We have in previous posts written about our concern with the bobstay that is attached from the waterline to the bowsprit. I have always considered this to be a weak point of the boat since the force of an impact here would be transmitted to the mast and rig and in a worst case scenario would damage the attachment points of the back and forestay. After our experiences in the ice of Greenland we realised that we will not be able to avoid ice collisions and in some conditions may need to purposefully ram ice. Therefore we are reinforcing the stem of the boat with a stainless steel cap so we can attach the bobstay higher above the waterline.
We will hire a smith to manufacture the cap in 3 mm steel to cover 30cm above and below the waterline and attach it with several through-hull bolts. In the middle of the steel cap we will have a triangle of 10mm steel to attach the bobstay. The triangle will also act as a ram.
The thought of jointing two materials with through-hull bolts below the waterline is not appealing so if anyone has any ideas or experience of doing something similar we would be happy to hear from you. Another question is how the steel cap will be manufactured since an asymmetrical bowl shape cannot be rolled.
I agree with your concern about the stress of breaking ice with the bobstay being transmitted to the rest of the rig.
The cap you propose would seem to protect the bobstay when breaking the smooth ice that forms on the surface of the water in harbor. It would not seem to be much protection against collision with a bergy bit, or pack ice.
I faced a similar problem with Issuma (there is a video of her breaking ice with the bobstay being strained at http://planetyou.discoverychannel.ca/mediadetail/3593633). To work around it, I moved the jibstay off the bowsprit and removed the bobstay. That worked well, though added complications to tacking by having two headsails so close together (almost side by side).
Before moving the jibstay off the bowsprit, I considered making the procedure for going into ice to involve first disconnecting the bobstay (at the turnbuckle) and then motoring only, not sailing. What I disliked about that approach was that disconnecting the bobstay turnbucke is not all that easy (depending on the seas), and there was no protection against accidentally hitting a piece of ice when the bobstay was attached (ie before realizing we were near ice).
As I’m not familiar with your boat, I don’t know how important the jib being out on the bowsprit is for the support of the mast, so don’t know how feasible moving the jibstay off the bowsprit would be for you.
Hey, im glad i found you site, very nice boat ! I really like the swingkeel, how is that rig working out ?
I´m happy for every input on the bowspread and the steelcap as im not sure about the design. Since my boat is plastic the bowspread is not fasten, it´s really just hanging in two bolts and are tightened to the hull from the pressure of the shruds. In to much ice it need to come off becouse i cannot push ice with it. but taking it off is problematic becouse it will than be hanging in the jibstay and might move around, and its to big to be stored on deck.
the idea of the steelcap is that we can move the chainplate of the bobstay 40 cm higher up, both pack ice and growlers we saw where very low at ts own waterline meaning we could be proctected from most iceimpacts.. The 10 mm chainplate would also act as a ram, and i´m aware of that it wound brake any growlers but i fugured that cutting into the ice would absorb more energy than a flat impact to the plastic hull. For this thrip I would be a lot easier if the boat was steel
Edwin, thanks. If you mean how is Issuma’s sailing rig working out after moving the jibstay 1m aft, it sails fine, but tacking is more of a problem than it was before. The outer jib always chafed against the inner jib stay when tacking–now it chafes more and gets stuck more. If you mean the swing keel, I love the swing keel, but it is definitely something that one needs to always think about “is it locked so I can put up sail, or unlocked so I can motor into shallow water?”.
I understand why you want to go with the steelcap, and agree that it will look after *most* ice impacts.
Before I moved the jibstay back, I experimented with removing the bobstay from the bowsprit (the turnbuckle was at the bowsprit end) and tied the bobstay end on deck. Then I motored thru some ice. The bobstay was standard stainless steel wire, probably 16mm diameter. The swaged fitting on the bobstay where it attached to the boat was badly bent when I broke ice with the bobstay disconnected from the bowsprit.
You mentioned planning to disconnect the bobstay at the lower end, which would be much better than what I did when experimenting, but you may still have to consider what breaking ice will do to the part of the steelcap where the bobstay fitting attaches (10mm steel in your plan). From your drawing, it looks like that part of the steelcap will usually be above the level of the ice, which is good, but if it does hit ice hard enough, I wonder if it will bend, complicating fitting the bobstay back on. Have you seen the photo in Willy de Roos’s book of how he put a cap on his boat? His design worked around that problem by having the bobstay attachment point being on top of the steelcap. I think you want the eye where the bobstay attaches to the cap to be protected from the ice somehow (ie, closer to the hull than the part that hits the ice).
Oh I meant your staysail main rigg, its beautiful !
I have not thought about the bending issue as the chainplate would be 10mm. But after drawing up the cap http://belzebub2.com/wp-content/uploads/2012/03/bend.jpg I realize its not the 10mm that will bend its the joint between 10 and 3mm. What do you think about adding material as in the drawing on the side of the 10mm chainplate to avoid bending. Maybe even reinforcing the 3mm right under the chainplate to 6 mm.
Another reason for the desing is the the angle of the bobstay cannot be any steeper in order to preserv the power ratio between bobstay and jibstay. Otherwise i could just have moved the chainplate up to the top of thecap.. now the chainplate follows the same angle as the bobstay but is moved up and out.
I like the staysail schooner rig–lots of flexibility in adjusting to the winds. It doesn’t sail as well as a sloop or cutter would, but it breaks the sail area into smaller sails, and the sails on my boat are as big as I can handle (without power winches).
Your latest drawing looks different than what I was thinking you meant earlier. I think it looks good the way your latest drawing shows it–the 10mm steel doesn’t stick out very far in this drawing, so there should not be much force that can develop on it to bend it. And having the filler on the sides or reinforcing to 6mm under the chainplate does sound good.
Yes, you don’t want to change the angle of the bobstay much, as changing that means you need to consider the strength of the bobstay, chainplate, bowsprit and bolts holding the bowsprit to the boat.
You’ve probably already finished your bobstay reinforcement, but, while walking the dock in Ketchikan, Alaska today I happened to see that Ariel IV had welded a triangular support piece into their stainless steel rod bobstay for ice work. No one was around to ask about how they liked it, but I took a picture of what they did and put it here: http://picasaweb.google.com/RosemaryRuth/TorontoBowspritWelding#5741495307206806130
Hi Richard,
Thank you for the image. We are on our way to newfoundland so we haven´t completed the bostay protection. We still haven´t found a good way to o it. Steel might be to expencive and plasic might be as good.