Your research & development work with curved deck has shown us a lot challenging points that need to be tried & tested and you have done great job in sharing your trials and tribulations that is always very interesting.
The first slider pivot swivel I was using had the boom 20 mm off the deck, the with new swivel it’s now down to 12 mm but that’s about as low as I can go otherwise any angle in the Jib boom has it hitting the deck.
Benefit you will find using the slider is that you can adjust gap between Jib Leech to back of the mast very easily & quickly that is handy additional option to fine tune helm balance.
The only reason I have been using longer 100mm slider was to test how far I could move the Jib “pivot point forward” before encountering any problems…but that’s another story.
Alan,
you are right, the bowed deck is a nightmare, far too complex and difficult, just to make me the life complicated.
OK, I tell myself that is a prototype and experimental model, but it should be a limit to my fantasy research !!!
The deck have some 8 points that need to be coaxially aligned when the deck is lowered to the hull for bonding.
Most of the points shall also be bonded inside to the supports at the same time as the sheer line that, btw, shall also be aligned with the hull sheer line.
Fortunately some one invented the adhesive tapes !!!
For sure this is the first and last experiment of this kind !
The internal supports system need to be optimized vs strength and weight, eventually with a monolithic construction !
Sorry to butt in , I would like to share some of my experience with honeycomb cores.
I have often wanted to build an entire model yacht using a Nomex core in the construction.
As always, you do not get anything for free.
Yes, it will be very rigid for the weight, but it will ultimatly be heavier than a monolithic construction, I can almost guarantee that.
The problem lies in the core. It is hydroscopic and if this is not respected, not only will you will have a boat that gains weight every time you go sailing, it will eventually delaminate.
The honeycomb degrades in the presence of moisture, eventually turning to mush.
When we use Nomex in yachts, firstly, we are super careful that the material is kept in a controlled environment until it is used in construction.
We have to ensure the skins “seal” the core and are free of porosity. To be able to do this at a model yacht level is difficult, but not impossible. But you have to do his for the inside and outside skins and with wet lamination, you maintain a resin rich matrix to assist in this, giving a weight penalty.
I have repaired and made many nomex cored parts both big and small with wet lamination, but the result is never, ever as good or as light as it would be with Pre - preg.
Whenever I use Nomex, my preferred choice is with Pre-Preg. As this gives a controlled, repeatable result for the least amount of weight & time.
Typically, a super lightweight prepreg panel would consist of:
2x 120gsm unidirectional @ +/- 45
100gsm Adhesive film
42kgm3 honeycomb core
100gsm Adhesive film
2x 120gsm unidirectional @-/+ 45
If you want the lightest panel possible that is watertight, make the two skins and cure them under vacuum first. Then apply to each side of the core with Adhesive film, vacuum bag and cure. Easy with flat panels, but not so easy with contours of a hull.
If you feel that a core is the best option:
My thoughts and advice would be to use a closed cell foam core instead.
One company is Airex, but there are many.
It comes in densities as low as 20kgm3 and does not absorb water.
It works well in wet lamination and good consistent results are possible with careful measurement.
Still though, the lightest construction is when you cure the first skin, then bond in the core, and finally cover the core with the second skin. Preferably vacuum bagged at each stage, but not essential as it depends on the shape and the skill of the constructor.
Again, sorry if I am teaching you to suck eggs, but I have thought about this a lot, and my conclusion is to stay away from Nomex…
I hope this is is of interest, Jim.
Thank a lot Jim,
I was aware of what you says. The nomex honeycomb is only meant for the flat deck and not for the hull as can be seen in the drawing above.
Unfortunately I do not possess aluminum honeycomb and autoclave as I was used to employ it for solar panels when I was working in Space business.
The problem I see, as experimented in the past, is that probably I have to laminate one side at the time. I do not have vacuum setup.
The capillarity do not work so well, therefore the honeycomb cells will have poor adhesion resin meniscus at the wall edges. Instead by turning upside down, the gravity will propagate better the resin from the tissue to the cell’s walls. All that is made on a window glass support.
I have already used for the ‘AZUR’ hull project the foam cut in ribbons of 2mm thick. This technique was already part of tread in this forum.
It may be possible that if the honeycomb do not give satisfaction I could turn to the foam in spite of resin absorption as for the balsa !
In the past, some 10 years ago I have made some experimentations, see pictures :
I hear you in the subject of meniscus… It is hard to encourage the correct bonding to the Nomex to give the maximum properties possible.
Alloy honeycomb is a definite No-no with Carbon fibre in model yachts. The risk of electrolysis is just too high.
I would be concerned using lightweight woven cloth with honeycomb core as it is almost impossible to get a pinhole free finish.
My recommendation for using the foam is that you can get a lighter construction because there is no need to have a 100% porous free skin. Your now free to use woven fabrics which are easier to apply, and you can use a lighter cloth as well.
It offers an advantage over balsa -as the foam does not absorb the resin which helps save weight. Certain brands allow thermoforming, allowing larger panels to be fitted and saving time and weight by reducing core joins (which also “print through” and can be seen)
The combination of 80gsm outside skin, closed cell foam core and a 80gsm inside skin should be adequate.
I like the use of water bags to consolidate the skin, very simple but it works! Just to have a few local voids as you did demonstrates that.
Your always going to struggle without a vac pump to get a void free result with cores.
Thanks Alan,
I would prefers to use only 2 colors, Ferrari red as you suggested as well the off white for roof and bulb.
Todays I was playing/building with small things but very important, the Eye-bolts specifically for this model and the cheap fairleads to avoid using expensive bearing blocs for the prototype.
Hi Claudio, I love the eye bolts you have made, how is the eye section made ? …solid brass rod, drilled & soldered to the thread ? and have you found it to be strong enough over time (don’t break at the join)?
Hi Alan,
for the Eye-bolts I use tread rod of 3mm and short tubes of 4mm and then tin-lead soldered. At the end I drill the ‘eye’ with 1.6mm.
During painting, the Eye-bolts will be painted also providing some protection against moistures.
The life time ? … Never made before, specific for this type of deck since nothing found on the market !! This one of the thing the a modeler shall do.
In the pictures above it can be seen also the sheeting route and guide for the Jib.
Much simpler instead the main sheeting !
Will the back stay be attached to one or two anchor point? What’s the benefits of each option? I can see that a one point anchor will need more reenforcement but less point of failure. What about the stability of the mast, or the complexity of the reenforcement?
Thanks again for keeping the pace. I really appreciate the evolution of every little detail. Very formative.
Today I wanted to check again the various single weights and compare with the design budget.
I do remember, that due to the external lamination, the measured Hull Displacement increased from 3673g (design) to 3853g, offering thus, additional 180g of volume, more then designed. This additional volume should not exist when the female mold is employed !
Nevertheless is not what I want anyhow, since my ‘goal’ is to stay as close as possible to the ‘ideal’ 4000g at the buoy.
I’m observing that the actual finished model weight will be close to 4168g against the initial design of 4113g. (post 19) and 168 over the researched ‘ideal’ weight, Appendages included.
Observing the budget variations along the construction, is clear that the deck was underestimated at design level, while the shortage of the fin and box and the obtained lower rig weight will at the end compensating each other.
The Hull weight of 488g includes all the supports.
Considering that I have exceed in the resin bonding process, the use of titanium dioxide did contributed a lot in the bonding weight, some weight reductions are possible and I do not exclude a gain of about 100g.
Further, a design revision of the internal supports will offer probably additional gains.
At the moment, I exclude any significant gain nevertheless some 15g at deck level and some 15g at hull level may be achievable.
The major aim is to find the way to reduce the overweight of 168g to reach the ideal weight of 4000g or at least staying inside 4050g.
Some grams could be recovered from the paint undercoats. I need confirmation from the next wet sanding, see actual weight from the pictures below.
My conclusion is that it is possible to stay below 4050g.
Hull wet Sanding and changing color >>> Red Ferrari !! , may be !
In the above Weight Analysis I forgot the bow, the stern cover plate and mast harness, this weight could be around 45g ! therefore the total deficit may be rather high : 69 + 45= 114g from the actual design and 213g from the ‘ideal’ weight of 4000g.
Wet sanding offered some 17g weight reduction while the RED Paint increased the weight by 14g.
The pictures below start suggesting what will be the final result !
