NASA Log skin fitting cracked!!!

[AndCur]

I am currently get my boat ready for the new season and to my alarm I have found that the log skin fitting is cracked about 90% of the way
round. The skin fitting was fitted four seasons ago and has been fine up until now. The crack is round the flange and is clearly visible from the
outside. The fitting sealed with silkaflex and was only hand tight. Has anyone else had any problems with these fittings.
When I remove this fitting I will be sending it back to NASA to see what they think.



<hr width=100% size=1>

 

[Althorne]

Andrew I take it that you haven't been keeping abreast of all the chat about Sikaflex and Nasa tubes over the past ten days? I would suggest you find and read them before giving Nasa any grief. Would be very interested in how you get on with Nasa though. Keep us posted.

<hr width=100% size=1>

 

[AndCur]

What is the title of post ?

<hr width=100% size=1>

 

[Althorne]

Sikaflex and skin fittings (posted 13th) go back to page 3 and should be there.

<hr width=100% size=1>

 

[AndCur]

Thanks i will have a read.

<hr width=100% size=1>

 

[Alpha22]

The only thing missing is the answer.

Nassa say dont use sikaflex. No one wants to use bathroom sealant. Where is the compromise??

I will call NASSA tomorow and report back.

D.

<hr width=100% size=1>Last weekend was shopping darling........ so this weekend is boating. (Duck!)

 

[Jools_of_Top_Cat]

Has anyone found a bronze fitting replacement?

It is 42mm isn't it, are they available?


I am really starting to worry about mine now!

<hr width=100% size=1>Julian

<A target="_blank" HREF=http://www.topcatsail.co.uk>Top Cat Homepage</A>

 

[AndCur]

Folks

I have a new skin fitting on order and will remove the old one in the morning
hopefully i will see what has happened. I have spoken to NASA who asked me
to send it to them. What they did say was use silacone sealant.
The whole thing has scared me and i would really like an answer as to what
has gone wrong!


<hr width=100% size=1>

 

[VicMallows]

Bronze Fitting: that's a good question. I bought a NASA duet last season because I was desperate for a new echo, and thought I might as well get the log as well, though have been managing quite happily with just the GPS for years after the NAVICO packed up (the transducer: the thru hull absolutely fine). Havn't fitted the log yet since a real pain because smaller than the old thru-hull.

The idea of machining one to suit is attractive, but probably more cost than justifiable.

Vic

<hr width=100% size=1>

 

[jimbouy]

What we really need is to hear from someone who has fitted one using silicon a few seasons back to see how it has performed.


I have just fitted mine using sikaflex, even though I had read the post mentioned.

Why?? Because I simply do not trust silicon.

My reckoning is that having used sikaflex and then glassed in the internal side of the tube, even if the outter lip cracks it is unlikely that water will get in.

We'll see.

I also have to say that when I first asked about fitting a log some months back the general concensus was use sikaflex, which is also mentioned in sailing Todays article on the Nasa Duet.

Bottom line may be that the nasa tube is poor. Which leaves an opening for someone to market a bronze alternative.

If anyone knows of such or considers having one machined I'd be interested.

<hr width=100% size=1> "It is a pleasure to give advice, humiliating to need it, normal to ignore it"

 

[salamicollie]

I fiited one over 5 yrs ago using silicone (Dow Corning Marine) and have no problems - If you have followed NASA's instructions and glassed in the skin fitting there should be no issue, even if the flange breaks off...

<hr width=100% size=1>

 

[Trevor_swfyc]

I also used silicone fitted two years ago so far no problems encountered, one thing obviously that would cause damage is if the boat was lifted with the strop over the log, trust this has not happened.

Trevor

<hr width=100% size=1>

 

[jimbouy]

I haven't glassed it in yet but will be doing so.

And, as I say, I think this is really the important bit. I agree that were the flange to drop off, the remaining sealant (be it sika or silicon) plus the glassing will make it safe.

Jim

<hr width=100% size=1> "It is a pleasure to give advice, humiliating to need it, normal to ignore it"

 

[DanTribe]

Re: Happy anniversary

This must be an annual event.
I started a thread on this subject on 17/3/03.
Nasa are aware of the weakness because they said to me that breakage of this fitting is not uncommon.
The instructions do show the tube to be glassed in but of course I knew better and didn't bother, but I have now!
I believe the problem is made worse if you regularly remove the paddlewheel because that must put a slight strain on the flange joint.
Glass it in.
Dan

<hr width=100% size=1>

 

[chriscallender]

Re: Happy anniversary

One thing I am not sure of - we know that NASA don't recommend Silkaflex and know that failure of the fitting is not uncommon - but have the failures that they have seen actually been attributed to some chemical action of the silkaflex, or is it just a poor quality fitting?

Mine is glassed in and I did use Silkaflex, my thinking was that the glassing would save the boat from sinking if the flange failed, and I am more interested in stopping water getting into the hull (ie use a quality sealant) than getting a long life from the fitting. If the fitting fails then I will replace it.

But I'd be really interested to know whether the failures seen have ever been analysed and directly attributed to using Silkaflex.... the wording in the instructions is not "it is dangerous to use silkaflex type sealant" but something more like "we recommend that you use siliccone sealant". If any failures had been directly atributed to Silkaflex I would have expected something much bolder in the manual.


Anyway I almost never remove the paddlewheel, its usually permanantly covered in weed, so I guess I should be OK!!!! For once lack of maintenance is a good thing!


Chris

<hr width=100% size=1>

 

[chriscallender]

Hmmm I wonder - could the thread be 1 1/4 inch BSP? According to a table I looked up that comes out at 41.91mm diameter, and a pitch of 11 threads/inch. If that were the case it might be possible to use a bronze skin fitting if the wall thickness is simlar to the plastic one. Would need to be cut to the right length but an interesting project if it happens to be the same thread.

Chris

<hr width=100% size=1>

 

[jimbouy]

Re: Happy anniversary

Nasa's exact wording

"It is advisable to avoid the use of mastic materials- use a form of proprietary silicon sealant.".... fairly non specific.

Your line of thinking is exactly as mine, although you put in to words far better than me.

I am also tempted to run a bit of epoxy around the edge of the flange as well.

<hr width=100% size=1> "It is a pleasure to give advice, humiliating to need it, normal to ignore it"

 

[l'escargot]

I fitted one three seasons ago using silicone after mine broke. I am lifting out next week and will examine it closely. I will report back if I find any problems.

<hr width=100% size=1>

 

[Birdseye]

Jimbuoy - silicone sealant is excellent, but like polyurethane or po;ysulphide rubber you have to get the proper marine stuff.

When Prout built my boat in 87, they used silicone for everything from underwater fittings to sticking down some of the joinery. No problems at all - indeed, when I had to remove a blakes seacock bedded in silicone, it took me 2 days to do it.

I have never been that impressed by Sikaflex. The polyurethane sealants I have use from 3m have always weathered better - seems to me that Sika is simply a trade name that allows them to charge ridiculous prices.

<hr width=100% size=1>

 

[VicMallows]

Agree with your comment on Sika as a brand. Locally we have a trade sealant distributor who does an identcal product at £3.33 / 310ml cartridge. It even used to be called '221 Sealant' but now simply 'Marine Sealant' .... I don't think they could keep up with Sika on the number changes! More importantly, it has a clearly stated manufactured/expiry date. The expensive stuff in the chandlers is liable to be out-of-date and useless before you even buy it.

Vic

<hr width=100% size=1>