Epoxy/glass mast for a cruising yacht?

[Inquisitor]

I like the sheep analogy!

Also, you being in another time zone, just means we can tag team!

Anyway... attached is an updated version. All I have done is tried to clean it up and describe the values a little better. No changes to the analysis. So the LPT done in the above still stands so far. Please let me know what's fuzzy. Don't anyone be bashfull!

Please anyone/everyone – feel free to change, comment, and critique the spreadsheet. This is meant to be a team effort.

I'm going to try to read the chapter on rigs this weekend in "Principles of Yacht Design” (POYD from now on… and yeah, its been a great help to me). Maybe I'll be able to at least understand which parts you're describing. These nautical terms are kill’n me! Line, sheet, halyard, stay… these are all ropes or cables… right? Hopefully we'll be able to start some tuning of the mast geometry... taper and thickness variations.

From a practical standpoint, it might be a good idea of what “stuff” you need attached to this beast or other features.

Spreaders - I know about the spreaders. Although, do you want to consider only one spreader… if feasible or are you going for a “look”. Every time I see a stay, I picture in my mind... POYD p. 146.

Track - I currently am sailing a Hobie 16’ so I see there is a track. In my case its a round slot for the rope built into the edge of the sail to slide up and down. I assume there are many styles.

Pulley at the top for the main’s halyard.

Several pick-up points for stays.

Do you want the pulling side of the halyard to be inside the mast?

Do you want a conduit so you can run wires for mast lights/radar or whatever else people really need on top of a mast? Enlighten me… cause I don’t have a clue of the practical side of cruising.

Can you give me pictures of any of these things? I like to be able to visualize what we’re designing.

[Robjl]

Quick reply... I'm trying to finish the rest of the boat. Double spreader rig because the mast.. say 240x160mm would have to be larger in a single spreader rig to get the required stiffness, this is the norm(on 40-50'cruising yachts) and so looks right. Also shroud angles get lower, tension gets higher and mast compression goes up!
Attachments vary.. I'd like to use "T" ball connections on the lower shrouds, cap shroud and intermediate shroud but don't know if the locally beefed up composite would take it, frankly I have concerns asbout their suitabilty, but just don't know. Forestay,twin backstays connect to masthead fitting, Spreaders are connected to the mast to allow for minimal movement. Eveyone has seen the slack shrouds on the leeward side, I personally don't like rigidly attached spreaders as I think it is an obvious fatigue point. Yes you need conduit in the mast for: Tri-colour at the masthead, antennas VHF & UHF, radar, Wind instruments etc. 1.5"minimum conduit seems excessive but is my choice. Also internal halyards, We'll need main halyard and topping lift aft and two genoa halyards and a spinaker halyard at the front..all internal ..all pretty standard. I've got the '96 version of Princ of Yacht Des. My rig is similar to what they illustrate on p200 Fig10.15 YD-40 rig.
With standing rigging, generally considered as the fixed wires/rods that hold the mast up, the wires that are oriented for&aft are called stays and the wires that hold the mast sideways( ie across the vessel) are called shrouds. For a cruising yacht 1x19 ss is fine once the loads are analysed the rigging can be sized. Forget rod rigging and exotics.
For Hull shape I used Prosurf and was very happy with it. But all my working drawings are on a CAD program called CADSMAN, it doesn't export very well. I'll see what I can do.
As to the spar I think we need rig design software and material strengths, If the design won't work with everyday readily available materials like epoxy, vinyl-ester,unidirectional, tri-axial or double bias glass, forget it.
The problems of a mandril mould (I've got some ideas there).. and vacuum resin infusion are enough for the one-off DIY.
All ideas welcomed.

[chandler]

I don't believe you can leave carbon or glass uncoated due to U.V. for any length of time.

[Inquisitor]

You are certainly correct. The fibers are practically impervious. However, the UV breaks down the resins which support the fiber and without the resin, its back to pushing a rope again. Dark paint is also bad. As it transfers too much heat which can reduce the resin's strength. That's why you generally only see fiber/epoxy boats and planes in white... at least on top. However, there is at least one plane manufacturer that permits darker paints on top, but they use autoclave (pressure and 350F cure epoxies).

So yes, we should paint these puppies (fogot... sheep) white!

[D'ARTOIS]

First of all Inquisitor, my sincere compliments. Your writing is clear, understandable and convincing.

I work with carbon from the beginning of '67 when it came around in aircraft production, together with the first industrial qualified epoxies.
I made a huntingbow for my sister using hd carbon extracted from the B1 in combination with SP epoxy and made a nice laminate that pushed an arrow through the doors of our garage and the backwall (both 1" fir) and still had sufficient power to disappear.

I think, but that is purely personal, that carbon lays up easier than glass. Sometimes glass turns out to be cohesive and bonds difficult.

For using carbon, the environmental conditions must be close to laboratory; i.e. draft, temperature changes and moisture must be controlled and adjustable. Actually, the same counts for glass/epoxy, in a lesser degree for glass/poly resin.

Such conditions, that can be met only in premises like those of NASA, or, otherwise in autoclaves, means that there is much more attached than - what you call so precise - "backyard engineering" -

I believe that he use of carbon, although very justified by your prior explanation of its advantages - is not for the amateur, unless (he or she) is prepared to set up a lamination station carefully.

Some years ago I was involved together with one of the foremost known shipyards in Holland that produces world top rated sailing yachts in a study of making a high tech expedition yacht for a single voyage through antarctic conditions.
To produce the mast for this vessel, I thought of making a Titanium TiVa4/6
core and a carbon outer skin, the core to prevent buckling and exploding and the outerlayers of carbon to add strength and stiffness.

The same process have been executed in the making of extreme light racingbikes frames.

What would your thoughts be reading this? Finally we didn't dare to pull through, later on the company bought a mastmaking factory (carbon and alu)
nd did have the technology.

Let's be clear: many top dollar yachts are now provided with carbon masts; but it still is something that requires a lot of knowledge and experience.

[Inquisitor]

Thank you D’Artois for the complement. In the short time I’ve accessed this site, I have spent many hours trying to soak it all in and I've only scratched the surface. I have been overwhelmed with the member’s analytical sophistication, man-centuries of experience and humor in any and every aspect of boating that I could possibly need. It gives me great confidence that I can successfully design, build and sail anything I can dream up. Any weakness in a field or technique I can just turn to this forum to fulfill. I wish any of my employments had been this open. I am only too happy to offer my abilities and time into the soup!

Hunting Bow – Jeeeeze! Your parents must have had a royal conniption! I gather, no dead bodies turned up in the next block.

Carbon layup – I have no personal experience on that one. I have only used room temperature resin with glass. I only used pre-preg for all others. Although, I note that Stewi (in an above comment) felt that glass “showed” that it had taken resin easier than carbon. As I’ve stated my issues:

· Mismatched CTE
· Large interlaminar stresses
· Microcracking type fatigue.

I won’t be using carbon, if we can’t get the glass one to work. My pockets just aren’t that deep. I’ll use Aluminum.

Titanium/Carbon hybrids – Very high tech. At one company in the early ‘80s I did some research using boron fiber and metal (no epoxy) as the matrix. We evaluated both aluminum and Titanium in that case. Also we often attached carbon/epoxy laminates to Titanium tabs. Wing skins of the AV8B Harrier to the Titanium wing root fasteners. Titanium works far better in bearing than any composite! The Titanium was gorgeously machine stepped scar joints so that individual layers could be terminated on various steps to reduce stress concentration factors. During the Regan years, I designed a high pressure torroidal (donut) fuel tank for a proposed kinetic energy, killer satellite. It used a nickel liner with a carbon/epoxy laminate. The tank actually surrounded the neck of the rocket motor to make a compact vehicle. Very interesting stuff! It’s been a long time, but if I recall correctly, matching stiffness and CTE between C/E and Ti was pretty easy. No big stiffness transitions like C/E and Aluminum… always a major headache!

I would have no qualm designing and building a C/E mast if I had access to an autoclave, clean-room and prepreg! But like my main premise for this thread… Why spend 20 times the money for C/E when I can get the same bending stiffness by thickness and mainly radius increases. Axial stiffness means next to nothing in mast design and the extra weight should still be less than a constant cross section aluminum tube. But only time will tell.

[D'ARTOIS]

Long time back, to be precise in 1988, I met during the HISWA symposium the late Gary Mull, well known US naval architect from San Francisco.

At that time I was in a heavy dispute with some marine-engineers about the use of welding versus riveting and glueing. At that time, Conny Van Rietschoten's Flyer was transferred into Alaska Eagle, whilst Conny was thinking about the building of Flyer II - in any case Gary was witnessing our dispute and started to laugh.
Later on he said to me - "Look, in yachtbuilding everyone tries to make things more expensive. I work sometimes for NASA and we are making fueltanks from paper."
These were more or less his exact words. In other words: keep things simple!

You name boron.

I have been in a Russian laboratory (Russians are probably 25 years more advanced in metallurgy than any other country, only they don't know it) where experiments with Boron as a metal were carried out. They said that Boron would be the metal of the 22nd century, just like titanium now. Boron is twice as light and twice as strong as Titanium.

I am therefore very much interested in your knowledge about carbon/titanium bonds. It does not surprise me that they were alread experimenting with the two in the '80s. I just think about the SR72(?)

About the hunting bow: yes, we live on a large piece of property, sissy is a very strong girl and she could easily pull the 100 pounds of the bow. I used a very rare african hardwood for the middle piece, zebrano, and the carbon for the arms, with titanium bolts to fasten the arms to the middle piece.

[Inquisitor]

Well it’s a sad state… that much of the world is going more high-tech and for no real good reason. Although the US is probably the worst in this situation, we are not near the only one. Look how many things use carbon/epoxy for cosmetics. BMWs and Porsches with C/E dashes. Golf clubs made of Titanium and C/E. Fishing poles out of C/E. Let’s get real! Does anyone but Tiger Woods really need C/E. Does a fish give one tinker’s damn about being caught on a C/E pole. It’s purely about discretionary money and lets sell it to Bill so he can brag about it to the Jone’s next door. C/E is great stuff… in the RIGHT place and the RIGHT amount and the RIGHT laminate! Getting all those rights right is the problem!

I’m off my soap box. I feel better now.

It’s been a long time, but I don’t think Boron will ever do what the Russians were saying. If I remember correctly, its rather toxic (I’m not sure if that was the substance itself or the process of making it and the by-products) We probably couldn’t produce it here in the US.

The Boron we used was created by using fibers out of silicon-carbide (instead of carbon) that were then vapor depositioned with the boron. The resulting fibers were EXTREMELY brittle and rather large in diameter as compared to glass or carbon. Looked like sub 1mm pencil lead and about as easy to break. They were fantastic in compression properties because they were like rigid columns. They didn’t need the resin to support them like carbon or glass. Obviously, they’d be the substance of choice for high-tech masts. They’d put carbon to shame!!!!

Carbon/Titanium bonds were ALWAYS done with a film adhesive that was cured along with the C/E Laminate/Titanium. The Titanium had to be specially prepped… but I don’t recall the prepping or the adhesive name. If everything was designed/prepped right, failure would occur in the Titanium. We designed it that way since the Titanium had better reproducibility of failure.

[Robjl]

Carbon,Boron Titanium,
I must be looking on the wrong thread.
I'm thinking maybe the CIA got to you.
Four posts with no mention of G/E.
Yes we know it it won't take UV... makes you wonder though why in so many uses it is exposed, dashboards, fairings, ... couldn't be used for appearance ...that'd be silly, that would mean it was just opulence.
I feel better now too.
Back to the spreadsheet, you don't mean change the blue figs in B67/68/69 do you. Sorry don't get it still, but I did warn you about my math.
It's 5.30 Sun here, I'll just cut out the last longitudinal bulkhead and be back.
See-ya.

[stewi]

This appears to be a workable project and I’ll leave the discussion forum of a “long term passage maker” to contribute and exercise in this project.
If Inquisitor does the math, than I would like to give some practical input.
File sharing: I could look up the file format of CADSMAN, but it would surprise me if I could not import the file in ACAD or Solid Works.
If we adapt the building method over a foam core, than the foam sections can be cut with a hot wire method along plywood ribs. In order to cut the holes, a path has to be cut for the wire. About 2 foot sections can easily be cut and I could come up with 20 sectional drawings for a 40 foot mast.
Fiber glass conduits for halyards and cables can possibly bought off the shelf , but I guess, eventually we’ll come up for a method to build them as well.
Along in the project, we may teach each other in the correct terms for ropes and lines. Although I know all sailing terms in German, I don’t know all the terms in English either.
The track for the main cars appear to be a bit challenging and we’ll certainly avoid drilling holes and attach an aluminum profile.
I propose to put down some layers of fibers, than glue in a strip of soft wood like balsa wood. When everything is done and cured we could use a router bit to cut a groove and than use a T-slot mill bit to cut out the wood.

[stewi]

For an aluminum mast I was using two L-profiles for the mast head.
For a fiberglass mast, we can hopefully come up with a better concept.
Is the mast going to be deck stepped? Should we exit the halyards in the mast foot?
How much is the mast to be tapered? Should it be tapered only from the second spreader on?

[Inquisitor]

You’re right Robjl, if we need Titanium/Boron, we need to take that to another thread. However the analysis we’re creating here will be generalized and someone wanting a carbon (or boron) mast can knock themselves out with it… sorry… knock one of those out also.

I know this sounds like a broken record, but I don’t want anyone making a mast without knowing what they’re getting into. At this stage:

1. the analysis is not based on actual loads of a boat… yet.
2. it is based on mimicking a known (properly sized and safety factored SF) aluminum mast.
3. nominally E-Glass/Room Temperature Epoxy, but is generalized to use any fiber/resin combination.
4. It checks axial strength in compression
5. It checks for the product of Modulus of Elasticity and Moment of Inertia (EI)
6. It allows the user to size the cross sectional dimensions of the composite mast until the margins are greater than 1.
7. It only uses the contribution of the zero degree plies of a laminate.

Advantages of this method

• It already has the SF built in.
• Simplicity.

Disadvantage of this method

• Does not have variable cross section
• We don’t know what that SF is.

Robjl – I’ve simplified the spreadsheet and renamed it to Mast Study 3.xls (attached below). I realized with this type of analysis (sized based on an established aluminum mast) we really don’t need to know anything about the spreaders. We are only sizing based on the existing cross section. So I’ve taken that all out (in this iteration)

Basic Instructions for using the spread sheet.

1. Work it from top to bottom. I’ve highlighted the entries in blue that you should or will be modifying.
2. Section 1 - Confirm the aluminum properties. All aluminum’s stiffness properties are pretty much the same. However their axial and shear strength properties are different (sometimes drastically). You should confirm what type of aluminum mast you are trying to copy. Drop a message on this thread if you can’t find properties for what you have. I or someone else may be able to get you something more accurate. If there is a difference between tensile and compressive yield strength, use the compressive one.
3. Section 2 – Enter your aluminum mast’s cross sectional properties. It currently only supports an oval. However, if you have specific values of A, Ix, and Iy from the supplier you could feed these in also. The length (L) is only for weight estimation, so you could just put 1 in if you don’t have that one yet.
4. Section 3 – Calculates the axial strength and EI values of an aluminum mast.
5. Section 4 – Composite Material Properties. As I’ve noted about a dozen times, these values are too optimistic for room temperature cure epoxy and even more so for polyester or vinylester resins! The stiffness ones should be pretty close. However strength ones may be half this value of 1.08E5 psi!
6. Section 5 – Here you can change the dimensions of the composite mast. Using %increase just modifies the x and y so you can quickly make changes that are relative to the aluminum mast. (Yes Robjl, you were right these are the main ones you want to change. They are now B48-51.
7. Section 6 – Here are the composite mast’s analysis. The margins (in red) indicate relative to the Al. Less than 1 – less strong. Greater than 1 – more strong.

Currently, it has Robjl’s aluminum mast in sections 1 & 2. And the geometry of the composite mast is identical to the aluminum. As can be seen (if you look at the margins) that it takes 0.24” thickness of zero degree plies and these plies weigh as much as the Aluminum mast. Obviously we have to increase the x and y dimensions.

Robjl you proposed a 50% increase in the x and y dimensions. Put 50% in (B48) and then fiddle with the thickness (B5) until you get margins > 1.
Next Steps

1. I’ve read through the POYD (I must have a first additon 1994) section on Rig Construction (Chapter 10) It all looks pretty strait forward.
2. I can start basing it on actual loads.
3. I’m thinking I may have to put this into a program since to do it for a general case, it really needs to have the LPT analysis of a laminate and it needs to handle other cases. eg I want no spreaders for the Hobie 20’ and am looking to do a no stay or no shroud mast for the 40’. For now, we’ll keep doing the spreadsheet for your design and I’ll have to run the LPT for you here.

Good Luck.

[Inquisitor]

Guess it'd help if I supplied the spreadsheet.

Da!

[Inquisitor]

While I’m slogging through the POYD rigging design chapter and getting it into the spreadsheet, it would be a great time to instigate a fabrication side of this project.

I hope someone else can take lead on this aspect. My background with room temperature epoxy techniques is nil. So with that…

1. I’m going to put in some technical requirements.
2. And, then I’m going to make some fabrication suggestions.

Technical Requirements

• There is no way in the world the zero degree plies can be made with cloth! The weaving is basically in a pre-buckled geometry (up, over, down, under – A nice sine wave). It is considerably less stiff and WILL ruin your day if you make a mast with it. I believe (meaning, I’ve never had it in my hands) there are some materials that have like a 99.9% zero degree fibers with an occasional (barely visible) cross tread. This might work. If someone knows what I’m talking about and has pictures or a web site, I’d love to see it. Properties would be a blessing! However, I am also thinking just a spool of glass thread. I’ll explain down below.
• The zero degree fibers must go from one end of the mast to the other. No butt joints. No lap joints.

That’s it! The entire key is the zero degree plies being as perfect as possible. The cross plies, though important don’t really contribute much (directly) to the major failing condition – Euler column buckling. They are there to keep the zero degree plies happy and together.

Fabrication Suggestions

Here are some thoughts – shoot them down at will. Not my background. I’ll learn from you all!

As you see I’m a little anal-retentive about the zero degree plies. I was worried about the little sine waves. I am worried about the big ones too. Waviness! I’ve carved foam and slathered epoxy on it, laid the cloth, squeegee more epoxy and low and behold the weave wasn’t strait! Go figure… I ain’t perfect.

I like the foam core idea Stewi mainly because it solves the local buckling problem completely. However, not to lay the fibers on directly. I think they’ll be too wavy! Now, you all might just pat my hand and say, “We’re damn good and the fibers will be strait.” Well, that’s all well and good for your masts. Mine… will have a bad lay!

I don’t have a good/quick CAD package, so I’ll just rig something up and take photos…

1. Rig up two “end pullers” something stiff like re-bar. You’ll get the idea and make it better. They must be at least as long as the circumference of the mast. So in Robjl’s case of his 50% bigger composite mast, they’ll need to be at least 37 inches. Separate them by the mast’s length (56 feet in Robjl’s case). (See "Mast Fab 002.jpg")
2. Wrap the glass thread or the 99.9% uni-cloth around them till you get the thickness you require. Stretch them enough so that all the “stuff” is strait.
3. Slather them up. Maybe have some fixtures that pull tight and rotate so you can turn them over and slather both sides.
4. Lay them on the Formica floor. (I’ve read somewhere that Formica makes a great release surface for laying up flat panels)
5. Get some other re-bar to press the top layer onto the bottom layer of fibers. (My beutiful assistant will now put the hundreds of pounds force needed to stretch the glass fiber over the 56' length and simultaneously press the top layer onto the bottom in "Mast Fab 003.jpg")
6. Vacuum bag and let cure (under tension).
7. Peel back the vacuum bag
8. Release the end puller tension.
9. I’m guessing (hoping) this zero degree laminate will spring back and hopefully “pop” off the Formica.
10. Apply the +/- 45, then the 90 degree layer of glass cloth/epoxy.
11. Vacuum bag to the Formica and let cure again.
12. Debag and hopefully you have a real flimsy panel.
13. Now take the foam core of the desired cross section and bond this flimsy panel with off-angle plies toward the inside. In my example, I’m thinking its ok to have the conduit touch the out side panel, maybe even gain some added stiffness because of them. Need to evaluate if we can get a good bond to an aluminum track or to try and make the track out of G/E. (see CrossSection.GIF)
14. Apply your -/+ 45, then the 90 degree on the outside and bag it again.
15. Wham, Bam, thank-you mam… take pictures of our baby and send them to me! I’ll have the cigar waiting!

My two cents worth… Go for it!

[Robjl]

I have today spoken with the high priestess of composite design here, she is I think an AE!! who consults for a major composite material supplier. All off the record of course as no-one wants to take possible liability.. we all understand that.
However I got the following:
For a mast:
1. 70% @ zero degrees/20% @ 45 degrees/ 10% @ 90 degrees.
2. Inner and outer fabrics to be 45/45 Deg.
3. Safety factor use 5.5
4. Hand layup of stitched fabric like double bias (45/45) = 50-52% fabric!
Hand layup of unidirectional fabric (0 deg) = 55% fabric
Hand layup +vacuum bagged add 5%.
Vacuum resin infused -5% !! but higher strength.
Figures of strengths to follow.. will advise.
Any comments from those in the know? How does that sound?