MdG71 said..
Second session with the carbon boom

That sucks, I hope they can do the right thing by you and replace it. I'm going to make my own. I don't even have the wing yet though.

Does anyone have a contact email for duotone international/ HQ...?

Macca1410 said..

MdG71 said..
Second session with the carbon boom

That is dreadful to see for the price they charge. I have a carbon boom coming tomorrow but thinking might just go with the standard boom now.
Are there any issues reported like this with the standard booms? If more durable for a third of the price might do that and sacrifice a bit of weight.

I've been thinking a wee bit about the mechanism of failure on the Slick Carbon Boom, it appears to be glued as well as riveted, if so that glue has separated out. However (postulating) I think the biggest issue is the rivet in the carbon hole of what is frankly, a very thin walled boom. If the pop-rivet only mushrooms a little bit inside the tube, not enough to spread the load, I think it is a prime candidate for pull-through or loosening. Once that happens movement can occur more easily and the glue is under greater stress.

Carbon is strong and stiff but in my view the epoxy is quite brittle, especially aropund the hole if it is drilled into it. When I drilled holes in the carbon tubes for my home-made echo booms (see the Videos posted elsewhere how they are made, pic of my Echo boom end below) I started to be really concerned about the rivets pulling out through the carbon; this despite me gluing an aluminium sleeve over the top at the end only (see below from DW Videos on it). I ended up putting a through-bolt, slightly heavier but felt more secure ia it went from Plastic-Alu Sleeve-Carbon Tube-Carbon Tube-Alu Sleeve-Plastic i.e. spread the load.

What I think this Slick Carbon boom really needs is a short, well-fitting length of aluminium sleeve on the INSIDE of the boom, so that when you crank up the pop-rivet and it "mushrooms" it has something solid to mushroom AGAINST that is less likely to pull through. At a pinch a washer or curved plate with a hole in it might work, but a sleeve would be better. For the Slick Boom this would then be Plastic-Carbon Tube-Alu Sleeve-Alu Sleeve-Carbon Tube-Plastic.

Anyway, just random thoughts on this. It bugs me when fundamental issues are not considered as well as they should be.



DW's Videos for Carbon Echo Boom for Ideas:

cheers

k.

I believe as you say, the issue is the flex/movement of the plastic paddle cap.
There is a lot of flex as it is a load bearing point.

A rivet is a poor fastener in this situation. And one into carbon never works.

The easiest fix would be to drill it out, and replace it with a small bolt with a nyloc thread.
A Barrel nut/ barrel bolt with a bit of lock thread, would be even better.

I am actually considering this on my aluminum boom, as I can plug the ends while I do it.

An Adhesive like E6000 or Goop + 48 hours of cure time and it's never coming apart. The stupid pop rivet would be just to hold things in place while the Goop cures.

jksmurf said..

Pacey said..


Using aluminium and carbon together is just a recipe for galvanic corrosion and failure

Gee Pacey, you're not wrong, but at least make a suggestion rather than shooting down my feeble thoughts on a suggested fix (which TBH, will still work better than the current design and have a decent design life in the timescales of use we're talking about ... ). Gluing the Alu Sleeve inside the Carbon one will provide a corrosion buffer of sorts anyway.

k.

OK, my guess would be forget the rivet and the aluminium sleeve. Then glue it in place with Gorilla Glue, that stuff is amazingly strong and expands to fill gaps. If you can get a carbon sleeve the right diameter to go inside that would make it even stronger.

G-flex is the stuff, I believe it was created for golf club handles.

jksmurf said..
Cheers Pacey, a carbon inner tube :-). I like it. Only really needs to be as long as the diameter of the Boom really. I'm still a fan of the rivet or a light through bolt as a backup though (aren't rivets Aluminium?), I'd hate for the thing to separate, Gorilla Snot or not.

Hardware store rivets are typically aluminium, but you can also get them in stainless. You can also get monel, which is what we used to use when rigging dinghy masts in the olden days. You can get monel rivets from marine shops like Whitworths.

I found the following list online and it shows the various materials in order, and monel is closest to carbon, slightly better than stainless and much better than aluminium:

Cathodic: Graphite
Monel
Stainless Steel
Bronze
Brass
Copper
Tin
Mild Steel
Aluminum
Zinc

Anodic: Magnesium

Here's a nice look at the Slick in action.

Your 4m is OK. Before you inflate the wing, push the boom all the way into the back sleeve. It is designed to have a bit more camber in the strut and the air pressure holds the boom firmly in place.

go to 3 minute mark

DWF said..

go to 3 minute mark

Mate great Video , thanks for the share.

so, are all 4m Slicks like this, ie. does anyone have a 4m with proper attachments?

I have been using the 4m Slick for about a 3 weeks now and is my go to size in 15-30 knots.

One of the differences between the slick and previous models, in the smaller sizes it requires a higher PSI. If you pump it up to the increased PSI you should have no problems with the boom sliding out in the smaller sizes.