30" Scratch Built Cat

[Norman2]

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

[lomdel]

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.

[Norman2]

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

[lomdel]

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...

[Jesse J]

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!

[Norman2]

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

[lomdel]

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

[Norman2]

30" scratch built cat

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

[Jesse J]

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.....

[Norman2]

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

[Norman2]

30 " scratch built cat

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

[lomdel]

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!

[Norman2]

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

[lomdel]

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...

[Norman2]

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