I need a quick answer!! I just bought a Sportsman Aviation Aero Princess .15 powered glow plane. The plane is very light, around 27 oz. I purchased 5 Hitec HS-81 servos (regular gears) for the plane... are they powerful/durable enough for glow applications? Thanks!!

whats the output of the servos?

This is a mini/micro servo. You are pushing the limits on the gears in them. Be aware that the gears are a THIN nylon with small teeth. Agressive manuvers and/or sudden strain have an excellent chance of stripping them.

The 37 oz torque SHOULD be OK PROVIDED you are doing Sunday type flying. Aerobatics and 3D manuvers will most likely push them over the edge and they will strip. If you need small servos check out the Bluebird MG servos
http://www.balsapr.com/view.asp?id=V443293&pid=T886880

I have used these particular servos in 46 powered planes.
See photo.

Hope this helps.

Mike another option is to buy the metal gear kit for those 81's if they cannot be returned. It would be much cheaper than buying new servos.

In a 27 ounce airplane you'll have no problem. I've run them in SPAD combat planes and have never had a problem with them. And also in Zagi's in full contact. and once in a while will break a gear but that is in a full throttle hit to the ground.

Dennis

Yeah, just to clarify, the plane requires micro servos, and the plane IS only 27 oz. I think they'll have enough torque, but I'm worried about the stripping of the nylon gears. I think I will stick with these for now, and either convert them to metal gears, or replace them if they strip...is this sound thinking? Thanks again!

you won't have any troubles. but have you priced the metal gear sets? you can repair with nylon for five bucks.

Dennis

If the Zagi loves them, how could you blow them?

Cement Floor covered with a piece of carpet. Full throttle straight in. Indoor combat is a blast. Though the planes take a lot of abuse. Actually i think i've broke more servo arms then stripping gears. A straight hit to the linkage from another plane tends to break the servo arms. My zagi is 25 oz. with a 1400mah nicd battery. And a few carbon fiber reinforcements along with some extra tape from prior damage.

I think the HS-81 will do but would still say it's a much safer bet going with the metal gears so that you aren't risking a sharp turn over the pits or anywhere and having your servo strip. Plus depending on where your servo is it can be a pain having to replace your servo's gears every so often. Just a saftey procaution and time reducer. But otherwise your servos will have plenty of power.

Metal gears in a 27 ounce plane? Thats less than two pounds!

Metal gears in a 27 ounce plane? Thats less than two pounds!

Get the HS85 then ... there is also the MG version of the 81 ... what servo depends on how you fly. I know guys who have flown 72" planes with Sanwa 102s only. Not wise but it does work.

HS 81 about 18.00 bucks, HS 81 MG about $24.00 bucks, times that by 5 X 24.00 compared to 5 X 18.00 is a $30.00 difference. I would personally pay the extra $30.00 because that might save you alot more money in the long run.

Mike ,


The regular HS81 servos will be fine. Most of us over in the 1/2A forum are using HS55 in some pretty wild aplications and are not having a problem. I have an Herr Pitts (glow Norvel .074) that weighs in at 27.5 oz. and it's doing fine with the HS81 servos. This plane has been flown to the limit with no servo problems. Also you really don't need an HS81 on the throttle. A gws pico would be a good choice and save some weight.

Darren

Hi everyone, and thanks for the advice! Since I already have the standard (nylon) HS-81s, I'll stick with them until they strip (if ever). If they do strip, they'll immediately get replaced with Metal Geared versions. Thanks again!

I think they'll be fine. I use them in a Zagi, and in some glow applications too. Order a set or two of metal gear sets for them. If they do strip (and I doubt very much they will unless you crash), you can upgrade them as you repair them.

Good flying,
desmobob

I think Hi-Tech has already scrapped it, the 81's, on their site.

HS-81's will not be a problem at all. These are miracle servo's. I have them in 1/2a's, 15, 25 and even 40 size planes. Anything over a 15 you will want metal gears. On the 40 size planes I run 5 cell AAA 700ma packs since the servo's draw a lot less current and make sure you have a solid mount. You can drop 8oz easily on the 25+ planes by switching to these and the smaller pack. I have 5 of these in my TT Giles 202 (40 size at 5 lbs) and they have performed without a problem for 60+ aerobatic flights. Same thing for my WM Clipped Cub (40 size). The most important factor is control surface slop. Surface flutter is the servo killer so make sure you have very little play in your linkage.

use them, they are very good servos. I use them on all of my 15 size planes without metal gears.

Mikeg4936,

Hitec makes a metal gear version of the HS81's I just ordered some HS81's for throttle and retract air valve operations and saw the other option.

Andy

awesome... thanks