Some little work today to search for a new alignment method and the decision to cut the transom :
ClaudioD
The introduction of angled transom is the perfect touch Claudio … very nice !
Hi Sylvain,
just playing with gravity, while the hull is standing orthogonal to the fin and for this I use a water level tool that can be observed in the pictures.
Outside this method, I found another one visible in the last pics using carbon tubes inserted in the fin box and trunk.
The box as well the trunk are finally laminated during this phase to insure the needed strength. The box and trunk are also equipped with transversal beams actually under construction. When ready the laminations will start.
Cheers
ClaudioD
Sylvain, many thanks for your encouragement - it’s much appreciated. I think what is more frustrating at the moment is that we’re finally experiencing suitable temperatures for epoxy here in the UK & I can’t sensibly get any workshop time!!
Claudio,
Many thanks for your explanations regarding C/L etc. I’d overlooked your ‘negative’ shadows on the building board to cradle the hull - all makes perfect sense now. As with Alan’s comments, I too like the slope to the transom although I think your CD43 represents a better aesthetic. I often find it frustrating when looking at designs / drawings etc where the back end appears to have been ‘chopped off’ - it’s almost as if the designer has just run out of ideas - mind you, being critical of the work of others is easy, armchair ‘designers’ should get off their backsides and actually try putting some drawings together!!
Keep up the fantastic work & regards for now,
Row
Hi Row,
I have integrated the n°3 hatch and taken the color mix of the ‘Giro d’Italia’ cycling tour with ‘pink and gray’.
It is not excluded to make the transom as on the 43-90 or something similar.
Today I have inserted a piece of foam as support for the transom cover when hull and deck will be bonded. The cut was cut and replaced by plywood shadows as support of the balsa bow.
The water level tool was moved at various places to verify the orthogonality, the alignment was checked again.
Cheers
ClaudioD
additional pictures of today work :
ClaudioD
Claudio,
Forgive my language skills but this is truly ‘Belissimo’ !!
Row
Thank you Row, I forgive you Row if you add another ‘l’ ! heheh !! >> Bellissimo !
This morning I was shortening the trunk brass tube, I forced too much but now is bonded again. The Fin Box is glass laminated
Claudio
wow that is stunning !!! class and performance excellent - I really like this hatch.
decision taken !
The mast step is replaced by carbon tubes inserted from deck to hull bottom. This is done for this prototype, but…
The tubes OD is 14mm. This will permit to insert mast tubes of 12mm as well 10mm.
The position may correspond also to strong wind and low wind.
I spent sometime to sand the deck and then sprayed with silver paint just to find out how many porosity holes will show up !
As expected 90% is plenty off.
I shall use a primer/filler
Fin Box under polymerization.
ClaudioD
Claudio,
When carrying out various calculations to establish COA, CLR, CoE etc etc, obviously these only provide ‘theoretical’ positioning data to assist with rig setup, fin & bulb position etc etc. Maybe this will transpire to be less of a problem than I can currently ascertain, but surely just giving yourself two carbon tubes as potential mast steps is somewhat limiting? As this ‘123’ is a prototype, I can’t help thinking that a deck stepped mast foot slide would give you a far greater positional range to achieve the required balance between CLR & CoE (obviously dependent on length of slide). Going with your current planned setup could end up being somewhat limiting, with only 2 fixed positions and then any further adjustment, in particular for the main, only coming from mast rake.
In terms of rig setup for this prototype it’s a bit of a non issue, however, if to achieve the desired balance requires mast rake, forward or aft, the positioning data must surely become more difficult to transpose onto the number 2 hull (hopefully!!) when looking for the definitive mast position(s). In much earlier threads (ie not about your 123 etc) I seem to recall that Earl Boebert advocated a removable deck/mast foot area precisely to work around this problem. In fairness the article was geared more towards far more traditional hull lines (he may even have been discussing J Class lead %'s at the time & how they don’t seem to follow the same rules as much lighter displacement hulls do - unfortunately I can’t find the thread at the moment).
Of course, I may just be looking for potential problems that just aren’t there (Oh, the joys of powerful opiates!!) and look forward to reading your thoughts on the subject, if that’s not too presumptuous of me!!
OK, so I’m off back to bed now!
Regards,
Row
Hi Row,
please get rest as much you can ! This is the best drug, the body will do the rest !!
Interesting question that embrace the full Architectural design.
Here a simplified drawing :
Here below is the method I use :
The first element available when drawing a model is the LCB extracted from the Curve of Areas as well the Displacement.
This is for me the most important one when starting setting the other elements.
From the Hull LCB I trace the “vertical line” that shall cross the CG of the bulb. So on one side you have the hull and below, at a given distance equal to the fin length, you have the bulb.
Than come in the Fin and for that I position it as such that the vertical line from LCB pass trough the 40% of the major chord. This is a trick learned from an old sailor.
In principle and according to statistical analysis, this is what is “practically” needed to mark the vertical line going to the CE.
This approach is also used on real boats.
The vertical line shall be close to the Fin leading edge (+/- 1 %). The error are very minor with a “slender” boat !
Assuming that the mast position is not satisfactory in spite of two options as for the “123”, there is still the jib “alternative adjustment”.
Assume also that all the available possibilities are not providing the good performances, there is simple way to arrange that and is to make a new sails with new shapes and proportions as done on real boats too.
The new sail CE will offer the real “lead” and at the same time will fix the mast position where only one step will be necessary.
I used in the past to search the CLR position with the pendulum method (kindergarten).
From books and diagrams the CE should be, as function of hull form, fin form and sail form, at distance from CLR of 6 to 12 % of the LWL.
The experience I have, the two methods give very close results.
About Mast rake, not yet mentioned, is still possible, all the Class M make use of that.
Example just measured : a carbon mast composed of tubes of OD: 14, 12 and 10mm and long 1700mm, under a weight of 500g, I measured a deflection of 11mm. 500g is almost nothing compared to the pull force of a back-stay.
Without pretending to pull a conclusion on this endless question, most depend on the personal experience gained on other drawn and constructed models.
In my opinion, when all thing are going wrong, then the easiest way is to make a new sail by changing proportions and shape between Main and Jib.
Cheers
ClaudioD
PS : I’m preparing the construction of a new deck and I will use the hull plug as support, avoiding the mistake done before when I have assembled the deck shadows separately on a flat support without taking into consideration that the joint line was a curve and not a straight line.
The false deck plate is bonded to the hull with balsa spacers at the end Hull and Deck will be separated.
Claudio,
Once again, I think I leapt to conclusions based on a fixed sail plan in terms of %'s of total for the allocation between main & jib. My own logic was a bit self defeating: having noted the prototype nature of the 123 I focused solely adjustments to fixed quantities - a ridiculous standpoint owing to the vary nature of it being a prototype…
My thanks for your detailed explanations, I really must try to ensure that the ‘grey matter’ is fully engaged before posting!!
Regards,
Row
Row,
me too I was reasoning in that way for long time, Mast step position, CLR, CE, CLB, Lead %, CF, until by practice I told myself, why not change and adapt the sail plan ! Much easier and cheaper.
Basically the CLB is my starting point as well the leading edge of the fin.
Of course I do my best and hope to do it right on the drawing table and at the first water time experience, but most of the time is an utopia.
When on testing, small tendency to weather helm can be counteracted by moving forward a little the jib or trimming the main, while the opposite can be achieved by reducing the jib area (take a scissors, may be useful for the first time !!!).
So why to make it complicate if can be done easier, some one, ‘Murphy’, said just the contrary !!
Just a small example : two boats, one narrow and one wide with same LWL , same tuning on paper, the slender will go much more strait on in close hauled run while the wider will start get more an more weather helm.
This can be observed in the pool without rig just artificially tilted ; pushing both hulls and you will see the wider making a shorter radius turn compare with the narrow.
This is to says that from one boat to another of the same LWL, there are variables behaviors
Cheers
ClaudioD
Hi Claudio, from experience I’ve found 12 mm carbon tube to be much stiffer than 10 mm on 1750 mm mast.
Cheers Alan
New deck shadows ready to be bonded !
ClaudioD
PS: Deck under construction …!
After 23 hours of effective work, the New deck is almost ready, actually drying for tomorrow filler work and fine sanding.
It will be covered with packing tape for subsequent lamination.
ClaudioD
Deck ready for lamination !
ClaudioD
Deck laminated with 1 layer of 105g/m² and 1 layers of 80g/m²
Expected weight : 66g +/-5
Peel Ply ribbon removed when the impregnation was achieved, about 30’. This operation remove the excess of resin if any.
Visible the surface status after Peel Ply removal !
ClaudioD
Claudio,
This is more of a general question really, but I noted from you earlier posts when the hull plug was being prepared that you didn’t go down your more usual route of giving the plug a couple of layers of, say, 85gsm on the external surface. Was this decision purely driven by time considerations and the fact that it was going to be subjected to the ‘packing tape’ release method, or were there other reasons behind your thought processes?
I’d imagine that if the prototype works as well as expected, would it then prove necessary to glass the plug (with all the additional work that entails) prior to producing a female mold for future (male) hulls to be pulled from?
Looking forward to reading your reponse,
Regards,
Row