Author Topic: Project Cedrus - Hollow Carbon Masts  (Read 5974 times)

Admin

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Project Cedrus - Hollow Carbon Masts
« on: July 23, 2020, 03:27:52 PM »
A friend on the beach just got a 90 cm Project Cedrus carbon mast for his New quiver of Lift foils.  Very impressive.  This thing has very low twist and is very light.  It is very stiff.  Looks like they are compatible with most foil brands. 

https://projectcedrus.com/compatibility/

Phils

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #1 on: July 23, 2020, 03:51:49 PM »
Only negative I know of is that they are reportedly a bit draggy

PonoBill

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #2 on: July 23, 2020, 04:58:57 PM »
That's a mast design I was working on until I discovered someone else was doing it and was already way ahead. Two channels glued face to face to form a rigid box with the leading and trailing edges being non-structural. I suspect they are not tapered--the easiest way to build it would be as long channels that you cut to length and then glue face to face, with or without a stiffening cross-brace between them. It could be done as tapered sections but the cost-saving element of the idea was to cast in long sections and then cut to length.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #3 on: July 23, 2020, 06:25:52 PM »
Contrary to what a lot of non-foilers think, I have never been hit or even touched by the leading or trailing edge of the mast.  In my opinion, flexible edges is solving a problem that doesn't exist.  Not only that, stiffness is the number one issue here.  Not extending the structural carbon all the way to leading and trailing edges will seriously limit the torsional stiffness (bending stiffness will take a minor hit as well).

PonoBill

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #4 on: July 23, 2020, 06:49:12 PM »
Actually, you've got that backwards. A box section is much stronger and resists twisting and bending better than two curved plates joined at their ends. A box section is essentially two I beams connected together. Every modern airplane wing is constructed this way--the leading and trailing edges are non-structural. Making the leading and trailing edges out of softer material is just a side benefit.

« Last Edit: July 23, 2020, 06:57:03 PM by PonoBill »
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #5 on: July 23, 2020, 07:31:34 PM »
actually we're both wrong!  I spent the last hour putting this into my structural simulation software because torsional stiffness is notoriously difficult to predict with back of the envelope and I was having second thoughts.  I found that the two below profiles are almost identical in torsional stiffness (within simulation error bounds).


this calls for some more looking so I'm going to stay up late and do some more sims tonight.  If we could reduce wetted area with the same stiffness, that'd be the ticket...

Admin

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #6 on: July 23, 2020, 09:54:52 PM »
I can tell you for sure that this is the stiffest carbon mast that I have twisted.  It is very impressive in that measure.  I didn't ride it but I could see what Phil said about drag being higher.  It was wider and thicker at the fuselage than the Axis Carbon masts (which I love). 

Another friend on the beach has an MFC setup which looks really cool as well but the carbon mast that he has is incredibly soft.  It twists significantly under light hand force.  I have never felt the Lift mast but where there are great foils and soft mast options only this might be a terrific option.

Phils

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #7 on: July 24, 2020, 06:35:52 AM »
I should qualify my comment about drag by saying that as far as I know, the draggy sensation has only been reported by kitefoilers on relatively small foils.  For the much bigger foils used for winging/SUP, it might not be noticeable.

Kyle's masts are known for being super, super stiff.  He has also done a great job of identifying some of the softer masts on the market and developing adapters for them.

AGK

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #8 on: July 24, 2020, 06:53:04 AM »
I have used a 27 inch first-generation Project Cedrus mast with Cloud 9 foils for kiting for two years, and now with Axis foils for winging.  So far performs equally (as far as I can tell) with the very good Axis aluminum masts, but significantly lighter.  Excellent craftsmanship and Kyle has been great to work with -- I've been, and continue to be, a very satisfied customer.

PonoBill

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #9 on: July 24, 2020, 08:03:28 AM »
actually we're both wrong!  I spent the last hour putting this into my structural simulation software because torsional stiffness is notoriously difficult to predict with back of the envelope and I was having second thoughts.  I found that the two below profiles are almost identical in torsional stiffness (within simulation error bounds).

this calls for some more looking so I'm going to stay up late and do some more sims tonight.  If we could reduce wetted area with the same stiffness, that'd be the ticket...

Cool. Try bending it in your simulation, though even if you just look at the two structures you'll expect much better stiffness from the box structure. The box structure has 90 degree ribs, the plates are stiffened only by the curve.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

BayAreaKite

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #10 on: July 24, 2020, 08:54:52 AM »
Thanks everyone, I appreciate the kind words, positive feedback, and good discussion. Forums are really valuable tools for me to discuss and market Project Cedrus, and I appreciate your willingness to let me comment.

Regarding drag... the mast is 19mm thick with a chord length of 120mm. This is coincidentally the same profile as the Axis mast. I worked with an America's Cup foil designer (I am a structural engineer, and not a CFD/aero expert) to optimize the section shape for stiffness, strength, weight, tendency to ventilate, and drag, in that order. The only people who have noticed the increased drag are kiters coming from small and fast wings (typically Moses) mounted to my mast. But at the same time, they are grateful for the increased stiffness so the tradeoff was worth it to me. My lift customers notice no reduction in top end speed, as those wings are a slower than Moses. So it's definitely wing-based, which makes sense as mast drag is only one component of total foil drag. 3 years ago I saw the direction of the sport towards bigger, slower, high lift wings, for which I designed Project Cedrus. Now the other brands are trying to catch up with stiffer masts, which will come at the expense of speed. I have a post related to drag here: https://projectcedrus.com/cedrus-development/aero/

Regarding stiffness, this is an area that I consider myself an expert in. You give up very little stiffness/strength by going with non-structural leading/trailing edges. That material is closest to the neutral axis of the beam, and therefore not contributing much to torsional or bending stiffness. I am confident, based on benchmark analysis and testing of various masts that Project Cedrus is the stiffest mast on the market. The Axis aluminum mast is up there as well, but 2x+ the weight. The safety aspect of the non-structural edges is only one. The primary reason for soft plastic edges is damage tolerance and durability. I got tired of repairing foils and fairing the edges after rock chips or damage due to flotsum. In larger quantities there would be more of a cost savings as well, but because I'm small batch production it's not really a $$ thing. A similar post on structural sizing can be found here: https://projectcedrus.com/cedrus-development/sizing-analysis/

Happy to answer any additional questions and thanks again for the positive feedback from my customers. This is a labor of love for sure, thank you for your interest and openness. Kyle


jondrums

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #11 on: July 24, 2020, 09:29:27 AM »
Kyle - thanks for posting those blog post links - great detailed information.  It gets me excited for sure!  the 19mm chord thickness is the key to this I think.  I'm only experienced with the GoFoil mast, which is 15.5mm thickness x 140mm.  Of course the other variable is wall thickness or number of layers of layup, etc.  So my analysis above was really not taking into account reality of what you've done.  From what I see on your website, it sure looks like you've done the work

The key metric I'm after is stiffness (bending and torsional) to drag ratio.   Drag of course is going to vary with both wetted surface area as well as foil profile.  I've been thinking for a while now that a lot of the masts out there haven't nailed this yet.  To me weight is somewhat secondary - once we go from aluminum to carbon, adding a few more layers isn't going to impact the weight substantially.

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #12 on: July 24, 2020, 09:32:12 AM »
Regarding drag... the mast is 19mm thick with a chord length of 120mm. This is coincidentally the same profile as the Axis mast.

Hi Kyle,

Happy to have you here.  You have built and impressive mast!  I twisted your 90 on the beach alongside my 96.  Yours is stiffer.

Did you mean that the above dimensions match the Axis aluminum masts?  The Axis carbon ones are thinner and with less chord that the aluminum ones where they stay wet.  The drag difference is notable.  Possibly that is an unavoidable tradeoff?
« Last Edit: July 24, 2020, 09:33:49 AM by Admin »

BayAreaKite

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #13 on: July 24, 2020, 09:38:38 AM »
Thanks Admin. Yes, I was referring to the Axis aluminum mast. Their carbon mast is solid, so they can get away with less chord/thickness. I understand weight may not be an important factor for all. For me (and my 105lb wife) weight is really important and thus it was the primary optimization variable. We have longer walks to the beach, flying to MX with kite gear, and general ease of use improve dramatically with a lighter weight mast. Of course as a kiter on a small board this is a very different scenario than a big SUP.

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Re: Project Cedrus - Hollow Carbon Masts
« Reply #14 on: July 24, 2020, 10:02:59 AM »
No doubt.  Weight savings is a huge benefit.  What is the weight of your 90 with a Axis adapter and a track plate?

 


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