IOM Do It Yourself DESIGN - Page 230 - RC Groups
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Oct 11, 2017, 02:54 PM
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Oct 11, 2017, 08:16 PM
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davidjensen's Avatar
The Max must have a tapered rear end which when it slaps the water it pushes it forward. I noticed the new Kantun 2 also has this type of rear end.
Oct 12, 2017, 03:11 PM
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Message for tillerman about the Nimbus


I finally got home and took some pictures of the block used to support the mast at deck level on the Numbus - see attached. I bought a set of them from Graham when I built the model (in 2001). I am sure you could make up something like this without too much trouble. The bottom of the mast is inside a cylindrical plug with a cone at the bottom, so basically it doesn't constrain the angle of the mast.

I don't have the issues with heading up to wind in gusts - the rig I have is also from Graham Bantock. Everything on the boat is built exactly to plan, or at least as close as I could get it!

If I can provide any more information or pictures, feel free to ask. I am not home much as I am working in Brussels, but I will follow up as soon as possible.
Oct 12, 2017, 03:19 PM
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Quote:
Originally Posted by Tillerman6
Paul.

No the mast is not constrained by any blocks at the deck level. But since my last post I have devised a turnbuckle arrangement behind the mast which pulls it aft. This has been fairly good as it takes most of the adverse bowing of the mast out of it at least 2/3rds of the way up.

There is a U shaped slider track on the forward deck with blocks in it, but that is short enough that it is not in the way of the mast pocket.

I would have to assume from your response about your own Nimbus that it sails fairly well and is balanced more or less. I am thinking now that I may have to move the fin forwards in relation to the mast so that the rudder does not get overpowered in a blow. Even though my boat is more or less balanced with a slight weather helm, it still kicks to weather if the wind is gusty and you are on a beam reach with the A rig,

So one last question for you Paul. How far forward of the leading edge of your fin is the rear of the mast? (assuming that you could draw and imaginary line vertically down from the rear edge of the mast?
Sorry - I didn't catch this reply . I see from your other messages that you have identified the correct position from the plans, so I guess you don't need me to measure it anymore. Also, if you are happy with the arrangement you mention above, you won't see anything of interest in the other post I made this evening... Hay ho.

As others here have recommended, I would certainly advise you to get together with some other sailors once you get the fin issue sorted out, to get useful tips about setting the boat up. The Nimbus is not quick compared to others when it's blowing, but in light conditions on a club pond with a good skipper (ie not me!!), it can hold its own. Like many older IOM designs, it will happily bury the bow if overpowered going down wind.
Oct 12, 2017, 06:13 PM
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Quote:
Originally Posted by davidjensen
The Max must have a tapered rear end which when it slaps the water it pushes it forward. I noticed the new Kantun 2 also has this type of rear end.
Can't see all that much resemblance between the Max and the Kantun 2. Some similarity (hard to find comparable pictures) but it seems to me the Max's secret lies in the stern sections, pictures 2 and 3. Squeeze a piece of soap, squeeze the Max and I'm betting the same thing happens. But how to combine that shape with a chine?
Oct 12, 2017, 07:21 PM
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Yes it’s quit different. Here is the K2 with a steep aft taper
Last edited by davidjensen; Oct 13, 2017 at 06:03 PM.
Oct 12, 2017, 08:21 PM
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Quote:
Originally Posted by davidjensen
Yes itís quit different. Here is the K2 with I steep aft taper
Like my Plan B but much more so.
Peter
Oct 13, 2017, 03:07 AM
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Quote:
Originally Posted by davidjensen
Yes itís quit different. Here is the K2 with I steep aft taper
Not the K2, I think. No bump in the arse. KS?
Oct 13, 2017, 09:49 AM
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Quote:
Originally Posted by Emintaka
Not the K2, I think. No bump in the arse. KS?
KanTwo:
http://www.mxcomponents.com/en/iom-c...-class-1m.html
Oct 13, 2017, 06:06 PM
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davidjensen's Avatar
I am assuming it has the same lines with a different deck.
Oct 13, 2017, 08:00 PM
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So if it doesn't have the bump, does this mean that the mast has to be stepped further forward,
or does it have a longer crane?
Oct 15, 2017, 04:25 PM
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setting keel/mast box.
Oct 15, 2017, 10:07 PM
Barry D USA 747
You're not setting the keel box with fin in place and set up in a jig?
Oct 15, 2017, 10:48 PM
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No. theres a line fore and aft on the hull to align longitudinal and the base. the stuff you see squares the box perpendicular to the shearline. The box is 10mm and fin is about 8mm and i use 3 set screws to true up the final keel blade alignment then epoxy to snug up the fin in the box
Oct 16, 2017, 10:03 AM
Barry D USA 747
I might try the set screw/bigger box next time or build a fancy jig. Last time I used some melamine, drew a center line then carved out a hole the shape of the fin, put packing tape on the bottom and epoxied it in place, then made a second jig to hold the boat on plane while I tacked the fin box in place, your method might be less hassle.
How do you make sure that the center line of the fin is perpendicular to the water line (fore & aft) - or racked per whatever the plans call for?


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