Fitting a Nasa Speed/log

[MattBarraud]

Dear All

I am after a bit of advice! /forums/images/graemlins/ooo.gif I have recently bought a Nasa speed/log instrument for my Hurley 22 and need to fit it. I have been quoted £500+ (with some other jobs) to do this by the local boat yard and so am wondering if it may be better to do it by myself.

According to the instructions all i need to do is drill the correct sized hole in the hull; put it through and re-seal with sealant etc. Now this seems simple in of itself but i know that in reality it probably isnt.

My plan is to dry out on a spring tide and let the boat settle on her side; doing the job when i have enough 'land' and hoping to finish it before the next tide.

My question really is two fold, has anyone got experince of doing this type of job and is it as simple as it sounds and also, do you all think it is folly just to try?

Thanks in advance

Matt

 

[Beadle]

It sounds sort of OK

If it were me I would text fit everything on a bit of plywood drilled with the drill I intended using.

I would also have a fall back plan to be able to seal the hole if anything went wrong.

I think I'd have a decent pump available too - if it leaks, its going to leak until the next low tide.

 

[VicS]

Welcome to the forum.

It is quite a large hole, 42mm, but provided you have a suitable means of cutting it there should be no problems. You will need some assistance probably fitting the "through hull" but not impossible to do singled handed. (some Gaffer tape to hold it in position etc).

What I personally would not fancy is doing it with the boat lying on its side. I think I would prefer to dry out alongside somewhere, scrubbing piles perhaps, and have the boat upright to work on.

Some means of plugging the hole would be sensible just in case.

There's no way I'd pay 500 smackers for a job like that

 

[MattBarraud]

Great ideas! Have tested the drill bit already so all ok there, am going to try and test seal a 'test tube' to the wood to get a feel for how to encapsulate the whole esembly in grp. Of course having never worked in grp doesn't help.

Does anyone know of any good websites with grp advice?

thanks for your advice.

Matt

 

[MattBarraud]

Thanks VicS

The boat lives in Exmouth estuary and we don't have anywhere that i could dry out alongside, but defiately worth doing, perhaps it may be best to borrow some legs?

Matt

 

[Loginname]

Why do you want to encapsulate it in GRP? All you need is some sealant.

You can dry out on the Exe. SFCC has facilities at Starcross. If you PM me I'll let you have the club bosun's number; I'm sure he could sort something out for you.

Alternatively you may be able to dry out by Starcross pier, but I would advise you speak to the owners first.

You may be able to dry out alongside outside Exmouth harbour, but I don't know that patch of the Estuary; I just go passed it!

If you dry out alongside you'll have more time to do the job. If you dry out on the sandbanks you won't have very long before the tide comes back in!

 

[Tranona]

Don't think you will want to set it in GRP. Bed it with sealer. Also make sure that the inside is square and flat for the locking ring to sit against. You may have to shape a pad to make up the curvature of the hull.

Can be done on a tide, but better to do it when you have an opportunity to let the sealer go off with the locking ring just up so that sealer squeezes out all round and then harden up the next day to compress the sealer.

 

[Hardley]

I have fitted one of these, with boat out of water, I would be waring of doing it afloat, between tides, and I am pretty experienced in gpr work.
The boat should be upright, you or someone else will need to go inside the boat.
The fitting must be upright, so you will probably need to build up the hull, inside, around the hole. A fibre glass paste would be the quickest way to do this, make sure you sand well and clean area to ensure paste will stick.
From memory I think you also have to Fibre glass over the base of the fitting.
If using any sealant, READ the instructions with regard to the recommended sealant, some sealants eat into the plastic.
Later I would recommend that you build a coffer dam around the fitting, so that when removing it, to much water does not enter the boat, this is a time when laying the boat over a bit helps lessen the pressure of water entering the boat.

 

[MattBarraud]

Never thought about Starcross, will look-up a contact via the website, - thanks for that!

In regards to the grp bit, the Nasa instructions state to encapsulate the whole area in grp but having never worked in grp am a bit worried about doing so.

Does anyone know a good quality sealant up for the job?

 

[Loginname]

Well I never! It does say that you should encapsulate it. I wonder why?

Mine has never been encapsulated and it was fitted to my boat long before I bought it.
I don't think I'll bother now; if it ain't broke don't fix it.

If you are going to encapsulate it do it at your leisure after the boat has refloated. The sealant should keep it watertight.

Sikaflex will have the right sealant, but I always forget the different grades. Someone will be along shortly with the answer.

 

[Tranona]

Having looked at the NASA manual, I can see what they are doing. Can't see any reason to do this as it means you can never remove the fitting without destroting it. Maybe somebody else has an explanation. I have always used a backing pad internally and set the whole lot in Boatlife sealer. Never leaked and can be removed.

Agree about putting a coffer dam around it to keep the water from spreading around the boat when you take it out to clean it - although mine goes straight into the bilges and is never much. But this is a refinement and is often done by bonding in a partial bulkhead in the locker - also keeps gear from damaging it.

 

[Dipper]

The NASA impeller housing has a habit of snapping off it is not encapsulated. I've encapsulated mine.

 

[l'escargot]

A few years ago there were a number of instances of the plastic fittings shearing - mine did - it is believed that some sealing mastics degraded the plastic causing it to weaken. Some people had metal fittings turned up to minimise the risk.

Note that it says only use <u>silicon</u> sealant. Fibreglassing the fitting in is a "belt and braces" way of doing the job.

 

[tyce]

Really easy to do, i fitted one last season only takes about half an hour with a hole cutter.
Glassing in is easy just get one of the small fibreglass kits from halfords, job done, total cost about a tenner.

 

[Tranona]

Thanks for the explanation. However, looking at the diagram in the manual, if the problem is shearing then it only moves the possible break point a little higher up. Raymarine fittings are also plastic and they don't require glassing in. Very odd!

 

[l'escargot]

No, the shearing happened where the plastic came into contact with the mastic - where it came through the hull. It is also where there is most leverage to cause a fracture. By glassing around the fitting, almost up to the top of the thread (only leaving enough to screw down the transducer securing cap) you practically remove any possibility of it shearing.

Mine had sheared threequarters of the way round, level with the inside of the hull. I kept finding a cup or so of water in the locker and thought it just needed a bit of sealant under the internal securing nut. Next time the boat was out of the water I grasped the nut to unscrew it and the whole of the internal fitting came away in my hand. I was just pleased that I had waited until I was out of the water to do it. That was at about 2pm. I was due to go back in the water the next day so I telephoned NASA, ordered and paid for a new fitting and it dropped through my letter box the next morning. Fitted and back in the water on schedule.

Raymarine may not specify glassing in, NASA may have changed the plastic in the fitting so that it is no longer a problem, but as I said it is "belt and braces" to glass it over and could prevent an awkward situation.

 

[Tranona]

So, guess it was inappropriate material! I looked at the NASA manual and it just shows GRP over the nut, not right up the thread, hence my comment. If bonding in is essential, rules out the use on a wooden (plywood) boat like mine - not that I need one!

 

[Andrew_Trayfoot]

Friend of mine had one sheer off in the middle of the Solent a few years back, I was sailing in company in another boat…
They used soft wood bungs and various bits of wood to keep the water out until we got into Hardway (Gosport). Then replaced it with a blanked off brass seacock.
Not surprisingly he decided to do without a log after that….
I have one fitted still, but it is totally disconnected as it never worked very well anyway.
I tried to get an ultrasonic log a couple of years back, but Echo Pilot has stopped making them.

 

[ShipsWoofy]

my first one cracked, though I think I was a little keen with the tightening to be honest.

The second I took a little more time over. The unit is fitted using 3M silicon, then a layer of polyester resin on mat and then I built a cone of epoxy to ensure safety if it cracked again, but also strength in case it was to be knocked accidentally. I am quite happy with the current fitting arrangement I have built in.