rubber motors

[davidchoate]

I took my Javelin to the park today to try out the way it flew with a slightly larger prop. I believe It's trimmed well. I was doing flights with 300 -350 winds on the motor (which I had attached to the rear peg). she flies level from the point of release; no climbing, gentle left turn, then a gentle right turn as the motor winds down, and avg. about 75 - 100 yds. is this ok that there is no climb? Do I want that? I've lost 2 planes in the last year to trees, but I know if I had more altitude it would increase my times. anyway, after 4 flights the motor broke. I would like to know if anyone knows what kind, and where to get , and what kind works best. also why are there two peg locations? I know Mitch moves his for balance, but is that the only reason? I must get that book I was told about, but I'm already involved in 3 projects at once, and my budget is gone. This being the holiday season now I got to save up for that ,and work is slow as well. But I'm still glad I went to the park flying today rather than my sister's house for Turkey today. now I'm gonna go work on my 500 P-40 project. I have the whole house to myself for awhile longer, and there's no distractions.

[davidchoate]

"Battle Damage"

[SteveM]

That little book is $12 new at Amazon with free shipping if you order $35 or more. Best price is a used copy that is about $11 shipped. Check the couch for loose change, you won't regret the purchase.

What comes to mind in order are:
Is it balanced?
How did it do in the un-powered glide test?
What angle do you launch at?

A few ideas I have are that you are nose heavy, the wing needs a higher angle of incidence, too much down thrust on the prop, and/or not launching with a slight up angle. You are expecting to get a climb, then level flight, and finally a glide down to ground.

The book also discusses the motor peg locations. He doesn't like how some older plans are done and moves it forward to where the fuselage is stronger. Not sure if that would apply to the Javelin, but the forward peg would be stronger and more friendly to the beginner.

The rubber probably broke because you didn't lube it or it got a cut or nick in it.

[stx44]

The Javelin is designed to be easy for learners to build. As such it is designed to balance perfectly with no clay if built per the kit and using rubber on the front peg. This give good flight times and patterns for a beginer.

The back peg is there so you can add longer rubber and add another 100 winds to get longer flight. However, you have two choices if you use the back peg:

Add weight to ballance

Move the wing back.

The second will make it less stable (reduces the moment of the control surfaces- the distance from them to c of g).

I would check the amount of downthrust you have. Also, how big is the prop you are using? Ive tried the 7" prop from the Edge, and have gone back to the kit prop because it performs better (I think the Edge prop's pitch doesnt match the planes flight performance).

Also, per the instructions, if you use the rubber at the length of the back peg, more than 300 turns WILL snap it. You also need to lube the rubber, othewise it will have a very short lifespan.

Hope this helps- but keep in mind Im not an expert- but I have been flying my javelin daily for the last few weeks and having a ball.

[davidchoate]

Yes, I was thinking about I have too much, but damn close, and the wing angle as well. I'm glad I chose the Javelin as my first serious attempt at FF. It is very well balanced, and easily adjustable. I was using the prop from my Edge, and also noticed a difference; not necessarily less time, but definitely a decrease in velocity. It is also worthy to mention that in the short time since I've been doing these"Free Flights" what I am learning about aerodynamics will undoubtedly help me to build into my RC planes better flight characteristics. Thanks to Mitch for being the one to motivate me into trying FF.

[davidchoate]

why am I having trouble uploading attachments? Oh, I already took my change jug to the coinstar last week. I used the money to make copies of some plans at Staples. I'm trying the Bill Parker idea, but not to his extremes. I don't want to have to cut out a wall to take it for a test flight.

[SteveM]

I'll give you a freebie then. According to the Don Ross book if you get failure to climb while under power then you either need more rubber, a smaller prop, a prop with less pitch, and/or add a 1/64" shim to the LE of the wing.

[davidchoate]

i replaced my rubber motor ( a tedious operation), decreased the downthrust, and reinstalled the kit prop. the wind today was between 5-10mph at times. Due to this factor I don't believe any of the info of my 3 flights was very useful. everyone different. I'm averaging an honest 10 sec. a flight. again I could not resist removing the 20g weight on the nose. It does climb without it, but like not in a good way. I did the "walk of shame" on my way home from the park again. My wing came off when she landed upside down and the wood covering one of the LG wires broke, but she'll fly again. She now has 9 flights on it. Maybe I will retire it if it lives through 25 or something.

[stx44]

Ok, replacing the motor shouldnt be overly tedious, my process is:

Cut the rubber to length and tie it off. Place it in a plastic bag and spray with lubricant (I use armourall, a vinyl spray for cars). Massage it in. Take it out, wind it up a little to squize the lube through the pores. Repeat the bag/wind. Then wipe off the excess. its now good to go.

I then use a loading rod (basically a long piece of wire with a hook at one end- coat hangers or tie wire works- it needs to hold in a straight line, not be floppy like electrical cord) is fed throught the nose hole and up to the access panel at the back of the plane. Hook the rubber on and pull it through, putting the rear peg in when its partly extended. Hook it onto your prop and your done.

If your using the rear motor mount, you should be able to get better than 10 sec out of a stock javelin, if its trimmed right. Trimmed just right and with 300 winds on, my stock javelin will clear 25 seconds on a good day, and run nearly a soccer pitch in a straight line.

Having said which, I broke it, and my typhoon yesterday..... Sounds like your day. Bit windy, had a couple of good flights, then a heavy landing resulted in snapped wing rubber and a bent prop. The typhoon had the same deal- heavy landing and the nose caved in round the prop button.

Free flight for me is all about getting it just right for that one magical flight, but there are a lot of bad flights leading up to the one great one..... just keep flying and adjusting and it will come together at some point.

[davidchoate]

Yes. I feel that way also. It's awesome when you get that 1 nice flight happen, but I don't mind the trimming-learning process either.Thanks for the rubber motor info. I used hand cream yesterday,I've been trying different things. Armorall next. What I did was ended up using a piece of solder wire tied to the rubber and fished it through, but still had to cut a section of tissue out of the bottom to get the peg through it. I know once I can trim my Javelin to climb,I will easily double my time.And this time of year it's dark when I get home so I really have just Sunday to fly.I also noticed that (on a new motor) after a few times wound and released that it is an inch or so longer. Is this normal, or did my lube react to the rubber. I have been using the Grey Rubber.Also I notice my tissue becomes relaxed after exposed in the cold awhile. This I expect normal, but wonder if it has anything to do with my plane flying different although I don't adjust anything. Oh well, I can't wait to get it to the field again. I honestly could have went RC flying yesterday, but chose FF. I think much of my failures as an RC pilot are because I skipped over FF, and really getting a hands on understanding of how things work aerodynamically.This winter I'm gonna spend doing FF and some display models( to improve my overall building technique), and next summer I will build an awesome RC model that will look and fly perfect.

[SteveM]

I also noticed that (on a new motor) after a few times wound and released that it is an inch or so longer. Is this normal, or did my lube react to the rubber.

For best results pre-stretch your motors - there's a book for that.

[Wildpig]

Cold weather will reduce the strength of a rubber motor. That might have some effect on your flight performance.

[Mitch]

Hi Guys,

I'm back home for a day... just trying to catch up on the events...

First of all. Do not take what I say as being the final word or the best way to do something. I feel I am learning along with you guys here.

as for rubber motors... I am using tan rubber for contests. It is only made from ONE source, so where ever you can acquire it (LHS or online) it is the same stuff. For me, I have had mixed results and have had some GOOD flights with the Guillow's grey rubber. I think it is all a combination of torque/pitch/size of the prop, and along with the model weight (wing load). I had some very nice flights with a Guillow's 400 Mustang with Guillow's grey rubber(new) and a 7 inch prop, only to be disappointed with the same model with different rubber and a different prop.

If you change to many things at once, you do not know what's happening...

Mitch... Keep Building, Keep Flying, Keep Learning

[davidchoate]

I plan on flying my Javelin tomorrow. I added 1/32" shim under wing LE, and 4g wgt. on the nose. also i'm trying a different prop from a 24" biplane. an old Thomas M. Scout.WE'LL SEE HOW IT DOES. i ALSO PLAN ON WINDING THE MOTOR TO 500 WINDS. i HAVE DONE SOME TESTING, AND THE MOTOR SEEMS TO HANDLE IT NO PROBLEM. MY GOAL IS A 20 SEC. FLIGHT. i AM HAVING PROBLEMS POSTING PHOTOS. IT SAIS "SORRY, THE BOARD ATTACHMENT QUOTA HAS BEEN REACHED". i'm pretty sure its because of that arguably distasteful pic I accidentally uploaded. I apalogized. It was an accident. I hope they forgive me soon cause I want to post my P-40 build very soon. I can always put it on Stick and tissue, but I like this forum best. I hope they forgive me sooon.

[davidchoate]

No flying due to snow yesterday.So I stayed in . I was going to remove snow from my Fathers driveway, but the snowblower would'nt start. So I stayed in and worked on my P-40 500 sereies, experimented with paints, and began to look over the plans for some kits I will build soon. a couple of them included a slip of paper inside for ordering Bill Ross's book "Rubber Flight". The price was $12.95, and said the book would be autographed by the author. Also there was one for the balsa workboards they sell. I recently went on the Guillows website to buy the book, and a 48" workboard(to do the PT-17 on) but could not find either a price or how to add it to my cart. Does anyone know what I did wrong?