We too are aeromodellers who have caught the Footy flu.
Attached are our first efforts at designing and making a Footy.
The hull weighs 29.6g as pictured minus the foils. It is 1mm balsa with 3/4oz glass cloth applied to the outside using West Systems epoxy and one coat of epoxy on the inside without cloth. The foils are from a Trex model helicopter blade. The hull fits in the box conventionally and is designed for a displacement of 450g using Carlson Hull Designer. Still lots of minor details to work out. The first float should be interesting considering that neither of us have sailed a model yacht before let alone made one. The only redeeming factor is that we did sail dinghies together in the past (distant past).
Welcome. Can I safely assume you are a husband & wife team? If so, I have to say, That is so cool. I am quite envious.
As for your design, the others say “interesting”. I say to you, do you sense the air of caution in their comment? The truth is, for newcomers, you are far too high up the usual learning curve for anyone’s liking. You are either design naturals or have been taking attentive notice of what is working on the water.
If it was not already your intention, & I wouldn’t be surprised if it was, I would like to suggest that you aim for light rigs, (my Mac rigs are 10-15g). Try for 400g displacement, & most important, if you want her to turn effortlessly (handy when tacking), put your c of g aft enough to get the bow above the water irrespective of how submersed the transom is. It may look a little odd, but trust me, it works!!!
It’s great that you posted pictures. Keep them coming, & ask if you are stuck with anything, that way we all learn from the suggestions given.
I will try to post a couple of pics illustrating my sheet method for your interest.
Thanks for the information.
Yes we are a husband and wife team.
We have been carefully studying this forum for some time.
The Mac rig has already been chosen and presently ours weighs 18g. The boat weighs 75.3g as pictured with no radio gear. The plan is a Hitec HS85BB for main sheets and an old JR NES371 for rudder. With a 10g Rx and 700mAhr LiPo batteries 400g seems achievable so that is the new aim.
Welcome to footying.
Gary (garyboyd) has said most of what I think - your boat looks very promising, and the rig looks sensible too.
My small contribution - if it is not too late - is that there are advantages in having the keel and bulb removable. . In your first pictures the fin is unsupported after passing thru the bottom. It will need some lateral support since it exerts quite a leverage at the top.
You don’t have a deck to bond it to - so how about daggerboard box which has a lateral brace to the half-decks. If you enclose the fin in a box you can retain it with a cross-pin (or bolt) and leave it removable.
I trust that you will have a matching pair to sail when the design is refined
andrew
still an aeromodeller
Unfortunately it is probably too late to go with the daggerboard box. The plan is to double up the garboard penetration and attach the top of the keel to the servo mounting rails. The daggerboard box does have an additional feature of allowing the use of different length keels. There doesn’t appear to be consensus regarding the length to use. Often it isn’t stated so the only thing we have to go by is pictures.
Yes the intention is to make a second boat for match racing. We live near an excellent lake but haven’t seen any other modellers using it.
No worries - a removable keel is really a convenience for transport and enables you to experiment with keel length and weight.
(There is a tentative thought that shorter keels may reduce “bobbing” )
On my boats with fixed keels I have bonded the boat end in place then adjusted the length to just exactly fit in the box - in other words as long as possible.
Do please heed Angus’s warning! These little fellers are capable of breeding like footys.
If you are not convinced of the seriousness of this state of affairs - just look at the signature blocks of people like Angus and AndyT. They started out normal enough ( ish) but failed to control the breeding urges of their footys!
regards, and keep showing us the pics, please
andrew
Peter & Clair Hi
I have thought of a way for you to get the additional support and still have a removeable keel ~ the addition for transom blocks may well be a solution
Good luck
PS I am a great believer in taking precautions so the receivers in my boats all have rubber balloons
Making a removable or changeable keel that fits into a box or trunk in the hull adds a lot of work to building a Footy. This is because not only is the box itself a lot of extra work to build in the first place, it (and the keel as well) has to be sealed from the moisture much better than otherwise would be needed, to prevent the wood from swelling and locking the keel in place, preventing removal until the wood dries out. A simple coat of urethane or varnish probably won’t be sufficient. I almost think it would be no more work to build two boats with fixed keels rather than one boat with a removable one. Transporting a fixed keel boat would only be a little more inconvenient (unless it is for airliner carry-on, in which case anything homemade that contains wires, batteries and electronic circuits is likely to be a problem with inspectors).
The universal solution to sealing problems, Footys or otherwise, is 3M 5200. Just make sure the parts are where you want them, because after that stuff sets up you are not getting them apart. Ever.
A cast fiberglass keel trunk is not that hard to make and is a light weight alternative to fabricating one out of wood. It also doesn’t need waterproofing.
The keel root on my boats (the part that goes into the hull) is 1 inch wide x 1/8th inch thick x 2 inches long. I make a 1/2 root shape that is over long with 1/16th acrylic bonded to a larger piece (overlapping on three sides) of 1/8th. I also cut out a second piece of 1/16th acrylic that is about .5 mm larger on three sides to act the part of the cavity mold. This is bonded to an 1/8th backup plate as well. Once both parts are waxed with mold release some 4 ounce fiberglass thats been wetted out with epoxy is laid over the part with the cavity in it and the plunger part is pressed in place and clamped until the epoxy is cured. Do this twice and you have two halves of the keel trunk. These halves can be glued together with a thin layer of epoxy and when that is set the keel trunk can be trimmed neatly and installed.
Guys, It’s never too late to rip it all out & start again. I’ve done it many times.
As you are talking keel fitment, I thought I would post a few pics showing the mast/keel box arrangement I developed mainly so that I could move either the mast or keel simply by changing the position of the spacers (made from the same balsa stock as the keel). This principle has been used by others to great effect.
To waterproof the inside I simply painted the inner surfaces with west system, placed a piece of plastic between the two halves, put the sandwich in a plastic bag & weighted it down flat. Once dry remove from the bag, peel the two halves from the piece in the middle to revile smooth, flat, waterproof inner surfaces ready to be bonded to spacers front, middle, & aft, & bottom of the mast cavity, to complete the box. Seal all surfaces of these pieces at this time. Reinforce along the top & bottom on the outside once you have trimmed assembly to fit the rocker & height of underside of deck. The sides of the box are 1/64th ply.
This method is a simple variant for a wooden boat & can be modified to your own preference’s, ie, in thickness, angle of taper on the keel, etc. The tapered end of the keel with captivated nut, glued in place with super glue, can be applied to the bulb end also.
Then again, If you are not prepared to wait as is often the case with me, you can just smear every surface with super glue & bond together once dry with more super glue. I usually CA for all joints of wooden hulls except fitting decks. There I will use 5 min epoxy only because you can adjust once initially pushed together.
The hull is now painted. The total weight of the painted hull minus foils is 54g.
The rationale of the hull design is.
1/ Narrower beam than the plans we could find online. This was suggested as the way to go in an article on the official Footy site.
2/ Low to medium rocker. Many posts have suggested that the Footy suffers from rocking horse behaviour. With high rocker and the inherent short water line the hull could be acting as a pivot point for the bulb to be a pendulum in the fore and aft direction. A disadvantage of low rocker is that the bottom of the transom will be below the water line. Therefore we narrowed the transom. This also reduced volume at the aft end of the boat.
3/ High volume in bow. Another disadvantage of low rocker is increase tendency to submarine. In flat water racing kayaks we have paddled, particularly in double boats, they have very low rocker and a great tendency to bury the bow and to keep going all the way to the bottom. As the low rocker is wanted for directional stability one solution used is to have volume in the bow above the waterline. In some classes like sea kayaks and surf skis this is taken to extremes with very large up swept bows. So we have made the deck on the Footy slope up towards the bow giving lots of volume up front. This hopefully will make the bow want to stay on the top of the water.
Still all theory at this stage as the model hasn’t even been wet yet and as many posts point out it is the thumbs that make the difference.
The present situation is everything is completed except the bulb and weighs 188g. See attached pic. The original design was for 450g displacement. This would give a bulb weight of 250 plus grams. Alternatively a displacement of 400g could be achieved with a 200g bulb. We haven’t decided which way to go yet.
That’s a mighty fine looking footy, guys. You can be proud of what you have produced there. You are also doing a great job with the feedback. Let us know what happens once she hits the water.
I hope you can find some competition locally. That’s when things really get interesting.
