Darin's P-Limited OPC Lynx build

[Darin Jordan]

Hi guys... it's been awhile since I've done a build thread...

Here is my latest project. I decided to give a Lynx a try for P-Limited OPC. No one around here has done one yet, so we'll see how it works out.

I purchased the hull from Ron Drake, and he pre-cut out the radio box to allow for fitment of the FE battery tray. I've cut it out further, and am in the process of fitting a new box now.

Room on this boat is TIGHT, so I'm still playing with the layout. It's looking like I'll be putting the servo towards the front, and I'm going to be running pull-pull cables for the steering, using the steering wheel from a Stiletto on a Spektrum S6030 Digital Servo, mounted in a carbon-fiber servo plate that I'm fabbing. I'm likely going to be running the cables on the OUTSIDE of the radio box, similar to what I did on my WoodStuff tunnel a few years ago. Works well and keeps them out of the way of the rest of the electronics, and also allows for a wider range of motor positions.

Batteries will be placed at the extreme rear of the box, with the ESC either on top, or just in front. Likely will be on top.

The front half of the battery box will have a flat cover, but I'm looking at building-up the back half to allow more clearance above the battery for cables, wires, etc. There is room under the cowl to go up quite a ways in this area.

I'm thinking about using this radio box, once I get it sorted, as a plug and making a mold of it, so I can lay these up out of vacuum-bagged carbon fiber. Might be a worth project to test my skills at that, and would reduce the weight a bit.

Lawless 3.5 lower unit has already been fitted, per the Lynx instructions.

More to come as I progress.

Feels GOOD to be building something once again!

[Doug Smock]

Darin,
Just a FWIW
On mine EVERYTHING had to go as close to the transom as possible. If the CG is too far forward the boat will stick while trying to get up and may have trouble hooking in the corners.

Lynx P-Limited OB Tunnel 003.jpg

The ESC and RX are underneath the servo. The crescent shape cut out of the servo mount is for a index finger so that the battery can be removed. That's how far BACK the pack (Hyperion 5000 35c) has to go.
Maybe putting the battery in the back will help. I think I looked at that but didn't like having to deal with the steering cables to get the battery in and out. I forgot where the CG ended up, if you'd like I'll measure it for ya.
Oh and you definitely want to table it and check the aft portion of the ride surfaces.

Doug

[Darin Jordan]

I have some other ideas for routing the pull-pull cables... when I'm done, they won't be in the way of anything...

Finished up the servo mount tonight. The blue tape is just protecting the carbon fiber plate surface. Hardwood mounting rails will be glued to the sides of the radio box (already done, actually) and will also have two screws on each side, just for good measure.

Will work on routing the cables next...

This setup/location gives me PLENTY of room for 4S packs... I can fit a 5400mAh 4S1P hard case RC car pack in there, and slide it all the way up to the steering servo. That should give me plenty of balance adjustement. ESC will lay on top of the battery pack, perhaps with a protective plate between the two.

[Doug Smock]

Good luck with it!!
Doug

[Darin Jordan]

Good luck with it!!
Doug

Doug... Which lower unit are you using???

[Doug Smock]

I'm running the Lawless and a hijack.

Lynx P-Limited OB Tunnel 002.jpg

[Darin Jordan]

I'm running the Lawless and a hijack.

[ATTACH=CONFIG]62841[/ATTACH]

Very cool... I have the LawLess, but am using a standard Dubro 3.5 mount... Instructions recommend a " 6-inch setback to the drive-dog face"... I'm still trying to figure out if that means the forward or trailing edge of the drive-dog... The leading edge of mine comes in exactly at 6"... I'm using the Hyperformance R/C stub, which is a bit longer than a standard K&B, so that may be pushing the drive-dog back 1/4" or so...

[Darin Jordan]

Had a little time to work on the Lynx project some more.

Used some .031" G10 for the radio/battery box covers, and some wrapped carbon for the 3 motor wire tubes. Time to sand, epoxy coat, and then do the finish work on the wood, then I'll glue it into the hull.

[Darin Jordan]

Someone asked what was done to prep the hull and how the bottom of the radio/battery box is configured... here you go...

I'm going to be adding some reinforcing to the transom area before I epoxy in the radio box. I don't really think it will need it, but an additional layer of 5.5oz Carbon weave won't add much weight and would go a long way to ensure that the transom doesn't flex. Just a little insurance... (I'm a strong believer in a little over-kill here and there... )

[Darin Jordan]

Got the radio box in place now. Epoxied it in place, using some fiberglass cloth around the aft outter edges as filler and to help hold the epoxy in place. After the first application of epoxy set, I applied a second application to completely fill in the gaps. Once this has set up, I'll peel off the tape and let it cure.

Next step is to start rigging...

[Darin Jordan]

Now that the radio box is in place, I turned my attention to the new Lawless 3.5 lower.

I started with a Pro Boat Stiletto square drive coupler, which are VERY nice pieces... they are precise, fairly compact, and made of stainless steel. Not priced too badly either.

To get started, I turned the OD of the coupler down to .385"... Could have gone down a little further to .375 or so, but, well... I just didn't.

With that done, I used my mill and machined out the hole in the top of the lower to 7/16" down about 1.2" from the top of the motor plate, directly inline with the factory cable hole. I finished this up with a .500" relief cut just down to the top of the case screws to provide a little extra clearance for the set-screw if needed.

I also cut a small relief on either side of the flat mount that the motor plate bolts to to allow clearance for the heads of the motor screws.

I chucked up the motor plate into the vice and centered on the existing coupler hole, and drilled up motor-mounting holes on 1" centers with 1/8" endmill, then opened these holes up to 5/32" to provide clearance for the motor mounting screws.

Put everything together and shortened up the teflon. I had one shortened flex cable left over from a previous Lawless mod I had, so I was able completely assemble the lower, finishing it off with a Hyperformance R/C stub shaft.

The finished length for the flex cable is 3.680" and has .450" length flats on either end, and I will be purchasing some more of them from Kris Flynn (Australia), who made these for me and gave me the original idea for modding one of these units this way.

Saved the weight of an adapter, lowered the motor down over 1", which not only lowers the CG, but also keeps it out of the wind for better aero, and shortens the flex, so less chance of it twisting. These Lawless units lend themselves fantastically to this type of motor adaption, and I couldn't be more happy with this!

[Darin Jordan]

I got the cowl mounting completed.

This boat being designed for Nitro, it's apparent that the cowling wasn't designed to easily taken on and off. To correct this, I came up with a slip-fit front mounting, with pins in the rear.

I used thick-walled 1/4" aluminum tubing and threaded it with 8/32" threads. For the front, I made the tubing length to fit just flush with the fiberglass. In the rear, I left the tubing about 3/8" extended out each side. The rears are threaded as well, but also have 5/64" pin holes drilled as well.

I glued everything in place, then added some G10 reinforcement to the front slots and the rear holes.

The aluminum screws for the front have large diameter heads, and were found at our local McClendon's hardware store. They have blue-Loctite on the threads and are set to just allow the front of the cowl to slide easily in place.

With this done, the only thing left to do to have the boat ready for testing is to lace up the pull-pull stearing, and put the electronics in place.

[Darin Jordan]

Finished up the steering system tonight. Nothing fancy. Just a simple 4-40 sized Dubro Pull-Pull cable system and a Pro Boat Stiletto Servo steering wheel on a Spektrum S6030 High-Torque (278in-lb @6V) Digital Servo. Cables have the nylon sheeth from a set of Dubro .032" Micro flyer push-rod set, which fits very nicely over the Dubro pull-pull cable. I ran it almost the length of the cable, which should help keep water from wicking up and into the radio box.

The front radio cover will be taped down most of the time. The rear cover will be removed regularly to service the battery. I placed the brass pass-through tubing and covers in such a way so as to not interfere with the taping. Once I put the covers in place, the cables will be easily moved out of the way to tape down the hatch sides. Took a bit of fore-thought, but I think it should work out nicely. Guess experience building 4 or 5 previous OPCs has helped. This one should be pretty easy to maintain and use.

Have everything dialed in and ready for final assembly. I need to get the ESC setup and intalled. I'm likely going to use some heavy-gage wires with contacts on either end through the pass-throughs so I can easily replace the motor or ESC without having to break the seal on the wires. Makes using the boat during the race season MUCH easier... and keeps the boat racing, rather than being repaired.

Will do the final setup on the lower unit and mount the motor and water cooling for the motor next. Could be on the water for testing shortly!

[Darin Jordan]

Finished up the Functional portion of my Lynx build last week, and took it to the Namba District 8 race yesterday (Saturday, April 21)...

Running a Thunder Power 65C 5000mAh "Pro Power" 4S1P pack (Soft-Sided pack... not the hard-case Car/Truck style), and a Castle ICE 100, converted to water cooling, powering a UL1 motor pushing a detounged ABC 42x55 prop. All of this is supported by the Lawless 3.5 unit (Fred Howe, and Lawless, ROCK, by the way! You won't find a nicer lower unit or a NICER GUY to order parts from, except perhaps Steven, of course! )

Finished weight of this package, as described above, minus paint, is 5lbs, 10.5oz...

After a couple of packs of tweaking/tuning runs to work out the positioning of the lower unit, which ended up no-where NEAR where the instuctions for Nitro would have it, the boat was rolling out nicely.

In the first heat, I was immediately contending for the lead, working lane 2/3, not yet being completely confident in the boat's handling. Nose was bouncing up a bit, and it didn't seem to want to make that final transition to the "step". 3 Laps into it, I turned in a little too hard and drove through Brian's rooter-tail, swamping the boat and causing it to flip over... ending my heat.

I moved the CG forward a touch, and lowered the unit down just a few thousanths. I also noticed that the 42mm prop just BARELY was clearing the cav plate, so I shimmed the plate up about .040" to give the prop a little more room.

Handing for the second heat was much improved, and the boat got a little faster. Again being a little cautious, I finished a tight second to Brian. This is getting fun!

For the third round, I made another tweak to the cav plate and otherwise, left the boat alone. Went back out, looking to contend this time. After running a couple of very tight laps against Brian, he slipped out a bit, I dove under him exiting Turn 4, and I ran away! This boat is REALLY getting fun!

For the 4th Round, Brian and I went through the 1st turns side-by-side, and he pushed it a LITTLE too close to the exit of 2, hitting the buoy and ending his round.... I took the win!

Brian and I ended up tied for the day... each with two 1sts, a 2nd, and a DNF! I think I've given him a reason to come to the races again! I don't think he's been seriously challenged in some time. I'm pretty sure he's blue-printing a new TS-3 as I type this!

I pulled data from the ICE 100, and the average Amps were 86, with a maximum spike of 113... Hardly a "stator beater"... Maximum ESC temp while running was 123-degrees... Motor felt ice cold...

Now that I know the boat is going to work for me, I'll be doing a couple of tweaks to make it easier to manage on race-day (getting packs in and out, etc.), and will be working on getting it painted and decorated up.

[RaceMechaniX]

What no run off?