Hi Row,
how is it ?
Yes is a plywood plate that will be the base plate of the Main Boom fairlead. Similarly there is another one integrated with the mast plate.
Details are at post 197 on the PC screen picture.
This area is also doubled with 2 glass layers.
Best regards
ClaudioD
PS: to answer the second question please see the below picture
A little lazy at the moments !! It happen time to time !!
Here below one example of sail and mast dimensioning.
Personally I use a 1/4 of ellipse to define the Main sail shape.
The Main Luff maximum is 1750mm as for the AC120. In this drawing is 1748mm.
The Jib is fixed to 50% of the Main Surface.
3 carbon tubes sections are used to assemble the Mast. The total length is 1960mm of which 110 mm are inserted into the Hull
The spreaders are at 650mm and at 1250mm from deck datum line.
First section diameter 12mm, second 10mm and third 8mm. Bonding overlap 50mm
The picture of the SW120 is added to show the roof profile.
ClaudioD
Claudio,
A little lazy? I hardly think so, and I don’t believe anyone’s going to begrudge you a few days off!!
Picture number 4, while not a Fife or Mylne, is a fabulous looking yacht and your work will at least enable the majority of us mere mortals the opportunity of owning something similar!
Anyway, back to the detail…
When you assemble the mast sections, where a thinner section slides into it’s neighbouring thicker section does that require any carbon tow wrapped around to prevent splitting - assuming you’re using pultruded sections? Also, where the spreaders attach, are you proposing to drill through the mast & slide spreader through a double thickness section and then bond or will the port & stbd spreaders be individual pieces bonded to the external wall of the mast?
I think that covers it for the time being…
Regards,
Row
Hi Row,
I’m puzzled about the choice for the servo winch or servo arm.
I have still to buy the second one and this is why the servo supporting plate is not yet bonded.
About mast tubes are of course cross fibers ones. For the spreaders I’m still thinking since this time will be turned back.
Below the spreader design principle
Cheers
ClaudioD
Hi Claudio - it is a new milestone when one start working on the rigging as you can start to picture the whole boat and how it will look like…
Question: what do you use to bond the mast sections together ? epoxy ? are your tubing 2mm thickness ?
Merci
Gilbert
Hi Gilbert,
not really, since I decided to remove the wooden Fin Box to gain some weight. Was not easy since strongly bonded.
Box only measured 39g without the dust and support estimated another 14g ! 53/55g for these elements is too much for this model.
I think I need to think about the others supports !
The carbon tubes are simply bonded with epoxy after sanding a little the surfaces for better resin adherence.
ClaudioD
Claudio,
I do like the simplicity of the servo arm over the drum type winches and it would be a shame to deviate from your original drawings. An advantage of the arm type over the drum is that high torque servos are becoming ever more affordable. Of particular interest is the cheap modern breed of digital servo offering full power at any position and the ability to run from 2S lithium packs for further weight savings. I suppose it’s only fair to point out that any servo can be run from Lithium packs given a suitable voltage regulator. Decisions, decisions…
If the biggest issue is driving down the costs to make the class available to as many as possible then you just throw in a Eurgle and be done with it. I know you’ve had success with them but having read Alan’s experiences with them I’d be deeply skeptical of going down that route - when you invest so much time & effort (and to a certain extent money) why risk losing control because of a 20 euro servo?
Food for thought if nothing else…
Regards,
Row
Just an update on my bad luck with Eurgle’s, 2 weeks ago sailing with Graupna Regatta winch fitted and fine tuning boat set-up, now the Graupna is strong and reliable as it gets (but slow & heavy) anyway I had the boom set at 10 mm from sheeting post (close hauled) in light wind and all was going fine, then as the wind speed increased I observed the boom had been moving out further than 10 mm 
After lot of head scratching, the penny finally dropped that I had my continuous sheeting circuit set-up wrong as the “tension line” was on the wrong side of the sheeting ring :rolleyes: now I have always set-up my winch circuits this way :dunce: so changed the circuit from set-up 1 to set-up 2 and solved the problem !
Driving home was thinking about my “learners mistake” and how this may have contributed to the problem I was having with killing so many Eurgles (6 in total) So I put another Eurgle back into the boat (lighter & faster 
) and took it out last weekend and sailed without problems for the whole day !
Now I still can’t trust an Eurgle yet, but I do think having the wrong circuit set-up may have contributed to burning out my previous Eurgles …early days yet, but thought it worth sharing.
Cheers Alan
Hi Row,
the point is that the arm servo require a lot of power.
to control the 78dm² under 10kn wind speed is necessary to have a minimum of 18kgcm with 100mm arm.
The Eurgle winch was barely sufficient for the AC100 and 56dm².
After search, I ordered the Savöx 1256 - 52g and 18kg at 4.8V and 20kgcm at 6V. priced 63€. Apparently is considered around as a good servo most of the time used on car models.
Cheers
Claudio
Hi Alan,
if the bloc was sustained by a spring or elastic, the tension would compensate the sheet tensioning on both sides !
Cheers
Claudio
Maybe I did not explain myself too well…sorry
I use elastic in the circuit for tensioning but on set-up 1, but it was on the wrong side of the sheeting point and when sailing close hauled and hits a big puff, the elastic stretches and lets out the boom automatically, when you don’t want it too !
Actually I’m using 5 mm maximum stretch limit in the circuit and this was the approx amount of boom variation I was observing under sail and was playing hell when sailing upwind.
Possibly with the Eurgle in set-up 1 holding winch in position the tension on the wrong side of the sheeting point was also stressing the winch.
In set-up 2 sheeting point is held in position by the winch and the boom position is not affected by varying elastic tension in the circuit
Cheers Alan
Alan
for me is the same ! a sudden pull will be absorbed by the elastic anyhow whichever the sheet side.
Cheers
ClaudioD
Yes that is what I thought too …but if the “block” is held by spring or elastic, causing tension on both sides of the sheeting point, when big puff hits the increased sail pressure pulls the booms out, as the spring or elastic stretches … not what you want is it ?
Illustration showing set-up 3 using block mounted on spring or elastic
To stop this problem and maintain a constant boom position, I found you need to have a fixed block position to have tension only on one side of sheeting point, not both…ideally using set-up 2
Cheers Alan
Hi Alan,
I’m not sure about what you says. I should make a set up like in the picture and verify if the attached weight change for constant deflection as function of the position.
My set ups are identical to your option 1 and I never observed any deviation of the boom, unless the servo drum can still rotate since underpowered vs sail area and wind force.
The Eurgle are not very powerful against 78dm². I remember that for long time the only winch available was the Hitec HS-725BB
and this servo was already to the limit for a class M with 72dm² and 8/9 kt.
Sometime is better to increase the fairlead-mast distance, loosing speed but reducing torque.
Similarly with a Arm servo, in close hauled position, the arm orientation is parallel to the boom just to counteracts the lever force.
Cheers
ClaudioD
Hi Claudio, your set-up looks like circuit used “below deck” with two sheeting points feeding two fairleads (Jib & Boom) I’m using “above deck” with only one sheeting point.
Hi Alan,
there are two possible setting : one with the servo winch, actually disregarded because too heavy and not sufficiently powerful, and the nominal one being the servo arm.
With the winch, the sheeting circuit is partially outside and crossing the roof side. Two fairleads for main and for jib.
With the servo arm all is inside but still with two fairlead due to the presence of the roof. See below:
Cheers
ClaudioD
Some progress although some material is still missing, like the brass treaded rod of 3mm.
Mast tubes bonded, spreaders prototype made.
Carbon Fin Box ready, but still in doubt for use ! Weight 15g against previous box for 39g .
Wedges to the hull to adds 3 stripes and allow recovery in height for a flat deck.
Not excluded to use 3mm Nomex honeycomb after recalling the idea from PM with Alan, in this case only 2 stripes will be added.
ClaudioD
Some additional pictures from last 2 days and today . These picture concern the hull. After removal of the fin box, it was necessary to restore/repair the fin box area and 2 local layers of 165g/m glass added.
The windows was externally covered with a rigid plastic film.
Interesting to see how look from inside - water leak test implemented to see if some pinholes are leaking !
ClaudioD
Claudio,
Your spreader solution looks extremely neat - what weight of carbon & how many layers did you use to achieve the desired thickness? Also, with the Nomex honeycomb, I know it’s been used for a number of years in ‘big boat’ construction for deck & hull cores, but what stops it from filling with epoxy which must surely then lead to weight gains?
The new fin box looks perfect, so why the hesitation in using it? Do you think it’s too light/not strong enough? When you laminated the carbon/epoxy for the fin box did you use the top end of the fin as the plug?
Apologies for all the questions, I’m just thinking/typing out loud & getting even more frustrated (if that were possible!!) about not being allowed to do anything & I’ve not even reached the halfway mark of my exceptionally boring enforced convalescence…
Regards,
Row
Hi Row,
For the spreaders I used 3 layers of 160g/m² and obtained a plate of 1.2m . Too flexible for the purpose !.
I’m preparing a sandwich composed of carbon 160g/m² and plywood 1mm. If still too flexible, I will add another carbon layer.
The Fin Box is apparently OK but to be sure that the two halves will not split, I should wrap some glass tissue and of course increasing weight !
To make the two parts, I made a two plug forms of half fin thickness out of plywood and wrapped with packing tape.
Out of the sandwich I cut also a Fin Box parts and compare the weights before final decision.
I received this morning the servo Sawöx 1256 and I was surprised that it turn only 45° each side. 60° are reached with the trim.
Reading the specifications, the speed was given for 60° and I’m told that it could work +/-60°, instead is just a ‘convention’ to use 60° as reference.
This is disturbing my plans since the arm was limited to 85mm and rotating 120°. Now keeping the arm at 85mm, I shall therefore use the joystick + the trim.
Finally I got the treaded brass rod of 3mm and made again a prototype for the U-bolt !
Here in Nice is too warm in the last two days and difficult for me to support it and watching my blood pressure !! Fortunately I can use air conditioning inside, but outside is another story !!
Cheers
ClaudioD