New Rig - Advice Required

[stom]

Graham's been good enough to sell me his old mast & Hyde sails from RV, so I'm now looking to use them on Norfolk.  I've got a few questions so thought they could all be grouped into one thread;

1.  Mast stump material - I need a piece 35cm long x 60mm diameter, does anyone know a recipe that will be substantial enough, or alternatively have an off cut lying around?

2.  Mast foot - the mast currently has an Aardvark heel, Would it be best to stick with this and try and get a matching foot, or is there another option?

3.Forestay/shrouds - can they be shortened easily, if so can you recommend somewhere I can get the job done?

4.Does anyone have an old 05 rules kite they would be willing to sell?  I'm happy to buy a new one, however at the risk of damaging it whilst learning to tame the bigger rig I'd rather use an old one until we are more sorted.

[phil_kirk]

The stump takes a lot of compression and some bending loads so needs to be strong.  As it is usually integrated in to the hull structure and provides a load path from forestay and shrouds through the hull it is not a thing you want to replace often.  RS800 mast off cuts have ben used very successfully. I believe that these are about 2mm wall thickness but please check. On E-numbers we used 1 layer weave, 6 layers of 300 gramm low modulus uni and 1 layer of weave all carbon.  So about 2.2mm wall thickness. We have not had a problem with it but it is not a long stump.  We tapered the stump lay up below the deck as it is laminated into the spine and shroud bulkheads and should be spreading load into them. 

If using medium of high modulus carbon you could also reduce the wall thicknes a bit further. I wouldn't go below 4 layers of uni though. 
None of the above is backed up by calcs. and success depends as much on good consolidation and a good cure as it does on getting the right recipie.

[Graham Bridle]

Re # 2 - I'd get something like this

http://www.ebay.co.uk/itm/NYLON-BLOCK-/281184000135?pt=LH_DefaultDomain_3&hash=item4177df5887

and get your tools out, nylon is really easy to work with.

Re # 3 - your nearest chandlers should be able to work with wire

[stom]

Thanks for the replies!  Getting the mast stump secured into the boat correctly concerns me the most.  I'm out of the country at the moment but will post up a sketch of what I intend to do at the weekend.  I'll also get some nylon ordered to make a new foot.

[roland_trim]

We have one of these:

http://www.ebay.co.uk/itm/hydraulic-crimping-tool-/181232452878?pt=LH_DefaultDomain_3&hash=item2a324bc50e

Will make up about 300 shroud terminations before the head fatigues off. The  ferrules and eyes are available from me or a number of suppliers

[stom]

So I've now made a new boom using the class mandrel, but after de-moulding have realised I have made a mistake of not using an inner layer of weave.  The recipe that I used was;

1x 300g carbon uni 50cm wide(goes around the mandrel just over 2 complete wraps)
1x 200g carbon uni for the first 1/3 length of the boom(takes the kicker & gooseneck loads)
1x layer carbon weave over the whole lot
Peel ply taped and then vac bagged.
Cured for 24hrs at room temp then baked at 80degrees c for 8hours

When I removed the mandrel the centre of the boom feels too thin(I can visibly make it deflect if I squeeze it)  Possible thoughts for rectification would be to add another layer of +-45 weave then add another final overwrap of 0/90 weave over the top of it.  Note that now this is off the mandrel I will have to use peel ply tape to consolidate as vac bagging will now be difficult.

Alternatively I start again from scratch with the correct recipe(I'm not so keen on the expense of a second boom going wrong...).

Any thoughts and advice would be greatly appreciated.

[Clive Everest]

Hi Tom,
Having the radial fibres on the inside and the out side makes a sandwich that gives the section significant hoop stiffness.
Putting extra radial fibres on the outside will not be as effective but you should still be able to stiffen it up sufficiently to make a good boom.

You should still be able to vac bag either by stopping the laminate just short of the ends and vaccing to the boom, or by using poly tube and putting it up the center and then back down the outside.

I can bring some poly tube to QM if you want.

Clive

[stom]

Thanks for the reply Clive.  The poly tube idea sounds really good, I'd like to take you up on the offer if possible?  I'm a bit wary of vaccing onto the boom as getting a good seal can be problematic.

[roland_trim]

Well done. It is only by making mistakes and actually doing things that we learn...


It might be worth test vaccing onto the existing laminate? You don't need to get sticky and loose nothing if it does not work?

For this I'd use a "Harris dust sheet" comes on a 25m roll from Screwfix and brown parcel tape (explicitly no tacky tape). Be very careful to only to vac the laminate and not accidentally seal up both ends :-)

[Steve_scott]

If the boom is hollow and of sufficient ID, you could run a bag through the section and seal it on itself externally.  Depeands how good you are with bagging and tacky tape! 

However, you should find that you can get a seal on the existing laminate without any real issues or if you can get the mandrel back in, just use that as support and drop the lot into a bag and vac it down.

 

[phil_kirk]

that is what clive and Born slippy are suggesting. 

Assuming there are no sharp edges the thin dust sheet and parcel tape method is a minimal cost solution. if cost is less of an issue then tcky tape and the official consumables is going to be more reliable.  the thin dust sheet would ned to be sealed into a tube and not snagged on the ends.

Alternatively apply the new layer of carbon and use peal ply tape and then shrink tape to consolidate.  A more reliable bond is achieved between the cured boom and the new layers if you smear a very thin layer of resin filled with Silica. This makes the surface tacky and helps the cloth to stand put.

[Phil Alderson]

You could reinforce the ends internally by making a tube on the mandrel with +-45 and then once it is off the mandrel splitting it lengthways. The split tube can then be coated with a thin layer of bog, and slid inside the boom.

You need to clean, and sand  inside the boom to get a good bond, which restricts how far up the boom you can thread the insert. The outboard end, and inboard to kicker attachment point would be of benefit.

[roland_trim]

Are you at the inlands? If yes it would be worth squeezing our boom for comparison. You could crush it in your hand at the far end (there is a stiffening ring there ).

[Stuberry]

How about cutting the entire boom lengthways and cleaning and sanding the inside. Then laminate one layer of weave around the mandrel. Then stick the 2 halves of the first boom back on. Then another layer of weave around the outside. Then vac as before.

Do also bear in mind that booms can usually be squashed side to side. Most reiforcement is at the top and bottom of the boom. So I would only really be worried if you can squash it in the up/down direction.

[stom]

Loads of suggestions!  Thanks all!! Yes we're coming to the inlands so I'll bring the offending item along for a squeeze test.....