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Thread: 30" Scratch Built Cat

  1. #31
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    I'm thinking twin super Vee motors on 4s would make this hull rip :)

    Heath

  2. #32
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    The guy who did my laser-cutting is very keen to help anyone worldwide out with similiar jobs on balsa and plywood. PM me for the contact details.

  3. #33
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    Default 30" Scrath Built Cat

    Hi, How do you guys secure the hatch. I am thinking of a base of ply around the
    outline of the hatch opening and High density weather stripping. Any help will be
    apreciated. Thanks
    Norman

  4. #34
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    Must guys just use hockey tape to hold it in place, this also keeps the water out..

    Heath

  5. #35
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    yep, I make a piece of balsa with my custom canopy and just tape her shut. If you wanna get fancy, you could make a little shelf, so the hatch doesn't fall in - they are WAY too cool looking when sitting nice and flush and the hockey tape is pretty clear so clean sailin!

  6. #36
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    Default 30" Scratch Built Cat

    lomodel Hi, Could you PM me the contact for laser cutting. I won' go through this
    again. Thanks
    Norman

  7. #37
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    Default 30" Scratch built Cat

    Quote Originally Posted by Jesse J View Post
    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
    Hi Jesse and all in this thread. Attached photos of latest progress. Have completed
    sheeting and first coat of white polyurethane sealer and primer. Use white so I
    can see any ding or imperfection. Once sealed will primer and fiberglass over
    silkspan. Still a lot of sanding and finishing before it is smooth. Now for the hardware
    from OSE. Regards
    Norman
    PS. Will work on hatch while waiting for sealer drying
    Attached Images Attached Images
    Last edited by Norman2; 04-12-2009 at 08:51 AM. Reason: forgot some info

  8. #38
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    Great job Norman! I've been busy and you snuck this update in on me. I like the staggerd strakes, I think I noticed that on the plans but forgot when I was adding them... Sorry if I talked you into hours of bandsaw torture, I kinda like cuttin stuff on my bandsaw (one of my good friends). The trick to the lasercutting is to make sure you know how wide your slots will be compared to the thickness of wood you will be slotting. I have never done laser cutting, but definitely like the ease factor!

    How ya gonna do the hatch?

  9. #39
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    Default 30"Scratch built cat

    Hi Jesse.It was hard work on the bandsaw but well worth it. I am using 1/32
    basswood for the hatch. Will post pictures soon. I am building a shelf all around
    the outline of the hatch opening 1/8 x 1/2" ply. It will sit on high density weather
    stripping and will self lock in front and two screws will hold the back. Pretty neat
    and my titan 29 never leaks. I will keep you posted. Regards
    Norman
    PS:I put the strakes in that position because I used to own and drive a 32' Champion Offshore cat and that is where it had the strakes.
    the rear ones act as a mini turn fin and keeps the transom from sliding during turns. Hope it works. regards
    Norman
    Last edited by Norman2; 04-13-2009 at 07:05 PM. Reason: forgot information

  10. #40
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    I have a few 3S lipos that I want to run my twin version on. Will 2x 540 6XL motors with X442 props have enough oomph?

  11. #41
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    Quote Originally Posted by Norman2 View Post
    Hi Jesse and all in this thread. Attached photos of latest progress. Have completed
    sheeting and first coat of white polyurethane sealer and primer. Use white so I
    can see any ding or imperfection. Once sealed will primer and fiberglass over
    silkspan. Still a lot of sanding and finishing before it is smooth. Now for the hardware
    from OSE. Regards
    Norman
    PS. Will work on hatch while waiting for sealer drying
    Norman. What sealer did you use and what is silkspan? I am a bit worried about the added weight of fibreglassing. Can't the hull run without it?

  12. #42
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    Quote Originally Posted by lomdel View Post
    I have a few 3S lipos that I want to run my twin version on. Will 2x 540 6XL motors with X442 props have enough oomph?
    I have played with FE calc a bit and for Twin cats use the Hydro settings which should reflect the fact that 2 motors are in there.
    This is still a guess. !!
    6XL on 4S over 442 props will show.
    101 amps 931W out of the motor 26.900 rpm 48 mph.

    The question now is do you have the 6XL cans yet ??
    If not, given that you have a bunch of 3S packs then you could go 6S on a higher wind motor and drop your amp draw for the same power output.
    See it....find the photos.....sketch it it....build it........with wood

  13. #43
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    Quote Originally Posted by lomdel View Post
    Norman. What sealer did you use and what is silkspan? I am a bit worried about the added weight of fibreglassing. Can't the hull run without it?
    lomodel Hi, I used a polyurethane sandable wood sealer by Valspar. Got it in Lowes.
    Silkspan a very light material used to cover R/C Aircraft wings. The fiberglassing
    is only a very light and thinned coat of resin just to impregnate the silkspan. It is
    very light but very strong. It could do without it but I need strength and a perfect
    finish. Regards
    Norman

  14. #44
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    Quote Originally Posted by Simon.O. View Post
    I have played with FE calc a bit and for Twin cats use the Hydro settings which should reflect the fact that 2 motors are in there.
    This is still a guess. !!
    6XL on 4S over 442 props will show.
    101 amps 931W out of the motor 26.900 rpm 48 mph.

    The question now is do you have the 6XL cans yet ??
    If not, given that you have a bunch of 3S packs then you could go 6S on a higher wind motor and drop your amp draw for the same power output.
    I do not have the 6XL cans yet, still counting pennies... It would be twin 6XL on 3S through X442 props. 101A or above is not my concern, the ESC will handle it. Going 6S would mean 4x 3S packs in the boat - too heavy!

  15. #45
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    Quote Originally Posted by Norman2 View Post
    lomodel Hi, I used a polyurethane sandable wood sealer by Valspar. Got it in Lowes.
    Silkspan a very light material used to cover R/C Aircraft wings. The fiberglassing
    is only a very light and thinned coat of resin just to impregnate the silkspan. It is
    very light but very strong. It could do without it but I need strength and a perfect
    finish. Regards
    Norman
    So you'll be applying resin over the silkspan without actually laying fibreglass cloth?

  16. #46
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    Hi lomodel, Yes no fiberglass cloth. That would be heavy. Silkspan is 1 oz per square yard.
    Will post photos. regards
    Norman

  17. #47
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    I reinforced the plywood motor-mount bulkhead with glassfibre and glued the rest of the frame in place. I decided to do the sheeting with 1,0mm balsa instead of 0,8mm(1/32") to strengthen the hull a bit.
    Attached Images Attached Images

  18. #48
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    Default 30"scratch built cat

    Hi lomodel, Looking beautiful and really straight. It is a lot of hard tedious work but
    you will not be sorry. I have fiberglassed mine and now on the final coats of primer.
    Need to wait for hardware, motor and esc from OSE which will be here next week.
    Will report progress. I am having a hard time making the canopy but I just may
    carve it from a block of balsa. How are you doing yours? Regards
    Norman

  19. #49
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    Norman, I would really like to see your latest pics. For the hatch I had the longitudinal and cross sections of the cockpit laser-cut as well (see far left in pic) and will fill the four corners in with some kind of foam that will be shaped and fibreglassed. That will be stuck onto the hatch cover with supporting strips beneath it. Will post pics after the weekend as well...
    Attached Images Attached Images

  20. #50
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    Default custom hatch

    I make my own canopies/hatches from insulation foam and epoxy.

    First, I find a canopy I like and trace a sideview and top view. I gluestick this to a square-as-possible rectangle of foam, so the topview and sideview are nice and orthogonal.

    I go to mr bandsaw and carefully cut out the two views, being careful to keep the piece opposite the paper with the trace (so I have a nice square base for cutting).

    Then I get my 80 grit sanding block and get the rough shape, taking off the sharp corners - but not altering the base. Hang on to the chunk of foam cut off the base for next process. Once you get the shape you like, drop down to 220 or 320 grit depending on your patience.

    Now get your hatch (I use a solid piece of whatever the decking was) and your base chunk of foam. I tape this hatch board to the chunk so it has the perfect curve of the deck. Then epoxy on the canopy where you have marked that it should go, I use a sharpie and eyeball it, but I am sure others will measure for precision. If you have the top chunk of foam, you can sandwich it on top of the hatch and add some weight to the top. Let this cure thoroughly.

    Now, get your favorite epoxy resin. I have only glassed one hatch, but you can definitely add some cloth to this step if you wan. Leave the hatch in its tape down from the last step, you want it to keep the shape of your deck and all the epoxy that will be applied will do a good job of retaining the grace. The first coat of epoxy is ALWAYS ugly. All kinds of bubbles will come out of the foam, so don't despair. let this cure solid, then add one or two more to be sure it is SMOOOOOOth as a baby's butt. I like to leave the high gloss finish, but if you want to do some final shaping, go for it.

    Last step. Eyeballing with a sharpie, I go around the bottom of the hatch about 1/2" within the edge of the canopy and then use dremel with cutting disk and retrace your pen mark. This allows you to remove all the foam and have more room vertically for electronics and airflow. Paint her up and tape her down! It is extremely durable and as cool as you can imagine!

    now get to work, wanna see it!
    Attached Images Attached Images
    Attached Files Attached Files

  21. #51
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    Default 30 scratch built cat

    Hi Jesse, Thanks for the advice. I am on my way to Lowe's to get the foam and
    the resin. My canopy will be smaller than yours which I am copying from my
    Champion Cat. But I got the idea. Thanks again. Will post pictures soon. Regards
    Norman

  22. #52
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    Thanx for that extended explanation Jesse! What insulation foam you using, the pink one?

  23. #53
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    Default 30" scratch built cat

    Hi lomodel. Probably using pink construction foam. Best for flotation. Regards
    Norman
    Ps: Yes Pink

  24. #54
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    Mine is the kind used as the base for the kitty. I just went to my LLS (lumber store) and asked if they had any scrap chunks, or dinged up boards; the guy took me to a 4'x 8' piece that had a corner broken off and asked me how much do you need? He then cut off a 24" x 4' strip and said, "tell em it is a scrap at no charge" It don't matter what color, just what ever is cheapest/free-est! if you like pink, then get pink. there are lots of colors and thicknesses, 2" allows for most custom and room for cutting. I prefer green or blue since that was free.....

  25. #55
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    Default 30" scrath built cat

    Hi, Well, am now in the process of primer and finishing. Installed hatch but you
    will notice it is a little bit indented. This will be corrected when I install 1/16"
    weather stripping which is what I use to seal my hatch. Now working on the
    canopy. More work. regards
    Norman
    Attached Images Attached Images

  26. #56
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    Default 30 " scratch built cat

    Quote Originally Posted by Jesse J View Post
    I make my own canopies/hatches from insulation foam and epoxy.

    First, I find a canopy I like and trace a sideview and top view. I gluestick this to a square-as-possible rectangle of foam, so the topview and sideview are nice and orthogonal.

    I go to mr bandsaw and carefully cut out the two views, being careful to keep the piece opposite the paper with the trace (so I have a nice square base for cutting).

    Then I get my 80 grit sanding block and get the rough shape, taking off the sharp corners - but not altering the base. Hang on to the chunk of foam cut off the base for next process. Once you get the shape you like, drop down to 220 or 320 grit depending on your patience.

    Now get your hatch (I use a solid piece of whatever the decking was) and your base chunk of foam. I tape this hatch board to the chunk so it has the perfect curve of the deck. Then epoxy on the canopy where you have marked that it should go, I use a sharpie and eyeball it, but I am sure others will measure for precision. If you have the top chunk of foam, you can sandwich it on top of the hatch and add some weight to the top. Let this cure thoroughly.

    Now, get your favorite epoxy resin. I have only glassed one hatch, but you can definitely add some cloth to this step if you wan. Leave the hatch in its tape down from the last step, you want it to keep the shape of your deck and all the epoxy that will be applied will do a good job of retaining the grace. The first coat of epoxy is ALWAYS ugly. All kinds of bubbles will come out of the foam, so don't despair. let this cure solid, then add one or two more to be sure it is SMOOOOOOth as a baby's butt. I like to leave the high gloss finish, but if you want to do some final shaping, go for it.

    Last step. Eyeballing with a sharpie, I go around the bottom of the hatch about 1/2" within the edge of the canopy and then use dremel with cutting disk and retrace your pen mark. This allows you to remove all the foam and have more room vertically for electronics and airflow. Paint her up and tape her down! It is extremely durable and as cool as you can imagine!

    now get to work, wanna see it!
    Hi Jesse. Sorry but I gave up on the canopy. Could not get the shape I wanted.
    Ordered an SV27 hatch and cowl and will do some surgical implant on my
    hatch which is 4" wide. No more frustrations. regards
    Norman

  27. #57
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    Norm, you gave up on the canopy, i just gave up on this whole @#$%^ build! I made a complete mess of the sheeting and broke a few balsa parts in the process and the bulkhead designs need some tweaking as well. It all went great, I cross sheeted the tunnel floor with 2x layers of 1/32" balsa, beautifull... Then the sheeting started and all went horribly wrong. I only spent about $50 on balsa up to now, so no big loss there, only frustration. But it IS my first scratch build...

    I'll probably tweak the design a bit and then start all over again in a few months. Tip: use 3mm Ply for the frame if you have access to a laser cutter. For a 30" cat, balsa just isn't strong enough!

  28. #58
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    Smile 30" scratch built cat

    Hi lomodel, Really sorry to see you gave up. Mine is ready to paint as soon as
    all my stuff comes in from OSE. I will set up stuffing tube and strut up, mask the
    strut and final paint. Cat will be medium metalic silver ( Mercedes Benz Color).
    If I may, some advice. When I did my frame with 1/8" balsa, once I glued it
    together on a jig, I fiberglassed everything with thinned out resin. This makes it
    super strong. I used 1/16" balsa for sheeting and no problems. I then cross grained
    with 1/64" plywood and no problems. The hardest part I have found is the finishing
    with Putty and many coats of primer. The other problem I encountered was that
    darn canopy. Finally gave up and ordered an SV 27 canopy which I will implant to
    my hatch. Well, when at first you don't succeed try again. By the way, this is the
    last time I try this. Next time I will buy a Jolly Cat hull. regards
    Norman

  29. #59
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    What was the order of sheeting you did? Sides or bottom of sponsons first? I am now also thinking about the 32" eBay cat hull...

  30. #60
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    Smile 30" scratch built cat

    Hi lomodel, I first sheeted bottom of tunnel, then bottom and sides of pontoons.
    I then reinforced all glue joints with more glue. I then added flotation and finally did the top. The whole thing weighs 15 oz. The chineese cat is pretty good
    but should be reinforced with some CF. I thought about getting one but was determined to build one myself. Regards
    Norman

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