Dash7ATP

I have a Herr model seaplane with a Norvel .061. This engine turns about 15,000 + with a 6 x 3 prop. It takes all of that to get it off of the water. Then it flies great at about half throttle. My problem is the engine will not idle down enough to allow me to make power on approaches. I have to cut the power completely to land or just fly it out of fuel. Problem is you can't just walk out to retrieve the model as you would at the field. So I want to convert to electric.

My problem right now is I can't find enough information on the motors I see on line to determine which one to buy that will give me the rpm I need with the 6 x 3 prop. I can't go with a larger prop due to clearance issues with the model. So....... my question to the group is this: what motor will give me about 15000 rpm with a 6 x 3 prop? I understand the Kv rating is given in a no-load situation. Also consider I'm trying to keep the weight down, as it's a small model. What ESC would fit the recommended motor? I would like to stay with a 2s battery pack (weight) but may have to go to 3s for the power.

Thanks guys.........

Dash

guapoman2000

Is it the Aquastar by any chance?

guapoman2000

If so, I would look at this recent thread about it and go to post #5 as I like Himax Motors. They are very good quality and won't break the wallet.

http://www.rcgroups.com/forums/showthread.php?t=651838

Dash7ATP

Yep, it's the AquaStar by Herr Engineering. I have had a Mig .061 (or the clone for it) on it from the start. As I said, I can't get it to idle down enough to make a power on landing, and without a retrieval boat, it limits when I can fly it. I have bought an electric setup from Grayson Hobbies and now that I see what you guys are doing, I think I'll tear into it and make a few changes. I already have the chines on it and that should help a lot, plus the electric should have more power than the Mig.

Thanks for the link to the AquaStar forum.

Joe

guapoman2000

Welcomed Joe.

Best of luck!

Dash7ATP

Guapoman2000,

Thanks again for putting me onto the forum. I had been sitting on my butt trying to decide if I really wanted to cut the glow motor mount off of the pylon, and proceed with the electrical conversion. Since we have a float fly coming up in about two weeks, I took the model down from the ceiling and proceeded to do just that. Conversion is underway. I had a two ounce tank built into the right side of the pylon, and have taken it out. There seems to be room for my 25A ESC, but running the wires into the fuse for to the receiver will require some more cutting . I'm also hoping to change the battery through the hatch, but of course that will mean taking off the wing for every flight. I really don't want to cut a hatch into the nose, but that may be the lessor of two evils. I have to think on that for a day or two. It would sure make things a lot easier and much faster, but much more prone to getting water in the model.
I'll keep you posted.

Joe

blvdbuzzard

I know I am late to this, but I used this motor in place of my TeeDee in a Mach None and Ace Super Pacer. Super scream on 3s.

http://www.hobbypartz.com/86ma68-2205-3400kv.html


Buzz.

Dash7ATP

Thanks for the post, Buzz. I'll keep this in mind in case my motor doesn't give me what I need.

Joe

aeajr

My Feedback: (2)

How is the project progressing?

If I were doing that project I would start with the weight of the RTF aircraft and work from there. Watts/pound is the way to size an electric aircraft. Then you back into the right kV in order to give you that wattage on a 6" prop. Might be a 6X3 or it might be a 6X something else.

A link to some information about the plane would help a LOT!


This may also be helpful:

EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT

http://www.rcuniverse.com/forum/m_7100376/tm.htm

Glow to electric conversions
http://www.electrifly.com/powersyste...brushless.html

aeajr

My Feedback: (2)

After some searching I found this. Is this your plane?
http://www.sigmfg.com/cgi-bin/dpsmar...nuF.html?E+Sig

I see it is 19 ounces. Let's assume that the electric version will come in a 22 ounces.

I would suggest about 100 watts/pound so you want something that can give you 130 watts using a 6" prop.


The tool I used to model the set-up can be found here. I used the Prop calculator
http://www.castlecreations.com/suppo...alculator.html

Since the 6" diameter is the limiting factor I worked everything around that. Could not find a set-up that worked well on a 2 bladed prop so I went to a 3 bladed prop.

I played with a calculator and came up with this combination. I have no idea how it will fit in the motor pod.

Himax 2816 kV 1550 with s 6X4 3 bladed prop and a 3 cell 1200 mah 35 C battery.

Master airscrew 6X4 3 blades
http://www3.towerhobbies.com/cgi-bin...?&I=LXFTE7&P=7
APC also has some 6X4X 3 blade props
http://www.apcprop.com/ProductDetail...tCode=LP06040E

Produces about 120 watts of power, about 95 watts/pound. About 21 oz of thrust.

I know nothing about seaplanes so I can't be sure that is a good fit but it is a start.


Again this is a first cut only.

Dash7ATP

Hi aeajr,
I guess I have been pretty lazy, since I haven't updated my progress on the conversion to electric. I completed it about two months ago and It has worked out fine. I'm not much on the electric technical stuff, but I did go with a combination a friend was using and it worked out great. The Herr Aqua Star is a neat little seaplane, but I did do a few simple mods to it. I lowered the back of the wing saddle about 1/8" for a slightly Higher AOA, and also added a little upthrust to the motor mount. It will high speed taxi on the water as long as I like and with just a tad of up elevator and it's flying. Mucho fun!

I put the ESC where the fuel tank had been and the battery in the fuselage. Since I didn't want to take the wing off every time I put in the battery, I cut a hatch in the nose deck and made a base for the pack to sit on. This meant connecting the battery with the prop about one inch aft of the hatch. Not good. Too dangerous. My fix for that was to cut the red lead to the Receiver and putting in a switch. This way there is no power to the RX and therefore, no danger of the prop starting while putting in the battery. It works great. I used the switch mount with the Pull button that comes through the fuselage. I used a 25 AMP ESC and mounted a heat sink to it from an ESC that had "let the smoke out". The photos below should show everything pretty well. I hold the hatch closed with the tape the boaters use for water proof their hatches.

For those who may be interested in making this mod, I hope this helps a little.
Joe



One more thing. To clean up the installation, and to keep the wires as short as possible, I cut the leads on the motor and ESC and soldered them together, keeping them as short as possible. I did have to add wire to the ESC to get the plug for the Battery to the hatch opening. I also had to lengthen the Receiver lead from the ESC to the Rx, in order to be able to add the switch to the red wire.