While being waiting for the polymerization, I just told about dual winch set up, one for the main and one for the jib.
The Sail Area will split and be more compatible with the servo power.
I’m thinking about Eurgle/Vigor type servos, 2 for for similar weight of 1 Hitec.
I let the observers to found about the advantages offered to trim the Jib independently.
ClaudioD
Another surprise !!!
The hull is sticky !!!
My old friend was telling me once, don’t mix or add products if you like to avoid problems with composites !!!
My opinion is that the primer was not sufficiently dry before the application of the epoxy resin. The primer manufacturer suggest 72 hours for dry process to be completed. My lamination started 55 hours after the application and wet sanding.
The pictures show that the primers was not dry and enter in conflict with the epoxy resin.
At the time I discovered the problem this morning, I got two options in front :
A - to wet sand the glass lamination and start a new lamination on top , or
B - to remove, by any means, the “sticky” laminated skin
My solution was option B because the lamination over the existing one would have increased the displacement by another 120g about due to the skin thickness and this is not what I was searching for since the external lamination on the plug bring already some 120g on displacement. 120 + 120 was too much !!
Now I’m going back to wet sanding up to the removal of the primer until the first glass lamination is reached !.
The hull parts pulled away, sufficiently easy, and put on the balance show 156g weight as was expected !!!
Here the pictures :
ClaudioD
A lot of elbow oil !!!
Almost 4 hour later, the hull is back to wooden appearance still with a tiny film of glass !
The hull is drying to remove residual humidity.
Next step wax again !
ClaudioD
it is remarkable the stuff you do:) best wishes and keep up the good work 
regards,
lukasz k
wow even my mirror doesn’t shine as much as your hull 
Can’t believe you got another setback - fairplay for sticking to it (just realised my choice of word here, no joke intended !)
Just brilliant to watch your work and progress.
Atb,
G
for lukasz,
nothing more then normal modeler work that like to get the work done as he desire. Often errors are made and from them I learned most of what I know !
for Gilbert
ça arrive parfois, sometimes it happen. If it is brilliant is merit of water spray, but it is also true that give a better look !!
ClaudioD
5 coats of Wax in 5 hours !
Master ready for New Hull lamination with 3 x 80g/m²
ClaudioD
PS : Hull laminated
New hull de-molded this morning after 15 hours of polymerization. I used my glass blades to help removal that occurred 3 minutes later.
Expected weight : 3 x 0.8g/dm² (80g/m²) x 2 because of epoxy resin x 32.0dm² hull surface = 154g
Actual measured weight : 152g
Now the hull is resting on the plug to complete the polymerization for 3 or 4 days, meanwhile I will prepare the counter shadows for hull retention during assembly and taking care about the Roof molding.
ClaudioD
the working plan is ready and counter shadows positioned.
ClaudioD
Hi Claudio, I like your glass blades idea
Hi Alan,
generally are the cutouts coming from the deck lamination after shaping the deck.
Soft hammering (in-out) will allow to separate the hull laminate without exerting (destructive) pull forces .
Cheers
ClaudioD
this morning …
ClaudioD
glass patches for reinforcement added and bonded . This operation is weighting 66g
Weight progression :
Bare hull 152g (3 x 80g/m²)
added Bow, Stern, Sheer lines stripes (samba) + 24g
Hull weight 176g
glass patches 165g/m² as per drawing 66g (33g tissue / 33g epoxy resin)
Hull weight 242g
All above operations weighted 90g, corresponding to 21.3dm² of 165g/m² glass tissue, resin included !
ClaudioD
…
Dear Claudio,
I had to explain the physics under an “H beam” to a friend the other day. I illustrated it with a trick learned in school, where you put a stripe of wrapping paper tape over and under a large rubber band. The rubber band gets rigid as the plastic tape on top of the curve cannot stretch to follow the desirable curve). I am sure you know the core sandwich physics well enough.
That leads me to cogitate about the hull construction. The idea was, would it be lighter and stronger to use a glass-balsa-glass sandwich? I will give you that it’s not logical for a mass production. But for the rest of us…
According to your 123 data, you have roughly 0,32m2 of hull surface. Three layers of 80g/m2 plus the same amount of resin leads to 154g. With an average of 140 kg/m3, a 1,5mm balsa core sandwiched between two layers of 40g/m2 glass will only total 119g. And maybe even a 1mm balsa would be enough.
Of course, this lighter weight doesn’t take into account the glue, the wood filling and the absorption of resin by the balsa. Then again, maybe there is lesser need for glass patches?
My question is, does your experience tell you that there is no gain in the end with a balsa core? Or maybe there is some other disadvantages that make you not consider this option?
Thanks again for your time and patience!
Hi Sylvain,
You have partially answered your question !
Some years ago I built a class M in that manner. At that time I didn’t got too many weight restrictions.
The balsa was cut in small patches of about 7 x 5 cm. The mosaic was kept in place during bonding with water pockets. The work was carried on along some days until all the patches were glued .
The hull was, at the end, like a rugby balloon.
Nice academic trial !!!
The question is : Why ?
In terms of strength, our models do not requires the strength of stain steel and much less of the titanium, therefore they are solid enough with fews glass layers. My lamination average vary from 4.5g/dm² to 6g/dm² as function of the hull length.
Once the body is closed, hull and deck, the assembly is sufficiently sturdy and adequate to sail also trough rough waters.
Until now I never heard of a hull breaking apart during sailing.
UV rays are more deleterious to composite material.
More recently I used foam ribbons to similarly to balsa patches for the construction of the Azur, another class M. http://www.rcsailing.net/forum1/showthread.php?6312-AZUR-a-New-Class-M-Marblehead/page4
The pictures below pertain to one of the Studio2 of 2004 made with 1mm balsa sandwich. the inner layer was 60g/m² Kevlar.
Hope to have answered to your observations.
Cheers
ClaudioD
My conclusion :
-
- Yes, it is possible to make a sandwich either with balsa or foam although not mechanically necessary in term of strength.
-
- The exercise will produce an heavier hull construction. 119g will be heavier then 2 additional layers of 80g/m².
Little progress but important … Fin Box for 20g !
Deck foil trimming , Fin restored to initial shape
and preparation for Roof lamination
ClaudioD
Dear Claudio,
I understand what you said… until conclusion #2.
A 1,5mm of balsa core spreading over 0,32m2 weights 67g. Sandwiched between two layers of 40g/m2 glass + resin (51,2g), it offers a grand total of 119g. That’s 3,7g/dm2, lower than your 4,8g/dm2 on the 123 hull. I had no instinct about the strength of this composition. If you say that it is way more than neccessary, then maybe we could spare the reenforcement you had to add, or even go with a 1mm core for a grand total of 96g (3,0 g/dm2!!!). But then again, this is not taking into account the resin absorption by the balsa and the initial glue for which I have no clue.
I am sure in the end that this approach is not the way to go since no racer use it. I was just curious to know why, since the weight factor seems, at least here on paper, to be a great weight saver.
By the way your patchwork technique was very cleaver!
I think the main issue with balsa core at such a relatively small scale is the resin absorbtion. With ‘full size’ yachts the benefits become more apparent owing to the larger thicknesses of balsa used and hence the relatively lower resin absorbtion. Thus with our small models the weight gains just aren’t there to be had and as Claudio also alluded to the additional strength gains aren’t required.Hope that makes sense…
Regards,
Row
Bonjour Sylvain,
40g/m² is too fragile, easy to be punched and against racing shock is definitively too weak with probables water leak risk.
Better to go to twice the 40g/m² or a single layer of 80g/m² each side.
Inside can be used the Kevlar of 60g/m². BTW, Kevlar shall never be used outside, impossible to sand if needed !
Balsa weight is very variable , but assuming 2g/dm² you get :
glass : 0.8 x 2 layers x 2 resin x 32 = 102.40g
balsa : 2 x 32 = 64g
Total Hull 166.40g , not bad when taking into account that no reinforcement are needed !!
This is what you may expect.
My hull came out with 152g and I added 2 x 33g for glass reinforcements = 216g - Under such evidence, the gain is of 50g and the balsa sandwich could be a good solution.
Today 50g would be very welcomed ! My last budget revision suggest 4036g against the 4050g as a goal ! some parts may still be forgotten like the pulleys !
We should try next time, but of course I need a female mold !
Patch work need some days to be completed since only few patches can be bonded at the same time. The mold shall also tilted to allow water pocket pressure by gravity to old in place the patches.
Was worth discussing the matter !
Ciao
ClaudioD
Hi Row,
balsa can be treated with special light varnish to close the porosity, but of course the weight will increase. Out of the 50g gain as said above, probably half will be going for the treatment.
My recent sandwich experience with 2mm foam was not good, the deck came out for 142g !
There are possible compensations by using soft balsa. I have some samples of 1mm, they go from 1.2g/dm² up to 2.35g/dm².
If I go back with my test samples, the best solution was 2 layers of carbon tissue of 93g/m² for 4.10g/dm².
My hull would weight 4.10 x 32 = 131.20g instead of 152g; better then nothing but expensive, 52 €!
Cheers
ClaudioD