NASA Log skin fitting cracked!!!

Folks

Just to update. I removed the skin fitting and the flange broke into lots of bits.
This was due to the plastic being so fragile which must be due to the plastic reacting with the silkaflex. I will be sending the fitting back to NASA in the morning. So hopefully they can come up with a answer to the problem which seems to be fairly common

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Interesting.

As a new starter i have to say that i wish Nasa would take note and give a specific recommended sticky stuff in their instructions. Perhaps even a fixing kit as they do with the in hull tube.

Also all i have ever seen in chandlers in store and the few onlines I looked in is Sika.

Where do I get marine silicon. I stuck my tube in with sika last weekend and will be glassing it in this weekend.

May be next year I'll redo it with a silicon, but where do I get some??

Jim

<hr width=100% size=1> "It is a pleasure to give advice, humiliating to need it, normal to ignore it"
 
Does that follow, necessarily? Could the flange have become embrittled by some other mechanism? I think nylons tend to absorb water. I don't know if the tube is nylon but I'm guessing it might be. If so, could that have damaged it instead?

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I've just incvestigatesd the technical properties of sikaflex for a rudder bearing. 291 & 292 are quite different. I'd tend to use 292 (which is a lot more expensive) for underwater fittings .. and ensure its cured properly before relaunching.

<hr width=100% size=1>I Have The Body Of A God... Buddha
 
why not ask NASA to come here and comment. Send them a copy of link so they can find it easily. If you tell them that their products are being discussed it's highly likely you'll get someone to respond

<hr width=100% size=1>Utinam logica falsa tuam philisophiam totam suffodiant
 
Here here,

The instructions with the unit are, to my mind vague, certainly to a first time DIY'er like myself. Mines in with sika now and will be glassed in over the weekend. But I am tempted to change it next year.

NASA if you read this. Seeing as there seems to be a problem, why not providean optional fixing kit as per the in hull tuibe which comes with everything needed.

On the otherhand if there is an weakness in the fitting it needs to be addressed.


jim

<hr width=100% size=1> "It is a pleasure to give advice, humiliating to need it, normal to ignore it"
 
jimbuoy - I've never found a problem in getting marine silicone sealant at a chandler so your comment puzzles me.

failing chandlers, suggest you try yellow pages under sealants or bearings. last time i was in a hayleys bearing factors i noticed they had 4 different engineering formulations of silicone sealant.

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Last year I repaced an Echopilot log with an updated one. I asked about replacing the skin fitting approaching 20 years old. Echopilot claimed that they had never had a single breakage of a skin fitting which apparently are made of glass re-inforced nylon. And sure enough the fitting was perfect, though I did replace it in the end.

Now Echopilot gear is not expensive. So why cant Nasa provide something similar?

Mind you Echopilot supplied a display head with nightime lighting that was useless - and when I moaned about it they said "yes, we know" !

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You have to remember that my experience is zero (as is my knowledge.. see my note at the bottom) and I have only been in to 2 chandlers on hayling island, both of which had racks of sika and the mail order company I actually got the sika from, recommended it as the stuff to use when fitting a Nasa log.

Last night I trawlled the Mail speed marine web site and of course you are right. But now it's too late for me. At least this time around. I'll change it next year.. perhaps by then the design will have changed or I'll have tracked down a suitable bronze fitting.

It really annoys me that the Nasa is IMO supplied for the DIY market with poor instructions and an inherant fault.

Jim

<hr width=100% size=1> "It is a pleasure to give advice, humiliating to need it, normal to ignore it"
 
This isnt the only problem with the NASA log. When I launched last Spring the log showed a very low reading. When I checked I found water had got into one of the metal slugs in the impeller. The consequent rust had spit the little tube surrounding it and the slug had gone - hence the low reading. I bought it because it was cheaper than other instruments - nuf said.

<hr width=100% size=1>Roger
 
Have not used silkaflex myself but evidently it is an elastic adhesive bonding agent, the word adhesive worries me I suspect it contains a solvent. I have now read the previous post on page 4 regarding this subject and the post by MAINLYSTEAM says that this is probably Zylene. Plastics are not inert and some are made brittle by prolonged exposure to solvents and chemicals, I have experience of a chemical company having to send out a hazard notice that a plastic container they had used would after only one year shatter on slight impact after exposure to the chemical it held.
It would be a good idea if NASA came on here and clearly stated if solvent based sealant could be used or supply the correct sealant with the log. The result of a catastrophic failure at sea would not be good news. In the mean time perhaps we should all carry a 42mm bung just in case!

Trevor



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Agreed

"It would be a good idea if NASA came on here and clearly stated if solvent based sealant could be used or supply the correct sealant with the log."

Couldn't agree more

<hr width=100% size=1> "It is a pleasure to give advice, humiliating to need it, normal to ignore it"
 
I'm replacing my NASA inside hull depth sounder - doesnt work with more than 30 metres of water or in soft mud - with a Silva through hull mounting sounder.
The Silva clearly says use polyurethane sealant. The mounting tube looks just as flimsy as the NASA one.

<hr width=100% size=1>Roger
 
My old man refitted seacocks to his Hustler with Bathroom Sealant some years ago. We laughed at him at the time, but its been fine.

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Yes Chris there is a way round this. You can buy a PH. Bronze water intake fitting which is 1 1/4 BSP. The scoop bit can be cut off with an angle grinder forming a flange. You are then left with a long threaded skin fitting which can be cut to suit the length of your impeller. The thread is the same pitch etc as the original NASA fitting and all that is left to do is polish up the internal face which has a rough finish but this is quite simple and you then have a much better fitting than the original.

Ted.

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OK

A slightly tongue in cheak comment. But already equiping Lady Jayne has more than doubled the cost and definately will not have dbld her value. I could have bought a well equipped example for less total out lay.

But I have enjoyed the buying, wiring, welding, bolting, sealing etc.

I don't think I have made any faulse economies. Good quality Lifejackets and safety equipment. Second hand Navico VHF. Second hand inflatable. New Nasa Target echo and Log.

Now when I first started my "adventure" it was even suggested that for my planned bay hoping and days on the Solent, some of the stuff, including the log, might not even be needed. I also hinted about being worried over the fitting of the log. So I got lots of helpful replies and even Pm's. Also one formite was good enough to send me a PDF of the Sailing Today article.

So just as I have the tube sika sealed in and ready to glass, the evidence against this mounts.

I am a little bit fed up. Arguably slightly to blame... but at the risk of repeating myself... Nasa market a product clearly aimed at DIY installation with very poor instructions. How the hell do I know if Sika is a mastic or a sealant..... I'm ignorant on these things. I have a magazine article that says use Sika I go into a well known Chandlers who sell the Nasa gear and am sold a tube of sika to do the job.

I am little confused as to how I should proceed. This morning I was all for glassing it "well" in and keeping a close eye until next winter when I would probably replace it in some way.

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