Keel Bolt tightening Oday 322
- Thread starter wkirk216
- Start date
Yes, use a half inch drive torque wrench to torque with an extension. Anything specific just ask.
Thanks, So the boat is on the hard and the keel is supported by block. My nthought is to just tighted the nuts and ensure they are solid. No water currently leaks in though i see some caulk seperation on the outside where the keel & hull come together.
Find out the size of your bolts then torque then to the torque specification for that size. You should be able to find a good value doing a search on the net for torque by fastener size. It will probably be pretty high so you need a good size wrench to get enough moment arm. For instance 100 foot pounds with a 12 inch wrench requires you to apply 100 pounds at the end of the wrench, are you strong enough for that? How about if it is 150 pounds?
For the keel joint get a paint scraper and scrape out as much of the old stuff as you can then apply new caulk to the joint, fair it and then paint it after it cures. Depending on the caulk it could take a while to cure, like up to 5 days. So do that early in the process.
For the keel joint get a paint scraper and scrape out as much of the old stuff as you can then apply new caulk to the joint, fair it and then paint it after it cures. Depending on the caulk it could take a while to cure, like up to 5 days. So do that early in the process.
The keel bolt nuts in our O'Day 322 are very deep in the bilge well. We found the forward three larger bolts to be 1" course-thread bolts (determined by a measured 1-1/2" nut flat-to-flat). We're having a difficult time confirming the size of the one smaller aft course-thread bolt. Looks to be ~ 1-1/8" nut flat-to-flat, therefore a 3/4" bolt. The bolt thread protrudes a good bit, making us think a standard deep-well socket won't be deep enough, and that we'll have to use an extra-deep-socket. Anyone have any feedback on those specifics?
Thanks everyone,
E & N
The torque specifications for the O'Day 322 are as follows: 280 Ft. Lbs. on the 1" bolts, 160 Ft. Lbs on the 3/4" bolts.
That is from my Manual from the last page in the commissioning section.
I bought the deep impact 3/4 drive sockets along with a 1/2 to 3/4 adapter from northern tools after searching everywhere for them with no luck.
My keel to boat joint is covered by a thin fiberglass layer to smooth out the gap and it looks very smooth and you can not see the seem.
Thanks for the info. Did you find that the torques were off when your tried to tighten them and or were they pretty much good to go??
They were in need of tightening, but I've only torqued them one time in the 3 years I've had the boat. I was just a little worried that tightening them to often might lead to compressing the fiberglass and cause more issues.
Yikes - I think you'll find 280 or 160 ft-Lbs almost impossible to acheive with a 1/2 drive torque wrench, sliding around on your cabin sole to get leverage. Just for perspective my keel bolts uses 1-1/4" socket and my manual states 140 ft-Lbs.
Double check the manual to be sure you sre not reading newton-meters, but if that what it says...
Before cranking up the torque to those levels you might want to do a few calculations regarding the compressive strength of the FRP (fiber reinforced plastic) to see if it can take the load without failing. See how much clamping force for a given bolt size and torque, then look at the backing plate or washer to figure out the square inches that will be in compression and make sure the material can take it. For polyester chopped strand or woven matt it looks like 21KSI is the compressive stress strength of the material. For design limits you might want to use half that number for a factor of safety of 2. For example a 1 inch fasterner torqued to 250 pounds will develop about 15000 pounds of clamping force. That is the compressive load that the washer or backing plate is applying to the fiberglass. Make sure you have large, rigid backing plates and the load is spread uniformly. That much load concentrated in a stress riser, as most bilges are not that flat or smooth, may be a recipe for disaster. Torque is a funny thing and friction in the joint makes a huge difference in clamping force. If you use 100 foot pounds just to turn the nut because it is all scored up and full of grit, then the joint only sees 150 foot pounds equivalent clamping force if the torque is 250 foot pounds. The torque to turn the nut is called the running torque and for self locking fasteners can be pretty high.
Jibes, do you know what the torque would be for our boats? Would it make a difference if you were tightening the keel bolts while the boat was blocked up with the keel supported as opposed to the keel hanging when the boat is in the water? I've often wondered if the space between the boat and the keel is different when the boat is suspended on the lift. The paint seems to wear off at the keel joint both at the front and back each year but I'm not sure if that is enough of an indicator of a problem. Could be just paint adhesion to the caulk.
The studs in our boats are 3/4 inch. I think Dave Mauney sent me the torque values once but I don't know where I stored them. You might send him a PM to see if he responds. They should be torqued while the boat is on the hard so you aren't lifting the weight of the keel with the torque of the bolts. That load will increase the friction force and lower the clamping force on the joint. With thousands of pounds of clamping force on each bolt there should not be any change in the position of the keel relative to the hull whether in the sling, in the water, or on the hard. That joint should be completely solid with no motion whatsoever. The torque on the bolts stretches the bolts so it is like having a massive spring clamping the joint together. This link shows for 316 stainless 3/4 inch bolts 131 foot pounds. That should do the trick. Other sites provide clamping force for torque and bolt size. This torque will provide over 8000 pounds of clamping force ON EACH BOLT. Since you have seven or eight bolts this should provide well over 50,000 pounds of force to hold up a 4500 pound keel. Hope this helps. http://www.engineershandbook.com/Tables/torque3.htm
Rudy at D&R gave me a torque of 160 ft-lbs for O'Day 34/35. I tightened to 150 ft-lbs with a 1/2 drive 150 ft-lb Klein bar torque wrench. Clicker torque wrenches proved very inaccurate and unreliable (tossed it). All this on the hard.
Goodwinds
DaveM
Goodwinds
DaveM
Thank you very much jibes and Dave. I'll check this out next time I'm down to the boat. I don't expect that there will be any increased space when in the sling but that would probably be the best time to add some caulk to the joint. I think I'll try to plan for this project at the end of next season. Knowing that there is 50,000 ft lbs of force holding the 4500 lb keel to the boat is reassuring.
There is not 50,000 "ft lbs" of force. Torque is a measure of a force applied at a distance creating a moment about an axis. So torque = F x d.
Engineering calculations are used on the screw thread that is analyzed like an inclined plane to create the clamping force on a joint for a given amount of torque, size of bolt, and pitch of the thread (the distance the nut travels in one revolution).
So the clamping force on your keel joint is just in pounds of force. On the hard you have about 7000 pounds of boat sitting on the keel joint assuming it is properly blocked. Then by torqueing the bolts you are applying over 50,000 additional pounds of force to the joint. Using DaveM's numbers it is even higher. Think of it as if you had a huge C-clamp and one side was in the bilge and the other under the keel and you cranked it down until on a force meter you read over 50,000 pounds. Since the keel is a cantilever beam subjected to all kinds of dynamic forces under sail this load should be adequate to prevent any relative motion between the keel and the hull under way. Assuming a worse case of a 90 degree knock down the keel is applying about a 9000 pound bending moment to the keel joint, assuming the center of mass of the keel is about 2 feet down from the keel joint. Fatigue is also at work due to the reversing loads as the boat rocks side to side but it is pretty low cycle fatigue. Given the industries' record of keel retention the factor of safety seems pretty good unless the boat was built with a really thin keel stub as Maine Sail showed on several posts.
Engineering calculations are used on the screw thread that is analyzed like an inclined plane to create the clamping force on a joint for a given amount of torque, size of bolt, and pitch of the thread (the distance the nut travels in one revolution).
So the clamping force on your keel joint is just in pounds of force. On the hard you have about 7000 pounds of boat sitting on the keel joint assuming it is properly blocked. Then by torqueing the bolts you are applying over 50,000 additional pounds of force to the joint. Using DaveM's numbers it is even higher. Think of it as if you had a huge C-clamp and one side was in the bilge and the other under the keel and you cranked it down until on a force meter you read over 50,000 pounds. Since the keel is a cantilever beam subjected to all kinds of dynamic forces under sail this load should be adequate to prevent any relative motion between the keel and the hull under way. Assuming a worse case of a 90 degree knock down the keel is applying about a 9000 pound bending moment to the keel joint, assuming the center of mass of the keel is about 2 feet down from the keel joint. Fatigue is also at work due to the reversing loads as the boat rocks side to side but it is pretty low cycle fatigue. Given the industries' record of keel retention the factor of safety seems pretty good unless the boat was built with a really thin keel stub as Maine Sail showed on several posts.
If you took high school physics you are more than capable of understanding. I simply took exception to your comment about 50,000 ft. lbs. Torque is just the force on the handle of the wrench times the distance to the center of the bolt. So for a 1 foot long wrench you need to apply 150 pounds to the handle of the torque wrench to get 150 foot pounds. Torque = Force x Distance (to center of rotation). If the wrench is two feet long then you only need 75 pounds on the handle for 150 foot pounds.
Clamping force on the joint is the torque converted to an axial load in the direction if the axis of the bolt. Think of the bolt as a spring. As you torque it the bolt stretches elastically. The bolt trying to return to its' original shape is applying a force to the nut, backing plate, keel stub to clamp them together with the keel. In this case each bolt applies about 8000 pounds of force to the nut and backing plate to clamp the keel in place. With say 7 bolts you have 56,000 pounds of force. More bolts, more force. Try reading this link to see if it helps. http://en.wikipedia.org/wiki/Bolted_joint
Clamping force on the joint is the torque converted to an axial load in the direction if the axis of the bolt. Think of the bolt as a spring. As you torque it the bolt stretches elastically. The bolt trying to return to its' original shape is applying a force to the nut, backing plate, keel stub to clamp them together with the keel. In this case each bolt applies about 8000 pounds of force to the nut and backing plate to clamp the keel in place. With say 7 bolts you have 56,000 pounds of force. More bolts, more force. Try reading this link to see if it helps. http://en.wikipedia.org/wiki/Bolted_joint
So it has been a little while since anyone has posted onthis thread and was hoping that there may be a resolve to the original post ofwhat the actual torque speck are for the keel bolts on the 322?
Keep in mind the cross section area is a square function so the area of a 1" bolt is .78 square inches (ignoring the root diameter of the threads for the sake of illustration for the moment). The cross section of a 3/4" bolt is .44 square inches. This just shows that a 1" bolt can take a lot more torque than a 3/4" bolt as the cross section is 77% larger.