My IOM scratch build... Vanquish - Page 2 - RC Groups
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Dec 04, 2007, 05:21 PM
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Originally Posted by hew565
Thanks for the info, I guess I'll be building a mast box/fin box combo! I'm waiting on some fiberglass, or fibreglass as you guys from across the pond call it. I'm looking at one layer of 4 oz/yd2 each side of the balsa core. It should be here in two days. I've read where many builders use 2 layers of 5-6 oz glass, but those do not have the balsa core. And I'm using S-glass over E-glass for the 15% extra strength. J L and Grizz, what did you use? How did your hull weight end up?
On my balsa planked star 45's, which were 1/16 planks I used two layers of 3.2oz satin weave from Worked fine with both layers on the outside, so with one inside and one outside it should be even better. Weight was about 16 oz for the hull or 454g. That included the frames which were 3 oz or 90g. If you can bag the hull it should be even lighter. If you bag I might go two layers outside and one inside.

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Dec 04, 2007, 06:11 PM
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Hi Hew & Grizzly

With regards having movement available at the butt of the mast, I would take note of how the professionally built hulls are fitted out. If you buy a ready made fin and box with the mast box as part of the moulding, then the mast butt is captivated in a fixed position at 18-20mm forward of the front edge of the keel fin. In IOM's, the balance is effected by the fore and aft rake of the mast around the fixed position of the butt. When a mast ram is used, it also pushes the lower part of the mast aft, round the same fixed point. So the butt cannot be allowed to move fore and aft. The mast box tapers from bottom to top only in the fore and aft plane, and is just a clearance fit athwartships. Further athwartships stability is effected by fitting a halfcrescent on the mast ram, or building in 'partners' (forks) at the upper deck level just above the mast ram. Make sure that you resin in a stainless washer where the butt sits. This prevents the tube from cutting in to the glass/balsa hull.
Have a look in: or where you will find illustrations of fin/mast boxes.


Last edited by isisagoodun; Dec 04, 2007 at 06:19 PM.
Dec 04, 2007, 06:53 PM
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Hi Ralph and Hew,

When I built my Noux I modified the design by augmenting the beam by 10%. I wasn't confident in my ability to build to the design weight so I increased the volume... I wasn't sure what effect this would have on the boat balance so I made my mast box such that I could incrementally move the mast step over a range of about 15mm. I did this by drilling three holes, aligned along the boat CL, in the piece of 1/4" AC ply that forms/plugs the base of the mast box. I fitted these holes with brass tubes to prevent wear. The plug in the step of the mast tube is fitted with an eccentrically drilled pin that fits in the tubes. Rotating the mast plug (180 degrees) allows me to select 6 different mast step positions. The aft edge of the box is raked 5 degrees aft of vertical to allow a wide range of rake adjustments.

Just one more thing to adjust incorrectly when I'm tuning...

Dec 04, 2007, 08:18 PM
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I have looked at several boats set up like that. The Noux has the integral fin/mast box with a 5* rake on the back side. I was also planning on a deck ram and partners.

I wish I could figure out how to bag the hull, but it is on the foamboard stations so I can't get to the back side. Once I glass the outer hull, and remove it from the stations, I can bag the inner layer of glass. I guess that's better than nothing. I'll put some peel ply on the hull and squeege the resin out as much as I can. I stained the wooden hull today in case I decide to leave part of the planking showing.

I hate waiting on parts
Dec 04, 2007, 08:59 PM
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How did the balsa take the stain?
Dec 04, 2007, 10:13 PM
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I may have missed in the posts what thickness of balsa you are using. My hull is 3mm (or 1/8th) balsa, and if you were to glass that with 4oz on each side she will come out too heavy - even if bagged.

I used 2.4oz on the outside, and would have used only 1.5 (or thereabouts) if I had it. I was using what I had on hand as the hull is a prototype for a second (and more carefully spec'ed) hull. The inside is sealed with epoxy sealer only - two coats diluted...

My hull is a little of the heavy side though I can get her down to 4kg for sailing - just.

Do a Google search for Anders Wallin's IOM Weight Budget if you have not already. I kept it by my work bench throughout the build. I guess if you were considering the Noux, you probably already have the weight budget.
Dec 04, 2007, 11:17 PM
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I think it was "Early American" stain. I may paint the deck and from the waterline down, yellow. And leave the sides clear. It depends on the look after glassing.

I used 3/32 balsa, and it is a little thinner after sanding. It will be even thinner once I sand the insides. I hope to get to the weight allowance Anders used.

I'm going to work on a plug to cast the lead bulb when I run out of things I can do, waiting on glass. I'm going to put wax onto a brass rod, like a candle. Then turn it in a drill press and shape the wax to the profile Anders used. Then make a plaster, two piece mold with it.

I also am going to try shaping some aircraft ply for the core of my fin and rudder. I have some carbon I will wrap around them and then bag them. I need to get the fin made so I can use it to make a fin box from.
Dec 05, 2007, 01:45 AM
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For your keel and rudder I would layer 1/64 or 1/32 ply with each layer smaller then sand to shape. Center can be 1/16. You should be able to find programs to spit out the naca family of air foils in cad. I then sized them to my chord, then found the point at which the thickness for each layer intersected the foil. That became my width of that sheet.

I did this for the star 45, even have them laser cut. Works really well. Then bag glass over the top using a food saver. my star fin was 8 oz and plenty stiff in a naca0006.


Originally Posted by hew565

I also am going to try shaping some aircraft ply for the core of my fin and rudder. I have some carbon I will wrap around them and then bag them. I need to get the fin made so I can use it to make a fin box from.
Dec 05, 2007, 06:17 PM
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Thats what I'm planning to do. I made a fin for a 36-600, years ago, and it was plenty stiff with no glass, just epoxy over the aircraft ply. Looks great too. Kinda like the Damascus steel sword blades.
Dec 05, 2007, 07:29 PM
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nigelpheron's Avatar
or the "Hamon", like on Mastoshi's super duper sharp buggars.

wonder how one those ancient blades would cut through the water as a keel...
Dec 05, 2007, 11:22 PM
Useful Idiot
The racing power boat models often use part of a stainless steel kitchen knife as a rudder
Dec 06, 2007, 01:55 AM
rcminiman's Avatar
Our guys here use stainless keels on their free-sailing yachts. They are sharpened up so they can cut through weeds. They are primarily used to take the knocks of hitting stones etc at the side when they come in to shore and nobody is there to catch them.
Dec 06, 2007, 02:07 PM
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you sparked my interest in comparing the IOM's. So I pulled up the two prints and put them into cad. The two photos show the two models overlaid. The black is the Vanquesh vs the Noux2. Looks like the Vanquesh has more volume forward.

Dec 06, 2007, 02:09 PM
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I might even have to build another boat this winter. I am going to be building two star 45's with some modifications for better heavy air performance. One more boat should not be too much more work.

Dec 06, 2007, 08:43 PM
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Glass arrived today, so I jumped right in. West Systems with slow hardner squeegeed on. Then peel ply over and stretched and stapled to the board. This was a mistake! Should have used smaller, 6" wide strips of plain plastic instead, and let them overlap each other. The big sheet did not stretch and conform to the curves like I thought it would, leaving wrinkles that let air under. That would have been OK, but after scraping excess resin out, the holes in the peel ply let air back into the matrix. Not a big deal, just another step to make it look right. I'll try the peel ply when I can vacuum bag the inside of the hull, it should work great as this is what it made for.

The deck was done similar, but no plastic cover. I'll have to coat again to fill the weave. Probably microlight filler in epoxy.

I also glued (2) 3/32" aircraft plywood together to make the fin. The hobby shop was out of 3/16, and this way I'll have twice the # of layers in the same thickness.

Thanks for the post, slotracer, it's great to be able to see the differences. Any chance you could do the same with some of the stations?

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