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  #76  
Old 10-02-2012, 06:50 AM
groper groper is offline
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Made the stringer that will be bonded underneath the bridgedeck down the middle, and directly over the tape join between the 2 bridgedeck halves. Its a piece of 100mm PVC pipe cut in half and used as a forma, layed it up with a few layer of 1000gsm uni and 600gsm d/bias tapes.



Once the stringer is faired, ill do the tape join down the center underside of the bridgedeck, then bond this stringer on top to hide the join, and finally add a small epoxy fillet down each side to seal the gaps and feather it out, all wet on wet.

Im at the point where i need to start thinking about interior furniture and fitout as all this stuff can start to happen now - before the decks and topsides go on. Im going to explore different material choices for the furniture in an effort to reduce labour - all the fillets, fairing and painting are very time consuming and also quite expensive using epoxy. Ive seen some new plastic high gloss products that cabinet makers are using these days and once the pieces are cut and glued, thats it - no more finishing or painting etc. Might be a slight weight penalty, but if used in small quantities, the difference surely has to be minimal considering theres no more fillets? Does anyone have any innovative ideas on easy fitout methods/materials that look good, reasonable cost and not too heavy, no finishing work like paint etc and low/zero maintenance?
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  #77  
Old 10-02-2012, 07:50 AM
jorgepease jorgepease is offline
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If you wanted to get really innovative you could try inflatable Super light, super tough, very little maintenance, and pretty easy to build for somebody like you. You would have to use some solid frame materials in areas ... just like rigid inflatable boats
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  #78  
Old 10-02-2012, 08:14 PM
groper groper is offline
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Ok complete failure... at the time i didnt even consider what i was doing, building a stringer of a half circle section - WHICH HAS A REALLY POOR SECTION MODULUS!!! So now my pretty little stiffener, has very little stiffness! feel like an idiot...

So im going to scrap this stringer and build another from a rectangular section PVC down pipe... live and learn eh?
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  #79  
Old 10-03-2012, 03:51 AM
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waikikin waikikin is offline
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Quote:
Originally Posted by groper View Post
Ok complete failure... at the time i didnt even consider what i was doing, building a stringer of a half circle section - WHICH HAS A REALLY POOR SECTION MODULUS!!! So now my pretty little stiffener, has very little stiffness! feel like an idiot...

So im going to scrap this stringer and build another from a rectangular section PVC down pipe... live and learn eh?
Groper, it's also only 50mm deep........... although "half pipe" stringers aint so bad when attached to the skin as they approximate a trapezoidal stringer at at low cost of effort(kinda quick & dirty- some times thats whats needed).
With that in mind a simple "trough" mold of of trapezoidal form made from melamine & plasticine & car bog that's deeper & has bonding flanges might suit & be molded smooth for less fairing with DB & plenty of uni sandwiched in the "cap".
Just some thoughts for you & regards from Jeff.
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  #80  
Old 10-03-2012, 05:20 AM
groper groper is offline
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Jeff,

indeed 50mm was not enough, i cant beleive i didnt even think about what i was doing at the time! But i did have some glass across the bottom of the semi circle, so it was an approximate trapezoidal section, but the theory says a half round section modulus is;


And so the section modulus of a solid half round (for simplicity comparison) similar dimensions i made was approx 0.1098*50^4 = 686,250

compare this to a solid rectangle section of the same overall dimensions and i get;

same 100mm width and same 50mm depth = 1,041,666 so almost double the stiffness just by changing the shape of it.

Ive since decided against the rectangular PVC pipe job, and yes your idea of the melamine mold would be much better, however ive since had another idea. Im going to infuse a 2 piece foam core flat panel on the table and bend it over into a V shape to form a triangular section stringer of 200mm depth with a smooth exterior. This will be MUCH stiffer and basically form more of a beam rather than just a stringer - which is what i think i need to really make the bridgedeck floor rock solid in the middle.

So I calculated the above section as a 2200mm long, simply supported triangle beam (worst case distance between main bulkheads and closest furniture in the cabin) and applied a 200kg load in the center of the floor and assumed no contribution from the floor panel like it wasnt there at all. Using the triangular section of this depth and 3mm skins i got the deflection down to;
d= (p*l^3)/48*e*i and figuring a value of 40Gpa elasticity modulus for stitched e-glass/epoxy, and the i = 1880066.667
mm^4 from the sectional area of the triangle with 3mm wall thickness.
= 5.9mm total deflection = much happier now

At 6m total length to stiffen the whole back deck and inside cabin area, whole thing should weigh about 15kgs - still happy
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  #81  
Old 10-04-2012, 03:58 AM
groper groper is offline
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So heres what the infusion of the soon-to-be triangle beam looks like;


It was very quick and easy to setup this one, only about 3hours to set everything up, vacuum on, and resin flowing...

Will fold it up tomorrow and see how it looks, i think im going to origami the ends of it to close the open ends by making a couple cuts - it should come together like a corner of a diamond, then held together via taping the inside...
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  #82  
Old 10-06-2012, 07:55 AM
groper groper is offline
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Saturday night infusion... i obviously have no life outside of boat building at the moment Just a big panel to cut up into various bits ill need soon...

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  #83  
Old 10-07-2012, 08:11 AM
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LP LP is offline
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Saturday night infusion... i obviously have no life outside of boat building at the moment
Partying and cavorting about are overated.

Very impressive work.
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  #84  
Old 10-08-2012, 04:13 AM
groper groper is offline
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Heres a bit more progress, sorry the pics are dark but there isnt much light under my boat building "dome"...

First the triangle beam we folded up;


Then the back deck area;


Looking forward from inside the saloon;


The saloon area;




Total boat weight this far = 700kgs...
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  #85  
Old 10-08-2012, 04:54 AM
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waikikin waikikin is offline
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Heres a bit more progress, sorry the pics are dark but there isnt much light under my boat building "dome"...

First the triangle beam we folded up;

Total boat weight this far = 700kgs...
Groper, thats a pretty tight radius on your triangle beam, what GSM is in the folded section? Jeff.
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  #86  
Old 10-08-2012, 06:02 AM
jorgepease jorgepease is offline
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Looking great!
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  #87  
Old 10-08-2012, 06:04 AM
groper groper is offline
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Ah ha, wanna know the tricks ay? No problem... it had a 2300GSM triax laminate (2 layers 1150gsm) when i made the fold. The radius is about 18mm and yes it was very stiff to fold. So, what i did was make a little dam at each end and pour boiling water into the channel left between the foam cores in the bending area. Put a peice of PVC conduit in there as a mandrel and once the laminate heated up beyond the HDT of the resin (which is quite low for 24hr old epoxy) then it was very easy to bend, held in place with straps and let the water out to cool

Afterwards, i added some unidirectional tape and a bit more triax in the channel on the inside to beef it up some more. I can stand on this thing supported at a 6m spacing and it only flexs a tiny bit. Great floor stiffener for sure... its awaiting paint and then ill throw it into the boat...
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  #88  
Old 10-08-2012, 08:00 AM
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waikikin waikikin is offline
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Originally Posted by groper View Post
Ah ha, wanna know the tricks ay? No problem... it had a 2300GSM triax laminate (2 layers 1150gsm) when i made the fold. The radius is about 18mm and yes it was very stiff to fold. So, what i did was make a little dam at each end and pour boiling water into the channel left between the foam cores in the bending area. Put a peice of PVC conduit in there as a mandrel and once the laminate heated up beyond the HDT of the resin (which is quite low for 24hr old epoxy) then it was very easy to bend, held in place with straps and let the water out to cool

Afterwards, i added some unidirectional tape and a bit more triax in the channel on the inside to beef it up some more. I can stand on this thing supported at a 6m spacing and it only flexs a tiny bit. Great floor stiffener for sure... its awaiting paint and then ill throw it into the boat...
Thanks groper, i love to hear tricks, that triax should work pretty good in that beam(0/45/45?). I used some(plenty) 1150 triax in a Crowther cat years back............. it was like wetting out carpet or seemed so at the time. Very impressive that radius achieved........... I'm just not that brave... & stuck in the 80s, here's something I popped off its mold tonight. All the best from Jeff.
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efficient 10m displacement powercat (build thread)-steps-096.jpg  efficient 10m displacement powercat (build thread)-steps-118.jpg  efficient 10m displacement powercat (build thread)-steps-119.jpg  

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  #89  
Old 10-08-2012, 07:30 PM
groper groper is offline
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Nice work Jeff! i need to make a similar set of transom steps myself soon... are you using vinylester or? - i just ordered some VE to do the fuel tanks...

Do you make molds for most things because its less work in the long run or are you building more than 1 boat?

Yes that 1150triax is definitely not very user friendly for wetting out, but with infusion that problem is gone. Yes the fibres were 0/45/45 - i figured this worked with the load paths quite nicely in a triangle arrangement.
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  #90  
Old 10-09-2012, 05:16 AM
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waikikin waikikin is offline
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Nice work Jeff! i need to make a similar set of transom steps myself soon... are you using vinylester or? - i just ordered some VE to do the fuel tanks...

Do you make molds for most things because its less work in the long run or are you building more than 1 boat?

Yes that 1150triax is definitely not very user friendly for wetting out, but with infusion that problem is gone. Yes the fibres were 0/45/45 - i figured this worked with the load paths quite nicely in a triangle arrangement.
Hi Groper, the steps are in iso poly, hulls are to be in iso poly & vinylester. I do it with molds because I like to & also like gelcoat & happy to take the weight hit, my boat is designed for that, sometimes it's more work, sometimes less, molds for "simple" stuff are quick & easy-melamine sheet/plasticine/car bog/wax/pva/carefully applied brown packing tape(styrene resistant)etc-what ever works, just shoot it together with a T nail fix out gun & smooth things up. The mold pic is of a transom mold with a craftwood "box" fixed to it & finished in black 2K- its a throw away, I hope to get another set of steps from it after a couple of small "touch ups" but will mold the same "tool" from the first set of steps for later attachment to the transom mold....... as I intend to make some more... one day/year/decade. I have tooling for the 12.4 meter hulls/hull decks, underwing/connective bulkheads/cabin etc will mold off melamine sheet, I got most all the small panels/soles/shelves & small bulkheads molded & usually mold in some detail like door jambs or return flanges if required, the hulls will come later........... I'm sneaking up on them in financial & time constraints, my workshop is 45mins one way from home & work 45mis in opposite direction! Thats why I do some little stuff in the garage.

All the best from Jeff.
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efficient 10m displacement powercat (build thread)-unan-003.jpg  
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