So I built a footy, and...

Footy Class General Discussion (Footy)
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…to my surprise, it sailed pretty well.

This is the first RC boat I’ve made. I used the carved insulation, fairly-quick-and-dirty method for the hull, although there isn’t any of the blue stuff around here so I used white expanded polystyrene. EPS resists attempts at refinement very successfully. I’m aware that every boat needs an excuse, so I have that covered already.

I thought there was an interesting challenge presented by the footy rule, and the easy entry cost. As far as I know, there aren’t any others around here in So Cal?

Anyway, here’s where I went with it:

  1. I figured in a length-defined rule, sailing length is king. I went with a diagonal boat, and used a fairly blunt, large-radiused nose to avoid “wasting” sailing length on such niceties as a cute bow. I read about Humphries doing this with the Russian VOR entry, and the reasoning seemed, uh, reasonable.

  2. I thought a plumb bow with some wave-piercing characteristics might be interesting, and together with a low-volume, narrow hull would be effective at dampening the waves. My max-beam is a ways aft, so the bow is a low volume, high leverage trade. The static trim is set to place the bow knuckle just in the water, and fully immerse the pinched tail, with the ballast and “stuff” all centered fairly far aft.

  3. Since the narrow hull rides so low, I used a pinched stern to avoid a large immersed transom, and get the max length in the diagonal box.

  4. With almost no form stability, I went with max depth, fairly heavy ballast.

  5. So far I have a McRig on the boat, with “looks about right” sizing.

The numbers are:
All up weight: 480g
Rig weight: 30g
Hull only (with batteries=4xAAA, servos, and rudder): 140g
Ballast: 310
Length: 340mm
Beam:55mm
Sail area: 231 sq. in.

My initial sailing observations in 2-8kts are that it presses the bow down fairly aggressively upwind, achieving approximately “level” trim. With just an hour of playing at a pond, I get tacking angles somewhere around 100 degrees. It’ll get stuck in irons if I tack in a lull, and it’s tough to get it going again since I can’t push the boom to weather!

Downwind, it’ll go bow down with a bow wave coming about two inches back along the deck, like pictures of subs motoring on the surface. When bigger puffs hit, it’ll dig in a little further but seems to maintain about the same speed. I didn’t have any wipeouts or broaches. I do need to spend a little more time on waterproofing, though!

Any wisdom gratefully received!

-Chad

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Chad ~ I like it well done

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Nice Chad, your next one will be even better.Nice to see some good thinking and logic,I belive you have the parameters for a sucessful boat there.
Keep developing and report on progress.
Look for the threads on the “postal races” and send in some times.A good way for isolated sailors to compare our craft.
Cheers
Brett

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Nice creation & welcome to the Footy world. You might want to communicate with Butch B who has been building similar looking all foam boats for some time. His “Shark” finished 3rd in the April Florida Footy Festival III hosted by www.tanglewoodmyc.com.

Photos of his boats can be seen at:

http://sites.google.com/site/sandpointsail/New-club-footys

Note that his servo arms are exposed at the top of the hull.

Butch works in an automotive repair paint shop and his finishes are very smooth as he uses multiple clear coats. If you need his email address, send me a PM.

The AMYA (www.modelyacht.com) will help you find clubs nearest you. Just enter your zip code. Happy sailing & keep us posted.

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Beautiful finish on that Polystyrene!
How did you go about carving and finishing that?
What sort of linkage is on the rudder?
For a first boat you raise the bar a long way…

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Thanks for the responses.

The “finish” is deceptive, I guess. EPS breaks out in chunks as you sand it, so the final shape requires lots of sealing and fillers to achieve a minimally passable smoothness- it’s not as easily remodeled as I had hoped, and all the surface coatings add lots of weight as well. When fillers are sanded, the soft foam compresses under the sandpaper. Maddening. This hull has water-based polyurethane, lightweight filler, more w/b poly, some spray paint, woops, it ate away a bunch of foam, more filler, more w/b poly, an epoxy coating, and finally another coat of spray paint. Next boat will not be EPS, for sure!

There is a single ply of glass (I used a Home Depot bag over the foam hull to allow it to release, and should have turned it inside out- the bag’s orange graphics were lifted by the epoxy!) glued down for a “deck” to cover over the extra holes I made for internal access and wiring. Waterproofing is a few pieces of that ubiquitous blue painter’s tape, removed in the pictures to allow internal drying following the last outing.

How do you waterproof servos sticking through the deck? Just pack the pivot arm with some dabs of grease?

My rudder is a sort of tiller arrangement, with a slot in the servo arm, riding over a screw sticking out of the tiller. The rubber grommet visible on top just keeps the rudder post from dropping. The sheet is a 1:2 arrangement to keep the servo arm short enough to fit inside the narrow hull. Another downside to foam hulls is that there is not very much room “inside”.

I started with the idea that the hull would be more or less expendable, and I would try to make the stuff attached to it removable. I thought I would have an incentive to make nicer components that way, if I knew that they weren’t doomed to go the way of the hull. So the keel is in a fiberglass case which is glued into the hull, the rudder has a removable tiller head so it can slide out the bottom, etc.

Again, thanks all for the responses and info.

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CM the best way is to make a circular a piece of (new) washing up flat sponge and trap it between the deck and the servo. When ever you prepare your Footy before sailing apply some silicone grease to the foam with a cocktail stick.

I as a belt and braces method go a stage further and strip the base of the servo as well and apply Holts “No-Crode” (a battery terminal grease) as a seal round the base of the servo before re-assembling it.

Everything else I put in a large rubber balloon inc batteries and the RX and then zip tie the neck apply some more grease and add another zip tie.

It costs an extra penny or two but hey ~ better that than shelling out for another 2.4Ghz 6 ch rx?
Hope this helps

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If you’re frustrated with sanding EPS, try using Plazamate or Highload 60. When you get close enough that coarse sandpaper is almost digging into the final shape, switch to really fine sandpaper and wet sand. You’ll be amazed how smooth you can get the surface with a little care. It can be so smooth and uniform that your eye has trouble picking up discontinuities to focus on, so it can get a bit tough to see what the shape is!

For hollowing out roughly, set up a Dremel so that it can hold an Xacto blade sideways. I forget what sort of tool can do that, but there was one with my Dremel kit. Kind of rough, but fast. Judge how much material is left by how much light can shine through.

You can get Plazamate or Highload 60 at construction or insulation specialty places. In the Boston area, try Sterling insulation (or Sterling something) in Waltham.