mast boot/chocks - chemists

[ShaunG]

I have a constant problem with water leaking through my mast boot, as well as the chocks always causing problems.

There is a product in america, which looks fantastic, seal the hole through the deck from underneath, pour in the 2 pack polymer and leave it to set. 3 days later you have a perfectly formed mast chock and boot at the same time. When pouring the polymer the hole in the deck is coated in vaseline to allow it to release when the mast is removed.

All the above sounds great and i would buy it but it but for the very high shipping costs ( delivered to my door the product is just under $400), however it has got me thinking, there must be many materials suitable in industry, without the marine price tag. Would anybody be able to point me to a suitable 2 pack, pourable rubber type material that meets a similar spec to the one below:

Pot Life @ 25°C 8-14 min
Cure @ 25°C 3 days
Shore Hardness 55-60 D
Tensile Technical Specifications, psi 4,000
Ultimate Elongation, % 200
Tear Strength (Graves), pli 600
Compressive Modulus, psi 55,000
Linear Shrinkage, in./in. .001
Izod Impact, notched, ft. lbs./in. 9.5

I have googled all the figures above and it has given me an idea of what the hardness of the polymer is, i am just not sure what to look for.

I would of course try this out elsewhere before using, i guess i would need to ensure that it would not damage alumininum, expoxy or grp and that a suitable material could be found for building coffer dams around the hole in the deck.

if any one could help it would be much appreciated, i pretty much failed chemistry and don't really know what to search for

thanks

ShaunG

 

[sarabande]

worth giving these people a call ?

http://www.alchemie.com/flexible_polyurethane_systems.htm

 

[earlybird]

Devcon market various grades of "Flexane", a 2 pot castable polyurethane rubber. AFAIK, available from various distributors. http://www.itw-devcon.co.uk/index.php?/devcon_mro/flexible_urethane_maintenance_and_repair_systems/devcon_flexane_60_80_94/ . Try them.

 

[ShaunG]

Flexane looks promising, thank you for that one. Hmmm looks like you can even make bushes (possible engine mounts) from the projects that are on online with flexane

Any one any further ideas or advice?

Thanks

ShaunG

 

[Salty John]

I fixed my mast boot leaks with duct tape. I changed the tape every year whether it need it or not. Worked for me.

 

[Simes]

Spartite

Like you I am looking for a replacement to the heavy cost of this product (Spartite).

The Flexane 60/80/90 looks like it will do the job with a 5Kg pack at 300 quid the cost falls by 25% for Talisman.

I am thinking that a well about 50mm deep around the mast and the mast wall smeared with Vasline (release agent) a couple of Kg should do each mast.

Thanks to Sarabande and to Earlybird for finding these links.

Simes

 

[michael_w]

I'd be careful with that spartite stuff. I've seen a 60' cutter being lifted by her mast when it refused to budge. Took the riggers a couple of days to drill and chisel out the stuff. Mast was pretty chewed up as a result.

I'll stick to hard rubber wedges, jubilee clips and a hypalon boot.

 

[glynnffc]

mast boot

I like the sound of hard rubber wedges. Can you tell me a supplier.

Thanks

 

[ShaunG]

Simes,

you got the product spot on, i would love to use their measurments but they don't list the size of the pack. I am going to measure up this weekend but reckon that a litre should do me nicley. I have sent a mail to devcon to check on the exotherm temp to ensure that it does not get to high

The shore hardness of the flexane94 (A97) seems to be comparable to the D55-60 of the Spartite, The only thing that is going to stop me is if the exotherm is too high.

i was planning to put the Decovon release agent on the mast, the gate and the deck partners, use grub screws to keep the mould in place and then sikaflex a thin bead around the gate and mast each year to keep it in place and watertight, this should stop the removing the mast problem as effectivly the mould will be free floating except for the sika.

Glynn

All being well i will have a load of selden rubber wedges spare in the near future, you more than welcome to them, or you could mould some wedges from Flexane 60/80 and use that, in hindsight it would be much cheaper than the selden ones ( if i remember right a 50cm*50cm *2 cm block was about £100)

 

[30boat]

I did that to my previous boat and it worked a treat.I used a semi hard two pot rubber compound.It took a few hours to harden and is still in place 10 years on.I coated the mast with vaseline to allow for lifting out.Don't know if it'll work.The best material for a mast boot is in my experience a section of a wetsuit leg or arm.It has to be slipped on before the mast is stepped and then,and this is important,made tight with a few turns of shock cord around the mast and the mast collar.That's what I did and got a 100% leak free boot.It should be protected from direct sunlight by a canvas hood.

 

[michael_w]

Try your local riggers. Remember you do have to put a jubilee clip round the wedges below the level of the partners, otherwise they tend to fall out as the boat flexes is a seaway.

 

[ShaunG]

Thanks for the ideas. I did get a professionally made mast boot when i replaced the mast. A perfectly fitted and moulded piece of thick rubber that was put on the mast before fitting.

However, the drain holes in the mast are quite low down, and the mast gate quite large, this meant quite a sharp turn to the top of the rubber that after 2 years of british UV (not sure where it came from, with the last 2 summers ) it has perished and is leaking again. I have used the usual amalgamating tape, but again beacause of the proximity of the drain holes it is not overly succesfull. The spartite style solution would be neat, only rise 5 or 10mm above the deck ring which should leave a further 15 or 20mm before the mast drains. In hindsight it would have been better to have had the drains drilled higher in the mast, but the vang (Hydraulic)attachment will still have been a pain.

I am waiting a response from Flexane/devcon on a couple of questions which i will post the repsonse to on here, but from the sound of 30boat, and others who fancy trying this, i will measure up this weekend and weather permitting give it a go the week after

 

[ShaunG]

I have just had a very helpful call from glenn at ITW in response to an email i sent them

The questions and answers are as follow:

1)What volume would a 500ml tin fill when fully set?
2)What is the maximum exothermic temperature when setting?
3)Will any damage be caused to Stainless Steel, Aluminium or GRP by the flexane, or is it inert to these materials?
4)What materials are safe to use as a coffer dam, Masking tape, foam, plasticine etc?
5)What material is suitable as a release agent, would Vaseline or wax be a suitable item?
How does Flexane compare to the specification of Spartite?

1) 500cc, 500cm3, specific gravity is 1.005
2) not too sure, will not cause damage to GRP, stainless, Aluminum or wood
3) no
4)any listed above, bear in mind they need to reasonably tempreture resistant
5) should be ok but not tested, any commercial release agent could be used and there is one produced for Flexane at £12 a can, if a bond is required then the primers must be used.
6) similar, although flexane will not be as fluid, it will more consistant between maple syrup and treacle, but will poor well and fill voids well. Ensure that the liquid is very, very thoroughly stirred or it will not set correctly.

All the above sounds good to me and i will be measuring up and trying it. RS Components stock the Flexane 94 at a good price with quick delivery. I will use vaseline as a release agent on my test and let you all know how it goes

 

[30boat]

I think you'll have no problems.The only difficulty lies in avoiding leaks down the mast.I wasn't careful enough and had to run below to plug a few.Better take your time and do it correctly.Silicone sealant is better than pasticine and comes off easily enough.
I would use wax release agent and on top of that vaseline.That's because wax will create a stronger film than just vaseline.Oh and remember to center the mast.It can't be corrected once done.

 

[ShaunG]

Thanks 30, I am a bit concerned about getting the seal. i have ordered a trial pot and will experiment tomorrow with bits as a seal and release agents.

I will post pics of the trial in case anyone comes back to this post in the future

 

[30boat]

Please do.

 

[ShaunG]

I have poured a test

My 500ml can of Flexane 94 arrived today from RS. I am using this can as a test to see what works

Test mould made up

View attachment 1401

I am using a plastic tub with 2 holes drilled in the bottom, 1 is covered with masking tape only and the other with foam from a jenny brush (i had one to hand) and masking tape to hold it in place

View attachment 1402

I am using a socket extension to represent a mast

View attachment 1403

The mould has been prepared with release agent (vaseline) on the right of the picture the masking tape has been left with no vaseline to see how it releases without a release agent. The socket has been half covered with masking tape and the other half with vaseline.

View attachment 1404

Following the mixing instructions the mould has been poured, the consistanct is similar to golden syrup and pours well. I used a hot air gun as per the instructions to help remove the air bubbles (although not in the above picture) which on the face of seems succesfull. The clamps are in place to hold the socket extension upright, as you will see i had a bit of a disaster with the socket falling over, i hope the vaseline works or it will be one lost socket.

I will update tomorrow when it is safe to remove from the mould, we should then have some data on what will work as a coffer dam and what will work as a release agent

 

[ShaunG]

looking good

i have just removed the flexane from the mould, got to say that i am very impressed, according to the specs it can be removed after 2-3 hours.

I can confirm that vaseline does work as a release agent. Foam does not work as a coffer damm as it soaks up the flexane.

When i use this on the boat i will be doing the following

1) ensuring all parts which the flexane will touch are covered in masking tape
2) All masking tape will be covered in vaseline
3) The above will hopefully prevent any issues when it comes to removing the mast as the only bond will be the masking tape.

The product at the moment is very firm and can barely be bent, it can however be cut with a knife. It is definetly firmer than the wedges that i have at the moment but no harder than wooden wedges.

The measurments of the block in the pics below is 145mm x 103mm x 30mm from a 500ml can. it is much smoother than it looks in the picture

View attachment 1407

View attachment 1408

View attachment 1409

View attachment 1410

 

[ShaunG]

if anybody wants a test piece to see what this sets like then PM me with an address and i am sure i can stick a bit in the post

shaunG

 

[30boat]

That's pretty much like the rubber I used.Mine was red but it was probably a siimilar product.Like yours it was quite stiff and really supported the mast well.
A picture of the whole thing when finished would be great.