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Posted by Ed Huntress on May 7, 2008, 1:19 pm
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> Thanks again Ed, so high tensile strength is what I'm after.
>
> Actually weight is a huge factor, these are for record attempt boats and
> any weight on the right sponson has to be minimized to help counter
> prop-walk. I'm running in a class that has a 120+ mph record and my buddy
> I mentioned just broke the record in his class running 103+, here's pix if
> you're interested:
>
> http://gallery.intlwaters.com/thumbnails.php?album=1002
>
> Here's the fin I'm talking about on my hull:
>
> http://gallery.intlwaters.com/albums/userpics/10068/normal_ScanImage011.jpg
Oh, those are cool, Terry, and they look like a lot of fun. We were
discussing here recently that my uncle raced model hydros like that in the
1930s, in a 35cc IC class and in a steam class (he used gasoline-fired flash
steam). I sure wish I had the photos of those.
>
> Wonder if one of the magnesium alloys might be better?
It looks to me like you have four engineering factors here: weight,
hydrodynamic drag, stiffness, and strength. Magnesium has roughly the same
ratio of strength/weight and stiffness/weight of most metals (titanium is
somewhat out of line, having high strength/weight but low stiffness for its
strength). So magnesium would result in a thicker, if somewhat ligher, fin.
I couldn't begin to evaluate the engineering options, but as a materials
freak, the first thing I would look at is unidirectional boron-fiber
aluminum composite. The second thing I'd look into would be a boron-fiber
epoxy composite. I'm not making life easy for you with that one. d8-)
--
Ed Huntress
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Posted by cavelamb himself on May 7, 2008, 2:34 pm
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Ed Huntress wrote:
>
>>Thanks again Ed, so high tensile strength is what I'm after.
>>
>>Actually weight is a huge factor, these are for record attempt boats and
>>any weight on the right sponson has to be minimized to help counter
>>prop-walk. I'm running in a class that has a 120+ mph record and my buddy
>>I mentioned just broke the record in his class running 103+, here's pix if
>>you're interested:
>>
>>http://gallery.intlwaters.com/thumbnails.php?album=1002
>>
>>Here's the fin I'm talking about on my hull:
>>
>>http://gallery.intlwaters.com/albums/userpics/10068/normal_ScanImage011.jpg
>
>
> Oh, those are cool, Terry, and they look like a lot of fun. We were
> discussing here recently that my uncle raced model hydros like that in the
> 1930s, in a 35cc IC class and in a steam class (he used gasoline-fired flash
> steam). I sure wish I had the photos of those.
>
>
>>Wonder if one of the magnesium alloys might be better?
>
>
> It looks to me like you have four engineering factors here: weight,
> hydrodynamic drag, stiffness, and strength. Magnesium has roughly the same
> ratio of strength/weight and stiffness/weight of most metals (titanium is
> somewhat out of line, having high strength/weight but low stiffness for its
> strength). So magnesium would result in a thicker, if somewhat ligher, fin.
>
> I couldn't begin to evaluate the engineering options, but as a materials
> freak, the first thing I would look at is unidirectional boron-fiber
> aluminum composite. The second thing I'd look into would be a boron-fiber
> epoxy composite. I'm not making life easy for you with that one. d8-)
>
> --
> Ed Huntress
>
>
Is this really a materials issue?
Or Temper?
--
(remove the X to email)
Now just why the HELL do I have to press 1 for English?
John Wayne
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Posted by Ed Huntress on May 7, 2008, 3:16 pm
Please log in for more thread options
> Ed Huntress wrote:
>
>>
>>>Thanks again Ed, so high tensile strength is what I'm after.
>>>
>>>Actually weight is a huge factor, these are for record attempt boats and
>>>any weight on the right sponson has to be minimized to help counter
>>>prop-walk. I'm running in a class that has a 120+ mph record and my buddy
>>>I mentioned just broke the record in his class running 103+, here's pix
>>>if you're interested:
>>>
>>>http://gallery.intlwaters.com/thumbnails.php?album=1002
>>>
>>>Here's the fin I'm talking about on my hull:
>>>
>>>http://gallery.intlwaters.com/albums/userpics/10068/normal_ScanImage011.jpg
>>
>>
>> Oh, those are cool, Terry, and they look like a lot of fun. We were
>> discussing here recently that my uncle raced model hydros like that in
>> the 1930s, in a 35cc IC class and in a steam class (he used
>> gasoline-fired flash steam). I sure wish I had the photos of those.
>>
>>
>>>Wonder if one of the magnesium alloys might be better?
>>
>>
>> It looks to me like you have four engineering factors here: weight,
>> hydrodynamic drag, stiffness, and strength. Magnesium has roughly the
>> same ratio of strength/weight and stiffness/weight of most metals
>> (titanium is somewhat out of line, having high strength/weight but low
>> stiffness for its strength). So magnesium would result in a thicker, if
>> somewhat ligher, fin.
>>
>> I couldn't begin to evaluate the engineering options, but as a materials
>> freak, the first thing I would look at is unidirectional boron-fiber
>> aluminum composite. The second thing I'd look into would be a boron-fiber
>> epoxy composite. I'm not making life easy for you with that one. d8-)
>>
>> --
>> Ed Huntress
>
> Is this really a materials issue?
>
> Or Temper?
If the object is to have the highest possible stiffness and strength for a
given density, it's really a materials issue -- and metal-matrix composites
look to me like the winner. Since the volume of material is low and the
objective is very high, it may be worth the effort and hassle.
And it is a hassle. Just cutting the stuff can be a nightmare. BTW, most of
the aluminum composites available today are not boron-fiber reinforced, but
other ceramics, like aluminum oxide and boron nitride.
--
Ed Huntress
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Posted by Terry Keeley on May 7, 2008, 5:51 pm
Please log in for more thread options Having the fin as thin as possible is the most important, then weight and
strength. Looks like a heat-treated Ti alloy is in fact the best choice,
other than some "unobtainium", LOL!
Thanks again for all your help, my goal is to travel our 330' course in 1.8
sec!
>
>> Ed Huntress wrote:
>>
>>>
>>>>Thanks again Ed, so high tensile strength is what I'm after.
>>>>
>>>>Actually weight is a huge factor, these are for record attempt boats and
>>>>any weight on the right sponson has to be minimized to help counter
>>>>prop-walk. I'm running in a class that has a 120+ mph record and my
>>>>buddy I mentioned just broke the record in his class running 103+,
>>>>here's pix if you're interested:
>>>>
>>>>http://gallery.intlwaters.com/thumbnails.php?album=1002
>>>>
>>>>Here's the fin I'm talking about on my hull:
>>>>
>>>>http://gallery.intlwaters.com/albums/userpics/10068/normal_ScanImage011.jpg
>>>
>>>
>>> Oh, those are cool, Terry, and they look like a lot of fun. We were
>>> discussing here recently that my uncle raced model hydros like that in
>>> the 1930s, in a 35cc IC class and in a steam class (he used
>>> gasoline-fired flash steam). I sure wish I had the photos of those.
>>>
>>>
>>>>Wonder if one of the magnesium alloys might be better?
>>>
>>>
>>> It looks to me like you have four engineering factors here: weight,
>>> hydrodynamic drag, stiffness, and strength. Magnesium has roughly the
>>> same ratio of strength/weight and stiffness/weight of most metals
>>> (titanium is somewhat out of line, having high strength/weight but low
>>> stiffness for its strength). So magnesium would result in a thicker, if
>>> somewhat ligher, fin.
>>>
>>> I couldn't begin to evaluate the engineering options, but as a materials
>>> freak, the first thing I would look at is unidirectional boron-fiber
>>> aluminum composite. The second thing I'd look into would be a
>>> boron-fiber epoxy composite. I'm not making life easy for you with that
>>> one. d8-)
>>>
>>> --
>>> Ed Huntress
>>
>> Is this really a materials issue?
>>
>> Or Temper?
>
> If the object is to have the highest possible stiffness and strength for a
> given density, it's really a materials issue -- and metal-matrix
> composites look to me like the winner. Since the volume of material is low
> and the objective is very high, it may be worth the effort and hassle.
>
> And it is a hassle. Just cutting the stuff can be a nightmare. BTW, most
> of the aluminum composites available today are not boron-fiber reinforced,
> but other ceramics, like aluminum oxide and boron nitride.
>
> --
> Ed Huntress
>
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Posted by Ed Huntress on May 7, 2008, 7:34 pm
Please log in for more thread options
> Having the fin as thin as possible is the most important, then weight and
> strength. Looks like a heat-treated Ti alloy is in fact the best choice,
> other than some "unobtainium", LOL!
>
> Thanks again for all your help, my goal is to travel our 330' course in
> 1.8 sec!
Well, good luck. Let us know how you do with it.
--
Ed Huntress
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>
> Actually weight is a huge factor, these are for record attempt boats and
> any weight on the right sponson has to be minimized to help counter
> prop-walk. I'm running in a class that has a 120+ mph record and my buddy
> I mentioned just broke the record in his class running 103+, here's pix if
> you're interested:
>
> http://gallery.intlwaters.com/thumbnails.php?album=1002
>
> Here's the fin I'm talking about on my hull:
>
> http://gallery.intlwaters.com/albums/userpics/10068/normal_ScanImage011.jpg