Since some months I was thinking about a New Model to be competitive in terms of speed against the ones sitting in the range of 39 and 50 Inches of length.
In my opinion, this development may be satisfied since many technologies has changed in the recent years and Rules did not changed very much to stay with the modern times !
I do recall the progress in the Digital Servos, Batteries, Keel construction techniques, and more recently the 3D Printing.
How long we shall ignore them ?
Old models developed in the 1930 and in 1988 are now out of date from technological point of view in spite of their excellent spread at International level.
My new model is called ESTEREL-45 and long 114.5 cm.
I have prepared a short PDF file describing the reasons behind this Design approach.
Often the time bring better solutions to an existing design project.
During my forced “rest time” I reviewed the Esterel 45 project.
Based upon the fact that, all the rest being equal, the lightest boat should be the faster.
The technology evolved and what was initially considered 4300g a good displacement, with more careful construction considerations, I found out that this limit can be lowered toward 3800g.
Of course not all parts are yet constructed, but I can anticipate that the major contributors to a potential weight reduction are the Servos and Fin and to a certain extent also to the Rig and as well the Hull and Deck material choice.
The recent class M “1290” construction proved that the Multi Chine shape generated a very strong hull.
There, I did used 3 coats of fiberglass of 80g/m². Today I would use only 2 layers.
In 2001 my “Studio 2”, a class M, was made with Carbon and Kevlar layers and weighted only 147g ! Probably it would not supported a lateral shock !
Considering that the Esterel 45" make use of only one Chine, but it is a smaller Hull than a M, I could make use of a stronger tissue than glass by using 93g/m² Carbon tissue combined with 68g/m² Kevlar or Carbon/ Kevlar.
The truth will be pop up once the model will be made. Noting that the shorter LWL will allow some margin of error before reaching the LOA.
Here below the actual Budget
Here below my last design trial aiming to total weight reduction. From 4300g down to 3800g/3850g and Sail Area of 73dm²
Not an easy model make to reach the design weight unless Carbon Tissue is used.
Many internal supports are based upon Carbon square tubes available with 4x4, 6x6, 8x8 mm
Some Options are supposed to increase weights.
Preferred solution Flat Deck with booms as close as possible to deck
Under consideration a 3 servos configuration: Main, Jib and Jib Trimmer/Backstay
This model being independent from known Class Rules, can be optionally equipped with 3 servos. Here a typical circuit example of a Jib Trimmer. Similar circuit could deal with the Backstay. 2-3kgcm servo is retained. Weight about 15g. The optional Jib trimmer servo is installed under the Deck. Additional servo functions may jeopardize the overall Displacement of 3800-3850g
A complete Servos and Supports setting is drawn. Modifications not excluded during construction to reduce weight overall. The hatch cover is still under design. Most supports are carbon square tubes 6x6 mm and 8x8 mm. For balance reasons the Jib trimmer servo is shifted right to let more space for Battery and Receiver. The Rudder Servo is external mounted on Deck.
Revised Flection strength W calculation of Carbon Tubes and Fin profile design. Using 4x4mm square carbon tubes + carbon sheet lamination it is possible to obtain a 6.5% profile. Leading edge with carbon sheet shaped and trailing edge with aluminum sheet for sharp shaping like a knife for better efficiency. Not sure about the number of square tubes, 2 or 3, most depend from each single strength. Ordered but not received yet. Use of 6x6mm square tube, while offering similar strength, is abandoned since Fin profile over 8% Rectangular Fin form 460mm (540) x 80mm constant profile.
Square carbon tubes 4x4x3x1000mm received. 10g each Details for the Fin trailing edge using aluminum sheet. List of materials for Fin assembly - 107g with only 2 square tubes before bonding. +10g for 3 square tube.
Measurement of carbon square tube indicate that the inner dimension is 3.1mm and not as assumed 2.6mm.
This imply a loss of bending strength. 3 square tubes may be used !
Yes, only the Fin is still under evaluation. Spacers of 0.25mm added.
Fin construction start tomorrow.
According to my calculations with the existing formulas, the 54cm long Fin should be more stiff than a carbon tube of 8x6mm 54cm !
Actually, before epoxy bonding, see materials updating is for 94g. Only 2 tubes used instead of 3.
some pictures of the work progress.
Some resin voids found on the opposite side as expected.
The voids should be filled up with the glass spacers bonding.
About the Fin Design:
The starting point was to obtain a Fin weighting less than 120g in order to satisfy the Esterel 45 construction Budget.
I was told about Helicopter Blades, but found too heavy for the size needed. May be someone have better experience on the subject.
The Fin was also supposed to have a Chord thickness below 7%, better if 6.5%
I discovered on the market the availability of carbon square tubes that are in principle mechanically stiffer than carbon round tubes.
The Fin is 80mm wide therefore : 80 x 6.5% = 5.2mm.
Thus the Fin thickness should be close to 5.2mm.
The Fin is actually composed of carbon square tubes 4x4mm plus glass spacers plus Fin carbon sheet lamination, for a total of 5.5mm of thickness.
5.5/80 = 6.8% that is lower than 7% but above 6.5% as indicated above.
The figure below show the ‘step by step’ design evolution.
Threaded brass rods are inserted between the two tubes. The rods will adds some local strength only.
The material necessary was weighting 94g before bonding and shaping adjustments.
Carbon sheets 540x80x0.5 mm weight 55g.
In spite of theoretical calculations I have no idea of what will happen !
Off course one may think about the use of 3 carbon square tubes to get more stiffer construction similar to a carbon tube of 10x8mm. It will adds about 13g only !
This is theory since the material used are not a monolithic assembly, but rather a multiple material assembly including epoxy resin, therefore some lower strength is expected.
The Bulb weight is 3000g
Square tubes, also available, are 6x6mm, too big for the purpose, 5x5mm not seen
I recall that a Carbon round tube 8x6mm has a W=34.33
About the Fin Design:
The starting point was to obtain a Fin weighting less than 120g in order to satisfy the Esterel 45 construction Budget.
I was told about Helicopter Blades, but found too heavy for the size needed. May be someone have better experience on the subject.
The Fin was also supposed to have a Chord thickness below 7%, better if 6.5%
I discovered on the market the availability of carbon square tubes that are in principle mechanically stiffer than carbon round tubes.
The Fin is 80mm wide therefore : 80 x 6.5% = 5.2mm.
Thus the Fin thickness should be close to 5.2mm.
The Fin is actually composed of carbon square tubes 4x4mm plus glass spacers plus Fin carbon sheet laminations, for a total of 5.5mm of thickness.
5.5/80 = 6.8% that is lower than 7% but above 6.5% as indicated above.
The figure below show the ‘step by step’ design evolution.
Threaded brass rods are inserted between the two tubes. The rods will adds some local strength only.
The material necessary was weighting 94g before bonding and shaping adjustments.
Carbon sheets 540x80x0.5 mm weight 55g.
In spite of theoretical calculations I have no idea of what will happen !
The Bulb weight is 3000g
Square tubes, also available, are 6x6mm, too big for the purpose, 5x5mm not seen
I recall that a Carbon round tube 8x6mm has a W=34.33
Assuming that this Fin Design will not support 3kg bulb within an acceptable flexion limit, there is the option consisting of the introduction of 2 additional carbon square tubes or even round at small weight increase still within the expected 120g. This morning after night thinking I decided to assembly the Fin with 4 square tubes according to this drawing.
The brass rod is positioned at 35% from leading edge.