I am in the process of installing Air Conditioning to our boat. Have the spot chosen narrowed down as the best of worst case senerios. Venting the salon and the V berth no problem, but adding air to the rear cabin means, I have multiple holes to drill through 3 bulkheads and 4 cabinets for a straight run. All doable with the hole saw and drill.....after moving a fuel line, water line, a propane line and 2 wirering harnesses I think Ive got a clear shot. My only hesitation right now is the decision of drilling a 4" hole 6" to the right of the port chainplate or 6" below the port chain plate. Loads in question lends me to the 6" to the right of the chainplate.......What are the groups thoughts?.....and afterwards anyone recomend backing plates around the new hole to distribute the loads? Thanks Rob
any structural engineers?
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Simple answer .....
STAY AWAY from chainplate bases. How's that for an answer from a structural engineer? Such structures on boats need to have a safety factor (purposely 'overbuilt') and any hole that you add (especially holes that are added outside of what known as the 'neutral axis') may in fact become whats known as a 'stress riser' .... removing all the 'safety factor' and making the structure very weakened for the function intended. Especially for dynamically loaded structures .... dont screw around with the 'critical' structure components. If you REALLY need to modify this base of support, consider to engage the original designer and for a consulting fee get him/her to approve and design the modification. Sorry.
STAY AWAY from chainplate bases. How's that for an answer from a structural engineer? Such structures on boats need to have a safety factor (purposely 'overbuilt') and any hole that you add (especially holes that are added outside of what known as the 'neutral axis') may in fact become whats known as a 'stress riser' .... removing all the 'safety factor' and making the structure very weakened for the function intended. Especially for dynamically loaded structures .... dont screw around with the 'critical' structure components. If you REALLY need to modify this base of support, consider to engage the original designer and for a consulting fee get him/her to approve and design the modification. Sorry.
THHHHHAAAATTTTTSSSS what I thought!
I have another option....I can reroute that duct through the same bulkhead however lower and away,,,that would give me say 4 feet from the chain plate,,,but through another cabinet,,,lot more work and loosing another cabinet (small one),,,but thats why I asked,,,I was nervous as hell drilling anywhere near that chainplate. The original designer is kaput,,,,so contact is not possible. Thanks for the heads up RichH!!
I have another option....I can reroute that duct through the same bulkhead however lower and away,,,that would give me say 4 feet from the chain plate,,,but through another cabinet,,,lot more work and loosing another cabinet (small one),,,but thats why I asked,,,I was nervous as hell drilling anywhere near that chainplate. The original designer is kaput,,,,so contact is not possible. Thanks for the heads up RichH!!
forget the rear cabin and use a fan
I use a fan on my legend 37. With the AC in the forward birth hatch a fan in the aft stateroom the whole boat cools down nicely. It has got to be easier than standing upside down in a phone booth drilling 4" holes.
I use a fan on my legend 37. With the AC in the forward birth hatch a fan in the aft stateroom the whole boat cools down nicely. It has got to be easier than standing upside down in a phone booth drilling 4" holes.
Naval Engineering Experience
A hole in any structure bulkhead should be reinforced with a collar made from stabile material with the proper thickness to replace the support of the removed material. I have the same situation on my boat. The previous owner drilled a 2 “ hole in a structural bulkhead without a collar. I want to increase it to a four inch opening and add the collar. Naval ships are made of steel. The collars we manufacture were like material and the same thickness as the bulkhead plus an 1/8”. I am not sure what to us in a wooden bulkhead. The collar also protects the duct line or cables passing through it.
A hole in any structure bulkhead should be reinforced with a collar made from stabile material with the proper thickness to replace the support of the removed material. I have the same situation on my boat. The previous owner drilled a 2 “ hole in a structural bulkhead without a collar. I want to increase it to a four inch opening and add the collar. Naval ships are made of steel. The collars we manufacture were like material and the same thickness as the bulkhead plus an 1/8”. I am not sure what to us in a wooden bulkhead. The collar also protects the duct line or cables passing through it.
Wood is not a homogeneous material
Doublers in steel transfer the stress very easily but wood isn’t so cooperative. You add a whole new set of problems if you try that with wood. It can be done and it’s a good thing to do if it’s engineered properly. But it’s not the sort of thing you can guess at and someone who knows how needs to look at this. Cutting holes near a chainplate is probably OK but it’s not the sort of question you can post to a group and get a competent answer especially without posting pictures and complete dimensions. Wood is not a homogeneous material so tearing between holes and bolts needs to be looked at very carefully. All the best, Robert Gainer
Doublers in steel transfer the stress very easily but wood isn’t so cooperative. You add a whole new set of problems if you try that with wood. It can be done and it’s a good thing to do if it’s engineered properly. But it’s not the sort of thing you can guess at and someone who knows how needs to look at this. Cutting holes near a chainplate is probably OK but it’s not the sort of question you can post to a group and get a competent answer especially without posting pictures and complete dimensions. Wood is not a homogeneous material so tearing between holes and bolts needs to be looked at very carefully. All the best, Robert Gainer
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