Quarantine build thread

Mr J

Michael Peterson status
Aug 18, 2003
2,250
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Regional Vic, Australia
Just a comment to provoke design discussion and your thoughts on your rocker numbers which I am sure you pondered deeply - I would have thought your reasoning is perfect for twinzer, but less so for a thruster which likes a bit of extra tail rocker. Is it because you see it producing an easier transition in a quiver that still contains twinzers? Will it be flat bottommed - a point made by Simon Anderson and I think GG is the concaved boards do generally have more rocker.

One thought I have is that your shape as is might be suited to a thruster set up with smaller rear fin e.g. AM or even the Rob Machado "Robber" twin plus trailer template - quite a deep albeit skinny trailer. I actually have the Robber template and it did work well in a thruster that I had built a little stiff due to the way I placed the fins.
 

One-Off

Tom Curren status
Jul 28, 2005
14,128
10,250
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33.8N - 118.4W
Just a comment to provoke design discussion and your thoughts on your rocker numbers which I am sure you pondered deeply - I would have thought your reasoning is perfect for twinzer, but less so for a thruster which likes a bit of extra tail rocker. Is it because you see it producing an easier transition in a quiver that still contains twinzers? Will it be flat bottommed - a point made by Simon Anderson and I think GG is the concaved boards do generally have more rocker.

One thought I have is that your shape as is might be suited to a thruster set up with smaller rear fin e.g. AM or even the Rob Machado "Robber" twin plus trailer template - quite a deep albeit skinny trailer. I actually have the Robber template and it did work well in a thruster that I had built a little stiff due to the way I placed the fins.
I've got a set of thruster fins. But I also have a board that was intended as a 2+1, but with the regular sized center fin (I think Ised a 6" bonzer fin) the board was too stiff, so I put in a thruster fin and it worked great. So actually one option I'm thinking about is a regular thruster center fin with small side bites.

Going with single to double bottom.

PS- with the handles on the doors I do pull downs (mimics the end of a paddling stroke) and then, with them over head, it mimics the beginning of a paddle stroke. I do sets of 30-40. Go for the burn.
 
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Tom Curren status
Jul 28, 2005
14,128
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I don't know how the pros do it but here's my sequence.

I mark for 1/8" vee on the side of the blank, then cut with flat sanding block. For some reason everything came out 1/8" on this board- 1/8" vee, 1/8" single. 1/8" doubles.
IMG_3730.JPG

Then I cut the single, starting after the nose flip, ending where the fins start. I forgot to take pics of the process. I carve out a channel in the middle, measure full depth, and then fair it out with surform and flat sanding block. A lot of 45/45 degree passes- at this point I think a lot about the direction of the water flow and try to sand in those directions.
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Then I cut the doubles the same way with the addition of another tool- the pipe section. I think you can see the 45 degree strokes

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Today I will start by fairing the bottom- making sure there are no bumps. There seems to be a bump where the doubles start and where they end (they look cupped at tail). Also, looking at the photos I see that my concaves (especially the single) end before the rail edge. I'm going to bring them out to about 1/2 from edge (where the rail tuck would be).
 
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One-Off

Tom Curren status
Jul 28, 2005
14,128
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33.8N - 118.4W
Just a comment to provoke design discussion and your thoughts on your rocker numbers which I am sure you pondered deeply - I would have thought your reasoning is perfect for twinzer, but less so for a thruster which likes a bit of extra tail rocker. Is it because you see it producing an easier transition in a quiver that still contains twinzers? Will it be flat bottommed - a point made by Simon Anderson and I think GG is the concaved boards do generally have more rocker.

One thought I have is that your shape as is might be suited to a thruster set up with smaller rear fin e.g. AM or even the Rob Machado "Robber" twin plus trailer template - quite a deep albeit skinny trailer. I actually have the Robber template and it did work well in a thruster that I had built a little stiff due to the way I placed the fins.
With regard to the rocker, even though it is less than a HPSB it still looks adequate to my eye, not too flat. The concave flattens it a bit to make it a wee bit more fishy. This was before I put in concave. Also in the doubles the rocker is accelerated by an 1/8". I might flatten the concave and flip the tail the last 3-4 inches to get rid of that "cupping" I was seeing at the tail end of the doubles.
IMG_3725.JPG
 
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One-Off

Tom Curren status
Jul 28, 2005
14,128
10,250
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33.8N - 118.4W
I went ahead and added a bit of rocker to the nose in the first 8". Probably not part of the planing surface anyways. So 4-1/2" now.
Then I kicked the last 4-5" of the tail, about where the rear fin is. So that is now 2". Tending more towards thruster numbers and away from fishy ones.

At this point I would break out the power planer and cut to thickness and do the first couple rail bands, but I checked the thickness and after all the work on the bottom the blank is already down to 2-5/8". I'm sure just doing the rails and clean up work will get me to 2-1/2".

Also, it sounds like all the neighbors are out in their yards, so I don't want to fire up the screaming machine. I'll wait until to tomorrow and then maybe just surform..
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Northern_Shores

Miki Dora status
Mar 30, 2009
4,487
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What density is your blank? I've tried with super light building insulation, but the beads just come off wherever and there is no substance to the material :/
 
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Tom Curren status
Jul 28, 2005
14,128
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What density is your blank? I've tried with super light building insulation, but the beads just come off wherever and there is no substance to the material :/
I found two blanks in my driveway years ago. I suspect afoaf. I'm guessing they are 1.5 or 1.7lb eps. It's fused pretty tight. Not worth using building insulation to save a few bucks IMHO.
 
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Tom Curren status
Jul 28, 2005
14,128
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A couple of days ago I went to foil the board. This a process where normally I use the power planer because it involves removing a lot of foam. But everyone is on coronacation, all my neighbors seemed to be out in their yards. I mowed for a few minutes and decided I was too loud. I didn't need to take off that much so I did most with the surform.IMG_3765.JPG



Foiled-
IMG_3766.JPG
 

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Tom Curren status
Jul 28, 2005
14,128
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33.8N - 118.4W
Rail banding. I do the bottom tuck first. I really should get a Fred tool.

The rough cuts of the top bands I would normally do with the power planer, but again, it seems like my neighbors are hanging out in their side yard which is a few feet away from the back wall of my shaping shed. So I plowed with the surform.

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Tom Curren status
Jul 28, 2005
14,128
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33.8N - 118.4W
Now's where my build veers completely away from the industry standard. Only a very few board builders do this commercially. I'm amateur, but have been doing one or two a year for about 15 years now.

Stringerless blank will have balsa rails. Don't call them parabolic because they're not.

I carefully measure my offsets for when I have to re-shape the rails. Then I carefully scribe 1/8" in from the hard edge. I'm going to do a hard edge the whole length (tip of my hat to GG. I got it from him. It works. Release, release, release). Then I cut off the rail.

To anyone who thinks 3/4" balsa rails sound stiff, look at the offcuts. Add the saw kerf and that's how much stringer there will be. I taper them at the nose and tail. Not much timber there.

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ghostshaper

Phil Edwards status
Jan 22, 2005
6,244
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OG compsand!

And that's lift, plane, release. Edit: or is that just for fins?

Looking forward to more updates.
 

PRCD

Tom Curren status
Feb 25, 2020
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Not to hijack the tread, but does anyone think we can turn this into a car-topper? I'm thinking stitch-and-glue hull and foilboard foils on either side with 5052 tubing amas (see this):

Edit: Like this, but a scaled version of the AC75 with foil board foils.
 
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One-Off

Tom Curren status
Jul 28, 2005
14,128
10,250
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33.8N - 118.4W
Not to hijack the tread, but does anyone think we can turn this into a car-topper? I'm thinking stitch-and-glue hull and foilboard foils on either side with 5052 tubing amas (see this):

Edit: Like this, but a scaled version of the AC75 with foil board foils.
I assume you put that here because I put it somewhere it didn't belong...no problem.

There's no way you're going to make a small version of the AC with two articulating foil arms. Maybe you could just slap a couple foil board foils onto the bottom of another build and see what happens?
 

PRCD

Tom Curren status
Feb 25, 2020
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I assume you put that here because I put it somewhere it didn't belong...no problem.

There's no way you're going to make a small version of the AC with two articulating foil arms. Maybe you could just slap a couple foil board foils onto the bottom of another build and see what happens?
I put it here because we're locked in, I have some left-over glass and epoxy and was thinking about building another boat and you seem to know something about sailing. I don't know anything about boat design. The AC75 class is intended to trickle down to production boats:

Choosing a rotating wingmast and soft sails rather than a wingsail that needs to be craned on board each time the yacht races is pointed to as having more ‘trickledown’ potential for other areas of sailing. But the decision has also been taken because once these boats are foiling, the restrictions on speed come from either foil cavitation or aero drag, and designers believe that it will be easier to manipulate a soft wingsail to reduce drag.
I can't figure out how the arms work. I assume they're raised by a cable attached to the spreader.
 

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Tom Curren status
Jul 28, 2005
14,128
10,250
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33.8N - 118.4W
I put it here because we're locked in, I have some left-over glass and epoxy and was thinking about building another boat and you seem to know something about sailing. I don't know anything about boat design. The AC75 class is intended to trickle down to production boats:



I can't figure out how the arms work. I assume they're raised by a cable attached to the spreader.
I worked at Dencho Marine in Long Beach for 4 years out of high school and while in college (3 days a week during the school year, full time in the summer). Started as a sweeper (sweeping the shop), worked my way up to interior carpentry and finally building hull and deck moulds (lofting). Dennis Choate was also a great shaper (ghost shaper for Phil Edwards in the 60's).

You're building "another boat." You've built one before?

When you say AC design trickles down to production, we're talking about really high end production, with years of time lag. The arms I'm sure are moved with hydraulic rams. I think there is very little from these boats you can apply to a DIY backyard boat project.

But to get back on topic- I put on the balsa. Not a really high tech procedure but it works. I check carefully to make sure there are no gaps and that I get a good "squeeze" (the right amount of epoxy squeezed out of the join. I've also learned to extend the balsa past the tail to make sure the curve is maintained right to the very end.

I always start off wearing gloves, but they gets slippery when covered with epoxy and the tape sticks viciously to the glove. I always end up using my bare hands. Hope I don't develop sensitization as I've heard happens. I probably don't use epoxy enough for that to happen.

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