Threaded rod ?

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Strathglass

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Can any formite please give me info on the breaking strain on threaded rod.

I am specifically looking for the breaking load on 10mm 316L threaded rod in extension.

It is for holding the deck down on a keel stepped mast between the deck collar and the keel step.

I would like to compare it with 1/19 SS wire.

Thanks in advance

Iain
 
Have you a company in you area that tests lifting equipment? if you have why not take a sample and they should be able to help by doing a load/break test.
 
AFAIK threaded rod is not tested, unlike high tensile bolts with the 8.8 etc etc markings on them. Some Government engineering standard places may be able to help. Even better maybe someone on here may know /forums/images/graemlins/smile.gif
Alex
 
I have no idea what the breaking strain would be however....The threads will provide stress raisers so the safe strain would be a lot less than equivalent smooth rod. ie for safety say half of that for smooth rod. Given that the area of cross section is what matters I would suggest the 10mm be considered equivalant to around 8mm dia of 1X19.(and that is pretty big) Obviously you can afford in this application to go a bit oversized without costing too much in money or weight but to my imagination 10mm threaded rod should do the job to reinforce the deck. olewill
 
this page gives both the Ultimate tensile strength and the yield strength
this being 5690 Kg/cm2 and 2957 Kg/cm2

The core dia of M10 is approx 8 mm and area 0.5 cm2

therefore Ultimate load 5690 * 0.5 = 2845 Kg
Yield (max working) 2957 * 0.5 = 1478 Kg

You then need to put a safety factor on to get normal working load
 
Thanks Roger and Orwell.

Between both of you I have the answer to my question.


Thanks again and a merry Christmas.

Iain /forums/images/graemlins/smile.gif
 
I have a data book here (an automotive one though), which quotes the tensile stress area of an M10 metric ISO coarse thread as being 58mm^2. The same book doesn't quote "316" stainless specifically but it does provide data for a variety of stainless steels, the WORST of which has a UTS of 450N/mm^2 in the annealed condition and the best is 600N/mm^2. The worst yield is quoted as 270N/mm^2 if that helps!
 
Don't forget that a cut thread reduces the tensile strength of the rod. If its a rolled thread that has a higher UTS than the cut thread and if its its been normalised and stress releived it's a bit better(But still under the original UTS of the plain rod)

A thread cut reduces the UTS by about 40%
 
Be careful! see the "Thieves in Brighton" post on the Motorboat forum! they might steal yours too! /forums/images/graemlins/frown.gif
 
Yes, I've read that one.

Took it would have taken me quite a while to weld all the bits together into two pieces each a meter long.

Still job now finished. and not quite easily removed.

Cheers

Iain
 
[ QUOTE ]
Can any formite please give me info on the breaking strain on threaded rod.

I am specifically looking for the breaking load on 10mm 316L threaded rod in extension.

[/ QUOTE ]

You mean "in tension". But you need to consider other possible forces than just tension, as they can significantly add to the loads on the fasteners. They can also cause work hardening, fatigue and stress-induced corrosion. 316 stainless is particularly prone to all these. To keep their stainless properties, all stainless steels rely on oxygen being present at their surfaces.

[ QUOTE ]
It is for holding the deck down on a keel stepped mast between the deck collar and the keel step.

[/ QUOTE ]I would want to consider the use of high-tensile steel of substantially larger section than necessary. Corrosion proofing plus a margin for corrosion. Peace of mind.

[ QUOTE ]
I would like to compare it with 1/19 SS wire.

[/ QUOTE ]

SS wire is hardened by drawing. This means it is stronger in tension per square millimetre of cross-section than typical stainless bar or threaded rod. Steel fasteners can also be hardened, so there are several strength grades of stainless fastener - look for grade 70 for the strongest, but beware because is is also the most brittle.

In general stainless steels are awful engineering materials and specialist knowledge and skills are required to use them properly. I don't think asking a couple of questions on a forum will give you the background you need to design with stainless steels. If you are not completely comfortable that the application is within your grasp then I'd recommend that you consider a material which has fewer bad habits, even if you have to do a bit of work to protect it from the elements. It's easier to replace a few fasteners now and again because they've been getting a bit rusty than is it to try to replace one that's just fractured in a big sea.

This is all just conjecture of course, for people who come along afterwards to pick to pieces.
 
Incidentally, am I being daft here? I didn't think there would be any load trying to lift the deck anyway????

Have I missed something?
 
The upwards pull on the deck only happens to a keel stepped mast when the deck is not fixed to the mast at the deck collar.

It is caused by the haliards and control lines which are led aft from turning blocks fixed to the deck at the mast collar.

My mast could be fixed to the deck using fancy adjustable hooks supplied by the mast manufacturer (Sparcraft F306) but I cannot use them as I had to mount the mast collar on a block of wood to keep the collar horizontal and to cover the deck curvature. This has made my deck too thick for the fittings.
Because of this I have to fit a tie rod between the deck at the mast collar and the mast step.

Cheers
Iain
 
The bottle screw I am using is a closed stainless one.
The strains should not be too much as many of the haliards are mounted on the mast.
The lower kicker pulley system is also fixed to the mast and the foreward reefing eyes hook on to horns at the gooseneck.

I have now fitted it and it looks quite tidy. It will run about 2" aft from the mast. I was originally going to cover it with heat shrink but have now decided to leave it exposed to the air.

Cheers
Iain
 
I've got something similar - again because of the halyard blocks by the mast.

I had the same model of boat 15 years before and that didn't have anything to keep the deck down, so I'm not sure it's strictly necessary. It does make sense though, so I'm leaving it.
 
I will explain what I have ended up with.
Then stand back for the flack.

My mast could be fixed directly at deck level using fancy adjustable hooks supplied by the mast manufacturer (Sparcraft F306) .
I cannot use them as I had to mount the mast collar on a block of wood to keep the collar horizontal and to cover the deck curvature. This has made my deck too thick for the fittings.

Because of this I require a tie.

I used two one meter lengths of M10 A4 stainless screwed rod, two closed body bottlescrews and some M10 nuts.

To join the two sections together I drilled out the left hand thread from one of the bottlescews to M10 clearance.
I then screwed the rod through this hole and into the right hand thread for about 6mm (thread was about 25mm long)
I welded through the two holes on the middle of the bottlescrew to secure the rod.

I screwed a nut on the end of the other piece of rod and welded it to the rod. The mast coller was already tapped M10 centrally just fwd of the mast and I had drilled through the deck and moulded in alloy plate at this position.
I screwed this meter long rod from outside through the deck collar and into the boat (using Duralac and 3M 5200 as appropriate). A nut was then screwed up this rod to the moulded headlining. I now has a meter length of rod projecting vertically from the roof just aft of the mast position.

The mast foot support is bolted to a 6mm thick 316 plate that is held in place by three keelbolts. I drilled this plate with an M10 hole centrally just aft from the mast position.
I unscrewed the left hand thread fork end from one of the bottlescrews and cut the two arms from the fork off but left the flat piece on the threaded rod. I bolted this piece of threaded rod pointing upwards through the M10 hole I had drilled on the mast foot support plate, then welded the threaded rod and the nut to the plate. The plate and heel step were refitted in position using appropriate sealants and insulation.

I was now in position to join everything together.
I screwed a nut and the body of a bottlescrew onto the left hand thread stub on the heel mounting plate.
I then screwed the rod with the welded on bottlescrew at the top onto the lower bottlescrew. This let me measure where to cut the length of the screwed rod to fit.
Once I had reassembled everything I screwed and locktighted the central join fully together. I could then use the lower bottlescrew to tension the strop then tighten up their locknuts.

One or two other points.
I have to use stainless as the fluxgate sensor is just fwd of the mast.
I have not put any swivels in the setup. May be taking a chance.
I think that the M10 screwed rod will be as strong as the 6mm hooks the mast manufacturer supplies.
I did all the welding and cutting off the boat.

I can always change things if I have got it wrong. But that will be another delay in completion and first launching.

I could post some photos if anyone is interested enough.

Iain
 
Rupert,

I was told by the owner of Contentous Eagle a few years ago that one time he undid the tiedown and the deck lifted several inches at the mast. He did not understand why!

Iain
 
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