+ Reply to Thread
Page 8 of 9 FirstFirst ... 6789 LastLast
Results 71 to 80 of 84

Thread: n-Arrow3b build

  1. #71
    Join Date
    Nov 2010
    Location
    Johannesburg
    Posts
    208

    Default Re: n-Arrow3b build

    Quote Originally Posted by tarmstro View Post
    Oh yes: move the rudder smoothly, don't ever hit it or release it hard! Move it the stick a little bit: only after the boat starts turning, you can move it another bit... wait for the boat to turn a little faster, then move the stick another bit.... then before you reach the new direction, start releasing... again slowly...

    Practice makes master.
    Thanks for always popping in and adding

    Guys, if you have the sail and bulb's COE etc. aligned correctly, will you still need some rudder to maintain a straight course? I reworked the Apsara and it's running far smoother but I always got weather helm that needed a bit of correction. this got progressivley worse in heavier gusts. Is that normal?

  2. #72
    Join Date
    Aug 2003
    Location
    Minnesota USA
    Posts
    3,800

    Default Re: n-Arrow3b build

    Just curious, but how long did it take to print the bulb plug?

    I am thinking about pulling out my wood lathe and trying a plug from wood.

    Thanks, Dick

  3. #73
    Join Date
    Nov 2010
    Location
    Johannesburg
    Posts
    208

    Default Re: n-Arrow3b build

    Hi Dick.

    My printer is new, it's cheap and I'm learning how to operate it properly so I ran it extremely slowly.
    It took about 2 1/2 hours to print in total, then I had to sand it down etc. which I'm sure was more work than a piece coming off a lathe would have been. I've never had the opportunity to use a lathe but I would assume that it's quicker by far with less finishing work needed.

  4. #74
    Join Date
    Aug 2003
    Location
    Minnesota USA
    Posts
    3,800

    Default Re: n-Arrow3b build

    Thanks for info. What did you use to calculate your bulb weight and shape?

    My grandson built his own 3d printer, but is off to college now. (Electrical engineering at North Dakota State University) but wants to build a CNC router this summer. (I get to finance the thing). so am keeping my eyes open for software or tables to provide initial input data.

    Dick

  5. #75

    Default Re: n-Arrow3b build

    Hi, Naphtalene
    yes, this is normal.
    Assume the boat is in perfect balance when sailing upright.
    Now heel the boat. CE of the sails is moving sidewards out of the midship line which will introduce a torque to windward (force is pointing forward).
    Simultaneously the CE of the keel is moving also sidewards (to windward). The drag of fin and bulb will increase this torque (force is pointing backward).
    The effect becomes worse when heeling more because forces and lever are increasing.
    In addition most hulls are getting asymmetric when heeling, causing an additional torque to windward.

    This is why in gust you let go the mainsheet a bit, but keeping the jib tight.
    Last edited by haegar; 10-28-2016 at 07:12 AM. Reason: errors corrected
    regards from Germany
    Joachim

    GER 253
    Micro Magic & RG 65
    http://p-sails.blogspot.de/

  6. #76
    Join Date
    Nov 2010
    Location
    Johannesburg
    Posts
    208

    Default Re: n-Arrow3b build

    Hi,

    Thanks for the confirmation and explanation on the helm issue

    Dick, there is a fantastic site I just found http://openbuilds.org/ they have builds and give all the info on what electronics etc. they are running.
    There are awesome builds that are mostly based around Aluminium profiles so the structural integrity/tolerences are very good. Theres a small one called "ThePlater" that is a scaled down version of a bigger version. Looks awesome.

    RE the bulb weight..... I used the bulb calculater and then transferred that into an online shape calclulater etc. I have almost finished putting together a "how I did it step by step" guide. I'll post it up soon

  7. #77
    Join Date
    Aug 2003
    Location
    Minnesota USA
    Posts
    3,800

    Default Re: n-Arrow3b build

    Thanks, forwarded the web URL to my grandson (now in college) to see if I can prompt him into building me a CNC that uses router. If we can get that working perhaps I'[ll look to laser for cutting bulk head templates and such.

    Also will look forward to your instructions for building when it is posted.

    Dick

  8. #78
    Join Date
    Nov 2010
    Location
    Johannesburg
    Posts
    208

    Default Re: n-Arrow3b build

    Ok, finally started prepping to pour a plaster mould of the bulb.
    I will update once it's completed and see if it comes out at the projected weight.

    I am also one year into building and that's a bit ridiculous. I am hoping to get going on the mould of the plug shortly too.
    Lots of talk and no pictures/progress at this point :(

  9. #79
    Join Date
    Nov 2010
    Location
    Johannesburg
    Posts
    208

    Default Re: n-Arrow3b build

    Good news!!!!!

    I got the calculations a bit out but never the less, a bulb made by me for me
    This is before I have cut the slot for the keelfin so I will be under weight, however I'm very happy with the result and can now work non refining the process.

    Click image for larger version

Name:	BulbInMould.jpg
Views:	22
Size:	112.5 KB
ID:	15929

    Click image for larger version

Name:	BulbOut ofMould.jpg
Views:	21
Size:	110.4 KB
ID:	15930

    Click image for larger version

Name:	OnScale.jpg
Views:	23
Size:	90.0 KB
ID:	15931

    Click image for larger version

Name:	PlugAndBulb.jpg
Views:	27
Size:	92.3 KB
ID:	15932

    The mould is straight plaster of paris. It worked out well as I discovered that if you don't have air holes then you can't pour in the lead lol.
    So I just grabbed an old screwdriver and carved those angular slots into the bottom half of the mould. I did three failed attempts where the bulb got halfway up and then the air block formed so I slowly added more.
    Lessons learned so far.....
    Pour hole must be on the mould split line.
    On my next attempt I'll put the pour hole lower than the the highest point of the form, and then vent from the highest point. That way the lead should be able fill all the way smoothly.

    Since this worked pretty well I'll do the write up on how I got the bulb shape/weights and pluged it into the Cad app for anyone who wants do do it themselves

  10. #80
    Join Date
    Nov 2010
    Location
    Johannesburg
    Posts
    208

    Default Re: n-Arrow3b build

    Oops, forgot to do the write up:(

    Been busy getting this done....

    Click image for larger version

Name:	IMG_0086.jpg
Views:	8
Size:	10.3 KB
ID:	16192

    I have printed a test mould to see if it is a viable technique for rudders and fins and I believe it shall be awesome. Here's the test single half from abs. I got warping which I'll address but you can see in the second pic that I got a very nice foil shape with my test fiberglass layup. It's 3x layers of that very fine surface tissue stuff as practice before I attempt the real thing

    Click image for larger version

Name:	IMG_0021.jpg
Views:	5
Size:	815.4 KB
ID:	16193

    Click image for larger version

Name:	IMG_0023.JPG
Views:	5
Size:	1.69 MB
ID:	16194

    I printed it at .1mm layer height and the finish was way better than I thought it would be. It would be a fairly simple bit of sanding to get it up to a gloss.

    It was recommended to try put a foam core in when I do a proper attempt at a layup so that is the next step. Print both halves of the mould with the revised rudder planform ( simpler shape for me to try layup) and to put a core in. Then onto the keel attempt..... pretty scared for that one lol
    Last edited by Naptalene; 04-21-2017 at 08:07 PM.

+ Reply to Thread

Similar Threads

  1. Build Log first sailboat build - footy Razor
    By jusval in forum General Discussion (Footy)
    Replies: 63
    Last Post: 03-13-2010, 07:40 PM
  2. What to build next?
    By JohnB in forum The Local Pub
    Replies: 12
    Last Post: 07-08-2004, 09:02 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts