Hello,
today ETNZ NZL-92 by Alessandro Strappaghetti has been launched!
Grat boat. I was there with my Alinghi SUI-75. We noticed that the mainmast position have to be 10 mm in forward respect the project position to find the perfect balancing.
Here one image e two videos:
http://www.youtube.com/watch?v=JLerxPScvIQ
http://www.youtube.com/watch?v=AAlLfvqFhVM
Cheers
Hi Matthias,
interesting films expecially the second one . Pity about the wind instability.
To note the different Sail Plans between the two boats, could you please tell us more about ?
When you suggest that there is a need to increase the Lead of 10mm equivalent to about 1% of the LWL, you should also mention the Sail Plan used indicating the geometric position of the CE.
On the ETNZ drawings the Sail Plan is only indicated to be 78dm², assuming that the modeler will decide which plan to use from 85dm² down to 73dm² in accordance with the prevailing local wind strenght.
I presents here the 78dm² Sail Plan that is called in the ETNZ Plans :
To note that in the Sail Plan drawing the mast is with 0° rake and the CE is 34mm behind the mast as reported on the ETNZ plans.
Therefore Matthias, with your suggestion, are you referring to that Sail Plan ?
This information is very important in order to better understand the design performances and facilitate the Tuning.
Thank a lot
Claudio
Congratulations Alessandro! :zbeer:
Your ETNZ looks and performs excellently…
I have put all my sail decisions on hold until i understand these conversations.
Cheers
Goose
Hi All & Matthias,
Congratulations to Alessandro on his new boat, looks like it performs nicely on her maiden sailing 
This weekend spend making keels & rudders, after 2 attempts think I have the keels down to 150 grams, next few days will be sanding to get right profiles before final lamination.
Made the mistake of also trying the “envelope method” for making rudders, thought it would be quicker :mad: ended up too heavy so reverted to Balsa/Carbon sandwich which is same as the keels.
Cheers K1
Remember my post 152? :mad:
Well it seems that any kind of mold release fits into that scenario so I said screw-it< and have gone back to things I know.
I put a layer of packing tape on my mold followed by cooking spray (spray on, wipe off) before laying up my hull.
Using Claudio’s calculations I tried to calculate the finished target weight based on 1 layer of 3.8oz glass and 3 layers of 2.8oz glass + resin, but my calculations were way out.
Mine came in at 279g which is within the limits Claudio mentioned of between 247g and 285g. Good enough for me 
Pic 1: Here we go again with the peelply
Pic 2: The packing tape/cooking spray release saw the form practically fall off the mold. No high tech here :pirate: Those stripes you see are where the peelply bubbled and didn’t touch the surface. They are low spots that will be filled and sanded. The rest of the surface is perfect and blush free.
Pic 3: You can see the tape lines inside the hull.
Pic 4: Back onto the mold for the next three days to setup.
I’m off to look at the rudder and keel fin…
Cheers
Goose
Hi Goose,
Another pleasure for my eyes !!
I’m start getting confused with al these ETNZ in miniature, they pup up from everywhere !
Tank you all
Claudio
Hi Claudio…
No, thank you!
Consider all these 120’s your children
Cheers
Goose
Lets talk about the rudder and keel.
I am going to try and set them up using my food sealer as a make-shift vacuum bagger just for fun
Rudder first:
How many laminations of what thickness balsa? [I used 4 x 1.5mm]
And because I don’t have any carbon cloth, I am going to glass the outside and include a carbon tube leading edge. What diameter carbon tube or rod? [guessing 3mm?]
Keel:
Claudio used 4 x 2mm. Is this because the final fin thickness is 8mm?
What diameter carbon tube or rod for the leading edge? [guessing 5mm]
Any comments?
Cheers
Goose
Hi,
as general information, extracted from my manual (in Italian) already loaded some pages ago :
Geometrical details :
First the two profiles:
for the FIN generally the thickness varies fro 7% to 8 % of the cord positioned at around 40-43% from the leading edge. Some modelers push even further using thickness of 6%.
To note that using low thickness do presents problems to introduce the supporting treaded rod for the bulb that generally is of 4mm dia.
For the Rudder the thickness varies from 9% to 12% and this is due to the fact that it is necessary to have lift also at large angle of incidence, due to the rudder swing angle.
A thin profile will stall with incidence angles above 5° rendering the rudder function inactive.
Personally I always uses 8% for the Fin, some time 7% and 10% for the Rudder.
The leading edge is a critical part of the profile, most of the performances rely on this parameter. I use most of the time a 2mm CF rod.
Lamination : the glass has about half strenght per weight compared with the CF, therefore you should double the number of layers.
For the Fin of a lenght below 450mm, I use 4 layers of 100g/m² of which 2 are oriented at 45°. With glassfiber of similar weight shall be necessary to use 8 layers. It may be possible that 7 or even 6 layers may produce an accepatable Fin with limited deflection.
Personally I have no experience and therefore I would not tell more about.
For the Fin 4 sheets of 2mm thick are OK for the Rudder as well .
More details can be found under the IACC120Cup tread from page 12 onward.
Good work
Ciao
Claudio
K1W1
Photos photos … i don’t understand without photos kekekekekeke
What brand of release agent u guys use? The mould release out so perfectly nice i wish i can do that when i’m building one
Paulin from Strasbourg - France is back to work !
This is the progress, the hull is ready for sanding :
…
…
Cheers
Claudio
Great progress from Paulin & Goose good job of the hull mate !
Ok Lamafever, here’s few pics on Keel & Rudder under construction, I could not find any CF sheet as most places are closed for summer vacation here & only thing I could find was CF Twirl.
I knew this was not going to be enough strength with just the twirl for the keel so picked up 6 mm rod and laid it on the chord line and slotted 4mm SS threaded into the 6 mm CF rod. For little extra strength also slotted in 3 mm CF rod halfway between the the 6 mm rod and tail edge of the fin, risky, but it’s all I had to work with :scared:
24 hrs after sandwiching keel together, took it out of the press & tested it with 8 kgs on the bulb bolt …whew ! no bend, so I was happy it’s strong enough. Unsanded weight 140 grams, hence after sanding (work-in-progress) and lamination I’m guessing it will come in at about 160 grams, which is 10 grams over target weight.
Rudder fin was straight forward (after my envelope failure) with sandwich 2 x 2.5 mm balsa with 7 strands of CF twirl. Ready for lamination weight 19 grams, so it will come in well under 75 gram target once laminated.
Cheers K1
Hi Claudio…
Thanks for that.
I used what I have on hand and cut my rudder from 4 laminations of 1.5mm balsa and created the rudder post from 4mm OD brass.
I will shape it and plan to use two layers of 3.8oz glass in my make-shift vacuum bagger.
I understand your recommendation for more layers and will add more if necessary.
I have carbon strand matting for the centre of the keel fin and will do the same with layers of glass and test.
Thanks for your ongoing help and encouragement.
Goose
Hey K1…
Lookin’ good mate.
How did you arrive at 8kg’s of test weight?
Cheers
Goose
Hi Goose, just hung empty paint tin on the keel bolt & added weight inside inside it until it started to bend, clamped top keel to the bench.
Can anyone tell me how to get the residue release wax off the inside of the hull ?
Further, I’m getting a little concerned that the hull is no becoming more rigid … still feels very flimsy
Cheers K1
If the fin started to bent, means that was just approaching to rupture !!! Why to push so far ? was a test ?
In mechanics the safety factor is generally fixed at 1.5 the max. expected load. Since the load is fixed …
The Wax is generally soluble with water, you can use also acetone .
Flimsy ! is normal …
Ciao
Claudio
K1W1,
The hull will seem to stiffen once the deck has been installed.
Usually the bare hull is quite floppy. Stiffens a bit when inwhales are glued on (the small timber pieces glued on to top inside of hull for attaching the deck to hull), but stiffens even more when some deck beams or deck are attached.
How flexible is your hull? - When you sit the bare hull on a flat surface it would be normal for the hull to flatten (beam increases) but not for the contact area with the table to be distorted too much.
If you dont have enough cloth weight, or your resin is still soft your hull could be too flexy.
Jon
Claudio, anything that I stress test I never use (rubbish bin) for the reasons you highlight as rapture weakens any component. With a target weight of 150 grams I needed to find the limits of what I had to work with and adjust the recipe accordingly. For a first timer it looks like mission impossible when you stand there with few sheets of balsa, strands of CF twirl & rods in your hand knowing it’s got hold 3 kgs rock solid. :scared:
I actually had made two test fins to find acceptable weight/strength ratio. I went through this process only because I could not buy the right ingredients described in your fin manual & I had no idea if what I had to work with (CF twirl & various CF Rods) would be strong enough, hopes this clarifies what I did.
Jon your question “How flexible is your hull? - When you sit the bare hull on a flat surface it would be normal for the hull to flatten (beam increases) but not for the contact area with the table to be distorted too much” I tried your explanation and thank goodness the beam does not increase when sitting on the bench, having never worked with FBG before is totally new territory for me, I do trust Claudios instructions & recipes 100%.
Claudio & Jon thanks for your continued support and piece of mind for “The Apprentice”
Cheers K1 :zbeer:
Hi Alan, just a thought (although I am sure you have looked into this already), check the datasheet on the epoxy you are using, it will have an ambient temp cure rate usually with elevated post cure recommendations.
Also be sure you are not laminating in high humidity,a simple dehumidifier in the workshop will help to control this. (controlling humidity will also reduce amine blush).
You would be surprised how easy it is to generate over 30 C for extended periods. Build a simple box big enough for your mould, put a couple of lightbulbs (or desklamps or tablelamps in the box), Or place the mould over a oil fin heater and inside a open bottom box keep an eye on the internal temp with a digital thermometer. you really do not want to raise temps too high with plastic glues (PVA) holding the planking together. I would be aiming for 35 celcius max to stay on the safe side.Leave the mould in the box for 12 hours. You will have a stronger, stiffer boat.
Three things…check the datasheet…ensure you are distributing the heat evenly (watch for hot spots) and don’t burn the house down!!.
Cheers…Gary
CLR - CE
Since I’m discussing about RC Yacht models the question is alway open.
At end, each one, via a good TUNING find the way out that satisfy his issue.
Some days ago I discovered in the Italian press* an article describing a new method to establish the LEAD between the CLR and the CE.
I just presents the two methods, the one I use since ages and the new one that is applicable so far, I understand, to real boats. How much of this can be transferred to our models, I ignore it, nevertheless may be worth a trial …
The drawing comparing the 2 methods to determine the CLR position :
The first, is the classic one I use for my models, This cardboard method is described in various places, forum, etc. I consider it a good approach to obtain a correct centering via the Tuning Process. The CLR is obtained taking all submersed surfaces. Obviously is not higly precise since not all the surfaces behave in the same ways as the hull and the bulb.
The second method is instead considering only the Fin surface with the exception that the surface is the one that go up to the Water Line.
Having established the new surface, an orrizontal line at 45% of the total height is drawn.
A vertcal line is traced at 25% of the cord from the leading edge. The crossing point with the 45% line, is the CLR.
Boat having fractioned Sail Plan should use a Lead from the CLR of + 3% to +7%
There is a lead range that is common to the two methods, but how much a model could “bear aways” with such a lead ?
Cheers
Claudio