MD 180 Broken Mast

[monstahfish]

I doubt warranty would let you go "a couple weeks" without your drive. That being said, nice work getting that out. Screw extractors are a life saver and a must have in everyone's garage.

[Mahigeer]

Are the shafts stainless steel?

If so drilling SS is very difficult.

Unless they are less grade of SS.

Regardless, good job on repairs.

[monstahfish]

Originally Posted by Mahigeer

Are the shafts stainless steel?

If so drilling SS is very difficult.

Unless they are less grade of SS.

Regardless, good job on repairs.

They are stainless but it can be drilled if done properly. Drilling stainless requires high pressure, low speed and lots of oil. If you overheat it, it will blue and break your bits.

[IN2DEEP]

Originally Posted by Mahigeer

Are the shafts stainless steel?

If so drilling SS is very difficult.

Unless they are less grade of SS.

Regardless, good job on repairs.

Def not a lesser grade stainless
The mast are made with Ph 17-4 SS which is heat treatable and is magnetic
The mast are much stiffer than 303, 304 or 316 SS of the same size.
As others have already said. Slow RPM with lots of pressure and cutting oil

[IN2DEEP]

Hobie probably thought that jumping up to .312 instead of .281 would eliminate the chance of breaking a fin mast

Good job on keeping the drill centered
I used a vice and a vertical mill to remove a broken one on a V2 drive last year

In our shop, we have better luck using square drive extractors instead of the spiral type


Tools used

[IN2DEEP]

After I broke a mast fin, ful-rac pointed out that it probably broke due to corrosion.
After close examination, shureasshit he was right
This drive was 3 yrs. old at the time. If you notice, the corrosion extends deep into the fracture. And yes, I do rinse everything off after every trip


This was the other mast that hasn't broken yet




Keep an eye on your masts on the drives that have been used in the salt for a few years

[alanw]

Originally Posted by IN2DEEP

This was the other mast that hasn't broken

You know we can't see your pictures?

[IN2DEEP]

Originally Posted by alanw

You know we can't see your pictures?

Anybody else not seeing my pictures?
Using photobucket as the host

[DanaPT]

Originally Posted by monstahfish

I doubt warranty would let you go "a couple weeks" without your drive. That being said, nice work getting that out. Screw extractors are a life saver and a must have in everyone's garage.

Absolutely looks like i need one of those thingamagies.

Nice work Tony... working like a surgeon.

[FISH11]

Nice work Tony, drilling out a broken bolt or stud is not easy because it's hard to drill centered and large enough to use an easy out that will bite well and hold the amount of pressure needed. In this case it helps that it's in a brass bushing and not rusted in. Even though this is a good post on a possible weak area. I wish you had told us about the nice Hali on board. I think the broken mast is because that mast had a defect other wise it would not have broken in that spot and not had stretch signs on the metal post instead of a clean break.

[ful-rac]

The mast was pretty hard, but like Shane said low speed, and also taking your time to get your drill centered as close as possible really helps. Starting with a small bit and stepping it up to a larger bit several times takes time so you have to be patient. At least it wasn't as bad as an exhaust stud...compared to one of those this one was a piece of cake...

...another thing that made this project challenging, is that the broken piece was recessed back into the sprocket about an 1" or 1 1/2...

Makes me wonder if Hobie were to score the mast an inch or so below the end of the sprocket to make a point where if the mast were to fail it would fail in a manner in which you could replace it without the use of special tools....Of course that would make a weak point...but that is the point...just a thought. It's alot cheaper replacing a mast as opposed to replacing complete spine assemblies...

[kirkdavis]

Originally Posted by ful-rac

The mast was pretty hard, but like Shane said low speed, and also taking your time to get your drill centered as close as possible really helps. Starting with a small bit and stepping it up to a larger bit several times takes time so you have to be patient. At least it wasn't as bad as an exhaust stud...compared to one of those this one was a piece of cake...

...another thing that made this project challenging, is that the broken piece was recessed back into the sprocket about an 1" or 1 1/2...

Makes me wonder if Hobie were to score the mast an inch or so below the end of the sprocket to make a point where if the mast were to fail it would fail in a manner in which you could replace it without the use of special tools....Of course that would make a weak point...but that is the point...just a thought. It's alot cheaper replacing a mast as opposed to replacing complete spine assemblies...

If the threads start that deep in the sprocket, it should reduce the cyclic stress where it broke, so I agree that there was something wrong with the part from the factory.

[alanw]

Originally Posted by kirkdavis

If the threads start that deep in the sprocket, it should reduce the cyclic stress where it broke, so I agree that there was something wrong with the part from the factory.

Or there is too much play between the mast and housing, or the housing flexes too much, and there isn't enough support past the threads. Or, Tony is just a beast.

[kirkdavis]

Originally Posted by alanw

Or there is too much play between the mast and housing, or the housing flexes too much, and there isn't enough support past the threads. Or, Tony is just a beast.

Well said.


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