Brainstorming home construction methods of curved foils.

Posted By: Seeker

Brainstorming home construction methods of curved foils. - 12/23/11 07:55 PM

I am looking for feedback/input on ideas for construction methods. In the process of building my F14, I have come to the point of needing to put in the dagger board trunks before moving forward.
Since this is a topic that many might be contemplating, possibly to revive an older boat (particularly an “A” cat) and there are some knowledgeable engineers/designers that check in on this board, I thought to explore the possibilities:
1) See if anyone has built successful curved dagger boards and their trunks (with fore/aft head adjustment) in a backyard/small shop scenario?
2) If so, what was the proven method? What lessons were learned along the way to make it better/easier/more precise?
3) If no one has done it without the advantage of CNC molds…what technique would give the fastest/easiest/most precise foil construction method for an accomplished craftsman in glass/composites?

Please keep in mind that this is not an AC funded undertaking and any expense that can be cut out of the plug/mold build process will be positive.

At this point I have determined that Curved boards are a non-negotiable for me. I say that just to keep this thread on track...I am not at all interested in debating straight VS curved board ...If you believe that curved boards are a waste of time and are just a fad, I respect your opinion but ask you do not bring that fight here. I am looking for collaboration to solve a problem ….to identify the best curved dagger board build method without CAD/CNC.

That being said I have determined to use a 1.45 meter radius, a cord length of 175mm, a cord thickness of 12% and a foil profile of an Eppler E836 (thank you scarecrow for the conformation on those choices!). I have built a male jig of the proper radius wide enough to layup two boards side by side if necessary. Rather than building two “one off” boards that are very labor intensive and leave myself open to going through the whole process from scratch again, if one is damaged or destroyed, I would rather make a female mold that I could use to reproduce the exact boards if necessary.

So far I have considered the following:
1) Building a female mold directly off my jig
2) Building two male plugs off the jig (one for port and one for starboard) then making female molds from that.
3) Build one male plug and one female mold that both boards can be built from (by using a blunt tip) which would also mean the board could be used on either side in an emergency. Acknowledging that it would be slightly less effective than a ¼ radius profile on the tips. As the jig is already built I cannot, (do not care to scrap and build another jig) lengthen it to accommodate radiusing the tips on both ends of the mold.

If a plug/mold method is chosen:
1B) Build the plug out of wood core/glass. (Concerned about possible instability of foil when laying up mold)
2B) Build the plug out of foam/glass (concerned about possible instability of foil when laying up mold if high quality/high density foam was not used)
3B) Build the plug out of solid glass (for stability, would require a great deal more effort in shaping and refining plug).

Also interested in any dagger board layup schedules in 100% carbon or carbon/S glass one has successfully used , even if for straight foils realizing that curved foils will put additional stress on them and require strengthening.

Serious comments and suggestions are greatly appreciated.

Best Regards,
Posted By: TheManShed

Re: Brainstorming home construction methods of curved foils. - 01/19/12 02:19 AM

So I'm not the only one who has gone though this mental exercise!
Posted By: Seeker

Re: Brainstorming home construction methods of curved foils. - 01/19/12 05:32 PM

Mike I have a parallel thread on sailing anarchy under the same heading name, 75 posts with a lot of different ideas on the subject. You may find something of interest.

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