IOM Do It Yourself DESIGN - Page 4 - RC Groups
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Nov 10, 2013, 11:47 AM
Registered User
Quote:
Originally Posted by D design
One reason narrow hulls have such full bows and sterns is to have enough boyancy to be class legal.
So you're thinking that the increased Prismatic coefficient is just a result (wanted or unwanted) of trying to build a narrow boat within the rules? That sounds quite reasonable, I like that.

I don't worry about pinholes. Once the boat is out of the mold I put on a rubber glove(sometimes) , dip two fingers into a can of primer, and rub it(hard) into the boat over an area about as big as my hand. I then rub it off with a towel and continue on with the next section til the whole boat is done. You can see the primer come through the pinholes on the inside. Because you rub the excess off there is minimal if any sanding or weight gain. It only takes about 15 minutes and you don't have to risk excess resin.
Don
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Nov 10, 2013, 01:30 PM
David Cook Victoria, BC Canada
I think you want enough volume to keep the bottom of the bow bumper out of the water most of the time. PP5 is my attempt at designing a good all round hard chine boat that will do well in light air. The impossible I've been told by the designer who has the record of the most boats built (Laser).

To increase the volume of a narrow hull, I added a second and duller chine just below the hard one. Time will tell if it works or not. Hull no. 2 should be sailing in a month or two.
Nov 11, 2013, 02:06 AM
Flying without a licence
FWAL's Avatar
Morning David
Just out of curiosity what is overall and waterline beam of PP5?
Mk
Nov 11, 2013, 04:45 AM
Registered User
Hi guys
I've been reading a lot about IOMs on many forums, so I am familiar with much of the experiments that have been carried out. Seattle IOM Newsletter is a great read.
I have been doing my own experiments, not on hull design, but the position of mast, Keel fin and bulb, and I wonder if these three components are perhaps as important as hull design.
When I tell you what hull I've been using for these experiments you'll probably fall off your stools with laughter.
Truth is it's a Hobbyking Phantom.
WHY?
The fin, bulb, rudder and mast are positioned so far forward that it only sails in very light conditions and I thought there was nothing to lose by moving everything back to positions more typical for an IOM.
the result is a boat that sails very well indeed.
Nov 11, 2013, 05:11 AM
Flying without a licence
FWAL's Avatar
Hi Ernie
Again, just out of curiosity what distance are you talking about? In IOM design there is a fair amount of difference in the mast location. An example would be comparing a V8 to a Lintel. Measuring from the Transom the V8's mast is 525mm whilst the Lintels is only 485mm (give or take a couple of mm) needless to say both designs are very good.
Nov 11, 2013, 05:18 AM
Registered User

How Intersting !


Hi Everyone,

I only discovered, and fell in love with RC sailboats a few weeks ago.

My first boat is a Dragon Force (love it) which looks like it'll be strongly supported here in the UK.

I shall be following this thread very closely as I also want to get into IOM (had a 'go' with a Widget in 20 kt wind -yee haa) and can't afford one unless I scratch build.

I'm planning my winter and researching like mad - thanks for all your input

Take care

Joanne
Nov 11, 2013, 09:04 AM
Registered User
Phantom measurements.
One critical measurement not on photos is the location of the CoG of the lead bulb.
I measure down the fin from the hull to the tip of the threads holding the bulb 36cm. Then from the transom to the tip of the threads 63cm.
This gives the location of the bottom of the bulb just below its CoG.
Because the transom is narrow I cannot place the bulb any further back.
This quite narrow hull at 170mm and narrow transom slips easily through the water and is faster than any of the older and wider IOMs in our club ( Italico, red wine. TS2, Jazz, to name a few).
I won all of the club races a couple of weeks ago with the Phantom equipped with home made mylar sails. When I reminded them that the kit only cost 58 GB they pretended not to speak to me again.
I would like it to point a bit higher, But I'm not certain how to achieve that.
My Italico points higher but he keel is 130mm a the hull and 80mm at the bulb. that's a lot more cord. Are there other ways to make a boat point higher?
Ernie
Nov 11, 2013, 11:42 AM
David Cook Victoria, BC Canada
Quote:
Originally Posted by FWAL
Morning David
Just out of curiosity what is overall and waterline beam of PP5?
Mk
max beam 161, w/l beam 160, sits nicely in water with transom just touching and the bow about 20 mm back from the aft edge of the bumper.
Nov 11, 2013, 01:50 PM
Love RC Yachts!!!
Ernie,
I don't believe a larger chord keel helps you point higher. The fact that in fleet racing everyone is pretty much the same is proof. If not, everyone would have gravitated to a particular size by now...

Good to hear you've got a cheap, kit boat to perform, well done. For more height, maybe try a touch more rake, or sheet the jib a little closer, so it doesn't luff as quickly.. A lib leach opening too early can be a cause too, which is down to rig tension ( mast pre bend, jib pivot geometry) etc....
Nov 11, 2013, 02:43 PM
Registered User
Quote:
Originally Posted by erniefoster
This quite narrow hull at 170mm and narrow transom slips easily through the water and is faster than any of the older and wider IOMs in our club ( Italico, red wine. TS2, Jazz, to name a few).
I won all of the club races a couple of weeks ago with the Phantom equipped with home made mylar sails. When I reminded them that the kit only cost 58 GB they pretended not to speak to me again.

Ernie
What an interesting result. Is your Phantom up to IOM specs Ernie, i.e. weight, waterline, one design sails etc?

Love the way you've modified it BTW

Take care

Joanne
Nov 11, 2013, 04:47 PM
Registered User
Just weighed the phantom 3940gm on digital kitchen scales, with 5 AA rechargeables. No bow bumper yet. So a bit of work to do and fettling with weight but clearly the potential is there.
Ernie
Nov 11, 2013, 05:44 PM
David Cook Victoria, BC Canada
longer fin chord or hard chines = less leeway (sideways drift/side going to windward)
Nov 12, 2013, 12:28 AM
Registered User
Edited
Last edited by Tractors R Us; Nov 27, 2013 at 02:18 AM.
Nov 12, 2013, 02:48 AM
Registered User
Quote:
Originally Posted by erniefoster
Just weighed the phantom 3940gm on digital kitchen scales, with 5 AA rechargeables. No bow bumper yet. So a bit of work to do and fettling with weight but clearly the potential is there.
Ernie
What a result - well done you!! I read the other day that most of the top IOMs (Britpop et al) all come in under weight and add 'corrector weights' low down at the CG - so being, say 200 gms under with other rechargeable options, your in good company Ernie.

Do you see any show stoppers for the Phantom within the rules? Look forward to sharing more successes.

Joanne

BTW, not surprised your club mates are upset - the place I'm sailing, there are hulls that cost c. 1,500. Mind you, the Phantom has now gone up, it's now - 71 + shipping from the UK warehouse


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