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Thread: Murphy 1800 Amphib Questions

  1. #1

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    Murphy 1800 Amphib Questions

    The logical place to ask the following question(s) is Murphy technical support. I've emailed tech support, called the main line, emailed sales, and no dice. Can't get ahold of anybody.

    So I'll ask my questions here as the well of knowledge is DEEP!

    I recently bought a set of 1800 amphibs in kit form, unassembled. I have the manuals, and am mostly literate, however a video or two would be very helpful. The google machine, and youtube yielded nothing. Any thoughts?

    Additionally, and the main focus of my question is the difference between the 1500A and the 1800A. According to their website, the 1800's are 21 inches longer and weigh 58 pounds more. Other than that what's the difference? I'd like to have 1500's rather than the 1800's, and wanting to know if this is possible, and if so, how.

    But if it's an apple/potato comparison trying to make a pinto out of a semi truck, I'll just build them as 1800's.

    Thanks gang,

    Sik

  2. #2
    WWhunter's Avatar
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    If irishfield is not busy hopefully he'll be able to answer your questions. I have a set of the 1800 amphibs still in the crate also.

    Have you posted your questions on the Murphy builders site? Might be the best way to get an answer.

  3. #3

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    Hey there Keith, been a while. I haven't posted on the Murphy builders site: didn't know it existed. You should come down for coffee one of these days.

    Sik

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    skywagon8a's Avatar
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    Quote Originally Posted by Sikorsky View Post
    ....Additionally, and the main focus of my question is the difference between the 1500A and the 1800A. According to their website, the 1800's are 21 inches longer and weigh 58 pounds more. Other than that what's the difference? I'd like to have 1500's rather than the 1800's, and wanting to know if this is possible, and if so, how.

    Thanks gang,

    Sik
    This is not really an answer to your question but is something which needs to be addressed. What is the gross weight and type of airplane which you plan to put these floats on? Generally a rule of thumb on size is that the model number is related to the buoyancy of the floats in fresh water. When floats are of the amphibious variety it is helpful to have a little extra buoyancy to compensate for the added weight, forward CG shift and open compartments occupied by the landing gear. If these floats are sized in accordance with the accepted practice, the 1800s would have the capability (using the FAA's requirements) of floating an airplane with a gross weight of 2000 lbs. The 1500s = 1667 lbs max gross.

    Another thing would be the difference in length of 21". Where specifically is this 21" located? If it is exclusively ahead of the step, removing it could effect the water handling characteristics in an undesirable manner. When the flat planing area ahead of the step is reduced, the ability in getting on the step with heavy loads can be marginalized as well as the ability to remain on the step while accelerating under certain conditions.

    ps, I used to work 2nd shift at Sikorsky. The highlight of that period of time was when I met Igor Sikorsky one evening as he walked through the factory.
    N1PA
    Likes Bill Rusk liked this post

  5. #5
    WWhunter's Avatar
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    Quote Originally Posted by Sikorsky View Post
    Hey there Keith, been a while. I haven't posted on the Murphy builders site: didn't know it existed. You should come down for coffee one of these days.

    Sik
    Hey Zack! Or better yet...you can stop in up here. I spoke with your dad a week or so ago about several things. Had planned on getting down that way, just been busy getting ready for that white stuff. Give me a call, I might be able to give you some more help on the floats.

  6. #6
    skywagon8a's Avatar
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    Quote Originally Posted by Sikorsky View Post
    According to their website, the 1800's are 21 inches longer and weigh 58 pounds more.
    Thanks gang,

    Sik
    Look again: http://www.murphyair.com/floats.html
    The weight difference is only 6 pounds. Minuscule for the flotation difference.
    N1PA

  7. #7

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    I like how the chart says “water rubbers” that must be something new for floats.

  8. #8

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    Quote Originally Posted by skywagon8a View Post
    This is not really an answer to your question but is something which needs to be addressed. What is the gross weight and type of airplane which you plan to put these floats on? Generally a rule of thumb on size is that the model number is related to the buoyancy of the floats in fresh water. When floats are of the amphibious variety it is helpful to have a little extra buoyancy to compensate for the added weight, forward CG shift and open compartments occupied by the landing gear. If these floats are sized in accordance with the accepted practice, the 1800s would have the capability (using the FAA's requirements) of floating an airplane with a gross weight of 2000 lbs. The 1500s = 1667 lbs max gross.

    Another thing would be the difference in length of 21". Where specifically is this 21" located? If it is exclusively ahead of the step, removing it could effect the water handling characteristics in an undesirable manner. When the flat planing area ahead of the step is reduced, the ability in getting on the step with heavy loads can be marginalized as well as the ability to remain on the step while accelerating under certain conditions.

    ps, I used to work 2nd shift at Sikorsky. The highlight of that period of time was when I met Igor Sikorsky one evening as he walked through the factory.
    Skywagon- All pertinent questions. The application will likely be an experimental J3. I have a set of brand new Baumann 1500 floats which are all set to go, and in all water applications is the preferred float, but no amphibious capability. We have rebuilt 1320's and 1400's (with success) so understand many of the issues of float construction. Also, absolutely agree with the pertinence of where the floats are longer. If the length is just added onto the aft portion it's no big deal, but if anything is altered front of the step, that will require construction as 1800's. I'd sure like to set eyes on a set, and would be willing to travel a reasonable distance to do so. There must be a set someplace in MN.

    Regarding weight, I was referencing the "net weight increase." Perhaps I should have been looking at the weight without spreader bars for a more accurate number. To me, 6 pounds difference would likely be additional length added to the back of the float.

    And Egor Sikorsky: totally cool. Mad genius. Crazy in a functional kind of way.

    Keith- Please pm me your phone number. I bought the floats for my dad to have something to do when he is at his girlfriends house. White carpet and 3m 5200 should be just fine don't you think?

    Sik

  9. #9
    skywagon8a's Avatar
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    Sik,
    You could remove a smaller portion of the section ahead of the step to arrive at an in between size without sacrificing too much performance but still reducing the length.
    N1PA

  10. #10

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    This pristine 1800 kit is now for sale. See posting with pics of a finished Murphy float.

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