HC14 to Sailing Trimaran!

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narfi
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Re: HC14 to Sailing Trimaran!

Post by narfi »

I cut out and started assembly of the rudders and board.
Epoxy coated the inside faces and then laid them in jigs with the bottoms taped together. 8nterior jig wedges were covered in packing tape so they won't stick.
Got the idea for this method from this article,

http://smalltrimarans.com/blog/how-to-b ... er-boards/

The rudders are 4ft by 10inch panels, the board is 8ft by 13inches. They are both oversized, I'll see if I cut them down before testing or after..... Easier to cut some off than to add more later. My goal for the board is roughly 6ft under water and whatever looks good for the rudders, I think with the two big rudders I should have plenty of authority..... But I don't really know what I'm doing so time will tell :)
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cape man
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Re: HC14 to Sailing Trimaran!

Post by cape man »

I'm confused. Can you do a sketch of what you're thinking?
The world always seems brighter when you've just made something that wasn't there before - Neil Gaiman

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VT_Jeff
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Re: HC14 to Sailing Trimaran!

Post by VT_Jeff »

Wow, what a great process for foils. I had to build a new rudder for my precision 18 some years ago, it was definitely not this high tech.

Your amas and beams are stout to the point that the canoe looks like a passenger on a catamaran. I'm wondering if the whole project is a top secret float rig for your plane. Lol
There are only two seasons in Vermont: boating season, and boat-building season.

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VT_Jeff
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Re: HC14 to Sailing Trimaran!

Post by VT_Jeff »

cape man wrote: Tue May 25, 2021 6:11 am I'm confused. Can you do a sketch of what you're thinking?
I was too until I read the linked article. The vees get bent into foils
There are only two seasons in Vermont: boating season, and boat-building season.

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Jaysen
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Re: HC14 to Sailing Trimaran!

Post by Jaysen »

VT_Jeff wrote: Tue May 25, 2021 6:46 am
cape man wrote: Tue May 25, 2021 6:11 am I'm confused. Can you do a sketch of what you're thinking?
I was too until I read the linked article. The vees get bent into foils
It will be interesting to see how that works. I'm thinking those are a bit ... large for the size boat. My 4000lb 24' long, 8' beam fat pig has a rudder that is 5'x2'. The fin keel is 4'x3' (and has 1800lbs ballast. Most of the cats I see have small narrow rudders. This includes the big cruisers as well as the pure wind-powered boats. There has to be a reason all the designers use smaller rudders and keels on these things.
My already completed 'Lil Bit'. A Martens Goosen V12 set up to sail me to the fishing holes.
Currently working on making a Helms 24 our coastal cruiser.
“Mark Twain/Samuel Clemens” wrote:Eat a live frog first thing in the morning and nothing worse will happen to you the rest of the day.
Jaysen wrote: Mon Apr 29, 2019 3:44 pm I tried to say something but God thought I was wrong and filled my mouth with saltwater. I kept my pie hole shut after that.

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Re: HC14 to Sailing Trimaran!

Post by Jeff »

Too cool Narfi!!! Jeff

narfi
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Re: HC14 to Sailing Trimaran!

Post by narfi »

cape man wrote: Tue May 25, 2021 6:11 am I'm confused. Can you do a sketch of what you're thinking?
Here is a diagram from the article I linked on http://smalltrimarans.com/

Image

I am doing a lower tech version of this idea.... no carbon spar caps, and to my own dimensions.
Is that what you were asking about? or something else?

narfi
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Re: HC14 to Sailing Trimaran!

Post by narfi »

Jaysen wrote: Tue May 25, 2021 6:58 am It will be interesting to see how that works. I'm thinking those are a bit ... large for the size boat. My 4000lb 24' long, 8' beam fat pig has a rudder that is 5'x2'. The fin keel is 4'x3' (and has 1800lbs ballast. Most of the cats I see have small narrow rudders. This includes the big cruisers as well as the pure wind-powered boats. There has to be a reason all the designers use smaller rudders and keels on these things.
There is a simple and logical explanation to why they do it the way they do.

Math.

and........

Experience.

I am too dumb to know the math, and not dumb enough to have gained experience....... isn't there a quote about experience coming from lack of wisdom and wisdom coming from experience or something like that? (the point being (my take away, not the authors intent) is that dumb people have more fun and have better stories)

From what I have read a well designed foil should be ~5% of your sail size.
I have a 80ft2 sail and have not ruled out the idea of some sort of head sail at some point down the experimentation path.
So a well designed board for this sail would be 4ft2 under the water raised to roughly 5ft2 if/when more sail(s) is put up.
So for my 13in panels the nose will be rounded off and the entire panel bowed out to form the foil shape, call it roughly 12in (should be a little over), this makes for easy math because for each foot under the water I get 1ft2.
Three things make me want to go larger,
1. future proofing for a larger sail(s)
2. accounting for my assumed inefficiencies
3. Because I do not know the balance angle the board will be used at it is possible i loose a significant portion due to not being submerged

The pivot point will be roughly 1ft above the water and if I am to fully retract it I am limited to the 6ft between the beams, that gives me right at the 5ft2 under water if straight down and less for any angle back and I am extending it a foot above the pivot point to use as a lever/bellcrank for moving it. So my plan has been 7ft long to account for all of those variables knowing it is slightly oversized, but I do not feel grossly oversized.... Perhaps I am wrong though :)

The rudders I have a harder time finding any significant math on, however it is a relatively short boat for its size and sail area. As an aircraft enthusiast, I know that distance to the rudder acts like a lever, the shorter the distance the larger the rudder needs to be to have the same effect, further you can push it back the smaller the rudder would need to be. These rudders will be mounted 24inches forward of the rear of the canoe which is already fairly short, so I know I need them oversized, I just don't have any standard on what normal or under or oversized would be....... I have less thought into them so far, but roughly thinking I will also cut a foot off of each of these making them 3ft of which roughly 2.5ft will be under water and remembering that at times only one will be of much use when one hull is out of the water.....

Does that thought process seem logical?

narfi
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Re: HC14 to Sailing Trimaran!

Post by narfi »

VT_Jeff wrote: Tue May 25, 2021 6:45 am Wow, what a great process for foils. I had to build a new rudder for my precision 18 some years ago, it was definitely not this high tech.

Your amas and beams are stout to the point that the canoe looks like a passenger on a catamaran. I'm wondering if the whole project is a top secret float rig for your plane. Lol
hehe, of course I am always thinking steps ahead and sideways anytime I am working on something, so I have been thinking about plane floats as well...... however......

plane floats are quite a bit different, they need to be planing hulls balanced about where the main landing gear usually sits but have the displacement to be stable when at rest....
So aircraft floats have a significant step just aft of the center, when they get up to speed, the rear section is out of the water and it is planeing on the forward section at speeds able to lift off the water, if it was a long traditional hull the water would suck it down as speeds increased and lift off would be impossible.

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VT_Jeff
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Re: HC14 to Sailing Trimaran!

Post by VT_Jeff »

narfi wrote: Tue May 25, 2021 11:50 am So aircraft floats have a significant step just aft of the center, when they get up to speed, the rear section is out of the water and it is planeing on the forward section at speeds able to lift off the water, if it was a long traditional hull the water would suck it down as speeds increased and lift off would be impossible.
Makes perfect sense, but would not have guessed that. Made me wonder immediately about using a foil under the float to reduce drag on takeoff, a quick google search indicates that others have posed the same question and that foils have been used on flying boats, but apparently not in conjunction with floats, just as an alternative. Interesting.
There are only two seasons in Vermont: boating season, and boat-building season.

Completed Paul Butler 14' Clark Fork Drifter
Completed Jacques Mertens FS14LS + 10%, Build Thread
Started Iain Oughtred Tammie Norrie

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