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A.B.'s Avatar
I am planning on making a new rudder for my IOM; current thought is to use 1mm carbon fibre sheet cut to correct size, form it over the rudder shaft while gluing the sides and bottom. Leaving a hollow rudder. Is there a need to close in the top? My thought was water in water weights the same as water? But when fin is measured and weight would be less? Thoughts? Andrew
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Nov 27, 2013, 03:36 PM
Love RC Yachts!!!
Give it a go!!!!
Nov 27, 2013, 04:06 PM
Flying without a licence
FWAL's Avatar
It's thinking out of the box for sure! Without a lid on the rudder so to speak could prove to be a bit draggy though.
Nov 27, 2013, 04:11 PM
Registered User
IOM Rule E3.2b
The keel and rudder shall not have openings through which water could flow when in use.
Nov 27, 2013, 05:44 PM
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A.B.'s Avatar
Is that so you don't have a split or slotted fin/rudder?
Nov 27, 2013, 06:12 PM
Registered User
You will have to ask the rules writers that one.I suspect that it is to keep the boats similar to give close competative racing.
Nov 27, 2013, 06:22 PM
John - In my private capacity
hiljoball's Avatar
The idea of a 'hollow' rudder that can fill with water may run foul of class rules.

You are discussing

3.2.3 (shall not have) have openings through which water could flow when in use.

It would be reasonable to infer that water running in from the top or bottom opening would fall under this restriction.

Again - this is a 'closed' rule. If you want to try something new. - ask first for a ruling from the tech committee..

John
Nov 27, 2013, 06:37 PM
David Cook Victoria, BC Canada
Thread OP
Quote:
Originally Posted by A.B.
I am planning on making a new rudder for my IOM; current thought is to use 1mm carbon fibre sheet cut to correct size, form it over the rudder shaft while gluing the sides and bottom. Leaving a hollow rudder. Is there a need to close in the top? My thought was water in water weights the same as water? But when fin is measured and weight would be less? Thoughts? Andrew
Andrew: Don has a real trick way to make rudders or fins. Don: Correct me if I get this wrong. He uses wax poured on a piece of plywood with 2 parallel rails to slide an aluminum cross section template over. This makes a female pattern which you make a male plug, then a female building mold. A lot of effort but does excellent work.

I on the other hand laminate 1/16" balsa together with epoxy resin (with contrasting pigment (black) to indicate the centreline. Add a layer of 1/32" balsa (or plywood if you want a heavier rudder) to use as a guide to shape. Move your max chord thickness and pivot point way further forward than what you think. I'd suggest around 20% from the LE.
Last edited by PorkyPig; Nov 27, 2013 at 06:38 PM. Reason: typo
Nov 27, 2013, 09:43 PM
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A.B.'s Avatar
Thank you john and Dave!. I will just stuff the top with blue building insulation. Maybe see you on saltspring in June or David in hoodriver in July. Thanks for your help.

Andrew
Nov 27, 2013, 09:45 PM
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A.B.'s Avatar
Then again if it's full of water can water still flow? Just askin
Nov 28, 2013, 04:53 AM
Registered User
A.B.

I think you can be assured that any modification made with regards to the IOM class rules has been tried/tested already. If it had any merit and was legal it would already be considered standard. Besides how would you envisage holding the shaft between to pieces of carbon without it turning in the structure? Might as well fill the space with a few grams of filler.

Tony
Nov 28, 2013, 04:58 AM
Registered User
Is this thread starting to get off track? I'm reading a whole lot of stuff hear about rig tuning etc etc, which is being covered on another excellent thread here, and not much about actual hull design.

As A.B. has just said "just asking"?

tony
Nov 28, 2013, 07:44 AM
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A.B.'s Avatar
Tony,

You are correct, I am sure all things new in IOM have most likely been tried, so this question is done. But just to answer why does the shaft not turn? Well if you think of two pieces of material in the shape of a rudder blade, them put thickened epoxy on the trailing, leading, and bottom around 1/4 inch wide, then put shaft on one side, with thickened epoxy on shaft. Now you take both halves put together and clamp leading and trailing edge. (Cloth pegs works good for this) . Hope this explains the process?

Andrew
Nov 28, 2013, 09:26 AM
Registered User
Quote:
Originally Posted by A.B.
I am planning on making a new rudder for my IOM; current thought is to use 1mm carbon fibre sheet cut to correct size, form it over the rudder shaft while gluing the sides and bottom. Leaving a hollow rudder. Is there a need to close in the top? My thought was water in water weights the same as water? But when fin is measured and weight would be less? Thoughts? Andrew
Andrew
If the top was watertight then the enclosed airspace would provide flotation so a hollow rudder would lift the stern but an open top would sink it(a bit)
Don
Nov 28, 2013, 11:07 AM
David Cook Victoria, BC Canada
Thread OP
As the person who started this thread, my thinking was IOM Design do It Yourself (as the title implies). In my opinion Design includes the whole boat, not just the hull. Do It Yourself is pretty self-explanatory.


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