along the lines of WTF... for some reason I have it in my head to build a scow hull rg65.... so I'm going to the extreme and taking the Dave Raison's mini-transat magnum 747, down to the rg65 level... while it won't have the canting keel of the minitransat, i would thinkt that the extreme beam would help keep it level while not needing to carry as much ballast... going to build it as a male plug as I have done past boats... We'll see what happens...
Hi Marc, interesting approach ! Let see what happen next ...nevertheless according to my reading, do not rely too much on form stability that on small models like ours is almost absent ! Cheers ClaudioD
to a point I agree as the viscosity of the water has not been scaled down... but when sailinga skinny RG like the round ranger against other hulls the RR does seem to heel more when the breeze kicks up and have a tendency to go submarine style. The 747 was designed for a single race in mind with lots of reaching and not as much upwind action with a canting keel. so i woudl imagine that the hull shape going up wind won't be as ideal. but we'll see what happens once I pop the hull out. At the very least it will be interesting (fugly) looking
In my view, the only way a wide hull can be faster, is if it goes planning. If you can do that you have a winner!! In any other situation, wetted surface is just too high compared to a thin hull... Anyway, I support thinking out of the box. I too like to experiment, so give it a try an tell us how it goes!
Tarm. Yeah I agree this might be a great hull for heavy air... but maybe doggish in light air... If only tunnel hulls were allowed
BTW - no bilge boards or double rudders, so as it heels to reduce wetted surface, you will need to address the rudder and keel length to keep them in the water. Normally these are sailed heeled which makes water profile much less, and then sailed "flat" downwind WITH spinnaker. Regardless - good luck and post photos. I know they tried it in the US1Meter class and wasn't successful.
Dick, i won't be the first slow boat I've built... No desire to thwart the rules. It will be class legal...it will have a single rudder on the CL, and a non mobile ballasted keel on the CL as well and while I have not I have not considered bilge boards, I don't see anywhere in the rules that prohibit bilge boards. it only mentions a single keel on the center line. anything not specifically prohibited is allowed... any boat that has a canting keel needs the bilge board since when the keel is canted to windward the boat would otherwise have no lateral resistance the down side with the bilge board... is that they would always be down... no way to make them retractable.. thus when the wind dies...ton's more whetted surface to slow you down...
The rules mention a keel on the CL, but they do not say anything about their shape. So why not a keel that splits in three or has a wing? This would serve the same purpose as bilge boards... Same rationale can be used on the rudder. Maybe a split rudder with an inverted "Y" shape. It's like having 2 rudders, but the rotation axis would need to be on the CL. And the axis would have to be away from the transom, as the rudder(s) cannot extend behind it while moving... Just some OOTB ideas...
Hi Tarmstro, two observations : 1)- To produce a planning condition of a model you need a lot of speed to create a lift force on a relative small surface. A lot of speed means something close to 2.5 times the critical speed compared to our average model critical speed of 0.7/1.2 Hi speed suggest also a lot of wind and therefore also wave formation that does not help either ! 2)- your suggestion about fin and rudder split simply adds additional wet areas and you can immagine what are the consequences ! Cheers ClaudioD
Hi Claudio. 1) I didn't say it was possible... nor did I say it wasn't. But I haven't seen it happen... (yet ) 2) I agree... but maybe some quantum gain can be achieved... I'm just encouraging OOTB thinking! Meanwhile... I will stick with proven approaches myself...
Tarm, Claudios Esterel is an exercise in thinking out side the box, nothing proven except Claudio's theory... you built it, and I don't know what kind of success you have had with it..but it has proven to be a very fast stable boat... I have no expectations about this hull.. the form reminds me of a plastic snow tobaggan or a barge... won't really know until its done... and on the water... I think my keel is long enough...nearly 12" from bottom of hull to top of bulb on my esterel my rudder is only 6" deep... which may be a problem... I may have to build a new rudder that's longer just to keep it in the water when the hull heels...
Marc, My post is not a criticism to your choice, but in my view you have forgotten the factor "speed" that is always playing the major role ! My design guides are always linked to the expected speed that that model could reach, knowing that at best will be sailing at 1.25 the waterline lenght and very rarely at 1.5. Planning start at a factor 2.5 and not before ! In doing that, my work at hull level consisted essentially in finding the most appropriated waterlines shapes that could favour the reduction of drag. Our models are not so fast as a wide snow board therefore the Lift Coefficients obtained cannot be compared in both surface and speed. BTW the speed factor is a squared coefficient (V²) in the Bernoulli formula. Substantially the real scow form is valid because of the physical contact surface and speed that can reach. (several Knots). Reynolds formula may be more related to explain. At model level, I would expect that some benefits could be achieved if the actual model speed is multiplied by 3 or 4 times the average speed of a RG65 and in my opinion this is impossible. In other words without speed very little can be obtained whatever the underwater form is. Esterel65 main aim was and is the reduction of hull construction weight (few grams), reduction of drift with the presence of a sort of anti drift immerged vertical surface during heeled conditions. At 35° the immersed "vertical wall" is about 30% of the total appendages areas when the Fin and Rudder are tilted and therefore being less efficient contrasting lateral drift. With that in mind, I hope that such a type of hull is reaching the buoy with a closer angle sailing up wind also because the sheer line, being above water level, the drag is reduced. All that with the aim to reduce as I can all parameters that are against the speed. Of course the speed is the one that the hull can allow in theory. Another element is to find an immersed shape not too deep in order to reduce the lateral wave hollow. Deep wave requires energy that is subtracted from the sail power and to this respect the scow may be an interesting form but the same form will also produce very little resistance versus lateral drift unless with the option of a very deep fin with more wet area ! I will be very happy to find at the end that my thinkings are wrong ! Cheers Claudio
no criticism at all claudio implied or felt... I feel like a child among gods when speaking to you...I don't do the calculations you do, nor do I have the smarts to even consider them. I basically sponging off of someone else design... it would need to be high winds and a relatively calm sea state for this boat to even have a snowballs chance in hell... I think the esterel is a brilliant thought and once built. it has proven some success...at least on my local level. I hope to attend a regional or NCR event soon and see how it does... as I said. this thing I building now might be better suited for serving the family turkey in november... its an easy enough hull to form, sand and lay up on a male plug... yet another project to to the list... Also, onthe plus side. you would not want me to have an inside overlap going into the mark... Can we say WIDE LOAD.... Hmmm I think I have a name for the boat...
well did a first sanding and then add a second coat of drywall mud for a second sanding... man, this thing is fat...
Marc, that is looking superb! Is it going to be fiberglass? What building technique are you going to use?
I may have enough carbon left to make one hull. not sure haven't checked the yet. but I also have the kevlar...and glass.. I have been looking for some stretchy latex sheeting. to try the "latex method" for a male plug. but so far no luck on finding. I got two more spots to check one a mom/pop hardware and a really good mom/pop pharmacy/drugstore. if that doesn't pan out I'll try my heat shrink stuff again... the bow isn't quite right yet either...eye is telling me the bow should look a certain way. but the pictures are telling me different...
I'm using this one: http://www.mjtrends.com/products.Transparent,.20mm,Latex-Sheeting#.VBL5UstdUgs I bought 3 yards, which was more than enough... If you use just enough epoxy so that you don't get a mess around the edges, then the latex can be reused many times.
Marc - up here, we have a serious interest in scows. Remember, Melges is in the next state East. Are you working from photos? I tried to get a set of lines from the Melges Shop back some time ago, but they won't release them to the public. Dick
thanks for the link.. I should be able to a final sanding today after work and at least get the heat shrink on the hull...so its ready for epoxy
dick, http://chevaliertaglang.blogspot.com/2012/07/teamwork-evolution-ex-magnum-747-david.html basically took the lines and traced them into a CAD program...and then scaled them up...