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Potential 10R sailor


Richard98
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Looking to build a 10R since there seem to be no second hand hulls around. I remember seeing a chined design on here some time ago, but can no longer find it. 

I know that this hull form is not necessarily the best, but I can cobble one together in a few days; as previously done for a foiling Mini40 not so long ago (now sold on) Also cheap as chips and light enough to come close to CF in that hull form.  Can anyone point me in the direction of the lines for that chined 10R ?? I do remember that it was a well known designer.

Richard

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There is always Nookie Bear, available as a plan from Sarik (https://www.sarikhobbies.com/product/nookie-bear-radio-10-rater-plan/)

OR   Vic Smeed's Spook   (All Radio Sailboats - Design: Spook)

If you are into 3D printing, there are a couple of options herehttps://3dprintedradioyachts.com/10-bananas-10r-first-major-regatta/

Edited by tiggy_cat
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Thank you Tiggy_cat, had a look at those two. Both pretty heavy displacement hulls I'm afraid. Pieces of Eight looks about the sort of hull ; Thank you Shaun. Long and thin and easily adjusted from lines for a 4Kg all up weight. 

Will try to see if any lines are available.

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From what was posted previously, I understood that Pieces of Eight was a very radical design i.e. it was special design for use in very light airs as it had a very short waterline length and hence a large sail area.  I also think that it a had a mast height which would now be illegal on a new boat.  Whether you think this is a good basis for a new boat is your decision.  You might be better of adapting a current design to chined construction.  You could use two chines and produce a cross between an Enterprise and a modern 10R.  Eat you heart out Dr Frankenstein.

 

 

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Thanks John, looked like a short WL as you confirm; Enterprise analogy noted.  What I need is a design with a long WL and, obviously narrow beam. Where can I find a list of boats and their characteristics ?

Problem is that 10R's seem incredibly rare despite looking like a very interesting and exciting class. Not a sniff of any older design (not vintage I must add) hull for sale anywhere.  

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Have a chat with Roy Stevens (roy 'at' grtayton.co.uk), I've currently got his 10r Sonix round the back of my dining table and I know he is looking to sell her - I sailed her in this years nationals the other month and thoroughly enjoyed myself, even won a race which is a miracle for me. Plus the price is very good.

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I am quite new to 10Rs, so am no authority, but to quote from a Yachts and Yachting article "Any boat can be a 10 rater and several Marbleheads have been successful in the class by conversion with just one larger rig giving 40% extra sail area" so this could offer another avenue to explore. Although not necessarily hard chine, there are lines available for a number of Marbleheads, including Brad Gibson's Indie.

Also PJ Sails offer the hull for their Tension design 10 rater for a not unreasonable £175.

 

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Thanks Dave; have contacted the Round Pond and got some useful info. Also lots of info from Australia.

Thanks also Ditton Dabler. Have been down the Marblehead route some time ago. My current interest in the 10R is to sail a boat with a really useful WL. The idea of the chined hull was to build something really quickly, not necessarily competitive. For example my last MIni40 centre hull only took a few days to knock together.

Will follow up leads on other boats.

Richard

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Now have lines for "Pieces of Eight" thank you Roger.

Looks a really interesting boat and was designed for the light flukey conditions that I sail in regularly. I will shortly start the build. I have changed my design requirements, as you may have noticed. The original long WL was to suit a potential foiling boat. I like the look of the 10R class so much that I have decided to go down the "class: route and will build a 10R accordingly

I am looking for a max luff top suit, in useable condition , if any one has any spare sails they do not need.  Will place a note on the "wanted" also.

Edited by Richard98
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  • 4 weeks later...
On 18/10/2021 at 10:43, Richard98 said:

Looking to build a 10R since there seem to be no second hand hulls around. I remember seeing a chined design on here some time ago, but can no longer find it. 

I know that this hull form is not necessarily the best, but I can cobble one together in a few days; as previously done for a foiling Mini40 not so long ago (now sold on) Also cheap as chips and light enough to come close to CF in that hull form.  Can anyone point me in the direction of the lines for that chined 10R ?? I do remember that it was a well known designer.

Richard

Richard if you are still looking, I have a Spook without a keel weight. A mast is available, as is a main sail. I have not cast a weight yet but I have turned a casting pattern. I am located in Derby and I would consider an offer for it before I progress.

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Thank you for your interest, Eric and for your offer to sell me your Spook. 

I began building Roger Stollery's design last week and attach a picture of progress, so far.  So I am not really looking for another boat any more.

However, would be interested, as I'm sure others would be too, in details of your build and some pics if you felt like putting them up on the forum.

Richard

 

IMG_9519.JPG

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  • 2 weeks later...

Flotation - Basin trials.

Floated in my test tank; Hickling canal basin at the end of our road. 

Bang on the WL marks  1150mm - thanks Roger. Now to cobble together a rig and go sailing. Will be using a smallish 20250mm luff before I work out the allowable sail area, now I know the WL. Tested with 3.5Kg ballast, all electrics fitted and a dummy weight for the rig.

Richard

 

on marks.JPG

basin view.JPG

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  • 2 weeks later...
  • 4 weeks later...

For comparison, a picture of the same sails on my Bentley.  I think this highlights the major problem with the 10R class.  Those sails are the maximum allowed for the Bentley's 1344mm waterline whereas the Pieces of Eight can have a significantly larger area.  In winds under about 7kts I don't fancy the Bentley's chances but over 10kts there is only likely to be one winner.  10R's are lovely boats to sail and very fast but you sort of need a different one for every wind strength if you want to race seriously.  Also probably best not to get me started on how hard it is to measure the damn things accurately.

Bentley.jpg

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With respect John, I’m not sureI agree with your take on the 10 Rater class. Those that do, or have raced them seriously have not found the need to have a specific boat style for a specific venue. The two examples posted above are possibly as far apart on the design window as you could expect that are still racing. Both can be matched and beaten in their ‘favoured’ conditions by well designed boats. it is actually an attractive aspect that 10raters have over other classes that there is so much freedom in design but sadly a lack of what is good about the class not being promoted and poor calendars help to keep it well hidden from designers trying their hand or new skippers wanting to sail the fastest monohull rc yachts.

It may be worth taking a look through past designs that have done well consistently. These are well thought designs that do well in all conditions. As for measurement, not so difficult, just a waterline and the largest rig that needs to be lower than 10. Some would say no harder than any other class, if you can find a measurer…

Edited by Brad Gibson
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Of course a well sailed boat can beat a badly sailed boat but hydrodynamics still applies.  If you accept the well known maximum hull speed formula (for displacement mode) then the Bentley should be just over 5% faster at it's ultimate hull speed (when upright of course).  If we assume equal displacements, one would expect the drag curves for the two boats to cross over at some point towards their maximum speed. The POE would be expected to have a lower drag at low speed, because of it's smaller wetted area but it's wave making drag will rise faster due to the shorter waterline.  The overhangs on 10Rs are intended to increase the waterline length when heeled so it gets a bit more complicated but having a longer waterline to start with is generally beneficial.

My comment about measurement accuracy is to do with the waterline length.  The overhangs of a 10R (particularly at the stern) make a very small angle to the water surface so that if you are 1mm out in height you will be about 5mm out in length.  Now add in the meniscus problem and I estimate you could easily be 10-15mm out.  Incidentally I haven't found a definitive statement on how to handle the meniscus effect in the rules.  I just know the Messrs Bantock and Stollery both say that you should try to eliminate the meniscus effect when measuring the waterline.  I believe there is a more accurate way for boats that have been designed using a CAD modelling system and that is to produce a graph of waterline length v displacement from the model.  One then only needs to weigh the boat to determine its waterline (and verify that the hull is built to the model.)    I found it very difficult to get repeatable results when checking my Bentley so in the end I took a range of measurements at different displacements and then curve fitted a graph to the results so I can determine the waterline length from the weight.  My worst point was indeed about 15mm off a fair curve between the other points.

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All very true what you say John in basic yacht design. Where 10s built to wide ends of the design window will vary is most often in both displacement and sail area. Static waterline length being long may be one thing, but a short waterline boat with overhangs, more sail area at a lighter displacement will usually sail right past on a run, increasing with wind strength. How they compare upwind is another matter, dictated heavily through righting moment as much as any static or heeled waterline. Does the heavy boat have a long deep fin for a high righting moment %? or …Does it have a shorter fin with a heavy bulb for a righting moment similar in % to the lighter displacement boat that has a lighter bulb set on a deep fin?

As I’m sure you are aware there are many options and parameters that can make designing a 10R a true test in design, like any open rule class. That those regularly doing well over time seem to have flowed into a narrow band of the design rule using the mix of variables mentioned above, shows the efforts designers have put in. Yes you can have a design pitched way out one end for a certain condition, but these types rarely are consistently near the top of results at competitions. No different really than what happens in any class with range of design.

I’ve seen no end of measurers offering the ‘right’ way to finding a waterline on an Rc yacht. Some tanks out there with no end of gadgets, screws, tin foil linked to batteries etc etc. To me most simple and repeatable is marking a brightly coloured strip of sign vinyl under a hull, with marked lines numbered at 5mm increments. Place the boat in a tank, then take a 9” x 6” mirror and slide it into the water to show the undersurface of the waterline and the accurately sight where that undersurface bisects the marked hull point. Record your measurements. I.e. transom halfway between 4 and 5… Do the same at both ends. Have a 10 minute break then do it again a couple of more times. When happy with consistency, mark those points on the hull. If you want a safety factor add 2-3mm each end for peace of mind.

Both of my own boats used for the last 2 worlds were measured with this method. Both were absolutely spot on when being measured in the elaborate tanks, with the measurer both times suggesting I could have been up to 4mm shorter on the waterline….the exact amount I add in for safety. 
so long as you can find a tank, it’s not that difficult, but no doubt I’ve been doing it wrong 😉.

 

Apologies Richard for not complimenting you on your build, great work in continuing to show home building is alive and well through all classes.

 

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Wow !!! this is suddenly so interesting.

You are both correct, of course, concerning  the design extremes and relative virtues; or not. I did consider Bentley, but that was the polar opposite of what I needed for something to suit the very light conditions that I usually sail in. Also the boat was built to a tight (very small) budget.

My brief foray into the 10R class has stirred my interest in a boat that allows true performance with a fairly simple rule and, very important, not a lot of weight to cart around.  The overhangs introduce huge scope for hull tuning  since they are not tied to the simple WL formula as they must be designed to heel to an optimum WL; or sail flat in light winds well below hull speed. Aiming for the best of both worlds.    These boats must be the most exciting class out there.

Why on earth the class has not got a greater following is sad. I have built a few Mini40's and the same comment applies. Although to be fair you have to invest in at least two hulls there.  Neither class has a useful web site or forum with any discussion (apart from the MYA here) The Mini40 only exists on Facebook and the British Model Multihull website has been out of use for ages. Nowhere to gather info or discuss two classes that should be generating more discussion than most, due to their many diverse performance characteristics.

I would love to get my hands on a current design, but my Pof8 provides some fun sailing at least.  I think I would go lighter ballast on longer fin, thereby reducing the displacement and all the consequent form drag. Appreciate that this may limit some venues.

Measurement: As pointed out, should not really be a problem. Totally agree about WL being the most critical item WL. Tried various tricks short of getting into the water myself. I used bright tape with increments marked and then photographed, sort of nearly consistent. Even thought about the foil and battery mentioned. No tank though. 

Adding surfactant to the measurement tank would decrease the meniscus, but hey ! getting a bit chemical here.  What about a floating gauge, sharpened to a point and pre set to the boats declared WL. Go/No Go.   Could be used at the water side, if calm, and the draft subsequently measured.

Thanks for your appreciative comment, Brad.

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