Bobstay bow fitting

Does anyone know a good product to fit a bowsprit to the bow? I've added extra lamination for streangth but I need an actual fitting/chain plate/u-bolt/ bow eye ....

Boat is 38ft, I'll fly a 75m2 code from it, other gear is specified to 1.5 ton of working load.  

I guess an Wichard U-bolt could be used, is there any alternatives?

 

money drain

Member
53
6
I'm planning to install the same on a 40 ft in a week or two. Beyond strengthening the area; I have ordered a few G10 tubes. The plan is to drill a hole in the bow, insert the tube with some glue. Cut the tube off inside and outside the boat, make inside corners smooth, then use gelcoat paste to make it also look smooth and protecting the hull from water. I have a 20mm dia SS rod from another project that I'm planning to use part of as a dogbone (might machine it down a bit, not sure), and dyneema on that.

A U-bolt is probably easier to install, but I figured I needed a project like the one above to gain more experience on this kind of projects.

 
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sailthebay26

Anarchist
603
11
Newport, RI
I've always been a fan of laminating a "shoe" to the bow that is laminated on to the bow sprit.  You just need to put a piece of plastic of tape to pop the laminate off the bow.  It is key however to have it wrap over the shear as that adds substantial strength.  Installation of the bow sprit is then done with through bolts in the shoe and bow.  Using a fitting will be tough as there can be considerable torque on the fitting.  If you are looking for a way to attach the bobstay to the boat then I would recommend the ubolt as a tube through the bow would need to be radiused to reduce chafe

 

mvk512

Member
53
8
So Cal
I have a Wichard U-bolt for the bobstay on my 38’, 92m2 C0 on a 0.45m prod.  It works fine with high loads.  The angles are important.  The u-bolt loads are mostly in shear.

 

Zonker

Super Anarchist
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Did you mean the bobstay? I'd totally go with the glass tube with radiused ends as it exits the hull sides and just eye splice through the tube.

Stainless steel fasteners in the splash zone where you never really look at them is a recipe for eventual failure. Not saying they won't last for years, but I think composite solutions for this is way smarter. If the bow is strong enough for 2 or 3 bolts in line, it will be strong enough not to get ripped off with a glass tube bearing on the skins.

 
@money drain and @Zonker sorry, yes it's attaching the bobstay as in the title - with a glass tube, are you suggesting I go straight though the bow from side to side or just straight forward out from the bow and set a dimond knot or similar on the inside? The compartment is allready drained as it takes in water from the hatch on top. I'm thinking I could use something like https://www.upffront.com/en_US/shop/product/l-bush10-si-loop-products-bush-10-silver-8275?category=369 to reduse shafe. 

 
20150311-230135.jpg
CkVCIBDSpe7yD47whHHKoX6ctOZnlQUAVgOr6uH7Zhs=w1698-h955-no


 

money drain

Member
53
6
I was thinking a single hole in my post, but fix the anti chafe myself with a G10 tube. Dogbone on the inside.

However, I think I like Zonkers solution better. Two holes on each side and a tube through them, I guess just as your picture show. As he pointed out, no metal parts that doesn't survive time (dogbone). Think I'll do it like that instead.

 

ryley

Super Anarchist
5,429
621
Boston, MA
Did you mean the bobstay? I'd totally go with the glass tube with radiused ends as it exits the hull sides and just eye splice through the tube.
I did this on my columbia, I used a piece of g-10 tubing with an ID big enough for the dyneema, and an OD big enough to distribute the load. side to side. It's glued in nicely and has never given me any trouble.

 

El Borracho

Sam’s friend
6,345
2,383
Pacific Rim
Ropeye loop sized to your load is the soft way to do it   www.ropeye.com 
Brilliant products. But a laminate engineer would need to advise on what load a particular hull construction can carry without delaminating. Seems very likely that some hulls would pull apart. Fiberglass is not particularly strong in the peeling direction.

 

Alberta

Member
Brilliant products. But a laminate engineer would need to advise on what load a particular hull construction can carry without delaminating. Seems very likely that some hulls would pull apart. Fiberglass is not particularly strong in the peeling direction.
Yes and for clarity you'd install the loop through the hull and can add reinforcement inside the hull (mine has a few layers of carbon - I'd need to check with Fred Courouble on what precisely was added) . Here is what mine looks like from the outside.

D7D3E1B4-8F64-4D7E-9396-CF078EFA7042.JPG

 
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El Borracho

Sam’s friend
6,345
2,383
Pacific Rim
Yes and for clarity you'd install the loop through the hull and can add reinforcement inside the hull (mine has a few layers of carbon - I'd need to check with Fred Courouble on what precisely was added) . Here is what mine looks like from the outside.
Gotcha. Good ideas. Converts the peel force into a much more reliable squeeze force. (Cannot see your image, though...) 

 

Zonker

Super Anarchist
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I was thinking of a transverse glass tube (not PVC). For the PVC tube you need to work harder to make it waterproof and it's not as strong.

It's also easier to just glass on some interior patches in a few flat patches to add bearing / shear capacity then in the tighter confines of the stem (just easier to reach)

image.png

 

El Borracho

Sam’s friend
6,345
2,383
Pacific Rim
Cannot think of anything to recommend that PVC tube. Stiffness is desirable in order to transfer the load deep into the structure without overloading the outside layer. Trogear uses fiberglass tubes with a titanium rod inside to great advantage (for the upper sprit mount).

@Alberta 's RopeEye application, in some cases, would need to address the upward pull and the prevention of tearing the hull skin. Especially with installs that have a steeper bobstay angle. Sealing out water (some boats) would seem to be a complicated technical issue with 'rope'.

 
How about an aluminium bushing up front of single hole, fill the bow with epoxy/ chopped glass to distribute the load and a stainless back plate at the inner end. In would run a single 10mm dyneema through with a simple "celtic diamond knot" inside. The compartment is drained and already wet from the top.

I have already added 20 layers of 300g glass rowing to the bow as a first layer of added strength. 

Is there a risk the 45 degree angle of the bobstay will still cut in to the bow? As for stainless, we sail the Baltic, much less salt and corrosion here.

350x350
image.png

   image.jpeg

 

Parma

Super Anarchist
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here
Yes and for clarity you'd install the loop through the hull and can add reinforcement inside the hull (mine has a few layers of carbon - I'd need to check with Fred Courouble on what precisely was added) . Here is what mine looks like from the outside.

View attachment 438978
Are those bobstays for a sprit??!! You really actually did that ?

 

slug zitski

Super Anarchist
5,073
808
worldwide
Does anyone know a good product to fit a bowsprit to the bow? I've added extra lamination for streangth but I need an actual fitting/chain plate/u-bolt/ bow eye ....

Boat is 38ft, I'll fly a 75m2 code from it, other gear is specified to 1.5 ton of working load.  

I guess an Wichard U-bolt could be used, is there any alternatives?
You could use a u bolt 

I don’t like them , u bolts  always seem to bend and leak 

 A pad eye is better

you could bore thru the centerline of the stem and dead end an eye splice 

the challenge  is to make it watertight

D311515E-8232-4E6C-A5A2-4124FC86E6C8.jpeg

4C203D85-D55E-4E32-86F6-85C41E84E7DB.jpeg

 
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SEC16518

Member
324
127
Ok....How about adjustment?  The dyneema will need to be tightened as it creeps.  A fairlead through the bow to a cleat could be adjusted easily.  Use a tapered line.

 
Ok....How about adjustment?  The dyneema will need to be tightened as it creeps.  A fairlead through the bow to a cleat could be adjusted easily.  Use a tapered line.
On my boat the bobstay is made in two pieces, both with an eye in the middle and about 80mm between the ends of the eyes. A dyneema lashing between the eyes allows tightening of the bobstay in the event of creep.

 
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