the option with the resin and lead shot came out very messy and very underweight.
It was supposed to be 337.5g but came out at 284.
So moving on I grabbed the old butane torch, threw in the leadshot and sat there nuking it.
Not very good either (neater) but at least I am in with a chance here.
I will need to remove material for the keel and I can drill some holes to get it on weight.
I have no clue how I got it that far out.
and it made this noise… I’ve never heard lead do this. Could it be part of the extreme weight?
But I used a rasp and it scraped like soft lead so it shouldn’t be a huge issue.
Any ideas where I went wrong?
How much extra weight do you guys give to allow drilling for the keelfin normally (I forgot about that completely)
I have tried doing a layer of resin over the top but it looks like it isn’t hardening properly.
Hopefully It all works out and I don’t have to start again.
Suffice it to say that I will remember to do it in the correct order next time.
I made the bulb plug out of 3mm balsa not 2mm so that I would have room to manouver when installing the fin.
In my head I figured “1mm is tiny” but that’s 1mm x multiple layers.
So I had quite a bit of excess lead. Perhaps adding a single sheet of 3mm would have given me enough buffer for the lead that will be removed.
Using the 3mm it will have also pushed the shape out quite dramatically from the foil shape the bulb calculater gave me… oy.
So assumption being the mother of all f__k-ups I will not say “1mm is nothing” again and tally forth.
Well things are still moving ahead but at a snails pace.
I have been working on the keel fin and rudder and have almost got the hull ready to mount on a board to make the mold.
I have also made a Claudio tool and made my first set of sails with built in Camber
I made the first set backwards …oops lol.
I am using the tiny crimps for fishing trace wire (#2) for luff rings on the jib.
I weighed them and together they came in at less than a gram so it would appear to be fine.
I think I have made too many layers of tape on the corners (3 on each side so a total of 6 per corner) and the eyelets are very big but that’s what I currently have
Im also getting ready to try another attempt at a bulb. I’m hoping to find someone with a lathe that will turn it for me and hopefully that will get me closer to the target weight
My brother helped me make these rigging blocks.
With the exchange rates and import duty/vat its extremely pricey to buy the commercially available ones.
So here are the pics of the bits and the original plan in sketchup.
I need to weigh them, and I’ll clean up the protruding carbon rod.
They seem to roll very nicely at this point
The main black bits are 4mm ABS and the white spacer is 1mm ABS.
It’s a good idea and nicely executed. If you are willing to learn from my friend’s experience, radius or chamfer, and smooth the edges where the line touches the block. My friend was using blocks of similar construction from a well known supplier. The sharp edges of the molded plastic pieces frayed the line until it broke. Do anything you can to get rid of your sharp edges and be sure that the line will/can not snag. You’ll thank me eighteen months from now.
New lesson…ABS is surprisingly hard to put a rounded edge on - especially on such a small thing:rolleyes:
Kind of got the fin and rudder ready.
Whenever I have tried to make one with a wood skin formed around CF rod I’ve managed to screw it up in one way or another so I thought I’d make a core and try mould it (not quite the plan anymore)
I didn’t take any pics unfortunately, hopefully it makes sense.
So i cut the flat shape of the fin and rudder out of an ice-cream container.
I then scuffed up the plastic and super-glued 3mm balsa on the top and trimmed it to the shape.
I then repeated the process on the bottom side, so I had the plastic sandwiched between the balsa.
I then marked where the profiles were to go as per the fin design… I grabbed the free design from Frank Russel’s Goth (http://www.frankrusselldesign.com/plans - a big shout out for all the free plans) as it had two profiles and their location supplied.
Then I sliced through the balsa/plastic sandwich at the profile points and glued the plastic profiles in vertically using the middle plastic as a guide centre-line.
It sounds dodgey but the almost finished thing looks pretty decent and it’s by far my best effort to date (at least its straight :P)
The rudder is at 8g including the carbon post and the fin is at 1/2 the allocated weight.
I would like to try the same option using CF or FG instead of the plastic for the next one.
I am also trying to figure out how to insert a carbon rod down the length of keel fin for strength - looks like I could break more than I fix though.
OK, that made very little sense so here’s sketchup…
Plastic core
Glue balsa
Mark profile spot as per plan/your idea
Splice it as precisely/Vertically as possible.
Glue in profile using the sandwich centre for alignment
Glue it back together and start sanding.
I am hoping to get back onto the bulb soon. There is a busy thread on doing bulbs that I picked up a LOT of problems i was doing so lets try it again.
Cheers
This is the plug wet. Hopefully that will be a good enough finish for the mould. At this point every time I have tried to fix a tiny blemish I mess up more so I’m just going ahead.
The crack in the bow is from my wife knocking it onto the floor… it was an awesome event of the build.
Here’s what I definately did wrong …
[ol]
[li]I didn’t sand the balsa enough. I was paranoid that I was going to go through but there is tons of wood left and I just ended up filling the gaps. Half of the following issues wouldnt have existed if I did more at thi
[/li][li]Forgot to epoxy/glass it before spray painting the hull (I did do the interior as per Claudio’s recommendation to strengthen the hull for sanding)
[/li][li]after fixing the epoxy/glass issue I used spraypaint again. It has like 0 filling properties lol
[/li][li]when wet sanding, I was doing it outside. If you hear the faintest scratching noise…STOP. Wash off the hull and sandpaper because grit seems to be attracted from the ether to your lovingly sanded hull
[/li][li]Left the hull out on occasions… see the crack in the bow, and the extra scratches my children lovingly gouged into it whilst I was at work.
[/li][/ol]
Just a thought… would seem that you could proceed with the hull as is - unless you want a female mold. If you are happy, you can add packaging tape, layup glass over it, fill and fair the glass, and then remove the hull. Any current scratches will be inside the hull layup and won’t be seen or matter. If, on the other hand, you want a mold to make additional hulls, then you do need to have a nice shiny plug as it will be the inside of the female mold - but on the outside of any hulls pulled from the mold.
Very good point Dick.
I think it’s good to go and there may be tiny flaws but I’ll keep going.
I wanted to attempt a mold so I can give it to the local boat club when I’m done.
If it’s a disaster I think I’ll do a male plug lol
Good idea to test the new hull and see if it is fast. (should be) - THEN give to club - or make the hulls yourself. If it doesn’t perform, chalk it up to “An Experiment” and dump the mold.
bwahahaaaa agreed!!!
It’s been quite a weird experience doing this hull. I’ve gone over threads/links (on here, the Lester Gilbert site etc…) and things that were complete gibberish before now make a bit more sense which is quite a cool feeling.
Granted, it’s a base understanding (and I have realized how bad I am at geometry/maths on the whole) but heck, even Claudio mentioned poking the boat with your finger to get the centre of the hull
Thats great news - tell the family you’re going for a picnic and pack the Narrow
I have been side tracked by this…
Got a Prusa 3d printer and I’m busy putting it together.
I have also figured out how to import a foil shape from the bulb calculater into Freecad, cut out a slot and size it to make a plug for lead casting.
No clue if it will be a success but It’s fun and I can fiddle to my hearts content now.
So hopefully I can actually get a proper move on shortly.
Ok,
Nothing has been done on the hull due to my 3d printer forays and learning how to do things in FreeCad.
HOWEVER things are starting to look like they can get back on track.
I can now import airfoils from the Airfoiltools website and create foils with whatever top and bottom profile I want (lots of questions incoming on this), slice them and mirror them.
If anyone is interested in how to do it using FreeCad (which is - as the name suggests- free) let me know and I can do a little tutorial or something.
That is an NACA0010 with 60mm top and 40mm bottom. Slots added for bolt at the top and carbon rods for strength. I did a test print (that went horribly wrong lol) of one half of the top section and it weighed in at 16g.
This looks like it would let me get in at Claudio’s weight budget for the fin but it needed a lot of cleaning and my printer setup is apparently rather lacking HOWEVER it would make a brilliant plug.
To be honest, the carbon skin method makes more sense to do but I have always laughed in the face of common sense.
I have also printed out mast cranes for both this nArrow3b and my Apsara. The Apsara has been undergoing radical reworking as the test boat for this build.
Hopefully I can get a move on now.
3D-printing in plastic? I would say plastic is not strong enough. For fin, it is important it does not bend/twist - remember you’ll have a 500-700gr bulb down there, forces on fin will not be trivial. For mast crane, I use just a 3mm CF rod through top of 6mm diameter mast (KISS).
ABS with those carbon rods as struts.
I am amazed at how stiff one half was using no infill.
The original plan was to print halves and use them as formers. Fill that with foam and sand to shape. Then put CF around that.
Should give a very exact shape … and yes it’s over complicating things but it’s good for a laugh
Then OCD people around the world can enjoy the folly.
I used 3mm carbon tube on the other build and the deflection I got on that rod instead of the mast was crazy. Perhaps the rod I got has more flex?
