Stability/motion when folded?

For all those DF800 issues which do not fit into any of the categories below.
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Tica
Posts: 2
Joined: Tue 08 Sep 09, 23:09
Your Country: Croatia, Istria

Stability/motion when folded?

Post by Tica »

Hello, I'm new to this forum. Considering buying a DF 800 SW for daysailing and coastal cruising in the Adriatic, so doing some research now.

One issue I haven't seen discussed is stability/motion when folded - how (un)comfortable is the boat's motion with both amas folded - in the context of living and sleeping on the boat for a few days at a time? The berth I would keep the boat in is occassionaly exposed to waves (nothing too big, but enough to get all the monohulls rolling),so wondering how the much lighter/smaller tri would do without the benefit of it's beam. The berth is too narrow to allow extending even one ama out.

Also interested to hear how the boat behaves at anchor - again in terms of overnight stays in sometimes less than perfect anchorages. I know multis are famously stable at anchor, but have no experience with small lightweight performance tris.

Thanks!
Double Horizon
Posts: 440
Joined: Wed 09 May 07, 0:18
Your Country: USA

Re: Stability/motion when folded?

Post by Double Horizon »

Tica wrote:Hello, I'm new to this forum. Considering buying a DF 800 SW for daysailing and coastal cruising in the Adriatic, so doing some research now.

One issue I haven't seen discussed is stability/motion when folded - how (un)comfortable is the boat's motion with both amas folded - in the context of living and sleeping on the boat for a few days at a time? The berth I would keep the boat in is occassionaly exposed to waves (nothing too big, but enough to get all the monohulls rolling),so wondering how the much lighter/smaller tri would do without the benefit of it's beam. The berth is too narrow to allow extending even one ama out.

Also interested to hear how the boat behaves at anchor - again in terms of overnight stays in sometimes less than perfect anchorages. I know multis are famously stable at anchor, but have no experience with small lightweight performance tris.

Thanks!
I have owned a 920, 1000, and currently own a 1200. I do not recommend keeping a Dragonfly folded in conditions that would get monohulls rolling.

The Dragonfly amas do go deeper in the water when folded to produce more form-stability (enough to raise the center hull about 4-6 inches). However it will still be top-heavy on a relatively narrow base, and rolling conditions (especially combined with storm-force winds) could cause an unhappy ending unless at least one ama is extended open.

You might be able to attach halyards to strong fittings each side on the docks (if the docks are floating), to limit roll for safety... or perhaps the marina can give you a larger shallow slip or out-water mooring where you can keep it open?

At-anchor with amas open you will enjoy very good stability with relatively minor motion compared with monohulls. When they are rolling 30-degrees to each side you will still be relatively comfortable, with about 5-degrees of roll to each side. The Dragonfly tris have "low drama amas" with both amas in the water unless heeled under sail. This is in contrast with some other tri designs that have "higher" amas with only one in the water, even at-rest.
Larry - Former Owner DF-1200
Mika Harju
Posts: 218
Joined: Thu 02 Nov 06, 13:19
Your Country: Finland, Turku

Re: Stability/motion when folded?

Post by Mika Harju »

Tica wrote:Hello, I'm new to this forum. Considering buying a DF 800 SW for daysailing and coastal cruising in the Adriatic, so doing some research now.

One issue I haven't seen discussed is stability/motion when folded - how (un)comfortable is the boat's motion with both amas folded - in the context of living and sleeping on the boat for a few days at a time? The berth I would keep the boat in is occassionaly exposed to waves (nothing too big, but enough to get all the monohulls rolling),so wondering how the much lighter/smaller tri would do without the benefit of it's beam. The berth is too narrow to allow extending even one ama out.

Also interested to hear how the boat behaves at anchor - again in terms of overnight stays in sometimes less than perfect anchorages. I know multis are famously stable at anchor, but have no experience with small lightweight performance tris.

Thanks!
These foldable boats are not engineered to stand big (or almoust any) waves when folded. From mechanical point of view the inner joint between main hull and akas can not stand the movement when amas are going up and down. My opinion is it is not wise nor safe to motor or keep these boats in berth folded when waves are bigger than 0.5 meters (here at Baltic Sea waves are short and sharp)
Last edited by Mika Harju on Sat 12 Sep 09, 8:44, edited 1 time in total.
Mika Harju
DF1000 Racing #8
Tica
Posts: 2
Joined: Tue 08 Sep 09, 23:09
Your Country: Croatia, Istria

Re: Stability/motion when folded?

Post by Tica »

I only thought of "folded" stability as something affecting comfort, didn't realize it could be a safety/structural issue. I've seen the thread below about heeling in high winds, but assumed conditions would need to be much more extreme than what I experience in my marina. With the typical wind patterns here you can get strong winds coming more or less across the bow and flat water, or moderate winds and a bit of waves on the beam.

The docks are fixed so no options to use lines to the dock. The boat is moored "Mediterranean" style, so I thought the two bow mooring lines - long, heavy and full of marine growth would have enough weight and drag through the water to significantly dampen the roll if I could attach them as far away from the centreline as possible.

However, in light of Mika Harju's post above, any forced stability would increase the loads on the hull-aka joints. Will have to look into it further when I actually buy the boat and get it here...

Getting a wider berth where I could keep one ama out is the best option - it solves the stability issue, and makes the boat much more livable at dock, so I'll definitely try that.
Double Horizon wrote:

At-anchor with amas open you will enjoy very good stability with relatively minor motion compared with monohulls. When they are rolling 30-degrees to each side you will still be relatively comfortable, with about 5-degrees of roll to each side. The Dragonfly tris have "low drama amas" with both amas in the water unless heeled under sail. This is in contrast with some other tri designs that have "higher" amas with only one in the water, even at-rest.
I was actually worried the DF 800 fell into that category of lightly immersed or flying-at-rest hulls, so was worried it might cause a fast bouncy motion, which I find very difficult if trying to sleep. So very glad to hear it's a low-drama-ama boat!
Mika Harju
Posts: 218
Joined: Thu 02 Nov 06, 13:19
Your Country: Finland, Turku

Re: Stability/motion when folded?

Post by Mika Harju »

Tica wrote:I only thought of "folded" stability as something affecting comfort, didn't realize it could be a safety/structural issue. I've seen the thread below about heeling in high winds, but assumed conditions would need to be much more extreme than what I experience in my marina. With the typical wind patterns here you can get strong winds coming more or less across the bow and flat water, or moderate winds and a bit of waves on the beam.

However, in light of Mika Harju's post above, any forced stability would increase the loads on the hull-aka joints. Will have to look into it further when I actually buy the boat and get it here...
!
One possibility is to use ratchet straps around the amas and akas near the hull/aka joint.
I do not know the exact stucture of DF800, but this works well with DF1000. I do this when taking the boat up for winter storage.
These straps prevents all the extra movement at the joint.
Mika Harju
DF1000 Racing #8
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