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Author Topic: XRAD'S Sterling B15M Chris Craft Corvette 48"  (Read 5131 times)

xrad

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XRAD'S Sterling B15M Chris Craft Corvette 48"
« on: November 13, 2015, 01:38:08 pm »

Just a peek for now as photographed in the back of my car early this am.  Just picked up this beauty for a bit more than the kit(which is hard to find). Been looking for a while and was lucky to find this locally. Has all the hardware and motors, brass props, etc.   More to follow...
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #1 on: November 22, 2015, 01:48:36 pm »

Well, what seemed like a well built model turned out differently. I think the build was done well, but unfortunately, there was a small crack in the paint just aft of the bow on both sides.  Sooooo....thought I would just repair the paint cracks. But for some reason, there was a a strange reaction between the epoxy and the balsa. seems like some oily residue was in the balsa, or leached out of the paint/epoxy combo. All of the paint /epoxy delaminated from the hull except at the bow balsa block. What began as a small repair turned into me peeling all the paint off the hull.  it all came off rather easily in a few hours.


Some of the original epoxy seemed to bond really well, especially on the original motor mounts and stuffing tubes. However, the universal joints (ADP 3.17 to 5mm) were cracked and could not be used again. So I had to order a stainless set (only come in 3.17x4mm) so these will have to be drilled for the 5mm shafts.


The hull was the rough sanded, and a spread of bondo applied. Then the long sanding process, all by hand due to the hull curves. Then came a filler coat of acrylic paste. I use winsor and newton. I know it holds paint well, and hardens fast, and has not cracked on any of my models, even when applied rather thickly.


then another sand. Soon to be applied will be a few layers of 1/2-3/4 oz fiberglass cloth with polyester resin. I also brazed up a set of struts and ordered a pair of opposite rivabo 60mm props from Harbor models. 


Comming soon: electronics install (x2 540 motors, mounts,cooling fans w/temp-speed control, voltage regulator, 6v batt install, and remote)
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #2 on: November 22, 2015, 02:02:30 pm »

here are a few original pics before I bought her:
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #3 on: November 22, 2015, 06:56:33 pm »

First layer of glass. Will eventually do the whole hull. A bit at a time. The small weave of 3/4 glass is sometimes hard to get the resin into for good hull contact. I like to brush on a thin coat of resin on the hull first, before laying on precut glass. Much better glass penetration that way.


Will do two at least 2 glass layers. second may be slightly heavier 1 or 1.5 oz...see what I have in the 'left-overs' box.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #4 on: November 28, 2015, 04:19:32 pm »

Had some trouble with the bondo fiberglass resin I bought at the local auto store. The resin took a week to set up even with extra catalyst.  May have been on the shelf for a while....


Anyway, 1 week later it was hard enough to sand down at the chine so that I could apply the side panels. I bought another bondo fiberglass resin can at home depot. This one has a 2 hour set-up time.  It has a working time of about 20-30 min which is perfect for laying up the four side pieces. I also switched to 2 oz cloth as I found a bunch in the left overs bin! Also, I used a 1 inch brush for thin base coat application and to spread the resin on the cloth. then i use a 1/2 in brush to get the bubbles out and for fine tuning.

there is a thin bead of green tape at the glass trim line.

coming along. Just waiting for the stainless 3.17 x 4mm shaft universal couplers.  These will have to be drilled out to 5mm on the big end for the stainless prop shafts.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #5 on: November 29, 2015, 09:36:03 pm »

Today's schedule
10a: final layer of 2oz cloth
12p: sanding
1p:   bondo filler
3p: sanding
4p: first coat of primer


came out pretty smooth. A few pits and bumps here and there which will show up better following a light sanding.... then fill w/acryllic paste, then sand...and so on...


2 hour bondo fiberglass resin worked great, even in my 45 degree garage!  But then i did have a small electric radiator/oil type heater sitting under the boat with a garbage bag 'tent,' so it was nice and warm for the 'cure.'
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #6 on: December 01, 2015, 11:42:16 pm »

The driveshaft measured out at ~.186 inch(thought it was 5mm!), a hair more than 3/8th. 5mm props still fit fine and the thread was fine too! I used a number 12 drill to open up the 4mm side of the stainless universals. The cut off about 1/4 inch from the prop shafts as they were a bit mangled. then milled a set screw groove into the shafts. luckily, these were 'soft' stainless and machined easily. 


the motor set up pictured is a tamiya 540 motor (2 for 12$ w/free shipping! how an u beat that?). Using standard chinabay speed control and a super tactic 2.4ghz tx/rx.  I have used Tactic before in several boats and these systems have not let me down.


There is a cooling fan and heat sink on the motor. Fan speed will be controlled by a small thermistor and dedicated DC speed control (small yellow thing w/5 wires).  Will add a voltage control to regulate power to 5v off the main 6v battery.  Motor speed and power will be more than enough for scale speed.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #7 on: December 06, 2015, 08:38:24 pm »

motors installed. Mixed 15min epoxy and let it sit for 12 min, then dipped the mounts into epoxy and put in place. Much neater process  then laying epoxy on the wood and then putting the motor mounts in place.  Have to time it right.


Motor cooling system installed. Uses 2 small 5v DC fans. You can see thermistor (yellow) in the cooling fins of each heat sink. Perfect fit and I just pinched the fins to hold the wires in place. Don't pinch the thermistor itself, it will crack. Drop of CA to act as a conductor heat sink-thermistor. 


Originally, I had the system at 6.3v (bat output), but this caused overheating of the micro fan speed controller, so I had to put in line an adjustable voltage regulator. System runs great at 4.0v.  You can see the soldering iron on the starboard motor and the motor turning.


Funny thing, one of the motors did not start turning when the thermistor was heated when at 6v. The body of the micro speed controller became warm-hot.   Then, I started hearing a radio sports station through the motor coil!!  You could hear it very clearly. The hotter the speed control, the better the reception.  Probably not the best chinabay fan and speed controller design...but it works now.


Of course, the heat sinks do most of the work, and the fans were just for fun. I don't expect anything more than scale speed out of this set-up, so heat really should not be an issue. 
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Shipmate60

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #8 on: December 07, 2015, 07:50:50 am »

I do like a good refurb, and this is just that.
Well done XRAD on such a complete job!!


Bob
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #9 on: December 07, 2015, 12:59:07 pm »

Thanks, Bob! 

Once the hull is painted and electronics installed, I plan to only just touch up the deck and superstructure as the original model was built to a descent standard including chrome plating of the pot fittings on the superstructure. I am going to refinish the original deck and re-plate the deck fittings as they show wear. Also, I have left the original transom finish including the hand painted name "Orpha Belle" as an tribute to the original builder. I suspect it was a wife or mother, and by naming her as such, it may have allowed the builder more 'quiet time.'

I just have to match the hull color to the aged ivory white of the superstructure.
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Perkasaman2

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #10 on: December 07, 2015, 06:26:21 pm »

You are making a good job of the refurbishment. I think dampness caused the hull cracks because the wood expands and splits the paint. Could be wrong  but that's my thinking. This is a big model and it should be impressive when it's back in the water.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #11 on: December 07, 2015, 09:54:33 pm »

Could be right. And there were a few cracked bow planks as well.  Looking for some aluminum flat wire for trim...maybe I will add...maybe not..
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #12 on: December 10, 2015, 12:52:55 am »

Here is something fun!  Plating the portholes.


Caswell plating kit Copper/Nickel.  you are supposed to plate copper onto pot metal before nickel plating. these were brass portholes. My boat has 3 on each side. They were painted and very corroded from resin.  There were epoxy windows and the portholes were epoxied into place, so corrosion was inside and out.  Anyway, took a bit of cleaning to get down to good metal. used pointed red stone in my dremmel kit, it worked great. then a polish on the buffer wheel, then some 600 grit.


Now I had basically shiny brass to work with. I tried plating nickel directly to the brass. It came out ok, but not great. So then I copper plated and THEN nickel plated and the coating was very nice and 'thick' and even with a bit of shine. Then I hit them all lightly with the dremmel wire buffing wheel. Then all the portholes shined like nearly new! After they are glued into place, I will touch them with a bit of metal wax to keep the shine on longer.  Someone already plated all the big superstructure fittings, so I won't do these. I will do the small deck fitting as they were not plated.


Caswell directions a bit lacking. you use the copper probe with copper plating and silver probe with nickel.  I poured a bit of  each solution into plastic containers then plated, rather than use their 'brush' system. Took about 1.5 min for the copper and about 60 sec for the nickel, turning the parts so that all sides exposed to the current evenly. If the solution did not look too degraded, I poured it back into the bottle. Careful, the original plastic bottles are tall and tip over easily! Ask me how I know..... As far as price, the caswell kit is a bit high for what you get. as soon as I have time to figure out how to make my own solutions, I will.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #13 on: December 13, 2015, 01:42:23 am »

3 coats primer and then 400grit light sanding.  Pic is of the first coat which has not covered the acrylic filled spots, takes at least three coats otherwise it looks dull when painted over. Then three coats of 'navajo' white, the closest color match I could find to ?30+yr old ivory white......followed by one coat of testors gloss.

pretty close match in a good light.

next up, bottom paint....have to wait a week for base coats to harden.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #14 on: December 14, 2015, 08:36:54 pm »

I always liked the look of swim platforms...not original to the design, but looks good so far...trim is aluminum pipe pressed flat and then drilled for flat top pins. Pins trimmed to about 1/4 in length. They are plated steel found at sewing stores, 300 for 2$.......


have to design the mounts, probably brass, and then plated....a few coast of polyurethane to go.


Found some nice color for bottom and front deck trim...tetstors dark red
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #15 on: December 20, 2015, 04:53:56 pm »

Made the rudders w/ 1/8th posts. Soft soldered to stiff brass sheet.  Made the wrong choice for paint, Testor's dark red...runs easily and has terrible coverage. I had the same problem with it before...but just forgot and used it again..  Go with rustoleum dark red enamel. Great coverage, dries fast , and sticks really well. Added waterline and hit with a few coats of testors gloss...... bottom almost done.  Swim platform and exhaust tips install to come....


I love the offwhite hull. The navajo white and dark red look great together.....
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derekwarner

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #16 on: December 20, 2015, 08:56:18 pm »

So xrad says...... "Go with rustoleum dark red enamel. Great coverage, dries fast , and sticks really well"

We can get it in OZ now ....must agree ...an excellent choice...extremely hard and mirror like finished surface, & the spray nozzle lifts off for soaking when not in use  :-))....far better than inverting & wasting 1/4 can when painting small repetitive work...... O0.......

Marketed here at some 20 cents higher than as inferior quality  >>:-( products .......the best quality paint in a rattle can ever used.........Derek
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #17 on: December 21, 2015, 01:38:28 am »

Thx Derek! Agree. ...and it's oil proof as far as I can tell...

I did get a bit of 'orange peel' due to low garage temp on final coat. Spray can was 'spitting.'   It was minimal and actually looks OK due to 'age' of boat..

A few more pics: brushed aluminum trim(it is not bent, it is cut to follow the curve...took several tries to get the curve correct...even with a paper template)...still have to do the rub rails. 



I might be switching the props around as most CC twins run outward....I guess that makes sense as the water want to fill in the void from the chine to the keel at the back of the hull, and outrunning the propeller tops puts them in the best current(with full prop immersion)?  Don;t know exactly...my catamaran runs best with in-running set-up(but only bottom half of props in the water..)..
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #18 on: December 24, 2015, 04:50:09 pm »

Rub rails complete with aluminum strip. Made the servo arms for the 1/8th rudder posts. drilled some brass sheet and soft soldered to 1/8th collars.  Few red drips to finish up on the bow...coming along nicely now that the hard parts are done....


I used blue marine axle grease for all the shafts, applied with a small grease finger pump.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #19 on: December 27, 2015, 02:26:48 am »

Twin  550 motors at full throttle would be way too fast for this boat. So with my trusty Tactic 3 channel  2.4GHz radio (less than $30 delivered!!!  :-)) ), I now have a way to resolve this issue.  This radio allows throttle and steering digital end point control. So not just servo throw/rate.   And forget buying 1/3 gear reduction. Just set the throttle end point. takes 2 minutes. These are now running at about 1/3 full speed/power. As opposed to a 1/3 gear reduction where you can run full power at 1/3 speed..

https://www.youtube.com/watch?v=S028dI9ropA&feature=youtu.be

Anyway, should get at least 30-45 min run time on the pond!

Made some repairs, including a windscreen which had to be aged to match the others. I am not repairing this model to a high standard. Rather, a functional restoration.  As stated before, I want to respect the prior builder's work/art by not redoing it all.  Plus, all the dents and dings, drips, and broken/repaired parts add character.... Best part is sanding the old wood and the sweet smell it has from sitting in someone's home for 30-40 years soaking up pot roasts and pizzas!

Also built a mahogany trimmed basswood bench. plated a stainless and brass pole/mount. came out OK...helps to fill the big open space of cockpit...
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #20 on: December 28, 2015, 02:59:08 am »

swim platform mounted with plated brass supports.  Screwed into stern. Can be removed if needed.


Final coat of polyurethane. She is almost complete ....  deck fittings to be remounted once poly is dry...
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #21 on: December 28, 2015, 06:29:52 pm »

Have not decided between bow safety rails or the original deck height hand rails...so until then, this is the final look.  Did a 'tub' test, floated level.  Plenty of bite from the two props at 1/3 power. Love how the water splashes up through the swim platform grates. Reminds me of my childhood, spending countless hours staring off the stern, prop wash churning up the dark green of Barnegat Bay. Will have to wait until a sunny day for the pond test.

My best guess is that there were three hands (including mine) in the pot over many years...and this is our product

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chris1

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #22 on: January 01, 2016, 08:44:48 am »

Hi xrad and well done on a great job. Lovely model.  Just some info on props. Modern high performance boats with surface drives do tend to have 'inward' turning props, although i have not understood the reasons yet.  What i can tell you with 100% certainty is that all twin engine motor yachts with submerged shaft drives have outward turning props i.e. port prop turns counter clockwise, starboard prop turns clockwise, going forward.  This has nothing to do with performance but everything to do with close quarter maneuvring.  We refer to it as propwalk, where the prop acts a bit like a wheel due to water pressure/density difference between the top and bottom of the prop.  This greatly helps berthing. To turn the boat to port we would apply forward on the starboard motor, which pulls the stern to starboard while 'pushing' the starboard side of the boat forward, and astern on the port engine, which, while 'pulling the port half of the boat backwards, also has the effect of pulling the stern to starboard.
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xrad

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Re: XRAD'S Sterling B15M Chris Craft Corvette 48"
« Reply #23 on: January 01, 2016, 04:16:45 pm »

Thanks Chris, appreciate your comment!  I was just reading about this.  You are correct , for immersed twins /independent drives, outrunning is preferred for maneuvering.  Some deep keel immersed twins have inrunners( generally considered as looking from stern to stem at prop tops) as the keel and hull pressure wave is more efficiently propelled through this way. Chris craft almost always had outrunners unless changed by the owner.  From what I have read on offshore cats, straight line stability and better efficiency is done with inrunners as only the bottom half of the prop is in the water.  Some top fuel hydros run twin props for stability(counter prop walk).   


From my model cat twin experience, inrunners were noticeably faster and had better characteristics(more predictable) in turns  while outrunners would make the boat snap into turns and the rooster tail seemed more confused...


Propeller physics is immensely interesting.  There are some cool research papers on pods on the net as well.  I am just learning a bit now for my hydroplane build.....
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