CFK Special Edition Micro Offshore Catamaran

[J Mack]

I’m looking at a Hydro and Machine Drifter Micro WE CFK Special Edition Micro Offshore Catamaran.
I would like to build it single motor/drive, looking at the photos on their web site it looks like they mount the rudder behind the prop, is there an advantage to an offset rudder?





http://hydromarine.magix.net/all-albums/!/oa/5962328-60148894/

[Panther6834]

First...I'm still fairly a newb, so don't take what I'm saying (in the next paragraph) as "written in ink". Although I might be further along in my 'learning', I AM still learning.

I recently (ok, several months ago) purchased the H&M Drifter Micro hull...although my plan is to build it into a micro twin, thus I want/need the rudder centered. As for the offset rudder, you have to remember/realize that micro classes are strong in Europe, and said vessels are competing on oval courses, just as the larger FEs are. As such, the offset rudder would make right turns just as easily as the larger FEs. If you want yours to be race-capable, and will only be running a single motor, it's probably best to stick with an offset rudder. However, if you just want to build yours for "pleasure" (ie. you'll be making left turns as frequently as right turns), then a centered rudder (as shown in the photos) would probably be a smart idea. As a twin (as I'm building), then the centered rudder (at least to me) is the only "way to go".

As a "bonus", if you do end up ordering the Drifter Micro hull, understand that the manual it comes with will be in German. It provides instruction on building a single, as well as twin, including all parts needed (based, obviously, on parts obtainable through H&M). I mention this because I do happen to have the manual in English. I spent a few weeks translating the original German manual into English, for which I emailed a PDF to H&M. I did this so that they could, if they wanted, include a printed English version with orders being shipped to English speaking countries and/or upload it to their website for people to download. I do not know if they have done either (only because I haven't actually checked). If you do order the Drifter Micro, and would like a PDF of my English conversion, feel free to PM me.


~ More peace, love, and kindness would make the world a much better place

[J Mack]

Thank you much @Panther6834 I will take you up on your offer for an English version of the manual, I've E-mailed M&H several times asking for the rudder and drive system part numbers so I could order what they recommend with the boat order.

I?m still not completely clear on the centered VS offset rudder on this hull with a single drive, I believe all of the pictures I?ve found of European Mini Cat hull builds have centered rudder regardless single or dual props and all the Asia and North America boats appear to be offset.

A friend/next door neighbor of mine just built a lake in his yard that?s about 75 yards by 100 yards and it has a small island in the middle so oval racing is most likely what this boat will do, probably just big enough for us to get enough speed to know we will need a bigger lake but still should be fun for weekend get togethers.
As of now a bunch of the guys bought the ready to run Tenshock Mini Mono or Oxidean Mariine Mini-Dom and I was looking to build something completive with them but with different hull. I?ve built and raced cars for 35+ years now off and on but this will be my first boat and I?d like it to be a nice one built right verses buying five or six cheap Chinese boats first. I can already see this getting out of hand in a hurry, we started out racing the 1/24^th scale Losi Micro Rally X cars in my building during the winters a few years ago just for a reason to get together and after a few races we all had custom one off cars with thousands of dollars invested in what was supposed to be a couple hundred dollar hobby.
Thanks again for all your help.

[Panther6834]

Message me your email address, and, when I get back home from Vegas (been at Scale Nationals this past week), I can email you the PDF. As for parts, the H&M parts, in including part numbers, are all listed in the build manual. However, it might be best to email Steve @ OSE, and use more easily-obtainable parts. That's what I did...I ordered the hull from H&M, but everything else from OSE.

~ Robb


~ More peace, love, and kindness would make the world a much better place

[J Mack]

Thank you Robb for posting this picture, looking at the transom a center mounted rudder looks like the easiest option without some sort of offset mount.



9ba5765165b0bbd236e9a0d0069b030d.jpg


Poking around the internet trying to learn as much as I can I found some links on the subject that may also be helpful to you too.

https://forums.offshoreelectrics.com...Why-the-Offset

https://www.radiocontrolinfo.com/rtr...an-hull-setup/


http://www.rumrunnerracing.com/fefor...ad.php?t=30589


https://www.modelgasboats.com/resources/tuning

[J Mack]

I have a few questions for you guys in the know.
I have done mutable searches and I’m still a bit foggy on some of the info I’m reading about prop size, motor KV verses battery cell count.
Mutable guys have built micro cats with single outrunner motors in the 3800Kv to 4400Kv range to run 2S batteries. I’m assuming that’s a prop seed of 28,120 to 32,560 RPM with this setup.
Best I can tell Hydro & Marine recommends a Lehner 1515-20, 2858 KV for this hull running on 4S to 5S and that would have a prop speed of 42,298 to 52,873 RPM
Looking at Tenshock’s web site they talk about their race motor setup 1515, 3750KV running on a 3S setup at 41,625 RPM prop speed and they are using a 32mm CNC prop.
My first question is am I doing this math right and these are real prop speed numbers?
I’m assuming these numbers are free speed motor numbers and once you ad drag with a prop they will be lower but it still sound like a lot of RPM to a non-boat guy trying to learn about this at my age.
Should I be looking at a motor battery combo in the 40K RPM range for running a single motor in this hull?
Thanks for your time!

[NativePaul]

I raced mini cats for years in the 4/7 offshore, 4/7 open, Mini Offshore, Mini Oval, and Mini Hydro classes, if your focus is ovals I don't believe there is any advantage to having a rudder behind the prop, if there is a left hand turn in there, that left turn will be better with a centre prop, but not advantageous enough to make it worth it around the rest of the course, a good cat with a rudder on the inside edge of the right sponson still turns left reasonably well.

I am not a fan of any of the drifters, especially not the mini one, too high and too narrow for me, they don't turn well in either direction. I love cats but there aren't really any commercially available mini cats that are designed for ovals any more, when my favorite mini cat maker went out of business I had to start making my own to compete withthe monos in offshore and the riggers in open/hydro.

While I love cats, if I were you I would get a Tenshock Mini Mono / Mini Dom, it will be faster around the oval, and self righting is great for minis, and probablythe biggest benefit, is if you all have the same boat the racing will be super close. Don't dismiss Tensock just because they are Chinese RTR, RTRs are only a small part of what they do, they are leaps and bounds beyond any pure RTR company, a proper race oriented manufacturer, and the Mini Mono has taken many titles including a 1st, 2nd, 3rd sweep at a Naviga world championships, the hulls are on a par with H&M, both wet on wet joined vacuum molded epoxy glass, and I rate Tenshock hardware above H&M.

Where on the Tenshock site do they say it comes with that? Could you be confusing it with the Mini Dom? The stock Tenshock Mini Monos I often see use a Viper 1515/14 4000kv motor for 2s packs, with 32mm prop (though most I see are running DrProps 33mm Naviga props), although some special order it with the 1515/17 to use 3s packs, it would have no chance of making the race runtime with 3750kv on 3s spinning a 32mm prop. Tenshock also make their own motors so they can be ordered with any KV you want, I know Oxidean Marine order it with a lower KV motor for 3s in the Mini Dom, I was assuming the usual 17 turn for 3200kv which is normal for a 3s mini, but as as the mini dom isn't intended for the race rules maybe they are sacrificing runtime and using the 1515/15 3770kv motor you mentioned.

I wouldn't recommend trying to run ovals on the H&M recommended motors, they are more of SAWs setups revving that high.

Minis generally us a bit lower KV than full size boats 4000-4500 is good for 2s and 2800-3200 for 3s, whereas full size boats would be 4500-5000 on 2s and 3000-3500 on 3s. Yes those RPMs are unloaded all the motor KVs apart from Lehner are quoted unloaded, and even with Lehners the batteries will drop voltage under load so you will only see those RPMs when the prop leaves the water.

In my mini cats, I ran 4200kv on 2s and 3000kv on 3s.

[J Mack]

NativePaul thank you for thanking the time for that reply!
I read the info on this little picture for the Tenshock motor/prop info for their race boat.
MKbanner.jpg

I bought two boats, M&H Micro Drifta and a Tenshock Mini Mono for my first boat build and I will take your advice for the M&H and just keep it for fun boat and race the Tenshock.

There is a member "cedric34310" at offshore-rc that has an H&M mico drifter that he built for speed and I was thinking that it sounded like fun and you just helped me make up my mind to build it that way. He will run 4S for speed the change to 3S for just running the boat for fun with same prop and motor.

https://jldyj65id3nibtc7uqezrckvte--...e/13/#comments

He says it is 1172gr to be exact rtr with 4S so I was thinking I will shoot to be at or under that weight.
SSS 2860 3900kv motor
esc turnigy marine 120a
accu a-spec 4s 2200 65 / 130c
three-bladed alu graupner 34

I don't know enough about how they can get real speed number but he says 116 Km/H with his boat.

https://youtu.be/9FYjFxUsu5Q

Both Tenshock and H&M said about four weeks to build hull then shipping to the US so I will just wait and see which one shows up first and go from there but I ordered hardware for them both and if you think I need to use Tenshock hardware I will get more coming.



If the top link didn't work this is the link to the micro drifter build in its native language.
http://www.offshore-rc.com/forum/ind...micro-drifter/


Thanks again for all your help.

[J Mack]

Oliver was very ill with the virus and all Hydro Marine orders were delayed until he was healthy. It gave me time to explore the different building options and learn a bit about building one of my mini-scords.
I added a second CFK Micro Drifter to my order and I'm going to build one for straight line speed and keep one for a future build.
Hatch.jpg

[Panther6834]

Sorry to hear Oliver got it...he seems like a great guy. When I reported the canopy (Drifter Micro) problem to him, he got a new one made & shipped even quicker than he had initially stated. While I was awaiting the new canopy, work started calling for me, so I had to "slow down" on several projects (mostly land vehicles), including the DM.

As for actually building my DM, that got completely put on hold. Just after I received the replacement canopy, we started getting even busier at work. Since January, we were (indirectly) contacted by FEMA to drive the nurses for all the vaccination clinic site in Oakland. Then, in March, Marin County & San Francisco opened vaccination clinic sites, so we got even busier. Even though the Oakland & Marin County sites have closed, San Francisco is still operating their sites...plus, our regular clientele type (mostly companies) has started picking up again.

So, now I have no clue as to when I'll actually get around to starting my DM. Nevertheless, can wait to see how yours turns out. In the meantime, I did pick up a lightly-used Tenshock Mini Eco, which was delivered two weeks ago. Haven't had the chance to get it in the water, but how to do that within the next 1-2 weeks (want to replace the Tenshock ESC...just not sure what's "best" to replace it with). Hopefully, H&M will be back to full-speed soon enough.


~ More peace, love, and kindness would make the world a much better place

[J Mack]

Yes Oliver seemed like a great guy to deal with and I wasn't in a hurry to get these hulls after the guys in the know like @NativePaul here and several others on another site all recommended the "Tenshock Mini Mono" for the racing deal we plan to do.
I’ve been reading about a Micro Maritimo and a Micro Drifter build on others sites and both are at or near the 120 Km/h. They both took very different approaches with the hull but the electronics were very similar so I think I’ll start there and work the speed up slowly and see how far I can get. Both of those guys are very experienced model boaters and are involved with SAW racing in Germany and France so I’ll keep my speed expectations realistic and ask lots of questions along the way.

The pond is dug and we are waiting for the bentonite before we can fill it again but one of my Mini Mono’s has been done for a while now just waiting for water.
paint.jpg

[NativePaul]

The Castle 50 Ice lite is my favorite ESC for minis, fitting my Eagletree adds 10% to the weight of the boat which skews the data so I really like an ESC that has datalogging. Without watercooling it weighs about the same as a watercooled 30A ESCs, and due to operating at about half its rated power dining 5 or 6 minute races its temperatures stay reasonable without watercooling.

Which Tenshock Mini Eco did you get? I think there are 3 or 4 versions now, 2 different hulls and straight or parallel drive options (parallel FTW). I currently have a Swordfish 40 in mine (wouldn't recommend), apart from the Castle 50 other popular Mini ESCs are older Castle 30s, Turnigy Plush 40s, and YEP 30s and 40s all with added watercooling.

Jmac, nice paint job.
You might want to change the turn fin if you have handling issues, not the best photo but this is one of the winningest mini monos in the UK, and you can see the deeper turn fin hanging off the back where it will give less lift in the turn.
IMG_8676.jpg

[J Mack]

Thank you very much Paul for all your advice, I read somewhere you liked the Castle ESC's and I bought a Castle Phoenix Edge Lite 50 AMP for my second Mini Mono and have the 90 AMP Castle for the Micro Drifter. This is my first RC boat build so I just used the Tenshock TS-BX40-ST speed control and will replace with Castle if need later.
I just asked questions on French website and the guys remove the TenShock turn fin and add what they call "Sponsons" to the sides, they say it gives better straight line speed and turns better so I try it on this hull, I will probably add the standard turn fin on the second boat when I get to that part.

These are better photos of the "Sponsons"
left.jpgright.jpg

I tried to make this boat light weight.

scale.jpg

[J Mack]

Waiting for the paint to dry between coats on the second mini mono I had some time to start making a rudder mount, I have a few more parts to make before I can glue it all in but this is what I got so far.
mount 1.jpgmount2.jpg

[J Mack]

Waiting 24 hours for the G/flex to dry is the hardest part, strut mount is done and now I need to get a fixture built to hold everything square when I glue it to the hull.
glue.jpg
st mount.jpg

[Panther6834]

That's looking REALLY good.


~ More peace, love, and kindness would make the world a much better place

[J Mack]

That's looking REALLY good.

Thank you, Oliver included a copy of your translated instruction with the hulls and it’s a huge help.

I glued the mount in the hull and making plans for diffuser, I made a quick foam mold for the carbon cover and need to come up with something for the vertical fences now.
a2.jpga3.jpg

[Panther6834]

Thank you, Oliver included a copy of your translated instruction with the hulls and it?s a huge help.

You're most welcome. I was hoping he would include those when shipping the DM to customers in English-speaking countries. Honestly, I didn't know if he would (printed and/or downloadable version), but I'm glad he is. If even one person is helped by my German-to-English translation, I feel those weeks translating it was well-worth the effort.


~ More peace, love, and kindness would make the world a much better place

[J Mack]

I finished the outside good enough for now, I copied a German boat builder for the skates and I will test these on this hull.


a6.jpg
I checked the linkage and I’ll start making the parts for the inside to mount motor and servo before I finish the outside.
a7.jpg

[NativePaul]

I have never tried it so could be wrong, but I think that although it will reduce drag, the downforce aft of the transom from a diffuser would be the last thing I wanted on a cat.

[J Mack]

the downforce aft of the transom from a diffuser would be the last thing I wanted on a cat.

I don’t know what it will do but now was the time to upsweep the rear if I wanted to find out, it will be easy to add some material to reduce the up sweep later if it creates an issue.
I’m asking lots of questions on other sites but only getting sporadic answers and I have zero experience myself so I rely heavily on the advice from people like yourself that have paved the road for the rest of us.
Do you think I should make changes now or put it on the water and see what happens?

FYI these are the two boats I looked at for inspiration.
This boat is said to run well and the diffuser from what I understand was a big help.
Difuser_4.jpgDifuser_5.jpg

This is the Drifter in Germany and he is running 130+KPH that I was trying to duplicate, I made mine as close as I could from the photos with the exception of the upsweep creating a diffuser.

IMG_5492.jpgIMG_5490.jpg

This is his second boat.

IMG_5331.jpg

Thank you Paul!!

[fweasel]

FYI these are the two boats I looked at for inspiration.
This boat is said to run well and the diffuser from what I understand was a big help.
Difuser_4.jpgDifuser_5.jpg

That's a Bulgarian cat modified by Mike W. The videos of it running triple digits are impressive.

[J Mack]

That's a Bulgarian cat modified by Mike W. The videos of it running triple digits are impressive.

Do you have links to the videos?

[fweasel]

Do you have links to the videos?

[J Mack]

Wow when you said impressive that might have been understated, that boat is a work of art in photos and the video is even better.


Thank you for sharing!

[NativePaul]

Do you think I should make changes now or put it on the water and see what happens?

Run it for sure, there is no science without testing your hypothesis.

Just because I think it will be bad, doesn't mean it will be, I have built some really terrible boats that I thought would be fantastic. Trying things out is the key to improvement, maybe at the start half your ideas are good and half are bad, but if you test them all out you find out which are which, apply the hits and drop the misses to improve your boat, and learn from both the successes and the failures, with that learned knowledge the percentage of hits to misses will increase.

[Panther6834]

I agree with the "you'll never know unless you try" theory. For Scale Nationals this year, I custom-built a Class 3 crawler that I considered to be a 'Capra', purely because it still used the Axial Capra cage, as well as a 3D-printed skid designed for the Capra...but, no other parts were from Axial, nor were any other parts designed for the Capra.

Knowing that the Capra was too tall, and had to high a CoG, to be 'comparative', I thought that, by custom-building my own rig, based on the Capra cage, I could build a truly comparative Capra-based vehicle. I still used portal axles...but, I used a variety of brass & machined aluminum parts to give it a much lower CoG. To make a long story short, some of my ideas proved to be extremely good...and, some weren't so good (of the 49 Class 3 rigs, I placed 37th...not too bad for my first time at Nationals). But, had I not actually tried all my ideas together, I wouldn't have found out which were 'good'to and which were 'bad'.

On a quick "side note", those 'good' ideas are now making their way into my new Class 3 comp rig, while some of the 'bad' ones are being "modified" for potential future use.


~ More peace, love, and kindness would make the world a much better place

[J Mack]

Trying to get everything set before I glue the titanium sleeve in the hull, this is the first time I’ve attempted going through the bottom of the hull and now I’m second guessing myself.
wire 1.jpgwire 2.jpg

[NativePaul]

That is quit a lot of bend for a wire, if there is anything you can do to get the motor lower down and/or further forward it will increase your reliability.

[J Mack]

Thank you Paul, I ordered some .098 cable but ETTI is the only place I could fine the 4mm shaft and they take 5 weeks to deliver.
Do you see any reason I couldn’t glue the sleeve in the hull and just run a stuffing tube through the sleeve later?