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[Corposant]

... Gang aft agley, an' lea'e us nought but grief an' pain, for promis'd joy!

This particular mouse planned to mount pieces of Lead in his Puffer build. He wanted them to be removeable because he didn't know currently how much ballast would be required ultimately (and everything he had ever fixed permanently, he had always had to unfix at some stage).

He spent an age mounting 2BA nuts and blocking them in with epoxy.



The first four were successful but the last two came adrift when removing the plastic shuttering. He thought "Oh bother!" (or something very similar).



In his own words:

In each case the area was de-greased with methylated spirit. The rear nuts were blocked in with freshly purchased Devcon 2 Ton (which is a slightly different colour from that used to secure all six nuts and the for'ard four blocks.

If I start again, I will have no confidence in the bond being able to support two 230g pieces of Lead. So ...

The current plan is to fix the detached blocks in place with Cyano. This should give a good bond but will not be easy - I have just realized that the current bout of "man-flu" is due to my becoming sensitized to the stuff! (Apparently this can happen to 5% of the population and I've just made the connection to a series of "colds" last March.)

Any comments, most welcome - but don't feel under any obligation!

Mike

[derekwarner]

Corposant ...I have little experience with fiber glass work....but the third photograph suggests that very little bonding to the hull [is any] has taken place with the AFT pair of square nuts

 .....so a few thoughts for consideration 

1. Coarsely abrade the hull pad areas & also the underside of the square nuts
2. Devcon adhesives are industrial class...so by ensuring you follow the material compatibility & installation instructions all should be OK
3. A simple plastistrut square frames say 3 mm x 3 mm larger than the square nuts would serve as a casting frame & so provide a deeper bed for the expoxy
4. After curing I am sure you would find greatly improved bond strength & so gently prise the balance four square nuts loose & repeat the alternate bonding process
5. I have little faith in cyano adhesives for such work

Similar epoxy bonding is also used full scale vessel engine room construction as an extension of the older traditional bolted joint work......good luck......Derek 

[Corposant]

Derek

Many thanks for your thoughtful considerations!

I agree it would have been better to abrade the hull surface (but there has been no problem with any of the other attachments).

The nuts are in fact brass 2BA (I chamfered the tops in the lathe). These were first fixed to the hull with Devcon and all the bonds appeared good.

My original intention was to surround them with beds the same shape as the pieces of Lead - 2 off 115mm long x 20mm wide and 2 off 50mm long x 20mm wide
(as shown by the pieces of wood in the picture):



This idea was abandoned in favour of 20mm square pads when I realized how much very expensive Devcon this would take! (If need be, I will fill in the gaps with something else - probably Silicone.)

I did indeed use bits of 1/4" plastic angle to make up the shuttering (stuck together with Cyano - hence my discovery that I have become sensitized!).

Last evening, I decided to press on with using Cyano to refix the loose blocks - on the basis that their bases were a perfect fit on the hull surface (and if it didn't work, I was no worse off).

This morning, they appear to have bonded well but at a considerable cost! I set up a fan to dispel the vapour but to no avail - I've been coughing and wheezing all night!
Mrs Corposant is not amused!

Regards,
            Mike

[dougal99]

probably too late but had you thought of using bathroom sealant to hold the ballast in place. Can be removed by judicious use of a knife and a little force. JMO

[CF-FZG]

The best adhesive, (that's publicly available), that I've found to reliably stick things to composites is Hysol 9462 - available from http://www.fighteraces.co.uk under the adhesives tab.  Some of you might also know it as 'BVM Aeropoxy'.

You could also use P38/P40 for what you need too


Mark

[Corposant]

Doug

Not too late! Some additional support is going to be needed to ease the strain on the epoxy pads - the chunks of Lead will apply considerable leverage! I will leave it until final fitting because my plan is to mount the main battery pack between the strips, so a little movement may be necessary. But your're right, bathroom sealant is going to be the material of choice.

Many thanks for your thoghts.

Mike

[The long Build]

How about this

http://www.modelboatbits.com/index.php?p=1_283

[Corposant]

Mark

Thanks for your recommendation. The initial requirement was for a gap filling adhesive to allow for the irregular surface within the hull. The cost of two part epoxy to make beds the same size as the Lead strips was, I felt, prohibitive. I will certainly bear in mind for future use, Hysol 9462 - it looks impressive!

P38/P40 would be ideal for ease of use and cost and may prove to be the best option but, at the moment, I think the slight resilience of bathroom sealant would be an advantage. If I had thought of using one of them in the first place, I don't think I would have had any problems - the greater surface area would have given adequate adhesion. Easy to be wise after the event - I should have posted the question before I started!

Mike

[Corposant]

Long Build

The help is now coming thick and fast! "Modelbond Gel" looks as if it could be even better than bathroom sealant (and at a similar price). I like the idea that it expands slightly on curing.

Many thanks for your advice.

Mike

[andyn]

Modelbond gel is nothing like silicon sealant at all. It is most probably the best glue I've ever used..

It sticks in about five - ten minutes, cures in 24 hours.
It dries white, and is sandable
It is stronger than whatever you're trying to glue is in the first place.
The only thing it can't stick (and believe me, Mark and myself have tested it on just about everything.. Including house bricks and Hannah's shoes) is PTFE. Which nothing sticks to.....

It expands very little, but is very useful that it does, as it fills any gaps.

Give it a go, you'll be glad you did.

Andy

[Corposant]

Andy

Thanks for the info. - it was the description "Gel" that made me assume it ended up resilient! From your description, it sounds great - I'll certainly be giving it a go!

Thanks again.

Mike

[wibplus]

Modelbond gel is nothing like silicon sealant at all. It is most probably the best glue I've ever used..

It sticks in about five - ten minutes, cures in 24 hours.
It dries white, and is sandable
It is stronger than whatever you're trying to glue is in the first place.
The only thing it can't stick (and believe me, Mark and myself have tested it on just about everything.. Including house bricks and Hannah's shoes) is PTFE. Which nothing sticks to.....

It expands very little, but is very useful that it does, as it fills any gaps.

Give it a go, you'll be glad you did.

Andy

Agree completely.    This stuff really is the mutts....    
I even used it to stick polypenko to GRP (then I found that I couldn't change my mind later)      

[Corposant]

Hi Wibplus

Sorry I missed your post this morning - been out all day.

Thanks for the recommendation. I'll certainly be placing an order! It sounds as if it might also be alternative to cyano in many applications (which I have become sensitive to and Mrs Corposant has forbidden me to use!).

Mike