Keel Bolt Torque

[Daydreams]

The keel had to come off my Seidelmann 37. When the lift put the boat down the keel compressed up into the hull. We took it off, cleaned everything up; put 4 tubes of 5200 on the keel and dropped it back down (3 days of work). I have torqued the keel bolts to 130 foot/pounds. I'm concerend that that might be too tight.Does anyone know what the torque spec should be and what the conequences of over torqueing are?

 

[RayK]

My experiences

NathanI have an S25 and have torqued the keel several times. It has 5/8" diameter studs and after some checking around the club and net, I came across a chart somewhere on the net that showed "typical" torque specs per bolt diameter.This was from a marine/boat manufacturing site so I thought it was realistic. When you torque a bolt (any bolt) you are inducing a little stretch to it so that it will have adequate tension to hold the parts together. The torque spec is indeed related directly to the material being stretched - diameter and coeficient of stretch (I have totally forgotten the actual physics..) which is dependant upon the alloy composition. I often wonder when I do the keel on my boat about the induced tension because you are tighting against a pretty elastic mating - both bedding and the fiberglass hull. I usually add a little to the chart spec because of that. A local yard operator of some reputation suggested that you tighten the bolts until you hear the fiberglass "just" creak with some crush - sounded just a little too far to me but he has been around for a long time. Obvously if you over tighten the bolts with respect to the strenght of the fiberglass hull, then you risk the danger of actually damaging the integrety of the fiberglass.Check the web for the chart, you will probably come across it - I just looked at my Favourites and I did not save it (at least on this computer)RayK

 

[Capt Ron;-)]

Torque Specs - Tek Specks

Nathan, made some calls and talked to an expert, one of the best.Evidently this info, good post RayK, is not as much of a mystery or secret as one would think.Most commercial engineering books will have this info: for mild steel and a 5/8 high-tensile bolt (aneeled or fired) sae course thread it looks like it is 98ft lbs for oiled threads, but different for a fine threaded.This is the kind of info you want to look at yourself and make a judgement call, so I only gave the one figure, but by that the OTHER post about the yard-guys recommendation is a bit over @ 140 ft lbs.I can't remember what it was when I last did it, but I usually know someone smarter than me that I can talk into 'helping'.Try this link...;-)Good luck.