Stemhead fitting, plan B...

[mdevour]

Greetings,

I’d like to pass this revised stemhead fitting installation by you folks who have experience.

The boat is a 16 foot plywood and epoxy centerboard gaff sloop based on the Weekend Skiff. The mast is about 13 feet, the headsail 25 square feet, the main 75 square feet. She will weigh about 200 pounds when finished and is supposed to carry two adults or the equivalent weight in children.

Here’s a picture of the bow, to give you a look at the construction:
http://www.eskimo.com/~mdevour/other_pictures/stemtop.jpg

The stemhead fitting I’m looking at is from TenderCraft Boats and is described as follows:


For stay and jib eyes, bronze. Length 4", depth of strap 2½"
http://www.eskimo.com/~mdevour/other_pictures/stemhead_fitting.jpg

From the picture it appears that I will need to bend it slightly to mount to my stem. Can that be done without breaking the casting? Would heat help?

The easiest way of mounting it would be something like this:
http://www.eskimo.com/~mdevour/other_pictures/stem_fitting2.gif

My question is will it be strong enough as drawn above? The two upper screws on the fitting would be approximately number 10 by 2” bronze wood screws. The ones on the face of the stem would end up being only about an inch long, but would be safely loaded in shear mode. The stem halves started life as a common 2x4 from the big orange box. Not inspiring, I know!

I believe I’m expected to pilot drill the screw holes and saturate them with thinned epoxy. Add bedding compound to exclude water and resist movement, and everything ought to be wonderful… right?

Adequate? Scary? How should I improve this? Please be explicit. My experience is limited.

Thank you!

Mike D.

[ 03-19-2003, 10:43 AM: Message edited by: M. G. Devour ]

[Art Read]

I think it looks fine for a smallish boat like yours. You're not talking about huge loads here. But just for ease of mind, you might be able to increase the length of that bottom screw if you just "offset" the drilling angle enough so that it passes by that forwardmost top screw.

Not sure about the best way to bend the angle of that casting, though. A little "fudging" shouldn't hurt too much, bronze has more "give" then you might guess, but a serious change of shape would probably warrant a little further investigation. Heat would be my first instinct, but I'm no metalworker and I can't say how a bronze casting will behave when treated like that. Good luck! Neat Project!

[ 03-20-2003, 04:49 AM: Message edited by: Art Read ]

[Mrleft8]

My suggestion would be to bolt it through the breast hook, and use the screws on the stem face.

[Paul Scheuer]

I'm sure that those fittings are routinely formed, without heat, to fit particular installations. Your's seems to be within reason. Be sure to form it in advance, (i.e. don't try to draw the front tang in with the screws). And don't try to form the sharp inside radius to match your profile drawing. Once you get the angle right ease off the wood slightly instead.

I like this approach better than the sandwich plan.

You can always add a ring lower on the stem if you find you need it, or maybe the traditional hawse pipes.

[TomRobb]

Are you sure it's cast and not fabricated?
If you're worried about the top screws pulling out, you might look for a fitting long enough to reach far enough to thru-bolt it.
On a little boat like that I'd be tempted to go with a spritsail on a freestanding mast. It's not like you're going at it hammer and tong with the IOR fleet. :rolleyes:
Simple is good. smile.gif

[ 03-20-2003, 10:32 AM: Message edited by: TomRobb ]

[mdevour]

Hello folks,

I'm at the school with my kids tonight and doing a little tinkering with the dagger board trunk and taking apart some of the parts that were dry-fitted last year.

In the morning we'll be stashing the boat in a corner and building a temporary buffet table over the top of it for an Irish Festival they're having on Saturday. That's the deal I made with the lady so we didn't have to move the boat outside under a tarp for the party! :rolleyes:

Art: Good idea tweaking the direction of the last screw. Thanks for your kind words about the project!

Mrleft8: To bolt through anything, I'd have to go with TomRobb's suggestion of a longer fitting. This one barely reaches the back of the stem, so a bolt hole would come out the front of the stem, getting me into stuff like mounting the fitting before glassing and finishing the outside of the hull... To be considered.

Paul: You wrote:

I'm sure that those fittings are routinely formed, without heat, to fit particular installations. Your's seems to be within reason. That's good to hear.


Be sure to form it in advance, (i.e. don't try to draw the front tang in with the screws). And don't try to form the sharp inside radius to match your profile drawing. Once you get the angle right ease off the wood slightly instead. Both those suggestions sound like really good advice! :D

Actually, the only reason I didn't radius that profile in the sketch is because I was using Corel Draw rather than a legitimate CAD program. What would be 2 or 3 clicks in AutoCAD ends up being a real chore in Corel, and I just didn't bother to do it. <sigh>


You can always add a ring lower on the stem if you find you need it, or maybe the traditional hawse pipes. Hawse pipes, hmmm. Damn. Need to track down what those are. Durn spotty education... :mad: :D

TomRobb writes:
Are you sure it's cast and not fabricated?Not at all! All I've got to go on yet is that teeny picture on their web page. If it's fabricated it will be easier to bend, right? When I call to order I will ask.


On a little boat like that I'd be tempted to go with a spritsail on a freestanding mast. It's not like you're going at it hammer and tong with the IOR fleet. Simple is good. Correct on all counts! The original plans don't go any further than suggesting an unstayed mast and a modest lug or spritsail rig. I don't even know if the hull will hold up under the additional stress of this rig.

What I can say in my defense is that I realize this is entirely untried and I'll be as careful as I can manage during initial testing. Finally, if all hell does break loose, I can always go back to those simpler rigs... so long as the hull is undamaged by my experiment. :(

My reason for attempting a sloop rig is to give us something to grow into. I figure it'll be easier to fit out for the more complex rig now than retrofit later. Whether it works out remains to be seen, though the project is certainly educating me in a hurry.

I am grateful for everyone's help and patience.

Thank you,

Mike

[John Blazy]

Don't bend it at all!! This is a great opportunity to fabricate a sweet little mahogony "ramp" or wedge under the aft part of the stemhead fitting. I know it may look a little different with the top part not parallel to the sheer, but if you couldn't bend the casting, this is what I would do. Extend the 'ramp' the whole length to the apex of the breasthook - it may look great, and it will also cover the end grain of the stem, sealing it.

[SailBoatDude]

I would not bend the fitting, but ramp it as well for two reasons. First it looks to be chrome plated and odds are the plating will fail at the bend, chip, flake or otherwise look like what happens to car bumpers after a little dent deforms the metal a bit. Second if it's cast (the price should give you a hint) it may not like being bent too much, without cracking. Bronze will take some movement, but you can never tell how much is too much. The crack may not appear for some time, but show up after several hundred cycles of tensioning/relaxing during use.

[mdevour]

John and SailBoatDude,

You raise interesting points. I'll think about that "sweet little mahogony ramp" if I don't get really good indications that the fitting can be safely bent.

At that point I should seriously consider fabricating my own fitting to suit.

The picture from the web site is black and white, so I don't think it gives any true indication of whether it's plated or bare. Plating would definitely not bend well. :eek:

I should probably post some questions about bending it on rec.metalworking or the artmetal forum. They may know some tricks of the trade that would work.

Thanks!

Mike

[Cedarhill Boatworks]

It will be easy enough to tell if its cast or fabricated. Look for the mould marks on the underside and the inside of the hole. There will most likely be a visible seam on the underside where it wasn't ground out perfectly. If it is chromed you will lose the plating as soon as you bend it or heat it.
Personally I'd rather see the bright bromze than chrome anyway, but thats just me.
The ramp idea seems the way to go. I'd use the loger screws in the front into the stem and shorter screws in the breast hook. The top screws are only keeping it aligned, it's the screws in the stemm that are taking the load.