Hi Gary,
all right what you says.
My resin do requires, to obtain strongher caracteristics, a post curing of 6 hours at 60°C.
A friend suggested a simple method at the condition to have a sunny day !
This is : …
A large garbage bag eventually Black with the hull inside.
Obviously should be exposed short after the first 24 hours of polymerisation to obtain the relative stiffening effects.
Cheers
Claudio
Claudio, thats very clever, i like it…a cheap enviromental friendly post cure…of course you need a summers day and they are very rare down here at the moment.
Although Epoxys are available now which have relatively good characteristics with room temp cure ie…usually around 22 c, even these epoxys benefit from elevated temp cure and most will enjoy 60 c for at least 12 hours…of course your plug/ mold must be capable of withstanding these temps without distortion.
A point of interest, several days ago we had a ambient local temp of 20 degrees C, I put my black hull plugs out in the sun in a spot sheltered from the wind ( I was speeding up the cure on mould release agent)…monitering the hull temp carefully with digital thermometer, within 5 minutes the hulls were at 47.5 degrees…in fact they got so hot I had to move them into a shady spot to lower temp.
Cheers…Gary
Gary that’s the missing step that I have looked, I did not read the data sheet completely which states “After hardening, 120 degrees for 2 hrs of the non-strengthened plastic material” how stupid am I :mad: Gary you a god send mate, thanks !
I have now put first hull over the mold and inside black plastic bags, it’s nice & sunny outside today around 25-30 C, will do same for second hull tomorrow.
:zbeer: K1
In reference to CE/CLR a suggestion for Matthias.
You mentioned in prevouis post on the launch of Alessandro new NZL-92 that he had to move the mast forward 10 mm, assuming there was too much weather helm.
If possible/practical, and interesting excercise would be to measure the new CE relative to the CLR and let us know the difference from the plan ?
Cheers K1
Hey Alan, you might find its too late for the hulls you have already built, my understanding is the heat should be applied before polymerisation is complete-3 days usually.
I do heat my resins and moulds before layup when needed, more heat=lower viscosity and faster cure.
I do not like heating up these much more than 20 c before the epoxy is into its second stage (initial cure),the green stage when epoxy is soft but not tacky, as outgassing from fillers or timber within the mould can cause lifting/bubbles in the epoxy.
Once this initial cure is over and the epoxy has passed into the final cure stage it will be hard and sandable but polymerisation and curing will continue for several days…of course this timeframe depends on the ambient temp at open stage and temps applied thereafter.
Hope I have not confused you and apologise for not mentioning this earlier…I feel uncomfortable offering advise when really I still have a lot to learn myself.
25 to 30 outside…bliss…how I miss those days
Cheers…Gary
No apologies neccasary it’s really good info Gary, keep it coming 
… , we never stop learning. We may have the good weather but no Rugby 
Hi K1
just to tell you that a discussion is going on to better understand from real tests what it is the best mast position that of couse depends from the CE of the Sail Plan.
Any CE has his mast position !!!
Cheers
Claudio
Naturally as you say the sail plan (C.E) needs to be referenced, Discussion !? the outcome of that discussion your having, would be very interesting to know.
I had a 1 meter model yacht that had an annoying weather problem, no plans so no information supplied with the boat on where CLR or where the LWL should be, so had to find through trail & error.
To roughly find where the CLR was, I used a very basic method of fixing a string along the CL from bow to stern, then put small ring on the string with another line running at 90 degree’s to the CL.
Put the boat in swimming pool without mast and sails and then positioned the ring in the centre of the string and pulled the boat sideways toward me.
After trail & error of moving the ring to different positions I finally had the hull drag toward me evenly from bow to stern, then marked the position on the sheer line and calculated difference between CLR and CE was … it was over 15 mm out, made up test mast step and trailed it, bad weather helm was fixed. After fine tuning on the water found with the mast moved 20 mm forward from it’s orginal position was as good as good be for that boat.
Very basic backyard type exercise, but it worked for me at the time, not knowing anything about boat balance at the time.
Cheers K1
In fact this is another method.
The one I knew is almost the same. You put the boat into the bath including fin, rudder and bulb.
With the finger or a pencil about CL you push the boat. Watching the direction of the bow , the finger position is moved until the boat move entirely at 90°. There is the CLR.
The best would be to tilt the boat of about 30° with a mass on deck and repeat the same exercise.
Ciao
Claudio
A simple way to prevent/reduce “outgassing” is to heat up the substrate. By doing this BEFORE you start laying up glass, the air from the wood has already outgassed, and as the wood begins to cool, it actually “pulls” the epoxy into the pores virtually eliminating all the bubbles and their associated finishing problems.
A simple (for our size) method is to buy an inexpensive heat gun (I suppose a hair dryer willl work but takes longer - oh, watch so the wife doesn’t catch you) and warm the wood to the point you can still touch it, but it is hot to the touch. Layup your cloth and use warmed (I put my cans in warm water before using them) epoxy to begin the process. With the wood cooling, and pulling epoxy into it, you may need to watch to assure there is no epoxy starvation from your cloth.
Be careful using the black bag - it can heat up very quickly. Consider they use them to heat water for showering on big boats ! We used the idea for quick big catamaran repairs. If you smooth the plastic down it will also act like peel-ply and provide a much smoother finish.
Hint - keep the fingers out of your hair if they’ve been in epoxy ! :rolleyes: Don’t ask ! :lol:
You make laugh like hell Dick about epoxy fingers in the hair …bit like tongue stuck to frozen mast …
Yea! with the major difference, the hairs can be cut… !!!
Claudio
Hi Claudio…
I would like to talk about sails one more time.
Originally the IACC120 plan was a 78dm2 sail and then you suggested a 72dm2 (rig 1) sail.
Luca suggested 70 -72dm2.
The range seems to be Rig 1 from 73dm² to 80dm² and not more than 60dm² for rig 2.
In a previous discussion, we determined that most of my sailing will be done in 8 to 8.5kts.
Are you still recommending the 72dm2 set for my rig 1?
Is there anything else to consider?
Many thanks
Goose
Hi Goose,
was my mistake suggesting 72dm² , as you said the min. from the Rules (Rig 1) is 73dm²
I think that you may go up to 75dm² but I would prefers that Matthias answer to that .
Nothing else at the moment except that I’m waiting more about the tests data of Allessandro .
Cheers
Claudio
Probably is not too early to discuss about Sailing Plans and Mast position in view of the fact that soon shall be decided how to construct the mast support.
This is the most important point that need to be known in order to ensure the correct sailing of the boat. Sail Plans are fully dependants from the weather’s conditions .
Each Sail Plan does have his CE and consequently his mast position.
As an example, here are two plans, one for 74dm² and the other for 78dm²:
Observing the position of the CE it is clear that there is a large difference, between the two CE there are 30mm .
If one would like to use both Sailing Plans to cope with the wind conditions of the day, he must know that the mast step shall be repositioned by 30mm as well the jib anchoring.
The CE may be in different position within the same total Surface if the ratio or distance between Jib and Main is different ; in others words a 78dm² plan may have the CE at 10mm or 40mm from the mast instead of 31mm, simply because the sail’s ratio or the relative position is different .
Therefore when one says that the mast need to be repositioned forward or backward compared to the initial drawings, this is always related with the Sail Plan and his particular CE actually used.
Note that the actual CE we take into account is simply the geometric center of the plan, in practice the CE position is changing all the times in accordance with sails angles and wind directions.
The designer may suggest, as a starting point, the mast step position, but variations are expected as fonction of the actual sail plan used. Test are obviously required to ensure a definitive mast position for that Sail Plans used and not for others.
For instance in my plans I suggested a 78dm² Sail Plan but I do not have specified the sails ratio. I have particularly mentioned that the CE-Mast Step distance is depending upon the Sail Plan design, therefore is not surprising that the mast need to be repositioned.
THIS IS THE “TUNING” !
Hope to have explained the concept to those that may be less familiar with the subject.
Claudio
Hi Claudio, everything is cystal clear, however, I noted that in the 74 dm2 sail plan post # 210 you had @ C.E 58 mm, now with this last post you have the 74 dm2 sail plan moved C.E back to 61 mm.
I know it is only 3 mm but I wondered if Alexsandro & Matthias are moving their mast step forward 10 mm (I say that without knowing their sail plans) why are we now moving the C.E further back and not forward ?
Cheers K1
Crystal clear? :snorkel:
I’m going to read that a few more times until it sinks in.
Claudio, would you clarify something for me?
Is the CE a fixed point on the hull?
Therefore, moving the entire rig back and forth to match the CE of the hull with the CE of the rig is what you call tuning?
I can imagine these matched CE’s would be a good starting point and would have to be tweaked on the day due to weather.
Just trying to get my head around it
Thanks
Goose
Hi K1
these sail plans are just traced for the purpose of the discussion and it is the proof that just changing fews details as for instance the distance from main to jib, that the CE is moving.
I don’t think that one can appreciate 3mm variation against performances.
All that confirm that the mast position is fully dependent from the CE and the CE is just the geometrical center of what is drawn before manufacturing.
Furthermore, from the drawing on paper and the setting up the real sails, there is another possibility to have changes much greater then 3 mm just as example.
So, in my opinion, the boat and the sails need to be “tuned” togheter, any change requires a re-tuning.
Just for fun, I will prepare plans for 76dm² with various CE…
Cheers
Claudio
As promised please find here 3 Sail Plans having the same surface but not the same CE position.
There are more then 3cm diference beween model A and model C.
If I have to choose I will make the model “C” since the bigger Jib offer better power in choppy waters.
Cheers
Claudio
Hi Claudio,
The message I take away from the subject of C.E is 1) to make sure you have enough mast step adjustment to allow for tuning the boat for different sail plans and 2) to allow for further fine tuning for different weather conditions.
As a starting point, I have two sail suits being made 78 dm2 @ 65/35% and 74 dm2 @ 65/35% then I can compare their performance in different wind conditions.
Ok show & tell time Yesterday was lamination day for the appendages following couple of days sanding profiles, I hate sanding. Purchased some 6 cm thick sponge, no large sheets available so had to buy blocks :rolleyes:
Being the cautious bunny that I am trialed firstly one rudder with 2 layers of 100 gsm cloth @ 60% compression ratio of the sponges, result bad lamination due to two things 1) Sponge join shows (I’m an idiot) 2) The sponge was too porous, so another sanding project which I needed like a hole in the head :mad:
Raked through the garage and found the missus sun mat & ripped out the styrofoam and tried that on second rudder … perfect !
Next laminated the keels same way using 2 layers 150 gsm cloth, the 2nd keel ended up with minor impregnations on the surface from styrofoam being used twice under pressure & possibly too much pressure by the idiot … me
The weight test :scared: The keel target weight is 150 grams, I knew it was tough call to make it and they came in at 180 grams, well at least it’s weight below the water. The target weight for the rudders is 75 grams and they came in at 29 grams.
As this is a monocoque contruction I taken the precaution of making up a hull cradle to ensure it will remain square for fitting & deck making & alignment.
Now begins my most favourite pass time sanding of the keels before I can start making the keel box & mast support, oh and better go and buy another sun mat for the missus otherwise I’ll be in the dog box again.
Cheers K1