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DIY carbon Bowsprit - best approach?

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What’s the easiest approch to building a short carbon bowsprit similar to the one on the link? I’m after a short code 0 sprit for my Prima 38.

Do I need a plug and mold approach with two halfs or can I ”simply” cover a plug with carbon and let it cure? As it will be white, any imperfections could be  filled and sanded before painting.

DoI need to bake it in an owen or will curing at room temperature be okay?

What about fittings, do I need to integrate stainless fittings to bolt it to the bow? And if so, how is that done properly? 

What is the best approach to make sure it fits the bow?

https://goo.gl/images/zFuppY

Any help or ideas on where to find a guide/ info would be very helpful - thanks!

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Layup a bow nose wrap as a base for the prod.   Shape high density foam (corecell) possibly with inserts for lines to pass and layup over that.   No oven cure needed.    Depending on the layup schedule stainless bolts can pass through with or without a G10 insert.

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what epoxy you will use? To get maximum from epoxy, do the post curing. If you don't have an owen, choose a epoxy with lower post curing temperature and make an simple insulated box with a open bottom and put few halogen reflectors under. They will generate enough heat for post curing

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If you look at the sunfast 3600 their bowsprit is more of a square section where the bottom is open. Pretty easy to make a mould, then layup your carbon, then fill it with foam and a carbon bottom skin if it shows signs of twisting. 

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@solosailor thank you very much, super helpfull! How did you bond the two parts togheter? What size is the boat? Would you see any problems building for a 2 ton load for a 38 ft boat flying a jib 0 from a halyard lock and 2:1 tack in the bowsprit? 

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@Alcatraz5768 I havn't choosen any epoxy, but an isolated box with halogen light sounds like a simple enough solution - thanks!

 

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56 minutes ago, Alcatraz5768 said:

If you look at the sunfast 3600 their bowsprit is more of a square section where the bottom is open. Pretty easy to make a mould, then layup your carbon, then fill it with foam and a carbon bottom skin if it shows signs of twisting. 

@Alcatraz5768 any idea on how much carbon you would need to get a construction like that strong enough? 

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How did you bond the two parts togheter? What size is the boat? Would you see any problems building for a 2 ton load for a 38 ft boat flying a jib 0 from a halyard lock and 2:1 tack in the bowsprit? 

Thickened epoxy bond.   Then more layers of carbon overlapped/tabbed/wrapped.   This was for a J/111 Code-0.   

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 any idea on how much carbon you would need to get a construction like that strong enough

How many square meters is the code zero? What is the SWL for your furler if you are using one? Will you use a bobstay?

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I would love to build one for my Andrews 43, but I won't start until I get an NA to do the engineering. Happy to build it, but cost of failure is high.  Mine would ideally have a through platform passage for the anchor shank.

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14 minutes ago, Zonker said:

How many square meters is the code zero? What is the SWL for your furler if you are using one? Will you use a bobstay?

Jib zero would be 45m2, I was recommended a 2 ton halyard lock, and to have a bowsprit that can handle the same lufftension  -  haven’t chosen a furler, bobstay - most likely unless you think I can do without :-)

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Get some engineering done before you do anything else, if you’re not competent as a minimum in composites, this may be a project too far for beginners. 

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Lot's of pieces to that puzzle. For wet layup over complex shapes, I've been using stitched biaxials or triaxials but they require vacuum bagging, IMHO. For post cure I use foam panels to make a rough box with gaps and shoot for 120F. Engineering your shape and layup, plus QC will be the hard part.

 

In case you're not aware:

https://trogear.com/

 

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21 minutes ago, lasal said:

Lot's of pieces to that puzzle. For wet layup over complex shapes, I've been using stitched biaxials or triaxials but they require vacuum bagging, IMHO. For post cure I use foam panels to make a rough box with gaps and shoot for 120F. Engineering your shape and layup, plus QC will be the hard part.

 

In case you're not aware:

https://trogear.com/

 

Please note the Trogear website recommends that you don't shrimp the kite nor expose the bowsprit to sudden shock loads. I'm guessing not really the answer for an ocean race boat.....

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26 minutes ago, lasal said:

Lot's of pieces to that puzzle. For wet layup over complex shapes, I've been using stitched biaxials or triaxials but they require vacuum bagging, IMHO. For post cure I use foam panels to make a rough box with gaps and shoot for 120F. Engineering your shape and layup, plus QC will be the hard part.

 

In case you're not aware:

https://trogear.com/

 

Every stage of that should be Vac bagged, especially the core to laminate bond. 

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13 minutes ago, Raz'r said:

Please note the Trogear website recommends that you don't shrimp the kite nor expose the bowsprit to sudden shock loads. I'm guessing not really the answer for an ocean race boat.....

From where he's at on the construction of a custom short sprit, he might check them out, not a recommendation, and he did say a code zero. One cool thing I noticed about the Trogear (which I have not used) for a code on a furler (which I have not used), is that they show the possibility of tilting up the sprit so you can reach the end and attach the furler, then lower with the bobstay. The OP linked to a photo of a nice custom sprit and it looked like it had non-skid tape every few inches for that reason.

Once again, not a recommendation, but Trogear's website shows quite a list of installs and they appear to be willing to discuss your application.

 

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Just make one. Put more carbon in if weight is not a thing, put less in if weight is really important, but be aware that you might have to make another one if it breaks. If you get an engineer involved it will cost more than having to make another one if you get the strength wrong. 

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I would recommend keeping it simple.  Do a splash of the boat and then use a carbon tube for the sprint.  Note you will want to play with the angle of lift to make it look right.  Once you have the tube bonded on add some carbon gussets to each side of the tube tying in the splash and 2/3 the length of the tube.  If you want the shape you have seen fill the area above and below the gussets with foam and hand shape.  A couple layers of db over the whole thing and you have a solid prod.  From an engineering standpoint the round tube is easy to crunch the numbers to determine the laminate

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Yes, I kind of like the approach of using a simple pre made carbon tube. A carbon tube supplier might be able some very simple calcs assuming a breaking load = furler max SWL x a SF and a bobstay. Much easier than learning how to do a good layup in carbon....

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3 hours ago, Bruno said:

Dragonplate square tube

Long square tubes, in any material, have a twisting issue. Tend to fail in unexpected ways. That’s why such spars are always round. Unless someone knows otherwise for this specific application...

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Last time I looked Dragonplate was hopelessly expensive for what you got. Lots of PR bullshit on their website.

For this application I think it's short enough you could use a square or rectangular tube. Maybe add more unis top and bottom because most of the load is bending in the vertical plane. Might be somewhat easier to laminate the taping from the tube onto the bow splash.

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On 9/1/2018 at 1:01 PM, daddle said:

Long square tubes, in any material, have a twisting issue. Tend to fail in unexpected ways. That’s why such spars are always round. Unless someone knows otherwise for this specific application...

One of the most interesting things I learnt from reading a very good book on racecar chassis design is that square tube only has a reduction in torsional strength of about 4% over similarly sized round tube. Surprised me. 

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4 hours ago, Alcatraz5768 said:

One of the most interesting things I learnt from reading a very good book on racecar chassis design is that square tube only has a reduction in torsional strength of about 4% over similarly sized round tube. Surprised me. 

That is surprising. Square sections have seemed quite twisty to me. Was it strength, or stiffness, in your data I wonder?

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The theory was, I believe, that a closed in shape is fine but an open shape like a channel etc was next to useless for torsional rigidity. The nature of the shape didn't matter too much. 

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