Hi Row,
you may be right and probably I’m a lucky man, but I’m also 76 and 46 years at work . Today is not all as good as I was 50. Actually I would pay to go back some years when I was obliged to go work every morning. At the end I wonder, because getting old is not free of charge but still happy to offer my help to sailing modelers, hope will last for some time …!!!
Meanwhile yesterday I passed on all parts the epoxy primer to highlight the surface cracks and adding some sealing before applying the epoxy resin inside to reinforce the planking. Polyester filler to all places to fill up the cracks.
A lot of manual sanding is programmed !!!
I told initially to have a sliding hatch and possibly using some permanents magnets to old it in place. The separation plane would been positioned, in this case, at deck level and therefore jeopardize possible water sealing.
As second talk, I decided to let the full hatch bonded on deck but opening a top window/cover. See sketch.
At this point I have two options : 1) add an internal flat wedge all around the open window and let the cover be simply embedded possibly with a couple of magnets, 2) to adds wedges to create an embedded throat, see manual sketch. The second option will offer better water sealing also because it is above the deck line.
The cover area as well the mast step are stepped to introduce a more sturdy surface.
The other open option regard the mast step, either with an embedded “mast box” or simply a plate step.
To make a better job I decided to make a full deck mold including deck, cockpit and hatch as visible in the picture below.
Today I will spend some time sanding the hull. Still on doubt if a Hull mold is necessary. I’m still on the learning figure !!
Certainly laminating directly the hull on the male mold, the hull itself will be a couple of tens of mm wider then the deck laminated from the female mold. The flexibility may cope with the situation and probably helping the bonding due to the expansion force against the ‘narrover’ deck. The hull will be equipped with a wedge all along the joint line.
Cheers
ClaudioD
Before and after sanding !
Hull rough sanding completed from 60 grain up to 180grain.
Wood filler applied to close small wood cracks.
Epoxy filler still needed for dots repairs.
Next step new sanding at 320 grain for surface finish and then ? application of white prepaint coat and ready for packing tape coverage.
After all these years, with your numerous designs and associated build threads, you managed to surpass yourself here. I don’t even refer to your design skills or your craftsmanship, although it could be applied, but to the time you devote to document every step of this endeavour. It may well be overkill for the RC sea dogs around here. But I want to testify that it is like a candy store for the neophytes like myself. Your past threads have greatly taught us the how and why, now we can almost see it cinematically. It allows us (at least me :)) to learn new things and tricks this way. Like the way you repaired the stern. It seems so simple now that I see it!
Why going for a female mold for the deck/hatch? Is it because it would be very hard otherwise to sand properly the wall and the lower part of the deck?
direct lamination on the plug may reveal difficult because of too many sharp corners. Plenty of air pockets expected. An Hull is like an homogeneous form and offering a certain fluidity of operations, therefore much easier to laminate directly upon the plug.
because of various recessed counter corners like the cockpit floor, the sanding is more complicate. Finishing work may be carried out more easily on the female mold in particular around the cockpit floor. See picture where the cockpit is a protruding element. The red lines are the one concerned including the cockpit floor.
Cheers
ClaudioD
Is also time to think about the appendices or at least preparing the material for cutting.
Template printed.
The FIN : core composed by 4 balsa sheets of 2mm - entrance edge with carbon rod of 3mm - trailing edge with aluminum sheet of 0.4mm . Max thickness of finished product 7.5% of chord = ~ 6.5mm
The RUDDER : core composed of 3 balsa sheets of 2mm. max thickness of finished product 10% of cord = ~5mm
The carbon rod will offer a better entrance finish
The aluminum sheet will allow to have finer finish of the trailing edge like a razor blade. This avoid a carbon brittle edge. .
Hull lamination completed this morning.
3 layers of fiberglass of 105g/m²
Epoxy resin 50% of total weight
Surface evaluated to 28dm²
Expected hull weight 28 x 3 x 1.05 x 2 = 176 gr.
ClaudioD
PS : While polymerization is proceeding I used a wood sealant to impregnate the balsa sheets for fin and rudder . This product will avoid too much absorption of epoxy resin during bonding. Just hanging for dry
Polymerization completed.
Hull easily removed from plug and surprisingly the weight is 157g against the expected 176g. I need to check the “dry surface” of the hull not yet calculated to verify the gap. Picture 100 !!!
Now the hull will rest some day on the plug to let the polymerization process to complete (one week).
I will dedicate this times to the appendices including bulb of 2950g.
Is the 105 gsm cloth a twill or plain weave?
Also, it’ll be interesting to see how stiff the finished fin is with a thickness of 6.5mm. I’m guessing that once it’s shaped you’ll be using carbon uni-direction cloth to make it as stiff as possible.
Looking good - just wish I could get on with my stuff. Unfortunately I’m having more back surgery next week (5th operation in 4 years) which will put me out of action for 10 - 12 weeks. What’s really annoying is that I’ll miss the J class yachts racing off Falmouth (1/2hr down the road) towards the end of June. So I hope you’re going to be really busy over the next few months & posting plenty of information to keep me occupied!!
Regards,
Row
Edit: Just seen your last post - hull weight is incredible, being nearly 11% under, certainly doesn’t look as if there’s any dry areas so any ideas where the savings have come from?
Hi Row,
I regret to hear about your problems with your back. I do have the same troubles since 82, but I refused all the times to get surgery and therefore I’m suffering more then necessary some times not always.
Hope you will be well in the next weeks. During the lifetime, the Health is the most important thing !!
Pity again for the J Class Racing !! I suppose is not the only races of the year !
About tissue is a plain one just because I did not got anymore of the twill type. For this particular slender hull, the plain tissue did not presented any problems.
The weight, I still need to calculate the real total surface.
To avoid troubles in the future, aiming to make a female mold, I removed the packing tape now. In the past I experienced difficulties because too sticky since was staying for long time.
Get all the best a lot of wishes for early recovery.
The tissue used was glass tissue of 85g/m² and not 105g/m² as retained.
The verified surface is 28.64dm² : dry 1306cm² + wet 1558cm²
28.64 x 3 x 0.85g/dm² x 2 = 146g against 157g measured, therefore 11g more then theoretical expected, that’s means that there is a small increase of resin weight.
All in all is very good.
Remain the fact that probably the total strength may be lower the expected unless and additional external layer is added.
Probably will be sufficient to use for the internal reinforcements an heavier tissue of 160g/m².