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Old Apr 04, 2006, 12:29 AM
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graham_mca's Avatar
Sheboygan, WI
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foamy footy...

Inspired by Bob Starr's footy 'Kitty' seen here... http://www.rcgroups.com/forums/showt...3&page=2&pp=15
I want to have a go at building a 'footy' of my own, possibly something very semi scale.

It seems that the open structure hulls of the two footy plans freely available can be tricky to put together so I started to plot a different method. As a veteran of hundreds of foam core wings I reached for the hot wire bow and this is what I have so far...
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Old Apr 04, 2006, 12:48 AM
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My plan is to use this foam blank and clad it with 1/16" balsa on the sides and transom, 1/8" or 3/32" bottom (crossgrain) and a 1/32" ply deck. The inner space will have balsa facings fore and aft.

The fore and aft faces of the openning are vertical so that they can be used to support the mast tube/fin support and rudder tube respectively.

With these and other templates I will be able to rake the transom either way and vary the deck angle/curve. This first effort has the deck straight and level.

I have started to attach the side balsa sheeting running the grain vertical so that it follows the curve of the hull easily... using Elmers waterproof wood glue and taping to hold it in place.

Graham
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Old Apr 04, 2006, 01:26 AM
Useful Idiot
Asturias, Spain
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Imho, the balsa cladding is overkill for something this size, especially considering that it'll need sealing. Probably, the only parts needing it would be the keel and mast attachments and possibly the rudder.
A depron meat tray would seem ideal for the bottom.
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Old Apr 04, 2006, 10:43 AM
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Cedar Glen, CA
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Graham,
Well, glad that this humble newbie can be inspirational! Looks good, too; I am sure you will do as nice a job as on your Mirror. Be careful of weight, these little guys need to be as light as possible. I used 1/16" balsa on my hulls and 1/32" ply on the deck. Any future hulls, and there will be, will be made strickly from 1/32" material.
I'm looking forward to following your progress on this technique.
Bob
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Old Apr 04, 2006, 01:13 PM
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Thanks for the input both, this is very much an experiment for me, my main interest being in seeing if this foam core is an easy way to build a footy hull. I have read several people who had problems getting the open hulls together at all.

I shall take your advice and sand the 1/16" severely to get down to 1/32". The use of 1/16" was based on the 2mm balsa recommendation found on the 'Bob About' plan. The core itself is very light (I should have weighed it, I will the next one). I think that cladding with 1/32" balsa will be easier than constructing the hull by 'tape and glue' with the wood alone... an accurate core will guarantee a straight and fair hull. At least with flat bottoms, extra chines could be cut but that would complicate matters.

Another way would be to put a thin balsa bottom on only, and glass cloth/epoxy or polycrylic the rest. I am thinking that these foam blanks can be used however you wish.

Graham
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Old Apr 04, 2006, 11:51 PM
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I weighed another foam blank of the same design and it is 13g or approx. 0.4oz. So I guess I am 13g 'in the hole' with this method but with the stiff structure I may be able to lose 13g of other structure to compensate.

The plus side is that I am finding that it is very easy to build. I should also say that I am playing around with a semi scale-like-footy idea here rather than a minimum weight racing design.

Full size inspiration for short fat sailboats?.... look here...
http://www.duckworksmagazine.com/sto...m/michalak.htm

and particularly here.... and similar.... http://www.duckworksmagazine.com/sto...box2/index.htm

What material is typically strong enough for the fin on these guys? 3mm balsa or 'liteply' maybe?

Graham
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Old Apr 05, 2006, 01:38 AM
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Cedar Glen, CA
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Graham,
I like your prototype, it's one I didn't run across. Are you planning in offsetting the mast too? As far as the fin, I used doorskin the first time, but did not care for it. I now do them in basswood. You might be carving into that foam before you're thru installing the servos anyway.
Bob
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Old Apr 05, 2006, 03:06 AM
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The weight of the foam doesn't seem to be much of a penalty given its benefits- easy build, unsinkable- Innovative approach, Graham! I like your inspiration too! neat looking little cruiser- Wasn't 'micro' one of Phil Bolger's 'instant boats'?
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Old Apr 05, 2006, 01:41 PM
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Quote:
Originally Posted by Aerominded
The weight of the foam doesn't seem to be much of a penalty given its benefits- easy build, unsinkable- Innovative approach, Graham! I like your inspiration too! neat looking little cruiser- Wasn't 'micro' one of Phil Bolger's 'instant boats'?
That's what I was thinking Aerominded... I really like this idea!

'Micro'.... that could well be, certainly sounds like one of Bolger's designs... but at the link it is in the plans list of Jim Michalak, I am sure inspiration goes round and round.

Bob... I will just call those boats 'inspiration' rather than 'prototype'... especially as I didn't find those links until after I had cut this hull

No I will have the mast upright and mounted up against the inner foam 'bulkhead', the offset mast does look nice though, does it make a difference I wonder? I do like the look of the partly balanced gaff rig and I don't see any reason it should not sail ok. I am hoping to be able to leave the foam pretty much intact Bob, I have allowed 3/4" more length in the 'cockpit' than in the 'Bob-About' and I have more width so I should get two standard servos in there ok... I hope!

I have lots of 1/8 x 1/4 bass strips, a laminated fin would be strong.

hull bottom on.... off to get some tube for the mast (I will use a birch dowel for simplicity) and rudder assembly.
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Old Apr 05, 2006, 02:49 PM
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Cedar Glen, CA
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Yes, you got plenty of room inside the hull. I built Kitty using the Razor hull design and it seems to need the more room inside because of the v-hull. You should be fine. I'm assuming you will put a transom rudder; I wish I had but I had already built the hull before I decided what I was going to do. Most of my inspiration came from pictures like this. Another good refrence I used is this page:
http://users2.ev1.net/~fshagan/gaffdeat.htm
Bob
BTW I do think a lot of the designs on that one page were modified or copies of Bolger designs
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Old Apr 05, 2006, 11:49 PM
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Thanks for the link Bob. I had planned on an internal rudder tube but I assume that a more rearward rudder will give better control due to it's greater moment of action. I am coming up against a little concept problem now though. Do I build this footy to suit the 'box measurement' system as is likely to be implemented here (USA) as it has been in GB, or go with the simpler definition of a footy being under 12" long (something which the box rule doesn't control suprisingly, apparently a 12.5" boat can be angled into the box... ridiculous if you ask me). The 'box' rule makes control connection to an aft rudder difficult. I think I will ignore it and just build my footy...

An aft of transom rudder will make for one less hole in the hull too won't it... cool.

I have laminated a fin from 5x 1/8 x 1/4 bass strips... from photos I think the Razor fin is about that wide, 1 1/4"? Did a little more work fitting out the hull this evening.... see below

Graham
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Old Apr 06, 2006, 03:30 AM
micro yacht nut.....
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Hi Graham,
Making class rules is not as easy as you may think.I am sure the Footy class would welcome your input.
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Old Apr 06, 2006, 10:10 AM
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Graham,
1 1/4" is just fine. I taper down to 1" from the bottom of the hull to the bulb, just 'cause I think it looks better. I am not so upset about the box rule, it allows for a lot of latitudes in design. There will always be people bending the rules, no matter what is adopted. Your hull sure looks great.
Bob
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Old Apr 06, 2006, 11:08 AM
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Hi guys... I wouldn't say I am upset by the box rule at all... nor do I underestimate the challenge of writing a class rule micro sailor.

I actually like the box rule and the only input I would have is to use the 'box' with a 12" max. hull length limit... simply so that a footy is indeed a footy. Could the box have a centre line marked on which the hull must be alingned? But I know such discussions go on elsewhere and this thread is just about a non-competitive footy.

If I go on to make a 'racer' I will make it 12" max 'and' fit the box... just in case

Oh and micro.... many thanks for starting all this and the Bob-about plan which is such a good reference for this first attempt of mine.

Mast height on your Kitty Bob? Looking at scale drawings of gaff rigs it seems that hull length = mast height, more or less... with the gaff rising above that. How heigh would you go from your practical experience?

Off to Toledo very early friday through saturday... anyone else here going?

Graham
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Old Apr 06, 2006, 03:44 PM
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Graham,
I wanted max amount of sail, so I made my mast the same as Brett's rig. But, now taking measurements from mine........might have made it illegal. From the deck the mast is 19.25" tall and the peak of my gaff is 21.5". I did use the gaff rig's page for figuring the ratio of the sail and made the luff 12". Soon as I make a sail block, I am going to try my hand at making a proper sail, which I think will work even better.
My next adventure into a footy will take advantage of the diagonal, only because I will need the length. But I gotta get a grip on Hullforms, to make it work first.
Bob
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