Your the master in weight control Claudio !
Cheers Alan :zbeer:
Hi Alan,
are you back ?
Cheers
ClaudioD
PS :
Hope to stay inside the specifications.
Due to the external lamination, I have additional 180g available before reaching the LWL, but I do not intend to use it simply because is not my intention to stay too far from the “magic” 4000g overall.
Of course, with this additional volume, and respecting the specification, the LWL will be some 10-12mm shorter.
Cheers
ClaudioD
And it is always easier to add weight to bring the boat in its lines then removing it !
Yes, PM’d you earlier today arrived back this morning (jet-lagged again)
If I understand your calculations correctly you will have roughly 70-75% righting moment ratio ? that’s awesome !!!
Cheers Alan
Hi Alan, nice to see you back !
In principle, the actual prototype bulb/boat ratio will be 2925g/4088g = 71.5% - The ideal would be 2950g/4000 = 73.7%.
Now I’m in trouble with the sheet length provided by the Savöx 1256 servo. During setup blanc testing I found out that the max sheet length was 220mm with 103° arm variation and 87mm long, while I was searching for 270mm.
I start testing the Servo/arm alone and discovered that the lever is providing only 80° swing and +40° with the trim. This with one transmitter Hitec Laser 4 and worst with the ancient Hitec Ranger III Sky limiting the total swing to 100° only.
Both transmitters adjusted for max ATV.
Actually I need to modify my mounting design inside the hull especially if I want to use a longer arm (vertical position swing).
Practically when sailing from close hauled to running, I will need to operate in sequence the lever and the trim and this is not very nice. It may be that I will chose to operate the servo horizontally, but in this case I need to short the Fin box to let the arm pivoting above the box.
Next time I will probably chose the programmable Hitec 7955TG including failsafe or a Futaba S9156.
Now back to work !!!
ClaudioD
The sheet length problem force me to modify the setup design and applying the reverse engineering approach.
The place inside is now “clean” !!
The vertical arm design solution is abandoned !
New setup with the servo arm swinging horizontally.
The Fin Box is shortened to allow lovering the arm and avoid roof interference .
The upper fin is also reduced from 102mm to 70mm.
The servo arm swing freely at hull ‘joint’ level.
Accessibility largely improved as was for the servo winch.
New servo support baseplate necessary !
New fairlead to be made !
ClaudioD
Progressing with the New servo-arm base plate + bonding of mast struts (aluminum ribbons)
I wonder why my brain was focusing on the arm vertical swing with the difficulties associated when the actual setting is much easier to be implemented and probably lighter !!
Accessibility very good, compared with previous one, especially when the servo substitution is concerned.
Finally I suppose that was a good idea to introduce the changes !!
Cheers
ClaudioD
Hi Claudio,
still following your progress with keen interest. would reducing the fin box by that much require to reinforcements to ensure it will stay solid as you’ll have a good bit of lead at the end of a long fin keel ?
cheers,
Gilbert
Hi Gilbert,
Is not uncommon, within certain limits, to have a short Fin Box see updated drawing with horizontal arm swing:
In this particular case the limits are higher of what can be used, ~85% of total hull height
In the 1 US meter Manual, from AMYA at page 23, you may see the fin box height at 50% of the total hull height.
BTW is another way to gain weight !! heheh
Cheers
ClaudioD
you know your stuff more then I do but I wanted to ask as I know in the 10R some try as much as possible to have the fin box as high up as possible to increase the distance from the bottom of the hull and reduce the effort there (I think !). but that c85% is a good measure to know. didn’t think you could go as low as 50% though (not too familiar with the US 1m).
And yes anything to gain weight.
picking your brain again if I may - on the Mini40 I am building at the moment (very slow as don’t have much time I can spare on the boat at the moment) I am gonna increase the mast section from 10 (way too soft on my other Mini40 resulting in not being able to control the leech of the main as the mast bends too much) to a 12 and since my section of 12 is too short I’m gonna use a 14 in the lower section and do like you a mast of 2 sections. I suspect that the longer the section of 14 the stiffer the mast will be but is there a “guide” if I may say so on the ideal length of the stiffer section vs the smaller section ? or is it a case of personal taste where for a stiffer mast I use a longer section of 14 or less if I prefer a softer mast ?
Cheers 
Gilbert
Hi Gilbert,
First, I would suggest to open a specific tread on the subject to call the attention of others modelers.
The Pultruded carbon mast tubes are selected as function of the length and number of spreaders.
In the present 123 design I use :
12mm for 700mm +
10mm for 600mm +
8mm for 550mm
- 110mm entering the hull
and 2 spreaders levels
About a Rule, I do not knows if any, but I suppose that each class as developed a setting.
Cheers
ClaudioD
A detail that was not mentioned yet is the struts / tie setting employed for the 123 design, see picture.
I used that solution because I don’t trust the bonding method.
Here a treaded rod is crossing the mast tubes at the base, but can be done with any other box. The 90° twisted aluminum ribbons are fixed with bolts at both ends.
On the actual setting ( see previous pictures) I simply hooked the aluminum ribbons around a carbon rod and bonded, hope will work but next time the full mast support will be assembled outside the hull for better access !
ClaudioD
PS: I found that table in my Class M records
Hi Claudio, I’ve been scratching my head last couple of days wondering why the aluminum struts, especailly when construction has been on diet 
You say that you don’t trust bonding CF tube …have you have experienced problems ? I have’nt, only curious if others have, thats all.
Cheers Alan
Hi Alan,
I don’t trust very much bonds when a direct pull force is applied.
I know that a “Cyanolyte Super Glue” publicity on TV shows a man hanging on the ceiling just with the shoes bonding in 3 seconds !!!
I do not have problems yet, but the illustrated method is based on plain metal strength and not on the resin adhesion.
The ribbon can be replaced by carbon tubes with the use of a metal rod as retaining mean and a drop of resin on top !!
Cheers
Claudio
[QUOTE=claudio;64113]A detail that was not mentioned yet is the struts / tie setting employed for the 123 design, see picture.
I used that solution because I don’t trust the bonding method.
Here a treaded rod is crossing the mast tubes at the base, but can be done with any other box. The 90° twisted aluminum ribbons are fixed with bolts at both ends.
On the actual setting ( see previous pictures) I simply hooked the aluminum ribbons around a carbon rod and bonded, hope will work but next time the full mast support will be assembled outside the hull for better access !
ClaudioD
PS: I found that table in my Class M records[/QUOTE
Thanks Claudio for your response - perfect timing for your thread there - having this V shape reinforce the attachement point for the spreaders ? reduce hull compression (as we used to experience when I was racing 420 when pulling hight tension on the shrouds resulting in pinching the hull and making the centreboard harder to lower or lift) ? does it relieve somehow the pressure of the mast in small area of the bottom of the hull ? or a combinations of a few elements ?
Hi , just a simple triangular beam, composed by mast, shrouds and struts, it avoid hull squeeze when pulling on shrouds as you observed on the 420.
ClaudioD
Servo arm board and Main fairlead board are bonded.
Fin fixation screw visible as well the jib sheeting.
ClaudioD
Jib Boom anchoring system under evaluation with Pull Test on sample.
First trial with 5kg
Second trial with 7.5kg
Third trial with 10kg
This test shall verify the soundness of the brass rod bonding inside the carbon tube. The rod has been corrugated with abrasive paper. Only 30min epoxy resin used without additives.
ClaudioD
PS : test performed and successful up to 10.3kg ; see set up
Second PS: I tried to test with 15Kg
First attempt: the hanging hook opened
Second attempt : the new plastic bag handles broken
With this test I checked two parts, the eyelet and bonding and the drilled hole to attach the hanging hook !
Alan ! I think now that I can trust this bonding !!! apparently stronger then 1.5mm brass metal rod and 4mm carbon tube !!!
Hi Claudio, I’m happy to see your faith has been restored in epoxy bonding, with extensive testing it looks great. 
I like to share how I make a Jib pivot, firstly I personally don’t to use “jib hooks steps” on the deck anymore as they always seem to be in the wrong place for me & I found aluminium slider from Cap Maquettes which allows to have a “step-less Jib pivot” position over 100 mm range & use my favourite construction material carbon foam sandwich with peel ply finish (for good bonding)
Cut base plate for the slider & struts running to keel line in position then drill holes in base plate and bond whole assembly together including slider nuts on the underside of the plate for easy removal of the slider if required later.
Once cured, temporary suspend the assembly on sheer-line stringers using two strips of wood that is screwed to base plate and bond struts to bottom of the hull.
Alignment of the deck to the Jib plate is perfect but before the deck is bonded to the hull you need to drill holes in the deck for slider bolts.
I had no problems with the assembly but once running in strong winds the nose dived under the water violently and the swivel holding the jib to the slider snapped, but it was only a matter of sliding in a new stronger jib pivot swivel.
Cheers Alan
Hi Alan,
thank for showing the system that shall be used .
It is very appropriate when you have a flat deck since you can use the sheer line as supporting reference.
The sliding (too long) is then directly in contact with the installed support.
I prefer to use a ring where the boom sheet is passing trough and anchored to the deck via a bowsie. This method allow to lower the jib boom as much as possible to the deck, generally less that 1cm. see picture of the AC100B
With the actual 123 bowed deck I’m working almost in the “dark” so I have to invent something else, like an intermediate board as a guide while bonding.
I was obliged to remove the shadows “0” for better visibility.
Other solutions may be too heavy !
About the bonding strength with resin I did not changed my point of view I simply increased the length of the bond and added a step + glass and this is what make the big difference, see sketch.
At the end, what it is important is to increase as much as possible, with any means, the bonding contact surface.
In my test I was expecting also the fracture of the carbon tube in the area of drilled hole.
4mm tube and 1.8mm hole.
Added two pics to show what could be the final assy.
For the next model I will go back to a flat deck with rounded corners and with Nomex Honeycomb where your sliding (shorter) will be used as your design.
Cheers
Claudio