Nacra 5.8 demasted while sailing

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tparrish

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Registered: Jul 14, 2010

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Posts: 43
Posted: Apr 24, 2011 - 08:29 AM

I am a hobie man myself, but a friend just bought a used nacra 5.8 and we took it out for the first time yesterday. I am familliar with the boat as I had sailed with the previous owner a few times and figured I could help my friend set up the boat as he is new to catamarrans. Everything went together smoothly and we were sailing in no time. After about 30 minutes we heard two loud pops and realised the mast was sitting on the trampoline right behind the front crossbar. The dolphin striker post broke between the mast ball and the front crossbar and the mast was trying to tear through the trampoline. We decided the safest thing to do would be to capsize the boat so we can get the mast down while on the water before it had a chance to tear through the trampoline. This is what we did and were towed back in by a friendly family on a pontoon boat (motor variety )The only casualties were the dolphin striker post, the trampoline has a huge tear from the mast and a pair of costa del mar sunglasses. Anyone have a similar experience or might know what would have cuased this? My thoughts are just fatigue over the years as we were not sailing hard at all. Luckily no one was hurt.

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Griff
Hobie 16
Tuscaloosa, Alabama
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Wolfman

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Posted: Apr 24, 2011 - 11:47 AM

I haven't had this happen but can make a pretty good guess as to the cause.

When stepping/unstepping the mast you have to rotate the mast 90 degrees. If you don't the bottom casting on the mast will either break or bend the dolphinstriker back. I would suspect that someone in the past bent the dolphinstriker rod badly and instead of leaving it bent (not the best idea but is will work in the short term) or replacing it, bent it back straight. Bending the rod once is bad because stainless loses a lot of strength when it yeilds (you bend it once) but bending it twice is REALLY BAD because now you have opened any stress cracks that may have formed. If this is what happened it is just a matter of time. Normally those rods are pretty close to bullet proof, a 3/4" stainless bar is rediculously strong.

Next potential cause is a VERY loose rig, if the rigging isn't tight (relatively) or hasn't been tight and the mast flops around it subjects the rod to a lot of extra stress. You may have been sailing with a tight rig but the previous owner could have rigged it loose as a goose. You want it tight enough that everything stays in place but the mast can still rotate.

Lastly the previous owner could have just sailed the crap out of it for 25 years. To cover that possibility I would suggest you also inspect and look at replacing the standing rigging asap because it is likely trash.

The good news is that it's an easy fix, a dolphinstriker kit from Murrays will run you about $70 and is a pretty easy install. The tramp can be patched by your local sail loft or a good upholsterer (you may have to get the material for them from Sailrite).

Regards,
Dave

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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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turbohobo

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Posted: Apr 24, 2011 - 11:54 AM

On my P18, the dolphin striker post passes through the front crossbeam, and srews to the baseplate, leaving about 4" of post above crossbeam, the ball screws onto the top of the dolphin striker post. The post is held in place by the baseplate which is rivited to the crossbar, bottom of the post is attached to the dolphin striker rod. Lot of stress placed on the post and is transferred through the rod to the crossbeam, so yes fatigue would be your probable cause.

Some things to look for as factors contributing to stress would be standing rigging too loose allowing mast to "jump" up and down on ball and sriker rod. Other cats have a "captive" setup where after stepping the mast a pin is inserted through the mast base, it's postioning just below the ball effectively not allowing the mast to "jump off" the ball, always check that this type of setup is rotating freely once mast is stepped.

Turbo
Prindle 18
yurdle

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Posted: Apr 24, 2011 - 02:13 PM

Got any pics of what's left of the rod?

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Rob
OKC
Pile of Nacra parts..
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tparrish

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Posted: Apr 24, 2011 - 06:42 PM

I will try to post some pics if he hasn't thrown the ds away.

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Griff
Hobie 16
Tuscaloosa, Alabama
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Edchris177

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Posted: Apr 25, 2011 - 08:25 AM

Just out of curiosity. If you tip the boat over, the mast is all that prevents the "platform" from going turtle. If the mast is removed with the boat on its side, doesn't it flip turtle?

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tparrish

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Posted: Apr 25, 2011 - 02:33 PM

The boat did turn turtle and was sitting on top of the mast wich was laying on top of the water with all of the rigging still attatched. It took a great deal of work to get the mast freed from the boat so we could turn it back over again. This was the only way I could think of getting the mast down safely while on the water with a minimal amount of damage. I would love to know of another way to get the mast down safely while on the water with a broken ds.

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Griff
Hobie 16
Tuscaloosa, Alabama
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nacraman57

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Posted: Apr 25, 2011 - 03:54 PM

Had to respond to Turbo's comment about the "captive" mast/ball system. The only time the pin is used is to step the mast. Pin is inserted, while mast is rotated 90 degrees and raised into position. Once the mast is stepped the pin MUST be removed! Can't stress this strongly enough! The reason? If that pin is left in and the mast comes down for any reason without being rotated, you will absolutely destroy that dolphin striker rod, and possibly break the mast base. Plus, it will be bound so tightly that you may have to hacksaw the rod off below the ball to get it loose. Prindles and NACRAS that use this system like a tight rig and that prevents demasting. DO NOT use that pin for that purpose!

Edited by nacraman57 on Apr 25, 2011 - 05:23 PM.
Edchris177

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Posted: Apr 26, 2011 - 04:16 PM

QuoteIt took a great deal of work to get the mast freed from the boat so we could turn it back over again.

So, if I have this right...you undid all the rigging & removed the mast. Now you are left with an upsidedown Cat. How the Hell do you turn that big of boat back over, without the benifit of the mast as a lever?
Reason I ask is
(A) I'd llike to know, in case it ever happens to my 5.7
(B) I read a post here about flipping the cat on its side, to step or unstep the mast. I have had my 5.7 on its side on the lawn, & can pull it over or right it solo, using the mast as a lever. I couldn't figure out how getting it on its side without the mast, or removing the mast, then getting the hulls eased down would be easier than stepping a mast with the Cat sitting upright.
It seems to me once you pulled the stick, those hulls would want to come crashing down. It also seems like a huge job to get the platform up on its side, to where you could attach mast & rigging.

Nacraman is right about the pin being removed after you get the mast up. I lowered my mast once, with the pin still in. I didn't break anything, but the pin was jammed so tight I had to cut it.

Edited by Edchris177 on Apr 26, 2011 - 04:17 PM.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
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Bombardier Invitation (Now officially DEAD)
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RG7351

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Posted: Apr 26, 2011 - 07:29 PM

I had the unfortunate occasion to intentionally drop the mast while my 5.8 was turtled. I believe that the masthead was leaking severely and we could not right the boat with the assistance of a powerboat.

The process of fixing such a mess goes like this:
(1) Pull the boat back to shallow-ish water and detach the rig. Don't lose it.
(2) Secure all appendages (rudders and boards).
(3) Pull the boat to very shallow water.
(4) Find several (quite a few) people to help. Assign some people to each side of the boat, most of the people will lift while the others keep the boat from wandering. Once you get the boat over, guide it down. This is extra fun if your boat weighs > 400 pounds.
(5) Take your lumps. You probably deserve it!

I'm sure Yurdle is laughing at me, even now.
turbohobo

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Posted: Apr 27, 2011 - 06:39 AM

Was not talking about the mast step link pin, read carefully, mentioned the "captive system" where after the mast is stepped a pin is inserted just below the ball almost touching the DS, this allows the mast to rotate freely but will not allow the mast to disconnect from the ball.

To illustrate, make a fist on your right hand, thumb facing you, now take your left hand and cup the wrist just below the fist, now drop your thumb across the wrist, you have effectively demonstrated the captive system.

Edited by turbohobo on Apr 27, 2011 - 06:40 AM.

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TurboHobo
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tparrish

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Posted: Apr 27, 2011 - 09:11 AM

EdChris it was a real booger to turn over. It took three large men and my buddies wife to turn it over without the mast. I hung on to the righting pole and my friends wife grabbed the daggerboard while two other men lifted the opposite hull out of the water. It was not possible until the third man came along and even then everyone seemed to be in a great deal of strain. It did work though. The pin was not inserted while sailing. I have to give it to you nacra guys, i was very impressed with how easily that boat tacked and pointed compared to my hobie 16. That is until our pleasent saturday afternoon sail was ruined. I am looking at this as a learning experience. I have since learned that the ds was bent when the po bought the boat. He straightened it out and sailed it very hard this way for many years. My thoughts are that we were just unluckly and the ds was just extremley fatigued and this was just the day it gave out.

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Griff
Hobie 16
Tuscaloosa, Alabama
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tparrish

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Posted: Apr 27, 2011 - 10:29 AM

Ds was bent below the crossbar and broke above the crossbar. A bent ds is not likely the cause here.

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Griff
Hobie 16
Tuscaloosa, Alabama
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Edchris177

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Posted: Apr 28, 2011 - 08:37 AM

Thanks for the info, I thought it would be a real bitch, with plenty of opportunity for damage to boat and/or people.

Turbo...I'm thinking the same as some others. On the Nacra the "captive base" is only captive while stepping or unstepping the mast. The manual says to put the pin in before raising, then,
"Remove the mast step pin to allow the mast to rotate freely while sailing"
The only thing that keeps the stick in place is rig tension.
I believe G Camicks album has a good photo of a non captive base.

Here is the captive base of my 5.7 after stepping, with pin (bolt actually, the pin is somewhere in the lawn) in place. You can see that if the mast falls anywhere except exactly sideways, the mast base will hang up on the DS rod & bend it, along with other damage. Only by turning the mast so the base slot lines up with the DS rod can the stick be safely lowered.
There is no danger to leaving the pin in place...as long as your mast NEVER comes down

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
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nacraman57

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Posted: Apr 28, 2011 - 12:04 PM

Ed, Thanks for the picture! I was trying to dig one up myself to illustrate my respnse to Turbo. I didn't mean to say his post was wrong and if it came off that way I sincerely apologize. I have seen Prindles with the above setup and I think some were retro'ed. I can't explain the back hole on your mast base, my bases have just the single hole in front. Didn't you and I talk about that some time ago? As an example of what can happen...one day at the beach a couple fellows were loading their cat on the trailer. To lower the mast, the guy in front pulled the pin on the forestay, and as the guy on the tramp stepped back to the rear crossbeam the boat overcentered on the back rollers. They had forgotten to strap down the hulls. Anyway, as the front started to rise, the guy on the back toppled off the boat, hulls came down, the mast came crashing down and bent the heck out of the DS rod. The mast got dented on the traveler track, mast base was cracked and it was bound so tightly that despite the twisting, turning and raising the mast it took a hacksaw to free it. A mast coming down out on the water probably wouldn't be as violent but would still suck. The pin I use is a 1/4 x 2 1/4 with a ring-ding on one end and here's another spot to pay attention. Several times I have lowered the mast only to find the ring-ding between the mast base and tramp. DUH! So, back up goes the mast along with much cursing, to rotate it so the pin can be pulled. Another free tip! It's better to unstep the mast BEFORE the Bud Light!
Edchris177

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Posted: May 04, 2011 - 04:30 PM

Yeah, it doesn't matter which way you rotate the mast, just make sure you do it so the ring ding is on top once the mast comes down. My neighbors kid gave me a hand dropping the stick last fall, then left. A bit later I noticed the head of the bolt was on the bottom, duh. I just walked back to the garage for the bolt cutters.
A couple of other questions for you. When you sent me those photos of your beam dimensions last year (very helpul, I picked up a proper size V brace outside L.A.) I noticed another beam lying on the floor. Do you a spare you want to sell that will fit a 5.7?
Also, if you ever fliup your cat over again, take some detailed pics of how you have your righting system set up. My bag works OK, but is slower than a pole I think. I would like to build a pole system, to make solo righting easier. I like the system you have 2 photos of, but would appreciate all the details, no use trying to reinvent something.
Jim Casto has an album "the best righting system ever made", but the photos are not a large enough file to blow up clearly, & I haven't had any luck emailing him.

Edited by Edchris177 on May 04, 2011 - 04:39 PM.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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turbohobo

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Posted: May 04, 2011 - 05:05 PM

No worries mates, no offense taken, I learned something about " captive mast systems".

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nacraman57

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Posted: May 04, 2011 - 08:20 PM

Hey Ed, The righting system on my 5.7 is the "Hawaiian" type righting system I use in conjunction with a bag. Works ok, but I still feel that the best, simplest system is a length of rope tied to the mast base and thrown over the hulls. The pole system I have is on my 5.0. It is a direct copy of Rick White's design. The only difference is that instead of stopper knots, I use a rope lock to quickly adjust pole angles if needed. The 5.0 is my solo boat and I learned early on if your trapped out on a screaming reach miles from home you damn well better be able to self rescue if things go south. The 5.0 has a homemade bob at the mast end, the aforementioned pole righting system and a block at the end of the pole to feed a rope attatched to a righting bag if need be. I'm going to take the 5.0 to the lake this weekend for the first sail of the season and will take some pics of the pole setup and post or e-mail to you. As for the extra beams you mentioned, they came from a 5.0 my brother-in-law had years ago that we just sailed to death. Sails blown out, soft spots in the hulls from stem to stern. We killed it. Saved the beams, mast, rudders etc. Was toying with the the idea of building a plywood-hulled Formula 16 cat using these spare parts. Can you imagine a 16' cat weighing in at or less than 300lbs.? Say, by the way, you're an aeronautical guy... what do you make of the pics of the tail rotor of the chopper that went down on the bin Laden raid. Obviously an H-60 , but, look a little "stealthy" to you???
Edchris177

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Posted: May 06, 2011 - 09:14 AM

I use the "knotted line around the mast" system now. Very quick, if I have a crew, takes more time to rig the bag (& generally I need it if solo). I was thinking that the pole would be quicker, do you still need a bag with the pole on you 5.0?
I can sail without dumping, but it's way more fun to go flat out on the edge in 20 kts wind. Solo on the 5.7 is a handful in those conditions. I'm hoping a pole would reduce righting time/effort. I liked the look & simplicity of the system you are using.
I don't know much about stealth, my ride weighs over 800,000lbs & we try to show up on the screens! Other than reducing sharp angles to prevent reflections & radar absorbing coatings I have little knowledge. I only flew fling wing a few times, we were always told they don't actually fly, but vibrate & make obnoxious noise til the earth rejects them!
Major issues with rotary wing are that max speed is relatively slow due to retreating blade stall, & noise. I think the ducted fan tail rotor was developed to to reduce the noise footprint over urban areas. Those long blades, with tip speeds near Mach 1 also make lots of noise. When I was in flight school Kelly Johnson was head of the Lockheed Skunkworks. Many are familiar with the U2 & the SR-71, but they also had myriads of lesser or unknown projects, & I'm sure not much has changed. A stealthy, fast & quiet rotary wing would be the Holy Grail of fling wing.

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
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nacraman57

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Posted: May 09, 2011 - 05:20 PM

Ed, funny you should mention Kelly Johnson as I had an uncle that worked in the infamous skunkworks for Lockheed. He would come out to the farm for vacation and it would take several days for him to decompress. He once told me that even though the SR-71 still holds altitude and speed records it was one of the last projects to be designed using a slide rule! Makes you wonder what's in the hopper now. Ironically, the titanium that went into that plane was imported from the Soviet Union! I had the oppourtunity to examine an SR-71 up close at Offutt AFB before it was moved to the Srategic Air and Space Museum in Ashland, NE. I remember running my hand along the underbelly and thinking that it felt like a bunch of pop cans riveted together. Anyway to avoid being accused of hijacking this thread I thought I'd better show you the righting pole you asked about that I made several years ago for my 5.0. It is an Alcoa seamless 6061 aluminum tube 2.25 OD, .083 wall. The hinge is made of the same indestructable acrylic plastic cutting boards are made of. The line is a .25" Marlow pre-stretched although I think some of the new space age Dyneemas might work better. At the end of the pole I installed a small block that I can feed a rope attached to a righting bag if need be. There are more pictures I put in an album in the Tech section.I used rope locks instead stopper knots to adjust pole angles. The angle that works best for me is straight and parallel to the mast. When the boat pops back up the pole swings straight back under the tramp Hope this pic shows up...if not go to the Tech gallery