Low cost tech developements

[phil_kirk]

Ideally everything should be made from the right materials which are donated or purchased at low cost.  However if you have to buy your carbonyou will want to make it go as far as possible.

I have experimented with the simple fronting plate.  Traditionally these are made from solid carbon.  I have used 10 layers of 200 gramm carbon.  That's quite an area of carbon.

I recently fitted E--numbers with a plate made mostly from glass and only the outer layers were carbon.  Since glass is a 5th of the cost of carbon that could relate to a reasonable cost saving for anyone on a tight budget.
I wanted the plate to be load tested before offering this up.  It has and Nick didn't manage to remove it at the inlands.

[roland_trim]

We'd  +1 this.

EJ's fronting plates were made in the same way. Carbon in the outer fibres only - Phil you are correct as this is the only place they do any work. As an additional pimpage. Add a small quantity of "Peruvian Darkness Liquid" into the resin and the glass layers turn black.

As the density of glass is lower this is also lighter?

[tim_unerman]

Born Slippy the density of glass fibre / epoxy is between 1.8 - 2.1 tonnes/m^3 and the density of carbon fibre / epoxy is between 1.5-1.7 tonnes/m^3. If both plates are the same thickness the carbon plate will be lighter.

[phil_kirk]

Beaten to it then but first to let the secret out 

I worked out that this detail alone would save about £15 if you had paid full price for your carbon and glass.

There are probably other areas where this technique can be used without reducing the strength of the boats.

[Tim Noyce]

Rather than starting a new thread I thought I would resurrect this one...

I have a question about 'fronting plates' after forceably removing the kite halyard turning block from the floor of Numb last night. This block was screwed into the floor with some nice cheap non stainless screws and so ripped out pulling a bit of floor with it and leaving some nice damp soggy holes in the deck. The block is located behind the front bulkhead and the only hatches are right on the transom which means that bolting the fitting is not going to be possible in this case. (I am normally a bolting person given the choice). I have some thin HD foam which has been laminated both sides with lots of carbon and so this should be more than sufficient to bog to the deck for attaching the new block.

Do people generally then screw down into this plate, or is it worth bolting the fitting to the plate before I bog it onto the deck? Thanks in advance!

[Tom K]

Timmy,

Best to bolt. If you bolt through the fronting plate, then run a bog fillet round the base of the nut, then put something over the nut end so glue can't touch the bolt before bogging to the deck you will be able to remove the fitting without removing the plate as the nut is captive.

[JimC]

Do people generally then screw down into this plate, or is it worth bolting the fitting to the plate before I bog it onto the deck?

I like bolting the plate with the nuts on the outside: then there's a sporting chance of replacing a fitting if I need to without messing with the plate. That means using hex head bolts, not screws. If the bolt heads are sitting above the plate and embedded in a really strong microfibre/silica mix glob of filler then the chances are good that they'll be usable for a few cycles of tightening/untightening. But often you don't have the choice and have to have the nuts on the inside and accept that the whole plate will need to be replaced with the fitting. In theory you'd think that if you put some kind of lubricant on the bolt the epoxy won't grip and you'd have a captive nut, but its never worked for me.

[roland_trim]

I have some thin HD foam which has been laminated both sides with lots of carbon and so this should be more than sufficient to bog to the deck for attaching the new block.
Do people generally then screw down into this plate, or is it worth bolting the fitting to the plate before I bog it onto the deck? Thanks in advance!

Attached is how we have done it in the past.

I would not be 100% anti the thin HD foam instead of plate. I it does carry a couple of unknowns in local crushing, but the major advantage of already being in your hands cannot be ignored. Put the side with the thickest laminate facing down and use penny washers to help it distribute. The key is that the fronting plate minimises flex under the bonding area. Any of this and it will crack the bond "peel" from the edges (not 100% sure that makes sense, the first you will see of the peel is when it goes bang).

I would not take the sketch as gospel. DC removed one of our fronting plates the other night from EJ,  alougth I think his crew pulled at a knot in the Spinlock as if it was a pulley.

[roland_trim]

I like bolting the plate with the nuts on the outside: then there's a sporting chance of replacing a fitting if I need to without messing with the plate.

We found they seem to release, but we do grind the head flat before bonding in (so no thread in epoxy). Whe you replace a fitting you do have to be careful to keep the screws or it is a painful cycle of insert new screw/take out cut to length/cry as too short/ start agian with a new bolt/ make it too long add washers on top.

[Tim Noyce]

Thanks for the tips chaps, I knew I could rely on you all!

I may well just bolt a saddle onto the plate and then I can leave it on there permanently as I can shackle or tie the new turning block onto it and not have to worry about the nut staying captive. I also may end up with a bit of a hole in the deck if I have to cut out the soggy foam so I will just make sure that my fronting plate is plenty large enough to cover over it all.

[Phil Alderson]

I have to say that I have always assembled the fronting plate with the nuts on the underside, and have never had a problem with the nut spinning. Having the nut on the inside means that you can remove the fitting and just leave a hole, or a flat screw head

I make the plates up in two steps first I assemble the fitting on the plate, and cut the bolt down. Then away from the boat I dab a hard mix of bog around the nut, and down to the plate. After it cures I remove the fitting (this checks if the nut is secure) put small squares of tape over the bolt holes and bog the fitting to the deck. For high load jobs I also put a couple of layers of glass or carbon over the top. Once cured I carefully tap to find the hollow, and drill the thin carbon out revealing the embeded nut behind the plate.

Pic from How To -Fittings

[phil_kirk]

As Roland said but we recessed the nyloc nuts into 10-12mm holes in the foam core of the deck. This reduced the amout of bog needed to bond the plate to the deck and thus is lighter. 

May be a good solution for you Tim if you already have the holes.

We also cut the bolts off flush with the end of the nylock so there is very little bog touching the bolt.  I have only had to remove the fittings once and did not have a problem with embedded nuts turning.  most of our blocks are lashed on to lacing straps/saddles so there is little need to remove many of the bolts.

[pratn0]

I'm planning on making some with soft loop attachments.

I will let you know how this goes.