Joysway Razor 37 inch bare hull mono assembly

I picked up an old, unused fiberglass hull and hatch that was the Joysway Invincible Razor mono. The hull is 950mm/37in. x 255mm/10in. I found the original instruction manual online from years ago when it was out. I also found some reviews of it at the time. This boat has lived in a few different configurations including most recently the Joysway Alpha/Hobbyking HydroPro Inception (although these are now ABS hulls with outrunner motors, but very similar to the Razor from what I can tell).
For $55 for the hull I figured, what they heck, I'll make this my first Fast Electric build/assembly (I have a few other boats, some FE RTRs and some scale models I built). Through some research on the forums and looking at the original instruction manual, I put together a parts list. Steve V. was kind enough to review my setup and made a few suggestions so now I have all the parts and I'm ready to build/assemble!
Here are some pictures of the hull and parts. I'll list all the parts out in a separate post along with a few questions for you more experienced modelers. My objective is to make this a sport boat that I can play with at the lake with my kids and our other boats. Speed is not my main concern. I was looking at 6S power and RPM up to 30k. 40mph is, I think, an achievable goal and for the ponds and lakes we run in, that should be fast enough. Faster might be more fun, but it needs to handle the high winds and waves we see most of the season in Northwest IL.
Attachment 171694Attachment 171695Attachment 171696

As mentioned above, here are the components for my 6-cell powered FE (the items with * I don't have yet)
Leopard 4082 1250KV 2.5Y Motor w/water jacket
TFL Carbon fiber heavy duty motor mount for 40mm motors
OSE Raider 6s 150amp ESC with connectors
Speedmaster Stinger Strut for 3/16"(.187") prop shaft (although I may swap this to my son's Stealthwake and use the Speedmaster strut I recently put on instead)
Joysway Invincible Razor stock rudder replacement
ProBoat Stealthwake rudder pushrod assembly
OSE .187 (3/16") cable : 3/16" prop shaft : 2.75" long
Speedmaster 1.5" x 1.5" Adjustable Metal Trim Tabs
Metal Turn Fins (1 Pair) : Medium : 68mm Long
OSE 5mm to 4.75mm (.187") Coupler
Graupner K Series Prop 42mm – 3/16” bore
Graupner K Series Prop 45mm – 3/16” bore
*** I'll use these props for testing and then I'll get a CNC one of the right size ***
1/4 OD K&S brass tubing #8131 for stuffing tube (I'm not using a Teflon liner)
13/32 OD K&S brass tubing #8136 for the wet well tube (the transom is already drilled for this size tube)
OSE Aluminum Small Water Outlet Black
OSE Tow Hook / Cleat Size- Small tow hook
Flex cable saver : .187 size
* Cowl locks OSE 4 piece hatch screw down kit
* Proboat drain plug hh-PRB0307 (maybe, maybe not)
* 5mm Thrust Bearing (maybe, if it fits in the TFL motor mount)
* Power HD 20MG waterproof metal gear, digital servo 20 Kg torque
RoaringTop LiPo (I have 2): 55C 6500mAh 3S2P (Hard Case)

Last post for now and the questions ...
1) The hull is a LOT more flexible than I expected. My ABS RTRs are stiffer. So I want to put in a layer of heavy fiberglass cloth. The inside of the hull is rough, so do I need to sand it first or just clean it and apply a layer or 2 of cloth? And what should I clean it with? This hull is old, so do I need to go with something heavy duty like acetone or alcohol or something else?
My fiberglass experience is limited, but it's inside so I'm not expecting perfection. I just want to keep this hull from snapping if it flips or crashes!

2) I would love to be able to add a flood chamber and have seen a few posts about how people have done it, but any links to how-to articles anyone has would be appreciated. Or any thoughts for or against is also appreciated!

3) The original RTR of this boat has the batteries on both sides of the hull mostly in-line with the motor which seems that the Center-of-Gravity (CG) would be way forward, but it must have worked. Assuming I do a flood chamber I would put the batteries in the middle like the Pro Boat Sonicwake either towards the bow or closer to the stern depending. Or, even if I don't do a flood chamber, is it better to keep the batteries centered and low?

4) With the target CG at 25% to 30% of the length [235mm/9-1/4in. to 282mm/11-1/8in.], I assume I need to rough lay out all the components AND batteries to figure out where to put everything. Does this sound correct?

Thank you in advance for any and all assistance!
My webpage with videos and additional info on this boat is at: http://myplace.frontier.com/~sv_design/jsirbuild.html

Update on the status of the build. I put a single layer of 5oz fiberglass cloth over the entire inside along with 2 layers on the transom. What a difference it made! I'm very happy! It added a pound to the overall weight so the hull minus the hatch is 2 lbs, 9 oz. I spent a lot of time playing with component layout to get the CoG correct. With the layout, the flood chamber is out of the question. Even with the motor almost up against the stern and the batteries in front of it, the CoG was way off. Oh well, if it flips, it will get rescued like my other boats, either with the retrieval boat or the tennis ball on a fishing pole. I'll post pictures of the layout soon. I'm finishing up the battery trays and ESC mount, then I'll get everything in and figure out the best way to get the CoG where I need it.

Here's the internal layout with almost all of the components temporarily mounted. I have not epoxied in the motor mount yet. I figured I would get the wet well and stuffing tube in first to make sure everything still aligns correctly.
I made the battery trays and ESC tray out of 3/32 inch aircraft plywood and put 4 coats of Spar Varnish on to make them waterproof (this is the same stuff they use on real boats).
I have not made the steering servo mount yet. I've tried a few different options between laying it down and standing it up. I think standing as shown will work the best but I have to fabricate the holder. I want the stuffing tube and wet well in first to make sure I have the room I need for the servo mount.
With this setup and the ability to move the batteries fore and aft, I can get between approximately 32% and 28% of the length for the center of gravity. I suspect it will change slightly once I get the prop, stuffing tube, etc. on, but should still be in the 25% to 30% range.
I was surprised at where everything sat to get to that 25% to 30% CoG. I had hoped to put the batteries on the keel line forward of the motor but it was way too much weight toward the bow. And moving the motor toward the bow pushed the batteries almost up against the transom. When looking at pictures of the stock boat from years ago, everything was pushed several inches toward the bow. I'm assuming the extra fiberglass I added changed the weight more than I had anticipated. But it still works!
Attachment 171808

I have the boat almost 90% built. All the major components are in, the CoG is where I want it and it floats in the tub (although the bolt holes leak until I seal them up later). I still have to install the receiver, water cooling lines, hatch locks and a few other miscellaneous components. Then I need to repaint the stern and bottom of the hull to fix the scratches I put into it during the build. Biggest issue now is that I'm at least a month, probably 2 months from having open water to test run it (darn midwest winters!).
Below are pictures of the progress. And as always, more details and videos of the progress are on my website which you can access in the above posts or below in my signature.
Attachment 171871Attachment 171872Attachment 171873Attachment 171874

The pond defrosted, at least for now, so we got out and ran some boats today. The big news is the sea trials of the Invincible Razor today. The first run was only about 2 minutes to get a read on how it runs and to gather some initial data with the 42mm prop. The weather was about 50 degrees F, sunny and breezy and the water was probably 40F so everything stayed really cool. It ran better than I expected for a first time out. I didn't get a speed reading, but I was happy with it. Amp draw maxed at 83A, max watts at 1,833 and max RPM at 28,020. I went back and ran it with the 45mm prop and it maxed at 120A but averaged 100A. That run was short because I wanted to check the Amp draw. Good thing it was short because I discovered that I got the water cooling line wrapped around the shaft, tore the motor mount from the hull and flooded the inside due to the shredded water line. The boat still ran for what we assume was another minute or so with the motor mount dislodged and spun around. Hopefully, once everything dries out the repairs won't take long.
The pond is too small for this boat and speed! I need the lake to thaw for some real runs!
Here's a screen grab from the video we shot. I'm editing the video now and will post it in a few days.
Attachment 172159

From your still picture it looks like it's running really good. With the KV of your motor being fairly conservative ( that's good ) I wouldn't be surprised if you could spin an X-447 or X-448 without taxing your equipment too much. As always experiment,and check component temperature.

Quote:

---

Originally Posted by sciesielka

I'm editing the video now and will post it in a few days.

---

Here's the video link (if the embedded video below doesn't work) to the short video: https://youtu.be/PwGx3Y2Sr_4
I have a longer video posted as well, but thought I'd post this one here to see if anyone has any feedback on how it's running. Thanks!
https://youtu.be/PwGx3Y2Sr_4

Quote:

---

Originally Posted by Panchothedog

I wouldn't be surprised if you could spin an X-447 or X-448 without taxing your equipment too much. As always experiment,and check component temperature.

---

Thanks for the feedback! I have 4 different Graupner 2-blade, 1.4 pitch props to test sizes including a 42mm, 45mm, 48mm and 51mm. I figured I'd go from conservative to crazy in my prop choices since they're so inexpensive. So far I've only tried the 42 and 45mm. I'll have to check everything again come summer since these first runs, temps barely got to "room temperature" since it was chilly outside and the water was barely above freezing.

Quote:

---

Originally Posted by sciesielka

I discovered that I got the water cooling line wrapped around the shaft, tore the motor mount from the hull

---

Upon further investigation, the water cooling line could not have gotten anywhere near the prop shaft, and from the looks of the motor mount, I'm pretty certain the epoxy completely let go from the hull on the one side. Then, when the torque spun the motor and mount over, it broke the epoxy on the other side. Also, the stuffing tube mount broke loose. Surprisingly, nothing else was damaged so it's just a matter of reattaching the motor mount and stuffing tube mount.

Any ideas how to better adhere the motor mount to the hull? I used 15 minute BSI epoxy on the motor mount. The inside is fiberglass so I'm putting epoxy on top of epoxy, not carbon fiber.
Attachment 172182

Sand the surface where the mount goes, clean it of with acetone or similar and glue the mount back in with JB Weld. Of course clean of the glue from the mount and redrill all the little holes to give the JB Weld somewhere to lock in to.

Quote:

---

Originally Posted by Peter A

glue the mount back in with JB Weld.

---

Thanks Peter! From what I have found through a quick search of the forum, it seems the best JB Weld to use is the "Original Cold-Weld" epoxy that comes in 2 separate tubes. Is that what you recommend?

I also saw that some people on the forum like the West Systems G-Flex, but from what I found, it comes in 2 versions, the "650 Toughened" and "655 Thickened." Anyone have an opinion on which is better for gluing in the motor mount once I clean off the epoxy I used that didn't hold?

I have found that the JB Marine Weld works really well. Almost never have anything come loose if prepared properly. Good luck

I successfully reattached the motor mount and with the various prop tests I did plus a pretty good/bad crash (high winds + choppy 'seas' + high speed turn into the wind = roll and flip), it stayed attached. I ended up using the West Systems G/flex 650.
I did all of the prop tests in a single run on the same day. I took my Hyperion Emeter v2 reader to the pond and after each short run, I took readings. The summary results are attached. The 42mm x 1.9 pitch took forever to get on plane and the 1.4x47 3-blade nearly maxed out my ESC. I do have a 1.4x51mm prop that I did not test and I might at some point. However, I'm really liking the performance of the 1.4x48mm and am seriously considering getting the CNC-4816-D prop which is the 1.6x48 de-tongued prop. We run the 40mm size of that prop on the Stealthwake and love it! So after testing each prop, I got about 6 minutes of running before the LiPo cutoff so I got a temperature reading which is a little misleading since the water is still cold (the Emeter has 3 thermocouples that I mounted on the ESC, motor and a battery to see how the temperatures rose during the run).
The next day we went back to the pond with high winds and choppy 'seas' and it ran great with the 48mm Graupner prop! The slow-mo video we got really shows it flying over the waves (video will be posted to our YouTube channel within a few days of this posting - link below). I just REALLY need to get to the lake ... mid-April can't get here soon enough. The pond is just too small for this boat and speeds.
Image from Excel file of prop tests: Attachment 172237

I completed prop testing and have ordered an Octura x447, sharpened and balanced already since I've never done that myself. This boat with this setup runs right around 40mph (64kph). I think it's running a little wet, but I didn't change anything as I wanted to get all of my data and speeds with the same setup. Besides, assuming I can dial it in better, the numbers and temps should look better too!
Now that I have access to a lake where I can run full speed for more than a few seconds, this should be a lot more fun. Plus, the lake gets bigger waves when it gets windy (no motor boats allowed on this lake) so I can play with stinger and trim tab setups to optimize what I have.

Here are all of the detailed prop testing results from multiple days starting in mid-March 2021 through early-April 2021, minus temperatures:
Attachment 172353

I'll post additional videos this month!

And while this boat's not a real fast FE, for the places I can run it and since I'm not racing it, this will be perfect ... until, or if, I feel the need for more speed and then it should be a pretty simple platform to upgrade! :biggrin:

I spent a lot of time testing to get the right prop for the Invincible Razor custom build and now that I'm running it for fun, I'm noticing more that it probably needs further setup work.

Here is the video over 2 days running it with the same setup, just different water conditions. I have not adjusted the stinger yet and I can shift the batteries back to get the CoG to about 26% compared to the 28% it's running at during these clips. Should I add positive angle to the stinger to get the bow higher? Or is this running well enough for just playing around at the lake and not racing?

As mentioned in the earlier posts, it's two 3-cell LiPos for 6S total, a Leopard 4082 1250kv motor, 150A ESC and a sharpened and balanced Octura x447 prop.
Motor and ESC temps stay under 90F and the batteries were just over 100F both days.

Thanks in advance for any advice! I added a link to the video but also embedded it here, so one should work.

https://youtu.be/sg1DVxHCMzg

From watching your latest video it does look a little bit wet for smooth water situations. Three things will loosen it up and potentially allow it to run faster. Put the batteries farther back, raise the stinger angel, OR raise the angle of the cavation plates. From photo # 4 in post # 6 I really can't see them that well but from what I can see they look like they could be low.
They should not be flush with the bottom of the hull, but be about 1/16"
above the bottom. If not they can cause a lot of drag, but with trail and
error adjusting they can control the ride attitude of the hull as much as
either of the other two methods. It also looks like you run in some pretty choppy waters, and for that you are probably right where you want to be.
Loose trimmed out fast settings are for smooth water and no or very light wind. Run that way in rough water or windy conditions and you will be
up side down fast and often. NO FUN.

Definitely drag issues at the transom. As Pancho said raise the height of the trim tabs 1-2mm, and get rid of that extra water pickup. That alone will cause the boat to run wet. The single pickup from the rudder is sufficient cooling. Run through the esc first, through the motor and out. You will then find your cog at 28% to be loose, and will want to be able to adjust it to up to 35% for rough water running. The boat is light in the nose which can be seen when it bounces off small waves, it is just the tabs and pick up drag making it run wet.

Quote:

---

Originally Posted by Peter A

Definitely drag issues at the transom. As Pancho said raise the height of the trim tabs 1-2mm, and get rid of that extra water pickup.

---

I originally had the trim tabs set approximately 1 to 1.5mm up from the bottom of the hull and parallel, so zero degrees angle. Based on your guys' recommendations, I made some changes. First, I was going to just remove the trim tabs but chickened out. Instead, I slotted the holes in the trim tab plates so I could really get them raised. For the one run I got in this weekend, I had them parallel to the bottom but they are 3 to 4mm up from the bottom (I assume that's a pretty good indication I may not even need them, correct?). I also raised the extra water pickup (haven't removed it ... yet). I kept the stinger at zero degrees angle and the same height from the last run and kept the CoG at about 28% again. One change at a time right!

With the trim tab change and the water pickup adjustment, it ran drier and overall handled better. I was also happily surprised to see that I gained 4mph [6.5kph] :biggrin:

When I get more time, I will also play with the battery placement and stinger angle to see what else this boat has in it!

Thank you for the advice!

I think my CoG needs to be moved and I'm hoping for some advice. I have been running my Joysway Invincible Razor quite a bit this summer so far and need some advice. I have seen my boat go airborne a few too many times, even when it's not that windy. With my batteries full forward in the battery trays, my CoG is 28/29%. I'm thinking I need to make new battery trays to get the CoG further forward, maybe 32% (which on this hull is moving the CoG an inch closer to the bow).
My question is, to get the best overall performance from the boat, a fun/sport boat, not a racer, should I move the CoG or angle the trim tabs more and/or angle the stinger down?
My thought all along was that I would only angle the stinger and/or trim tabs down when the water gets rough. To keep the thing from going airborne, I move the CoG. Is that correct?
Thank you in advance for the help!

boat is running well in the video i watched (first one) you should be able to get higher top speeds though .1250 kv is not alot .your going to need a big prop . i spin a x447 or a cnc x448 on my pursuit with a 1600kv motor on 6s and i get speeds just above 60mph .comes in with motor under 120 degrees ,esc too
nice build .i dont boat much anymore but i enjoyed your video .carry on

ps- yes your boat is running too wet .you need to get the hull up out the water more .try raising the stinger more .