model RC racing yacht uni project beguinners help

[yachty4000]

I doubt 10mm thick vac mould will be that light.

You could probably get a lighter structure from Balsa or my preference would be to do a hard chine design which I did for my uni project which was lighter than all the high tech boats made of a thin plywood they basically do 2-3mm plywood which is a couple of layer of veneer. With a slightly thicker deck and keel box to stiffen the structure. Try searching the internet for information on the Rythem a Graham Bantock / Marine Modelling one metre that was built this way.

[ivor Bittle]

You could do worse than to visit my website at www.ivorbittle.co.uk

Ivor Bittle

[Tcubed]

Ivor your site looks interesting but it needs updating or something because i can not get in.

[FlyingFish]

Ivor, your website draws interest especially article 2.6. Thanks!
Phil

[bhnautika]

Squires500 the thin polycarbonate construction sounds good if you can get the panel stiffness without too much internal structure. I am assuming that you are doing some kind of industrial design course, if so has the uni got a small 3D milling or printing equipment the max size of 500mm makes it perfect for milling hull/s in foam either as the hull or a mold.

[ivor Bittle]

Do the obvious. Use Google and search Ivor Bittle. It works for me. Do not use Firefox.

[squires500]

the polycarbonate isnt 10mm thick its more like .1mm thick it is very thin and quite hard although as mentioned it is flexible i believe most of the flex of a hull will be removed when a deck is added too it, i have only seen an example of the hull.
the course im studing is systems engineering at ANU, and we have full access to their machining tools everything from mills a 5 axis cnc flow jet, to spanners and saws. there is a good bet that anything that can be made can be made there. the hull mold they have which you can either use or you can design your own, seems to me to be very wrong in design it has a large bubble shape to the front of the boat and tapers in from there, it seems most conventional yatchs start thin at the front then taper almost to the back of the boat, i beleive this is to give a more laminar flow.

thanks for the site ivor it looks great but im not going to read it at the moment as it is 530am and i just got home from work

[squires500]

the group is now faced with a difficult design consideration and that is multi or single hull sailing boat. the benefits as i understand them are that a single hull appears easier to design, will fit nicely into our design constraints, a maximum of 500mm long 300mm wide and 200mm deep for the main hull segments.

however the multihull catamaran has benefits such as being lighter(no keel), and having slimmer hulls and less drag, hence a faster overall boat.
however as we are limited to those constraints i would like to know if 300mm wide is wide enough to create a stable multi hull model.

what are calculations can be used to determine the stability of both boats?
and anything else you think might help.

[bhnautika]

Squires500 I think its about time you started to delve in to the black arts of navel architecture, things like righting moments, GZ and their relationship to heeling moments. Lights boats, be they mono or multi don’t need big rigs to make them go, it’s the power to weight thing. No matter which type you choose the same rules apply, also if you designing a hull to construct, you are doing it once for a mono or doubling it for a multi so the design time is the same. The length/beam on the mono I wouldn’t go below 3:1.

[squires500]

thanks that gives me somewhere to start, i have found that there is a thing called capsize velocity for a multihull boat which tells the maximum wind that the boat can stand before capsizing, i assume i might be able to compare this righting moments

[bhnautika]

Squires500 due to the small size of the intended model you are going to have a lot of trouble with scaling issues so using rules for full size boat may not be appropriate. Finding the max wind strength for capsize may require real world testing with different rigs for a certain wind range.

[yachty4000]

I would build a monohull ever time. Having sailed model multihull (mini 40) and raced monohulls mainly one metre.

The dynamic effects are huge the ballast ratio / beams are always so high that transverse stability shouldn't be a problem. One of the key factor in longitudinal stability this drive rig selection in terms of how much sail area you can carry downwind without nose diving and a secondary consideration is tacking. A true conventional multihull will not recover from a nosedive hence the monohull suggestion and will have no oppurtunity for helmsman error in a transverse sense.

The point about using conventional scaling above is very important. RC Yachts are always overpowered if looked at in a conventional way due to wind shear gradients, over scale keel fin arm lengths and scaling effects.

Model multihulls under 48" LOA(1.2m) are a disaster in anything but the lightest air. And I love multihulls! Stick with a mono in this size range unless you know the wind won't exceed 5 knots.

[ivor Bittle]

There is a much-sailed design at the length you require in Britain. It is called the Fiesta. It has been very well worked out.
Ivor Bittle

[squires500]

does anyone have the formula for scaled windspeed?