JavaMoose

Hey all, I'm starting my first scale RC build and I've bitten off quite a project. My Wife is on an 87ft USCG Patrol Boat and their Master Chief is about to retire. This has been one of his favorite commands, so I'm making an RC model of his cutter as a gift for his retirement party (in FOUR months!!). She is going to be 1:40 Scale, which will make it a 26" model (if I'm doing the math right). All lights will work and function, as will the rotating radar assembly and rear lift gate (the 87ft patrol boats have a lift gate which can launch and recover their fast boat at any speed). I've just got the plans from Capt. Al at [link=http://www.coastguardmodels.com/]Coast Guard Models[/link], great guy, btw.

I'm a design engineer at a large plastics distributor, and have Vacuum and Ther****rming equipment as well as a 3-Axis CNC and CNC Laser Cutter at my disposal. The plan is to ther****rm the hull from 1/16" Vycom Ultra White - a super tough PVC that is UV resistant and can take some serious hits and age with out getting brittle. She will be twin engine and twin rudder, just like her Momma. I'm thinking of using the Robbe F-14 Navy Twin Stick, as the real cutter has twin-stick control, with the optional switches for lights. I would love to add sounds as well, but that will depend on budget. As for electronics and drive, haven't decided yet. I would like to keep the speed scale, the real cutter can do 25 knots, I'm not good enough with The Math to figure her scale speed - but I'm sure one of y'all are. So, check back in the following weeks as I will be photographing this project every step of the way.

Here is the real cutter, in all her glory:

Deathwish

My Feedback: (6)

A 87' foot ship is 26.1" or 1/40 scale. Simple math 87 feet x 12 inches / by scale you wanting (40) = 26.1".

JavaMoose

See what I get for rounding off the .1"

The only problem I see with 1:40 scale is that my hopes of getting some things pre-made, like the armored doors and manhole covers, to save time isn't going to happen. Lights and radar assemblies, liferings, barrels, etc. - look like they all can be had in 1:40 (approx) size. Going to be a lot of fabrication on my end...

Deathwish

My Feedback: (6)

Lol i was looking for the video of you hammer but couldnt find it. Got another link? Here's what am currently working on. I have two of them in the work's got ore picture's coming (Don't have a digital camera but i do have a scanner) HeHe.

USS Missouri Build
http://www.rcuniverse.com/forum/m_6480413/tm.htm

JavaMoose

Been watching your build, those scale warships are so cool. Guess I don't have a version of that video online anymore, will work on getting it put back up.

If this build goes well, I plan on doing a 1:20 scale version to keep for myself. At 52.2" long, should be something. Just gonna focus on the "little" one for now though.

dshindle

Looks like a great project. I hope you will be able to post many pics of your build! Can't wait to see the hull you produce.

Deathwish

My Feedback: (6)

Yea 1/40 is easyier then 1/192 scale. I can't find many part's for mine. SO i have to make most of mine. I how ever scored big on the ship fitting's and a hull for 50 buck's. Same guy i got my first hull off of. He's on here too. Since the first hull we became pretty much friend's and try to keep in touch.

patmat

Neat project and I envy you those tools!

#1 priority- design the topsides light, then build them lighter yet. This is a smallish model, and top hamper will be a major issue for stability and wind. More of the weight that is lower, the better.

Speed- water doesn't scale linearly, thank you Messrs. Froude and Reynolds. At 1/40th of 1:1 speed, the model will look slow. It needs to go faster than that to achieve a scale "looking" plane and wake.

Displacement DOES scale, by the cube of course... I couldn't find the loaded displacement of an 87' WPB anywhere, but if you do find it, it wll be in "long tons". That x 2200 lb/ton x 40^(1/3) will give you the model weight in lbs. But consider a scale a little bigger, maybe take her up to 36" long?

Good news- it's easy to overpower a scale model, hard to underpower it. A pair of 500-ish stock motors on 7.2v hooked to scale diameter props (no gear reduction) will get you close to where you need to be.

Pat Matthews

JavaMoose

Pat, thanks for the tips. I have been worrying about the topside weight as well, she is fairly tall for her length. Good thing is, the PVC I am using is VERY light for it's strength, so hopefully that will help. I have been thinking about power though, I would really like for him to be able to run this model for at least 1/2 hour before he has to worry about the battery - but I also need to take into consideration ease of recharging. I was thinking about getting some low-cost 14.4v or 19.2v cordless drills and using the motors and batteries from them - any thoughts on that idea anyone? Been done before?

patmat

Hard to say on the motors... sure these have been used before, but you never know what you're getting until you open it up and waste the tool. Usually better to buy from a hobby source that can tell you what you're getting.

Variables:
In any given motor frame size (e.g., 540, 600...), the big variable is in the windings. Finer wire can get more "turns" on the armature, fatter gauge allows fewer turns. More length of little wire = higher resistance, while short & fat wire = lower resistance... which governs current flow, and thus motor speed/power and current consumption.
What motor do you need? For non-racing (scale) planing applications, something along the lines of Graupner's "Speed" series motors works, and can be had inexpensively: www.hobby-lobby.com

For batteries, cheap tools will have cheap batteries. The big variable there is capacity in mAh. For easiest recharging, stick with NiMH packs... in sub-C size, cells of reasonable capacity will be 3000-4000 mAh. Some online hobby sources have incredible pricing on 7.2v and 8.4v r/c packs. You don't need fancy extra cost "matched cells" etc. for scale. Also get a "smart" charger to protect your batteries.

cyclops2

Tenergy sells +3000 ma cells & packs. Stay with flat packs to keep the weight very low in the hull.

Is the model supposed to get on plane ?

Rich