HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jun 13, 2002, 03:47 PM
Experienced Member
Schluter60's Avatar
East Hartford, CT. U.S.A.
Joined Jan 2001
63 Posts
Quote:
Originally posted by Vinnya42
for saftey sake even though my ground is rock hard and I use a hammer to get in and bang it back and forth to get it out I use two. One is connected to the bungee and the other is tightly tied to the first stake 12" away as a backup and to distribute the load over both stakes, this might be an idea if your at all worried.
Vinnya42,

Excellent idea with the second backup stake. Some guys attach a small drogue type parachute to slow the approaching stake should it release, but I like your idea better. I have never (knock on wood) had a stake even come close to releasing, but it's better to be safe than speared!
Schluter60 is offline Find More Posts by Schluter60
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 14, 2002, 05:41 PM
.: Looking for Thermals :.
Ricardo RW's Avatar
Chile, Quinta Región de Valparaíso, Los Andes
Joined Jun 2002
868 Posts
Guys,

Is this pedal launcher suitable for bungee 2M sailplanes with a highstart?

TIA
Ricardo RW is offline Find More Posts by Ricardo RW
Reply With Quote
Old Jun 15, 2002, 05:46 PM
Registered User
mtayl's Avatar
Boulder, CO USA
Joined Sep 2001
1,405 Posts
I'm in the final stages of building one so hopefully by tomorrow evening I'll have a web page up at www.yourzagi.com with a complete printable parts list and (I hope) a picture of it that you can click and zoom in on for various pieces. Should be fun to do if the slurry bombers fighting the fires don't land on my house first.

I do have a question. For people who use these routinely, how important is it to have a 20 degree upward slope versus 10 versus 5, etc. For the initial tests I'm planning on not glueing the vertical posts in so I can play with it a bit, but I'm curious as to how much speed the plane can actually achieve in only 5 feet? Is it enough to generate some lift?

I still need to find a local supply of bungy cord or surgical tubing. No one seems to have any. Maybe a boat or marine shop? Any recommendations on an online place to get it and which is better, bungy or surgical tubing?
mtayl is offline Find More Posts by mtayl
Reply With Quote
Old Jun 15, 2002, 06:44 PM
Crashez-vous sans stress!
Dan H.'s Avatar
Chicago
Joined Nov 2001
374 Posts
Matt--

I've never looked for hi-start tubing in retail stores, figured it's too obscure.
Hollyday Designs may still have some tubing.

Here is a good general info hi-start page, but appears to be an australian vendor.

Here's a supplier with good prices on shorter lengths--10' of a higher diameter tube may be good for a pedal launcher application: Reef Scuba

Regarding the leg lengths, I thought these designs allowed for adjustable legs by having two tubes, one of a smaller diameter that fits into the other, and a series of holes drilled through and a cotter-pin type retainer arrangement. If they don't maybe they should.
Dan H. is offline Find More Posts by Dan H.
Last edited by Dan H.; Jun 15, 2002 at 06:46 PM.
Reply With Quote
Old Jun 15, 2002, 07:07 PM
Registered User
mtayl's Avatar
Boulder, CO USA
Joined Sep 2001
1,405 Posts
Quote:
I thought these designs allowed for adjustable legs by having two tubes, one of a smaller diameter that fits into the other, and a series of holes drilled through and a cotter-pin type retainer arrangement. -- Dan
Hmmm. Interesting idea. For the longer vertical posts that raise the rails up at the end, I have cut various lengths of 3/4" PVC to play with the slope angle. Here's a rough assembly so far and I'll be taking it apart again for photographs. I'm about to drill the holes for the release bolt.
mtayl is offline Find More Posts by mtayl
Reply With Quote
Old Jun 15, 2002, 07:09 PM
Crashez-vous sans stress!
Dan H.'s Avatar
Chicago
Joined Nov 2001
374 Posts
Quote:
Originally posted by guru_dick
Is this pedal launcher suitable for bungee 2M sailplanes with a highstart?

TIA
You shouldn't need a launcher like this to hi-start a Gentle Lady or similar 2-meter gasbag. And you wouldn't want bungee-launch type loads on that kind of airframe anyway, as you could fold the wing or otherwise damage your model.

As I understand it, "bungee" type launches are for smaller, stronger, heavier, higher speed planes that stall at relatively high speeds, like 25mph or higher, that make handlaunching difficult (and for slope nuts to test their high-speed ships away from the slope). Bungee setups are typically short (10-20' of bungee material and a short lead line of about the same length or whatever's practical) and are designed simply to accelerate the model to a blistering speed at only a slight climb angle (or straight & level), then up elevator is cranked in for a zoom of altitude gain. Bungee towhook locations are usually well ahead of the CG to keep the plane tracking level during the rapid acceleration.

A proper hi-start uses a longer length of tubing and a much longer length of line, so you get a very long, relatively slow release of energy and the line allows the model to stay on tow until 100-300 or so feet of altitude is reached. The towhook location for hi-start and winch launching is very close to the CG (generally just ahead of it), so the model can climb on the hi-start energy without being pulled nose-down. When the plane stops climbing, the rubber is out of stretch, and with a little dive maneuver you fly off the tow ring (the parachute on the ring is design to open when the line goes slack and helps lay the line back down on a downwind line). [Edit: In low wind the model will fly itself right off the tow ring.]

When you've stretched a hi-start to the proper length (there are some guidelines somewhere on the internet, but you can also just experiment: 4-5 lbs of pull is a fine starting point for a 2M but the optimum will be higher), you hook up the plane and just give it a gentle toss at a decent climb angle like 30 deg. If the plane is trimmed properly and the towhook location is right, the model will find its best climb angle and kite up on the line all by itself, and all you do is mind the rudder if needed until it's time to dip to drop the line.

Hobby Lobby and NSP , among others, sell hi-starts if you don't have one already.
I have one of NSP's Pinnacle Standard hi-starts and I like it. It's a well thought-out design: day-glo line, quality hi-vis parachute, good stake with a day-glo head, comes with a cord reel for storage. I also have an up-start for smaller gliders (2M or less) that was cheaper but does not launch nearly as high.
Dan H. is offline Find More Posts by Dan H.
Last edited by Dan H.; Jun 15, 2002 at 08:17 PM.
Reply With Quote
Old Jun 15, 2002, 07:41 PM
Registered User
mtayl's Avatar
Boulder, CO USA
Joined Sep 2001
1,405 Posts
Thanks Dan! That answered a bunch of my questions.
mtayl is offline Find More Posts by mtayl
Reply With Quote
Old Jun 16, 2002, 11:56 AM
Experienced Member
Schluter60's Avatar
East Hartford, CT. U.S.A.
Joined Jan 2001
63 Posts
Pedal Launcher Generate Lift

The Pedal Launcher that I built started with a 10 degree angle and I increased it to 15 degrees which works fine for me. These planes come off this thing like they are shot out of a gun, and as soon as you can react it has past the launcher and you have COMPLETE control of the surfaces. You can climb, turn and complete a small circuit without turning on the motors. Naturally you will turn on the motors and you can perform any move you like. The initial 15 degree angle just insures enough initial lift until you take over radio control, maybe 2 seconds into the launch.
Schluter60 is offline Find More Posts by Schluter60
Last edited by Schluter60; Jun 17, 2002 at 11:29 AM.
Reply With Quote
Old Jun 16, 2002, 12:33 PM
Registered User
mtayl's Avatar
Boulder, CO USA
Joined Sep 2001
1,405 Posts
Oh, very cool. I'm going to order 20' of bungee for this thing. I've heard you can stretch out it 40'-60' or so? I need to get a fishing scale to measure the pull and all of the various connecting rings and 'beaners and stuff.
mtayl is offline Find More Posts by mtayl
Last edited by mtayl; Jun 16, 2002 at 12:36 PM.
Reply With Quote
Old Jun 16, 2002, 01:21 PM
Registered User
kushal_22's Avatar
Kamloops
Joined Dec 2001
6,844 Posts
Where are you ordering your Bungie from?
kushal_22 is offline Find More Posts by kushal_22
Reply With Quote
Old Jun 16, 2002, 04:22 PM
Registered User
mtayl's Avatar
Boulder, CO USA
Joined Sep 2001
1,405 Posts
I found 2 online stores this morning which seem to specialize in the bungee kind of supplies.

http://www.superiorbungee.com/
http://htbbungeecords.com/

I have not checked any of the prices yet, but I'm going to need things like the connectors, metal rings, etc. Some of it I could probably get at the hardware store as well but I think I would prefer to have a "professional" do the bungee connector end of it.
mtayl is offline Find More Posts by mtayl
Reply With Quote
Old Jun 16, 2002, 06:03 PM
Garbage in, garbage out
Arizona E-Fly's Avatar
Tucson, Arizona, USA
Joined Sep 2001
61 Posts
Here is yet another variant of the pedal launcher.

Foot release is by Multiplex (for way too much money). We have built two more similar to the Multiplex foot release from a spare plank of wood and a couple of nails. Much cheaper.

In reality the rails are generally not needed. Projetis, Zagis, Twinjets all launch from ground without any problem. Rails add "cool" factor though

When I attach a payload to the belly of the twinstar then the rails do become necessary or else the payload would drag along the ground. Not good. Rails work fine. Angle of rails is also of little importance, since most models are already flying at a steeper angle of attack by the end of the rails. These rails are 4 feet and seem long enough, but main consideration was cargo space in vehicle.

Fish scale says pull is about 6 lbs for projetis and zagi launch, stretched to 10 lbs for heavier twinjets, twinstars, etc. Haven't folded any wings yet

I prefer ROGs but if you don't have wheels, this is the only way to fly unless you know a good chiropractor.
Arizona E-Fly is offline Find More Posts by Arizona E-Fly
Last edited by Arizona E-Fly; Jun 16, 2002 at 06:15 PM.
Reply With Quote
Old Jun 16, 2002, 06:10 PM
Garbage in, garbage out
Arizona E-Fly's Avatar
Tucson, Arizona, USA
Joined Sep 2001
61 Posts
Someone asked about bungee launching wings?
Arizona E-Fly is offline Find More Posts by Arizona E-Fly
Reply With Quote
Old Jun 16, 2002, 06:29 PM
Registered User
kushal_22's Avatar
Kamloops
Joined Dec 2001
6,844 Posts
I would really like to take a look at the hook you have on your projeti. By the way GREAT color scheme!

Malcom
kushal_22 is offline Find More Posts by kushal_22
Reply With Quote
Old Jun 16, 2002, 09:55 PM
Garbage in, garbage out
Arizona E-Fly's Avatar
Tucson, Arizona, USA
Joined Sep 2001
61 Posts
Towhooks are made from 1/8" steel rod purchased at LHS. I cut it into 1 1/4" lengths, and bent them 90 degrees at the 1/2" mark, then filed the cut edges smooth. Towhooks done.

Projeti: Cut 1" 1/4" balsa stock, cut foam, glop in glue, insert 1" wood piece. Drill 1/8" hole for hook, glop in glue, insert hook. Towhook installed.

Zagi: Same thing but added 1" by 2" plywood piece for increased glue to foam area.

Twinjet, Twinstar: Easiest. Just drill 1/8" hole in wood spar running down fuselage centerline.
Arizona E-Fly is offline Find More Posts by Arizona E-Fly
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
PVC pedal launcher in UK? stegla Electric Ducted Fan Jet Talk 21 Feb 08, 2003 03:15 PM
PVC Pedal Launcher Slope Nut Electric Plane Talk 11 Sep 24, 2002 11:18 AM
PVC Pedal Launcher dave_lilley Modeling Science 2 Aug 25, 2002 02:35 AM
PVC Pedal Launcher dave_lilley Site Chat 0 Aug 23, 2002 02:20 AM
pvc pedal launcher hmx Electric Plane Talk 3 Jun 05, 2002 03:19 PM