Sloice is getting a little attention and activity with a view to having her on the water at Burton at the end of the month.
Colour scheme is to help me remember which way she is going, and in honour of Flavio, Ago, and all other Italian enthusiasm:D
battery is a 2S1P 600mah lipo - but AAs fit precisely.
Once I discover good mast and keel locations I will dispense with the long (Sanderson) slot that allows infinite adjustment.
With the penetrating wisdom of hindsight I now realise that I need to standardise all my transom-mounted rudders so that they are all interchangable betwween boats - so in future I will standardise on dimensions
Congratulations Andrew! That looks great! I like the concept of building a central backbone upon which to attach the working parts of the craft - rudder, keel, sail - and IN which to house the associated gear. This allows the hull shape to essentially be an afterthought and allows quite a bit of flexibility for experimentation. In my drawings, and I draw more than I build (I know, just do it!) I call this the central skeletal concept and mentally separate designs into this versus the more standard exoskeleton concept where the rigid hull handles the structural issues - it allows more flexibility in part placement.
I am a fan of Gary’s adjustable keel box. I don’t trust my ability to judge where the optimal final placement of fin should be. My current problem is that I made the sides out of 1/64th ply and they warped in. I have a heck of a time getting the fin to fit. time to sand some more.
I have some thoughts on the transom mounted rudder and a design that I have actually produced. I will put that on another thread.
Sloice must be one of the most extreme examples of a ‘cod’s head, mackerel’s tail’ design seen since the Spanish Armada – to the point that her hull is essentially aerofoil shaped in plan view. Given her rather boxy cross section, it may be expected to behave like a foil and to generate much more lift (i.e. side force) than a conventional hull.
It would seem likely that the centre of lift will be at the usual 35-40% from the leading edge (i.e. the forward waterline ending). This contrasts with the normal situation in which the centre of lateral area of the canoe body is used as a proxy for the Centre of Lateral Resistance/Centre of lift of the canoe body. This generally puts the centre of action at around 50% of the waterline back from the stem – so it is likely that Sloice’s rig should be a little further forward than one might expect.
This is a fairly mundane matter of ‘suck it and see’. If the experiments are unsuccessful, the initial sibilant in that expression may usefully be replaced by a labio-dental fricative [OK you clever buggers!]. More fundamentally, such a movement of the rig on its own would result in a large out-of-balance couple between the side force generated by the canoe body and that generated by the fin. This will inevitably result in directional instability – possibly a good thing, possibly bad, depending on your attitude and skills as a driver.
However, it is not an inevitable consequence of Sloice’s hull form. It is conventional in Footy (and most other) fin/bulb design to plonk the bulb on the end of the fin with roughly equal amounts of bulb sticking out at either end. I know of no very obvious theoretical advantage in this. I strongly suspect that such geometry on e.g. America’s Cup boats is at least as much a result of structural considerations (the desire to sling a very large lump of lead on the end of the thinnest foil possible) as any hydrodynamic benefit. Moving the CG of the ballast away from the neutral axis of the fin will tend to generate buckling forces in the fin, which at the very least complicates the design problem considerably.
In a Footy, we do not have the same problem. Buckling is not an issue and the greater torque generated by the bulb if the fin’s positioning on the bulb is asymmetric do not look to be a problem either – particularly as it seems to be increasingly accepted that moderately thick foils are the order of the day. So it might be a good idea (repeat MIGHT!) be a good idea to move both Sloice’s rig and fin (but not bulb) forward.
My Learned Friend Mr. Sanderson is now going to go out and design the Sanderson Bulb box, which allows the bulb to be adjusted relative to the fin by a Cunning System of Little Lead Wedges!.
In days of yore, during my initiation to vane sailing, prognathous bulbs were illegal in the Marblehead class. The lead had to be hung with no part of it forward of any part of the keel fin. Vane sailing (except for the skiff sailing version) ran as match races between two boats (mostly), first on a windward leg and then a separate leeward leg with different points awarded for each leg. After a pairing had sailed together they were matched against new competitors.
These Marbleheads sailed upwind very close to the wind and their rigs were pretty far forward by today’s standards. This was also important because the aft part of the hull had to have room for the vane steering gear. The older designs were very much in the cod’s head configuration with narrow sterns. They were really optimized for sailing upwind because the point system of scoring heats rewarded the upwind leg with a higher score than the downwind leg. Today’s model boats tend to have broader sterns to discourage the stern sinking on offwind legs, and are also influenced by ocean racers.
Footies tend to sail nose down so they don’t really need the broad sterns on most other model boats. In fact, revisiting old Marblehead designs would probably be a blueprint for good Footy design. The older vane boats weighed in around 22# for a 50" long hull which is sort of similar to the displacement values of Footies. That was my inspiration in designing my latest hard chine boat, “Tanto”.
Andrew, I’m very impressed mate. Proportions look great. Nicely balanced. Get yourself a good selection of rigs & I recon there will be no more bringing up the rear. Most boats will be looking at YOUR rear. I seriously believe there is a lot of merit in the cod shaped hull. I would suggest get the C of G aft enough to lift the bow just out of the water because there is not much rocker. This aids quick & effortless turning. The standardised rudders/mounting brackets is a valuable lesson learned. I look forward to our next meeting & seeing & racing against sloice. I can only hope I’m not one of the guys looking at your rear.
Sloice posed some interesting problems I had not met before - and it has taken several weeks for them to get mulled and solved:
A) my smallest receiver fits in the space - but crystal and servo plugs don’t
Solution: Cut-out the hull side and bustles till everything fits
B) servo leads don’t reach receiver
Solution - fit extensions
C) keel box is toooooo long and occupies much of the availble space in the hull
Solution: Find best locations for mast and fin - make the next Sloice with minimum keel /mast box
D) keep water out
Solution - adhesive film or tape over whole length of hull: Pray
E) need fairlead for macrig sheet - needs to be on the midline about where the receiver is
solution: Fairlead will be magnetically fixed outside deck film and collapse for measurement (I may, too)
F) Batteries dispose to suit sailing requirements
I am using 4 AAA cells in pairs - they will be moved around to achieve a Gary-beating trim. They CAN go right aft under the rudder servo if necessary
G) switch - on this rather exposed boat
Again - magnetic, Not a reed switch - a little rare-earth magnet will cling to a plated steel contact directly - closing the circuit. ( No, it will Not be possible for a Folgore bowsprit to break the circuit)
Amazingly the basic construction included conduits for wires to run fore and aft past the keel box, so installing the servo extension leads and battery leads has not been a problem
Read your E-Mails young man. Are we to see you and Sloice at Watermead this weekend ?
My new moulded hull is still unfinished - but the Razor has been revamped with new servos, batteries, fin, rudder and, most importantly, a new coat of Valspar. You can now see the waterline.
Andrew, How could you possibly let us down especially when i had decided to sail one of my bottle boats to try and keep you company with our own event at the back of the fleet playing ram the leaders as they lap us
So come on spill the beans ~ especially as you are not going to be there to tell us all about your new ideas!!!
Sod it now I will have to consider some other cunning idea…
Rgds
AndyT
:zbeer:
Note that blunt bows push a lot water in front of them as the last Sloice photo illustrates. While she does look fleet in the light winds thats a pretty big wave front a couple of inches forward of her bow. And, as Andrew alludes to in his post, the blunt bow doesn’t resist the nose diving downwind. So, on Sloice II, perhaps the waterline bow should be pared down to a sharper entry graduating to the blunt shape as the bow nears the deck-line for reserve bouyancy.
Andrew Sloice is certainly looking good will you be at Bourneville?
I do hope so ~ I will certainly look forward to seeing you both then.
I have thought of a name and colour scheme for your MkII version of this lovely looking Footy
“Ploice” It should have a blue and white chequer stripe and have a flashing blue LED with sound board with a siren and “Pull Over” when other competitors are getting in the way. As you go past you could activate the other sound channel to say “Jumper” or some other obscenity.
