For my I found a fishing sinker that is already the shape of the bulb (missle shaped) I only have to cut the slot for the fin to fit into it.
What are the weights of some of the footys out there? I am wondering if 14oz (398 grams) is light or about on par with the rest of the footys.
Vince
Can someone explain to me why Footies are all so “stubby” (for lack of a better word) looking. Why can’t they be more like a minature IOM or USOM.
Thanks
Don
Don Case
Vancouver IslandI think that the footy hull is largely determined by servo size.
Gio
Don,
Its a little reason called the “cube law”
well documented on this site somewhre.
basically speaking a “half” size boat has 1/4 the sail area amd 1/8th the displacment…( a footy is less than a 1/3 of an IOM)so a Footy doesn’t look like an IOM and a IOM doesn’t look like a 30 footer.
Vince, my two “Halfpint” footys are about 500g (17.6 oz), and my new one “MiniMe” will be 600g. I seem to remember Brett saying that 500g was a good ballpark weight, but he also told me he made one that displaced 650g that was really good “in a blow.” Could be that yours will be the ultimate light-air footy.
That’s all I can offer, since I don’t have actual sailing experience with these little boats. My bathtub isn’t big enough for me, my footy, and my rubber ducky. [:I]
Bill
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>Originally posted by Brett
Don,
Its a little reason called the “cube law”
well documented on this site somewhre.
basically speaking a “half” size boat has 1/4 the sail area amd 1/8th the displacment…( a footy is less than a 1/3 of an IOM)so a Footy doesn’t look like an IOM and a IOM doesn’t look like a 30 footer.
<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
Well maybe, but an IOM looks a lot more like a real boat than a Footy looks Like an IOM. If shrinking an IOM to a Footy results in a stubby boat then it stands to reason that shrinking a real boat to an IOM size would result in a basketball. Could it be that people are trying to put as much beam as possible and then putting in a lot of freeboard bacause even a ripple is a tsunami to these things?
Don
Don Case
Vancouver IslandDon, the stubby look you questioned really is the cube effect that Bret talked about - it’s just that the smaller you go, the more pronounced the effect appears.
I recently did some USOM design work which resulted in a very narrow 5.5" beam hull - narrow even for USOMs. If we try to use a similar plan for a 1 foot LOA, the beam would only be 1.5" which would not be wide enough for servos, and would result in a displacement far too light to stay upright in a breeze. The only way to get adequate displacement would be to deepen the hull like the old “plank on edge” designs around 1900.
My “Halfpint” hull takes this approach, but the beam is still about 3 3/4" to make it practical. I don’t think I’d try to go narrower and still fit radio gear in there.
The other way to get adequate displacement and stiffness in a 1 foot length is to widen the beam so you don’t have to go as deep in the rocker. That’s what my “MiniMe” design does, as do many of the others here.
Since the boats sail in the same ponds as the bigger ones, freeboard needs to be similar, so yes, they look stubby (good name for your first footy [^]) but most of us think the look is kinda cute.
Bill
Don,
a 1/3 scale IOM boat would have to weigh 148g…its length would be 333mm( 306mm is a footy)
Go ahead and build it and see how it sails and let us all know of its performance.
BTW the 2.5kg IOM ballast will be 92.5 g at this scale this will leave you 55.5 g for your hull/rig and radio…good luck!
A good exercise for you and you will learn lots about scale effects and the cube law.
I can have a small wager with you if you like,I think my 500g “stubby” footy will beat your longer 1/3 scale IOM in all except the lightest of breezes…
A 4 kg IOM scaled up to 6m would weigh 816kg…my 6m sports boat weighs less than 500kg…so a IOM is stubby compared to it.
This the effects of “scaling”
So you see all size boats have to be designed to suit there purpose if ultimate performance is what your after.
The lightest footy we have done over here is 350 all up…quite IOM ish…good in light brezzes.
I lent it to a guy,must get it back and take some pics.
cheers
brett
A Couple of guys up north of me made some nice little yachts 326mm long.
displ is 250g I belive…kinda scale AC looking.
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Looks like a nice boat. Good name, too. At that heel angle, it doesn’t look stubby, either, although it might if we see the plan view. Wonder how they came up with 326mm LOA? If they knocked off the overhangs, it might come down to 306mm! Seems to me that such a light boat would be awfully tender, though. Strictly light air?
Bill
I had been in contact with the Servo City guys about some of their smaller servos which they say can be modified for 360 degree roation. For others like me (electronically challenged) this represents a possible source of supply for the “Footy” class - either mono or multihull.
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”> from Brian Pettey [bpettey@servocity.com] at servo city:
Richard,
Sorry for the late reply. Yes, we can modify the servo for you, we do it all the time. The smallest that can be done is the HS-85MG servo. The final gear is 360 which allows it to be modified. All of the smaller servos have a half-moon final gear. Thanks
ServoCity
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So if looking for a small sail winch for the “Footy” - give them a look.
Hey guys, here’s some progress pics on my comp entry “MiniMe.”
The first shows the hull just out of the mold, next to “Halfpint” - I thought Don in particular might be interested in the contrast of the two design approaches.
The second shows a mockup in cardboard. The cabin is a piece of an unsuccessful Halfpint hull. I thought the result looked a little cartoonish, and I was going for more realism.
The third and fourth pics show her being built. I refined the look by moving the cabin forward more, and lowering it’s profile. Now it has the look I wanted, a semi-scale Mini6.5.
Now I’ve shown you mine, so show me yours!
Bill
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Looks great…very clean look, nice work!
Vince
Nice work everyone!! will open a new thread soon posting the Comp rules and details.
Here is some hull lines I have been working on,wanting to try a lighter displacment,This one displaces 300g.
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Well it is finally done! I will get it out on the lake this weekend…hopefully.
The weight came out to 14oz and it has a 5.5oz ballast ball on it (fishing sinker, not painted yet). It made of 1/32" basswood sheeting and the sails are kite ripstop (awfull color, but had it on had).
I like it, and I hope it is alot of fun!!
Vince, WHat do you think of my rigging job?
Download Attachment: [ Footy done SMALL.jpg](http://www.rcsailing.net/forum1/data/vinnya42/20051279227_Footy done SMALL.jpg)
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Vince, the boat turned out really nice. I don’t think the color of the sails is a bad thing. With such a small boat, visibility might be important - I’d want to see you coming to avoid being T-boned by that “destroyer” bow! [:D] Rigging looks good, too. Post some pics when you get it in the water…Bill
Ya I guess the bow is alittle sharp, but with less than 1 pound of force behind a T bone I think everyone else will be fine.
Vince
Footy 1st time on the water!
Winds were 1-4mph and the footy went to tack and took off!! I then turned into the wind and I couldn’t get it to head into the wind, the boat went great in every direction other than into the wind. I moved the battery back to the very back of the boat and then it would head up wind at about 45 degrees max. The footy really does a great job in light wind and moves pretty quick for such a small boat.
Do yal think it was just the CG being too far forward? Any ideas about making the keel fin or rudder wider, I need to use a bigger battery pack but anyone else have issues with going into the wind with these small boats?
Vince
[:-batman] Vince, from your photos I would suggest that you have the whole rig to far forward.[:-drunk]
The first thing is to find your centre of lateral resistance. Thats easy.[:-goldfish][img]../forum1/images/speech/icon_speech_oops.gif[/img] Put the craft in a bathtub full of water, you only need enough to let it float. Push the hull sideways with something with a fine pointed end,(pencil, knitting needle, table knife) Move the contact point until the hull pushes sideways without swinging. That is your centre of lateral resistance. Now to find the centre of effort of your rig. [:-graduate][img]../forum1/images/speech/icon_speech_ok.gif[/img] On your sails or if you prefer on some paper patterns of your sails, find the centre of each sail. Do this by marking a pencil line from each corner to the middle of the opposite edge. You should end up with an intersection of three lines in the middle of your sail. That is the c of e for each sail. Now to find the c of e for the complete rig you need to draw a line between the two centres of effort. The rig centre is along that line. the exact point is determined by the size relationship of the two sails. If both are the same size then the point is half way along that line. If the main is bigger than the jib, say 75% to 25% then the point is that same ratio along the line.[:-moptop][img]../forum1/images/speech/icon_speech_ok.gif[/img] Now we are on the home straight.[:-magnify][img]../forum1/images/speech/icon_speech_duh.gif[/img] It is most desirable to have the centre of effort just slightly behind the centre of lateral resistance. By how much is the subject of much discussion and could be a new forum thread on its own. That is for you to try and come up with the best setting for your design. I would venture to say that because we are working with only 12 inches of total length, it may be that this is the most critical factor of any FOOTER design.
Good luck, if any of this ramble is not clear come back with questions.
[:-weepn]
Do it NOW before it`s too late.
comments on Vinces Footy pic from the UK Footy guru Richard.
Richard has done a lot of work with my “BobAbout” design and his own designs as well.
He is a very good builder and knows how to sail these things really well.
Here are his comments.
Brett,
I notice that Vince has got his boat onto the water for the first time. He has experienced a little difficulty. The following may help if you want to post it on the forum.
Glad you are on the water, even if it is in tricky conditions for a Footy - very low wind speed. Suggest you try the following approach:
From your pics the rudder and keel look OK for size and position. In any event too late to change now without a rebuild. By the way as the boat becomes pressed down-wind, and it will, your ram bow will give reduced buoyancy…hmm!
Trim the boat in the water so that the bow and stern extremities are just above/touching the water.
Check that the mast has a slight backwards rake in this trim. Your efforts to move the CG of the boat back probably had the effect of giving you more mast rake - not the way to do it though.
Now check the sails:
Flow in the foot of the sails, a little twist in the main, matching curves on the leech of the main and jib.
Everything free running.
Try the boat again, preferably in more wind. Single chine hulls point up a lot more readily when the boat is heeled. They need careful handling to beat well in very light winds.
Let speed build up before attempting to tack.
If the problem persists then the centre of pressure of the sails is too far forward. This can be corrected by either increasing the back mast rake a little - it must still “look right”, or move the mast back in the boat. You may need to put another mast tube in or even a small mast box. I prefer a box - more flexibility.
The sails of your boat look colourful, but perhaps rather manly. I have found that the clear plastic sheet(cellophane) used to wrap cut flowers at florist shops is an easy and effective material to use. The corners and other areas with tie holes in will need a piece of deck patch reinforcement and the leech is best reinforced with narrow mylar tape. However, it works well and is cheap and easy to source.
I am attaching a couple of pictures showing “florist sails”. The main has a small grid pattern on it, the jib is clear.