IOM Do It Yourself DESIGN - RC Groups
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Nov 05, 2013, 11:20 AM
David Cook Victoria, BC Canada
Discussion

IOM Do It Yourself DESIGN


With the IOM General Discussion Forum being about IOM in general, I thought it would be good to start a Forum for those of us who design or want to design our own IOM (International One Metre).

I've designed 7 IOM over the past 5 years with relatively good success at the club level. I'm now trying my hand at becoming a pro with 2 designs, both narrow beam with hard chines with multiple chines.

I've had the good fortune to learn from some talented mentors. If you want to ask or discuss a design problem/solution specific to the IOM, feel free to join in.
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Nov 05, 2013, 12:03 PM
Registered User
I have also designed 7 IOM's. DC1-DC7. They have all been one offs although I still have the molds. I design using Hullform Pro. The last 3 boats have been chined although I'm still not completely convinced there is any advantage to them. All my boats have been designed from scratch although I can't deny following trends(read chines). I design them trying to keep the CB and CF from moving back and forth with 30-40 degrees heel. PC is about .56-.58. Hoping to learn something from this thread.
Don
Nov 05, 2013, 02:59 PM
Registered User
blackrgb's Avatar
This is cool. Thanks David for starting this thread. I am designing an IOM for my Winter project. David you are well aware of how important it is to have a Winter project in this part of the world where it rains no stop.

I am focusing on hull drag. Hoping to manage the boundary wherein the laminar flow is converted to a turbulent flow rather than separating. This is a little outside the box, so if it doesn't work I will just forget I sent this
Nov 05, 2013, 04:20 PM
David Cook Victoria, BC Canada
One area that interest me is keel fins. I've noticed on the top professional designs have the max chord thickness is very far forward and quite thick for its relative length. Having a fin with low wetted-surface obviously reduced drag.The max draft forward induces lift easier (I've been told). A light fin also allows for more ballast in the bulb which improves the CoG. My next boat will have a long and wide keel fin box to try everything between a Creed and Bantock.
Nov 05, 2013, 04:20 PM
Flying without a licence
FWAL's Avatar
I'm currently building my fourth IOM design since starting in RC racing three years ago. I don't use any software, just a pencil and basic geometry, balsa, FG and West Resin.
Performance wise my previous designs appear to be as fast as any other modern IOM but there's always room for improvement! My latest design is looking to improve the aerodynamics over the foredeck and enhance the endplate affect. Aggressive rebated chine to help prevent leeway and a narrower rounder transom to reduce drag. Fingers crossed.
Nov 05, 2013, 04:26 PM
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ToniGe23's Avatar
Quote:
Originally Posted by FWAL
I'm currently building my fourth IOM design since starting in RC racing three years ago. I don't use any software, just a pencil and basic geometry, balsa, FG and West Resin.
Performance wise my previous designs appear to be as fast as any other modern IOM but there's always room for improvement! My latest design is looking to improve the aerodynamics over the foredeck and enhance the endplate affect. Aggressive rebated chine to help prevent leeway and a narrower rounder transom to reduce drag. Fingers crossed.
Hello mate,
I need to speak to you I have sent you a PM
Nov 05, 2013, 04:55 PM
NORTHLAND NEW ZEALAND
D design's Avatar
this thread is a great idea. Too much v8 vs britpop ect chit chat on the iom general discussion

Im going to play around with rudder winglets on a hull that dosn't change CB at different heel angles.
Nov 05, 2013, 05:14 PM
Don't lie to my dog.
Gregg28's Avatar
I'm watching with interest. I have done several Marbleheads, USOM, 36/600 and RG65s. I am thinking about an IOM. I do have some ideas.
Nov 05, 2013, 05:25 PM
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blackrgb's Avatar
Quote:
Originally Posted by PorkyPig
One area that interest me is keel fins. I've noticed on the top professional designs have the max chord thickness is very far forward and quite thick for its relative length. Having a fin with low wetted-surface obviously reduced drag.The max draft forward induces lift easier (I've been told). A light fin also allows for more ballast in the bulb which improves the CoG. My next boat will have a long and wide keel fin box to try everything between a Creed and Bantock.


Having the maximum chord thickness far forward allows for a longer trailing and sharp edge which MAY??? improve the increase in efficient lift versus the wetted surface(skin friction) and form drag dynamic. Per the Kutta Condition:

.........A body with a sharp trailing edge which is moving through a fluid will create about itself a circulation of sufficient strength to hold the rear stagnation point at the trailing edge........


It is a good idea to take a close look at keel fins. Here is a comment Graham Bantock made:

"Interestingly, the largest genuine gains (i.e. a gain in all conditions rather than in one specific condition) in performance over the last decades have been about 5 to 10 times greater from better foil design than from better hull design. Although this does not mean we should ignore hull design, it does indicate that the most profitable area for research is in the foils. Happily these are also the easiest to replace."
Nov 05, 2013, 07:58 PM
David Cook Victoria, BC Canada
For those wondering where to put your fin fore and aft I've been told 2 methods and both came up with the same location.
1. Geoff Smale (RIP) told me he aligned up 25% of the average chord length from the leading edge with the CLR.
2. I was told second hand Claudio puts the fattest part of the fin in line with the CLR.
Nov 06, 2013, 02:08 AM
Registered User
coolmobility's Avatar

Lurkers


I'm sure I won't be alone in subscribing to this thread to see new and novel design ideas and practices. Should be interesting to those of us not skilled enough or brave enough to scratch build but may try new keel and rudder designs on our commercial hulls.

Thanks for starting this Cookie, should be very interesting to read.

Even if we don't contribute past this statement, on behalf of all us 'lurkers', reading the contributors gems of ideas and results of test rigs will be very interesting.
Nov 06, 2013, 02:20 AM
Flying without a licence
FWAL's Avatar
Quote:
Originally Posted by D design
this thread is a great idea. Too much v8 vs britpop ect chit chat on the iom general discussion

Im going to play around with rudder winglets on a hull that dosn't change CB at different heel angles.
Hi D
I used to campaign a F16 which used T Foils. They certainly felt different and dampened pitching. However, they also dulled the feel and took the spark off the boats performance. I would imagine that the majority of the time the drag caused was out weighing any performance gain. During my most successful events winning both a Euros and Nats I didn't use the T Foils but altered the aspect ratio's of the appendages.
Just food for thought!
Mk
Nov 06, 2013, 03:07 AM
Registered User
ndeverell's Avatar
All good

Very interesting so far

Maybe we will be able to brainstorm a world beating IOM here!

cheers

Neil
Nov 06, 2013, 03:11 AM
Flying without a licence
FWAL's Avatar
Quote:
Originally Posted by PorkyPig
For those wondering where to put your fin fore and aft I've been told 2 methods and both came up with the same location.
1. Geoff Smale (RIP) told me he aligned up 25% of the average chord length from the leading edge with the CLR.
2. I was told second hand Claudio puts the fattest part of the fin in line with the CLR.
I'm certainly not going to dispute the above findings. Although, I personally don't get to hung up on a precise position. I have worked out (very quickly nor scientifically) that as long as the max thickness of the fin is within 16mm of the CLR then there is no real noticeable differences.
There is however a possible placebo affect, max thickness in front of CLR should produce better pointing and vice versa which definitely would occur outside the +/- 8mm margin of error.
Nov 06, 2013, 04:03 AM
Registered User
This could be really interesting. You might be putting your point of view (amateur designer) against somebody who has vast design experience and due to their non de plume not even be aware of who you're talking too.

FWAL your comments about fin position is interesting. In Australia Tim Brown built Pikantos with Mark Paterson fin and rig positions are well known to be very quick. I understand they are only a few millimetres different from Graham Bantocks measurements.

As for me I've designed built and burnt more IOM's than I care to remember. Using Hullform certainly keeps the costs down.


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