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Thread: 30" Scratch Built Cat

  1. #1
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    Default 30" Scratch Built Cat

    Hi, Recieved my plans today from Jesse J and will start cutting forms this week.
    Wil be posting photos of progress as it comes along. Hope this works.
    Norman2

  2. #2
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    Man that is just teasing !! You can't just tell us you are building a cat and leave us hanging.....that's cruel.

    You are doing a twin drive right ??? Of course you are . Please tell us it's a twin.
    What sort of power are you looking at throwing in there. Obviously lots, but just how much ??
    I will be following this one closely as I want to get on with a twin drive 30+" cat as soon as the rigger is finished.
    See it....find the photos.....sketch it it....build it........with wood

  3. #3
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    Default 30" Scratch built cat

    Hi Simon, Just completed cutting bulkheads from 1/8" balsa and will glue
    them together this week. I will take a photo and post. I do not think it
    will be a twin but maybe. Just want to make sure I can complete hull and
    if it looks OK I will then decide what power to use. Will post pictures and
    photos.
    Norman

  4. #4
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    Great! glad you got the plans and are having fun in the cutting process. The main struggle with this build is making dam sure the sponsons are true before sheeting. You will save yourself hours of bondo/sanding/bondo if you spend some quality time truing up the base of the bulkheads. I have even added strips of balsa just to ensure flat ride pad. My first one of these had a pretty lumpy base then my atrocious first fiberglassing really put it on the shelf.

    Post pics, even of the bulkheads, I am always glad when I do, cuz you can't once you get to sheeting! Ahhh, the inocent phase of the build. ENJOY!

  5. #5
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    Default 30" Scratch Built Cat

    Hi Jesse, Again thank you for the plans. I am going to follow all your tips in
    building this cat. I have built several plank on frame kits with balsa sheeting
    and have been able to have a very smooth finish. What I usually do is fiberglass
    all the insides. Once I sheet I use two coats of fiberglass, sand the nibbles and
    then use silkspan with thinned fiberglass resin. The only change I think I will
    do is to square off the transom. I am attaching photos of my latest scratch built
    52" Frigate. Hope you like. I am really determined to make a nice cat.
    Regards,Norman
    PS The frigate can be maybe considered fast FE as it is powered by Twin 700 BB
    Graupners and it is very fast. Does not turn well but it does move
    Norman
    Attached Images Attached Images

  6. #6
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    nice looking frigate, any vids?

    I have changed the stern as well. first couple square. this micro i tapered and it looks way better, much more realistic. I can post pics if you want to see more specifically.

    let me know if you have any more building questions, I am sure I have encountered the same ones.

  7. #7
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    I managed to redesign the plans to 810mm length with a 150mm wide tunnel and modified it so that brace F becomes a slightly tilted plywood twin motor mount. The plans are available as JPG, PDF or DXF for those who want it... That is a CAD rendering below, not the real thing yet.
    The single drive version is also available in the same format.
    Attached Images Attached Images
    Last edited by lomdel; 04-02-2009 at 11:14 AM.

  8. #8
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    Quote Originally Posted by Jesse J View Post
    nice looking frigate, any vids?

    I have changed the stern as well. first couple square. this micro i tapered and it looks way better, much more realistic. I can post pics if you want to see more specifically.

    let me know if you have any more building questions, I am sure I have encountered the same ones.
    Hi Jesse, Was able to glue framework together. Unfortunately there is no one that
    can laser cut within 200 miles from here so I cut it myself. During the week end
    I will complete the cutouts on the bulkheads and add some bracing between each
    one to make sheeting easier. Will use 1/16" balsa and then 1/64 ply. As you can
    see, I indented the part of the transom to make up for the in-line hardware I am
    going to use. Did not want it to be too far from the transom. However I will be
    sheeting the top so it will not be seen from above. Will keep progress report.
    Regards, Norman
    Attached Images Attached Images

  9. #9
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    I changed the total proportion of this twin drive version of mine and shortened it to 770mm for a stiffer structure. Below is the drawings, I will again add a 3D rendering later today... (added )
    Attached Images Attached Images
    Last edited by lomdel; 04-03-2009 at 05:24 AM.

  10. #10
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    Right on Norman! looking good! Glad to see progress. Is the indentation for the strut?

    What hardware are you planning to use?

  11. #11
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    Norman. I don't mean to hijack your build thread, but I would like to build mine parallel to yours. I believe we can use this thread of yours to pool information, tips and answers 'cause this would be my first scratch build as well. My balsa and ply cut-outs would be done this weekend and I should start assembling the frame next week some time. In the meantime I am following your build with interest.
    How are you going to do the cut-outs in the bulkheads now that everything is assembled and glued?
    Are you going to glass fibre it finally after sheeting? One tip; if you sheet the tunnel and deck with balsa, do it cross-grain not parallel. The cross-grain would add more lateral stifness to the frame (an old aircraft building technique).

  12. #12
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    Default 30" Scratch Built Cat

    Hi, You can hijack this thread any time you wish. The more information out there
    the better. The indentation in the transom is for the OSE In Line Hardware. Just did
    not want it to be too far from the transom. I will cross grain the sheeting but I
    will be using 1/16" balsa and cross grained with 1/64" ply. Then Thinned Fiberglass
    coating over silkspan. I have found that this makes a pretty strong and light hull.
    I am doing the cutouts today with my trusty mini-dremel. Let us see what we end up
    with.
    Norman

  13. #13
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    Default 30" Scratch Built cat

    Quote Originally Posted by Jesse J View Post
    Right on Norman! looking good! Glad to see progress. Is the indentation for the strut?

    What hardware are you planning to use?
    Hi Jesse. Yes the indentation is for the OSE In Line Strut. Did not want the strut
    and rudder to be too far from the transom. Photo attached. Regards
    Norman
    Attached Images Attached Images

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    Wait a minute, where did you get that? I have been searching for that very gem for a long time now. I LOVE it! Could be the answer, do you have a link to a place I can get me one too?

    Yes, I have cut out the bulkheads with my trusty dremmel too, much better to make a strong frame, then remove excess weight, good job Norman.

    Next one of these I do, I may go straight to ply on the tunnel; cross grain and then 1/64th, I have found, needs reinforcing for the motor mount any way, otherwise some nice carbon fiber would do - I got me some of that 1/32" would be perfect.

    Nice to have a parallel build to cheer eachother on! I will be following closely! good job guys. Are you gonna race them when finished?

  15. #15
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    Default 30" Scratch Built Cat

    Hi Jesse, The in line strut/rudder is available at Offshore Electrics under
    Hardware Systems. Steve can fix you up with one. Regards
    Norman

  16. #16
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    If I decide to use two of these http://www.astecmodels.co.uk/catalog...roducts_id=553 , where can I get two counter rotating 4mm flex shafts assembled with 4mm drive shafts?

  17. #17
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    I am just finishing some bearing struts that run 4mm bearings and then it steps up to 3/16 prop stub. I am doing this because I wanted to keep the struts smaller for 2S-4S stuff. I am now working on some bigger 3/16" shaft struts with bearings. They also have a lube hole for the bearings.

    I can make the shafts for you if you do not find any.
    Attached Images Attached Images

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    Those look GREAT Jeff. Could be the answer.

    However, how does one resolve the problem of prop sizes: counter rotating come in 42mm and 47mm, nothing in between? How does one have much of a selection?

  19. #19
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    Hey Jesse. If it were me with limited choices on props then you do your build for the KV/Volts. Should be no problem running the 47s on 6S 12-14 XL. I have not done it but seems no problem amp wise.

  20. #20
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    Quote Originally Posted by Jesse J View Post
    Those look GREAT Jeff. Could be the answer.

    However, how does one resolve the problem of prop sizes: counter rotating come in 42mm and 47mm, nothing in between? How does one have much of a selection?
    I have a similar issue although the whole Cat is still in the concept stage.
    GHraupner have the CF props in R+L rotation in 40, 42 , 45, 48mm dia.
    The pitch on these seems to be a bit of a point of discussion as some tell me they are 1.2 and others say they are 1.4.
    I will use these when it come time to do a Twin cat and use rpm to get speed.
    30krpm will be my min calculated shaft speed using 1.4p as a constant. IF they are 1.2 then they will unload and scream !!!!

    Just a thought.

    btw Jeff that work that you do is spectacular. I love it and aspire to make parts that could look half as good.
    See it....find the photos.....sketch it it....build it........with wood

  21. #21
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    Yo Norman, how's progress? I know you are doing single drive, but this size cat is entering into the twin realm. What size motor/esc are you thinking? Batteries? Updates please

  22. #22
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    Default 30" Scratch built Cat

    Hi Jesse, Well I have started the 1/16" sheeting. Did some during the week end
    and some today. Will let it dry all day and start putting in flotation before I do the
    bottom. Well I know I will get all kinds of feedback but I am going to start this out
    with a 700 OSE SC brushed, Jetti 600 60 amp ESC. 14 NIMH 4600Mah cells, .150
    flex and Octura X447, OSE IN-Line strut/rudder, Water cooling for motor and ESC.
    If it floats and runs halfway decent I wil go to brushless and lipos. Did not want to
    invest too much to see it sink on the first try, I have to learn how to set up cats.
    I am good with my Mono but the set up is tried and tested in racing here in our
    local club in LSO. Will post photos soon. Regards
    Norman

  23. #23
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    I had never thought of doing decking first... Always started with bottom, sides then decking. Guess there are more than one way to skin a cat, eh?

  24. #24
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    On my side, I had the balsa and ply laser-cut tonight. That was really cool to watch . I didn't have my camera with me so I took a few cellphone pics, see below.
    I will post pics of the cut-outs and the pre-glue assembly tomorrow. You will see I had strut G cut in two options, one for twin motors and the other one as a single motor mount. I have actually decided on the twin 8XL on 4S each spinning X442 props set-up, but I like to have a back door open...
    Attached Images Attached Images

  25. #25
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    Default 30" Scratch Built Cat

    Hi, Looking super. I wish I could have had a laser cuter near me because I spent
    many hours cutting out mine with a scroll saw. regards
    Norman

  26. #26
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    Quote Originally Posted by lomdel View Post
    I have actually decided on the twin 8XL on 4S each spinning X442 props set-up, but I like to have a back door open...
    Is this cat is 30" to sponson rear or 30" overall ??
    I ask because TWO 8XL's sound like a LOT of power in there. Unless someone tells you that it is certifiable madness to do so then go for it.

    I'm watching this one
    See it....find the photos.....sketch it it....build it........with wood

  27. #27
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    Norman. It is a great advantage to have access to such a machine. The total cutting time for all the parts was about 25 minutes. They were cut to an tolerance accuracy of 0,1mm. The pieces fit together perfectly.
    Simon. The main stringers is 770mm total length and 764mm to rear of sponson. If you think 2x 8XL is too much, what would you suggest? 2x 9L's on 3S would have more or less same rpm but be lighter and I have some 3S packs here.

  28. #28
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    Here are a few pics of the cut-outs and a pre-glue temporary assembly. You will notice the two motor mount options that I can still decide on, either twin or single...

    I am going on holiday for a few days so this project will be dormant for a while.
    Attached Images Attached Images

  29. #29
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    Quote Originally Posted by lomdel View Post
    Simon. The main stringers is 770mm total length and 764mm to rear of sponson. If you think 2x 8XL is too much, what would you suggest? 2x 9L's on 3S would have more or less same rpm but be lighter and I have some 3S packs here.
    Go hard for the 8XL IF you already have them, I seem to remember that you got a few a while back.
    I can not say if a pair of 8XL's is too much, I want to know if they are.
    I am keen to go 8L or 10L on 4S Given that I have some good 4S packs here.
    To do this I need to buy motors and speedies.
    From one supplier the motors are nearly the same price for a L or XL, A 100A or 125A speedy each should be plenty.

    I am still doing my research on 30"+ Twin drive Cats and would like to pop into this thread to help. If anyone objects, shout out.

    I am watching
    See it....find the photos.....sketch it it....build it........with wood

  30. #30
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    I don't have any 8XL's but I do have a some 3S Lipos that I could use. To use them I must go with the 9L but I am a bit unsure... I PM'ed Reddywatts for some advice. Anyone else with suggestions would be much appreciated!

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