DRAGONFLY Trimarans User Forum

Hello wise counsel.

Took Turas out on her shakedown cruise this past Friday. Many thanks to you who helped made it happen.

All went well (motoring only) except an unexpected net failure! The whole family had taken up on the port net / trampoline for lunch while at anchor.
Our total weight was 472 lbs (214 kg) (3 kids, me and wife) so I'd not expected any problems with capacity.

An unexpected and loud POP and we all went in the drink. Kids were lifejacket, baby was mad she got dunked into the cold water, but we even saved half of lunch!

Investigation upon return was the block was badly corroded inside the port aka. Photos (me holding the block is the starboard block not showing such corrosion)... https://www.dropbox.com/sh/066ddd2z4y09 ... e_J3a?dl=0

2 Questions...
One, do I replace both while I'm at it to hedge against another failure? And two, I need a solid replacement that won't break the bank...looks like the Harken / Ronstan equivalent is $100+ bucks..any guidance is most appreciated.

Thanks again..
Rad

Preventative maintenance is always a good thing on a boat. Otherwise things fail and usually at the worst possible moment, as you experienced in this case.

You might be able to find suitable replacements at a marine consignment store or eBay. Otherwise, shop your best deal. It costs what it costs for the parts. At least this is something you can easily fix yourself.

I would replace both. Look for Lewmar Synchro - very affordable and strong.

Did the boat fold when the block failed (or start to fold)? If you were sailing when this happened this could have been really bad. I strongly suggest backup anti-folding system which would prevent folding even if the lines, blocks or wire failed. Also, if there was so much corrosion, I think you should very carefully inspect the wire and the flitting that was attached to that block.

I've never seen such badly corroded block. I've seen exploded blocks.

I really think you should look over every block, fitting, line and wire, backing plates, pins again. Then replace anything that is questionable.

My 800 SW have a diagonal alu bar behind aft AKA preventing the AMA to fold in case of trampoline failure - should be ok safe.

I use the aluminum pole with locking pin to secure the ama forward. The tramp failure was the surprise and luckily we were at anchor!

I've ordered a Ronstan double block off of eBay and expect it to solve the problem.

I'll def heavily inspect both tackles for corrosion...and load them up with some lubricants too.

A good but hard lesson on inspection, prevention and pre launch checking!

Regarding aluminum bar to prevent folding: it is not secure enough. It is probably only good to prevent folding when anchoring or motoring.

Please search in the forum about a capsize where the aluminum bar just broke off at the attachment point.

Quorning switched to using a safety cable from the forward ama/aka joint to the main bow.

Many owners implemented similar set-up on their own. I also did this after I read about the above capsize.

What model did break the alu-bar?
I feel safe enough with the trampoline rope and the alu-bar.

I believe George is referring to a Model 1000. The folding (net) cable failed and the aluminum backup struts were not supported strongly enough at the cockpit wall attachments.

The remedy was to reinforce the bow with fiberglass and backing plates from inside to provide a strong attachment, and attach cables from the bow to the outer ends of the forward cross beams.

I also have a DF1000.
I added a line on each side with a snap shackle to the ama.
The center hull attachment is simply tied around the aft end of my bow platform and it's plenty strong imho.

Steve B. wrote:I also have a DF1000.
I added a line on each side with a snap shackle to the ama.
The center hull attachment is simply tied around the aft end of my bow platform and it's plenty strong imho.

The 1000's that came equipped with bow platform already had reinforced areas where the platform attaches. On my 1000 I judged it sufficient to replace the platform's aft attachment bolt (10mm) with a screw eye of the same diameter. I used that eye as the forward attachment for the new safety stay.

Edit - I also found out at that time that a 3/8" bolt is an exact replacement to a 10mm bolt, so close that the threads match and the nuts are interchangeable.

Must be strong enough to tie dyneema ropes to the bowsprit base plate. No big forces with no movement/momentum. BUT these will possibly interfere with my huge gennaker coming down!

Stefan Kolmodin wrote:Must be strong enough to tie dyneema ropes to the bowsprit base plate. No big forces with no movement/momentum. BUT these will possibly interfere with my huge gennaker coming down!

Maybe -- if you use the gennaker for gathering fish.

Wow, never thought that the strut would fail...I'll have to look into the fixed cable / line to bow solution.

Question, should there be / could there be weep holes on the underside of the aka?
The corroded block was sitting in a slush of salt and water. I rinsed it well but the standing water is an issue...do the akas drain at all?

I just looked at my 920: all 4 akas have drain hole at the inboard end. All of them appear to have a 3-4 inch (8-10 cm) round hole at the outboard end. It's difficult to see. My boat is partially open in the backyard. I can just barely see it.

Perfect. Thanks.
I'll double check my akas and may have to get the drill out...

Just to close this out, my aka's on the SW800 does not have any weeping / drainage holes so I'll have to remedy that I think.

I replaced the corroded block with this from eBay- Ronstan RF74202 Series 75 Core Block Double Non-Swivel

Overkill, yes. But it was cheaper than the Series 60 oddly enough. Works well and clearly has capacity to spare.

This system is certainly high on my inspection list regularly now. Thanks for everyone's input!