revintage

Joining cut down carbon mast

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The time has come and everything is prepared for joining the two pieces from a broken Flying Phantom Elite 9,6m mast. The section is 180x76mm. The mast is quite stiff and made for a main and jib of 23.5sqm+asymmetric. I will use it with 15-16sqm on a trimaran foiler I am building.

From FP: FP Elite masts is built of a mix of T700 high resistance pre preg carbon for the strength and softness fore and aft, it is reinforced with M40J high modulus carbon for additional stiffness sideways. It is cured in autoclave with 6 bars of pressure.The tube is tapered in the top to save weight, reduce drag and improve the trimming of the main sail.”

The top is 2m and the lower part is 6m. Managed to get a 60cm sleeve out of the cut away pieces around the break. 

My idea is to only go for the inner sleeve and a  bag with a low 15psi when epoxying. Maybe adding a narrow outer sleeve of something like 1” over the joint. Instead of an inside spreader reinforcement, I added it on the outside using G/Flex, 3rd image.

Talked to Wests UK branch Wessex and they agreed G/Flex 655 would be an option, but PRO-SET ADV-175/ADV-276 would be better as it could cope better with high temperatures.

Still wonder if 105/206 thickened with 406 Colloidal Silica would be a better choice?

 

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Actually ordered 2 cartridges PROSET yesterday:).

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Hi Zonker,

Read my last post.

About some flex it might though be beneficial. I have used G/Flex for many years together with glas and carbon(not for masts though) and the joints don´t get flexy, but prevents moving stuff from cracking. 

But the PROSET is on it´s way, so it is not an issue anymore. Even if it has better Tg, I am thinking of painting the mast white.

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Used colloidal silica / West to join this one at the spreaders

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Hi vmg,

Suppose your joining method was more advanced than mine. 

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Maybe not, but VMG's mast is painted. A-Cat rigs (similar construction) have been successfully repaired using West Systems  105/206, but it is highly advisable to paint them after as the HDT for West Systems is ~119 °F (some gain from post curing, but not much),  and carbon parts can exceed 140 °F in the sun in warmer climates.

Pro-Set can also be thickened and is a better choice for this due to the higher performance nature of the resin (better flexural modulus, better tensile and compressive modulus', HDT's north of 170 °F). A comparable product that might be harder to get but has better HDT performance at lower temperature cures is MGS 285.

You can track down T700 and M40J to replicate the original laminate tapered over the break. That will be much better than the proposed repair, as your small outside sleeve is going to create a hard point in the mast (even with the internal sleeve). Generally its best to use an internal sleeve of about hlaf the original laminate, than an external laminate that gets bagged to the rig that is 1/2-3/4 the thickness of the original laminate tapered out to zero over approximately 18in total. Others may have better rules of thumb, and in general it is better to err on the side of too stiff, but also better to try and match the laminate closely to get the same bend characteristics as a new stick.

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6 hours ago, samc99us said:

Maybe not, but VMG's mast is painted. A-Cat rigs (similar construction) have been successfully repaired using West Systems  105/206, but it is highly advisable to paint them after as the HDT for West Systems is ~119 °F (some gain from post curing, but not much),  and carbon parts can exceed 140 °F in the sun in warmer climates.

Pro-Set can also be thickened and is a better choice for this due to the higher performance nature of the resin (better flexural modulus, better tensile and compressive modulus', HDT's north of 170 °F). A comparable product that might be harder to get but has better HDT performance at lower temperature cures is MGS 285.

You can track down T700 and M40J to replicate the original laminate tapered over the break. That will be much better than the proposed repair, as your small outside sleeve is going to create a hard point in the mast (even with the internal sleeve). Generally its best to use an internal sleeve of about hlaf the original laminate, than an external laminate that gets bagged to the rig that is 1/2-3/4 the thickness of the original laminate tapered out to zero over approximately 18in total. Others may have better rules of thumb, and in general it is better to err on the side of too stiff, but also better to try and match the laminate closely to get the same bend characteristics as a new stick.

two things....

t700 and m40j..... wow, talk about opposite ends of the extreme.   t700 is.... meh and m40j is nasa.

when i broke my rig, bigger section thin wall, it was suggested that 12:1 was enough..... that would have been a 12mm scarf.... 24mm total. i went with 300mm

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5 hours ago, basketcase said:

, it was suggested that 12:1 was enough..

Nope, 12:1 is OK for glass but for carbon, which can have much higher loads something like 50:1 is better, 100:1 isn't unheard of.

So a 1mm mast thickness - 100mm either side of break or 200mm overall.

That sort of very shallow angle is hard to do. I believe in aerospace they have jigs that plane down the skin at just the correct shallow angle for a scarf joint like that.

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5 hours ago, Zonker said:

Nope, 12:1 is OK for glass but for carbon, which can have much higher loads something like 50:1 is better, 100:1 isn't unheard of.

So a 1mm mast thickness - 100mm either side of break or 200mm overall.

That sort of very shallow angle is hard to do. I believe in aerospace they have jigs that plane down the skin at just the correct shallow angle for a scarf joint like that.

On race boats, we use a template and a zack.

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6 hours ago, Zonker said:

Nope, 12:1 is OK for glass but for carbon, which can have much higher loads something like 50:1 is better, 100:1 isn't unheard of.

So a 1mm mast thickness - 100mm either side of break or 200mm overall.

That sort of very shallow angle is hard to do. I believe in aerospace they have jigs that plane down the skin at just the correct shallow angle for a scarf joint like that.

Also very difficult to achieve ply drops and taper with the standard weights of carbon available.

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11 hours ago, basketcase said:

two things....

t700 and m40j..... wow, talk about opposite ends of the extreme.   t700 is.... meh and m40j is nasa.

when i broke my rig, bigger section thin wall, it was suggested that 12:1 was enough..... that would have been a 12mm scarf.... 24mm total. i went with 300mm

Actually he's not that far off on what it actually is(same modulus but different supplier so different names) 

Its pretty normal for mast laminates to combine standard and high mod fibres. High for the 0 axis on standard for off axis.

 

The pro-set ADV 175 rubber toughened was the right choice for the DIY'er. Its very forgiving to work with for the properties you get. 

 

Hysol 9462 would have slightly better properties but is alot more toxic and harder/more expensive to get in larger quantities. You need to prep differently as well and watch the humidty, temps as this can throw it off course pretty fast. 

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7 minutes ago, IanA. said:

Actually he's not that far off on what it actually is(same modulus but different supplier so different names) 

Its pretty normal for mast laminates to combine standard and high mod fibres. High for the 0 axis on standard for off axis.

This

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I scarfed mine at 1 degree, which was about 8" on either side of the break.  This was at the recommendation of carbon airplane manufacturers.

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Should have joined the mast with the inner sleeve by now. For some reason the Swedish distributor delivered the wrong PRO-SET, adv175/adv275 instead of the ordered adv175/adv276. Unfortunately he hasn’t the correct one in stock.

Must do the joint right now and have two options of toughened epoxy on hand, West G/Flex 655 and Gurit Spabond 340LV. Gflex has a quite low Tg  of 67C while Gurit has 80C. Living at latitude 60 N, a low Tg might not be a problem, especially if I paint the mast white.

Anyone familiar with Spabond?https://www.gurit.com/-/media/Gurit/Datasheets/spabond-340lv-ht.pdf

 

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22 minutes ago, revintage said:

Should have joined the mast with the inner sleeve by now. For some reason the Swedish distributor delivered the wrong PRO-SET, adv175/adv275 instead of the ordered adv175/adv276. Unfortunately he hasn’t the correct one in stock.

Must do the joint right now and have two options of toughened epoxy on hand, West G/Flex 655 and Gurit Spabond 340LV. Gflex has a quite low Tg  of 67C while Gurit has 80C. Living at latitude 60 N, a low Tg might not be a problem, especially if I paint the mast white.

Anyone familiar with Spabond?https://www.gurit.com/-/media/Gurit/Datasheets/spabond-340lv-ht.pdf

 

I haven’t used the West product so I can’t comment on it, but I’d happily use Spabond for this. Work tidy and use peel ply wherever possible. 

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Do you have the 175/275? I don't know Spabond. I do know G-flex and it's fantastic stuff, but too much elongation for what you are doing

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7 minutes ago, Russell Brown said:

Do you have the 175/275? I don't know Spabond. I do know G-flex and it's fantastic stuff, but too much elongation for what you are doing

Have returned it as exp date was due april 2020. 

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Maybe you could get it back at a discount. I'm sure it's fine. What is the diff between the 275 and 276? I've used a lot of the 276. It has tiny grains of something to keep from squeezing all the epoxy out.

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3 hours ago, mad said:

I haven’t used the West product so I can’t comment on it, but I’d happily use Spabond for this. Work tidy and use peel ply wherever possible. 

Just ordered the Spabond as I  trust it to be on another level than  the G/Flex, even if I have used G/Flex before and been satisfied with it.

Spabond also sells at 30% lower price in Europe than the West products. 

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26 minutes ago, Russell Brown said:

Maybe you could get it back at a discount. I'm sure it's fine. What is the diff between the 275 and 276? I've used a lot of the 276. It has tiny grains of something to keep from squeezing all the epoxy out.

Checked with Hamish at West/Essex UK and he informed me the 275should not be used in this application. Have no idea for the reason, for this but the toughened epoxys like 175/276 is said to have better peel strength when heavily loaded. To me the 175/275 looks OK when comparing figures. The tiny grains(rubber?) might be to get the recommended bond thickness of 0.2mm or to give flex? 

"PRO-SET Assembly Adhesives are pre-thickened, two-part epoxy adhesives used for secondary bonding of laminated composites as well as steel, aluminum, cast iron, concrete, stone, and most woods.
Adhesives based on PRO-SET 175 Resin are paired with Fast (273), Medium (275) or Slow (277) hardener. They are suitable for most composite bonding applications.

PRO-SET ADV-175/276 and ADV-176/276 are Toughened Adhesive systems that deliver exceptional toughness and superior peel strength for heavily loaded applications and difficult-to-bond substrates including pre-preg, sheet molding compound, metals and most plastics."

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Spabond is good stuff and if cheaper/easier to get I wouldn't hesitate to use it for the initial bond. I would stick with something like Pro-Set LAM-225/229 or MGS 285 for the actual work of applying additional carbon to the outside.

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Yes, I know Spabond. Good stuff with high shear and nearly as high modulus as the Proset.

Comparing the two, both room temps; Better properties if you bake both.

Property             Spabond    175/276

Tensile                     37              44 MPa

Tensile Mod           2.85           3.16 GPa

Lap shear (steel)      29   13 MPa

Tensile strain          7.7        6.2

So.... Spabond is a better "glue" especially in shear. Proset is a little stiffer and a little stronger as a stiff resin.

Both are good. If I had to choose I think I'd pick the Spabond but not by much.

 

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I don’t know anything about carbon fiber but typically a mast is not made ‘for a sail configuration of XYZ’ as you state in your original post.

 

Mast design relies just as much on the righting moment of the vessel it’s on as that’s what the rig is working against. Two boats with identical sailplans but dramatically different righting moments will require dramatically different rig designs.
 

I see that you are plopping it on a tri (lotsa righting moment) and hoping you had an intelligent rigger verify the mast will be appropriate for that.  Seems like you are on the ball enough to either do that or already know it’s good enough.
 

 

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Have had a long mail discussion with Composite Technologist Martin Armstrong at Gurit UK. We came to the conclusion that you either do a long taper and laminate on the outside, OR as we decided, only go for the bagged inner sleeve made of the same mast section using SP 340LV HT. Note he recommended tapering the sleeve on the inner side.

Surely a professional job with laminating the outside would be optimal but I consider this to be second best using a mast I got almost for free.

This is the same method as CST uses on dinghy masts, but they use a dedicated and very tight sleeve without bagging: https://cst-marine.com/how-to-join-your-mast/

The FP mast is made with UD fibers on the inside and 45 degree biaxial prepreg on the outside, see image. 

We also decided to use a 2cm wide sleeve of the same mast section over the joint. It is absolutely not necessary, but as Martin said when I asked about adding it: 

"I keep think yes and then no – using biaxial reinforcement or cutting a 0/90 at 45 degree to the fibre – will give the best reinforcement of the joint, but is it required?
If I was doing my own mast I think I would put it around the joint – is it required? Most likely not, but it is not much extra weight and it would make me feel better when I am trying to get that last few percent from the boat."

Will receive the cartridge Monday and the  weather will also be cooler next week with temperatures just above 20 C, perfect for doing the job. Will then wait a few weeks before loading the rig.

 

 

 

 

 

 

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I've also seen sleeves for alloy masts where they don't taper thickness like a CF laminate but instead cut a V shaped notch in both ends and both sides of the sleeve (well rounded arc at the bottom of the V

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Hi Zonker,

I have had contact with Geoff Dobbs who earlier was president of Sailcraft Canada. He sailed with a joined Tornado mast without trouble for many years. As I have four broken F18 mast that I got for free, I was about to join pieces from them for this project, when I found the FP carbon mast.

A few pix of what Geoff and I decided on when using 4.8mm Monel rivets. The sleeve in the images is short and and a test of how to do the grinding&cutting. Was also to cut V´s at the ends of the real sleeve. Will try this if the extremely stiff carbon mast doesn´t work like intended.

sleeve.jpg.c3894537832e604dd8223179fd884608.jpgsleevmast.jpg.26f67865a0e6a7e3e6dec715ea0ce027.jpgflatmast6.png.84bfbf0fcd19507e480316052721432a.png

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Adding to the above, 25x2mm aluminium strips should be added at the sides and 20x2mm in the nose where the reinforcement has been grinded off. 

 

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Time to join the pieces. Just eight small clamps needed. The long alu clamp is  a piece from  cut up F18 mast. A 15x4mm T profile in the mast track. The bag in place with the connection coming out through the mast foot. The Gurit will arrive later today.

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On 6/27/2020 at 2:16 PM, chris95040 said:

I don’t know anything about carbon fiber

From the guy that can't figure out fixing a new mast step...................<_<<_<

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3 hours ago, mad said:

From the guy that can't figure out fixing a new mast step...................<_<<_<

The guy sent me a love letter because I liked your post:wub::D.

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Not the least bit fair - anyways i thought it went down like this:

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21 hours ago, revintage said:

The guy sent me a love letter because I liked your post:wub::D.

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Oh isn't that sweet :lol:

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Did a small conversion of the clumsy 8mm hounds fitting using a Fiberfoam A-cat T-terminal, before joining the mast halves. Cut the old one away using a angle grinder with plenty of water for cooling. I did the machine set up in friend Per’s workshop, he drilled the two holes and left the boring Dremel work to me.

 

 

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That's a pretty small terminal to be using in this application. I would have stuck with the original or looked for a beefier T-terminal, I'm guessing the loads on your trimaran foiler will be about double that of the A-Cat, based purely on a weight and righting moment guess, coupled with the choice of mast....

Where did Geoff break and repair his T mast? I'm asking as I have two damaged F18 rigs in my yard. I've been pondering what to do with them for a few years, I think cutting the good bottom off one and sleeving it to the other (compression damaged about 4' up from the base) would work well for a spare rig that has basically the same bend characteristics as a new rig.

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1 hour ago, samc99us said:

That's a pretty small terminal to be using in this application. I would have stuck with the original or looked for a beefier T-terminal, I'm guessing the loads on your trimaran foiler will be about double that of the A-Cat, based purely on a weight and righting moment guess, coupled with the choice of mast....

Where did Geoff break and repair his T mast? I'm asking as I have two damaged F18 rigs in my yard. I've been pondering what to do with them for a few years, I think cutting the good bottom off one and sleeving it to the other (compression damaged about 4' up from the base) would work well for a spare rig that has basically the same bend characteristics as a new rig.

The terminal isn´t that small, its diameter is 9.5mm with a break load of ca 2 tons. As I only sail in lakes with quite flat water, I am not the least concerned. About RM you are close, but the RM is not more than about 1.6 times that of an A-cat. With a jib and 1 m lower mast CoE of the sail plan will be lower. One big difference though, as the design wind of the A-cat is 14-16 knots, the design wind of my design is 22 knots. I intend to sail up to max 20 knots where the load will be in the ballpark of 1.4 times. But you never know, I might be tempted to add sail area ;-) . The rig will be using a wishbone boom, putting less load on the standing rigging, compared to a typical beachcat with 10:1 mainsheeting.

Geoff  found two defective mast laying at the factory.  Probably wanted to test his theories as he was an aerospace engineer(majoring In aircraft structures), ie he had the knowledge about riveting things together.

The joint was below the upper diamond fittings. I have saved all our conversations and started to make a "mast joining instruction" from that. Will go back to see how far I got. He also mentioned that the joint would be more resistant to buckling.

I guess it will be less demanding with a joint very low. Dobbs joined the mast where they mostly break, ie between the spreaders and the upper diamond fittings. 

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Revintage,

   The A-Cat class rules have a championship wind limit in the 22kt range, so that is what the masts and fittings must handle.

   If you don't mind sending me your mast joining instructions that could be very helpful. Yes, down low the tension forces on the mast are lower, the point they typically break at between the spreaders and upper diamonds is the point of maximum load on the rig, i.e peak compression and tensile loading. If the joint is sufficient there it will certainly work lower!

Best Regards,

Sam

 

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Hi Sam,

14 hours ago, samc99us said:

That's a pretty small terminal to be using in this application. I would have stuck with the original or looked for a beefier T-terminal, I'm guessing the loads on your trimaran foiler will be about double that of the A-Cat, based purely on a weight and righting moment guess, coupled with the choice of mast....

Did a ballpark calculation using Rm for stainless 316 and found the terminal would break at something like 4000kg, while stretching would begin at around 2000kg. So no worries:).

Sent you some info as Message two hours ago. Note that I implemented what Geoff told me in the sketch below and got OK from him.

 

flatmast6.png

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Went out to my backyard and the longest top I have is 6.6m when clean cut. Will probably build a 9.6m mast from that one, to be used with another project with 5.8 hulls and Inter 20 main(18sqm) and Tornado jib. I also have a NOS undrilled Marstrom alu Tornado mast tube, but the more aerodynamic section of the C2 mast is tempting to use.

The second shortest top is 6m and can be used together with a lower 1.9m stump for the tri, if the carbon mast doesn´t work.

Below is the pattern marked out on piece of mast tube.

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