Propwash in Pa

I currently use a highstart w/ 75’ of tubing plus about 150’ of line. Launches consistently are roughly 250’, go strait over the top, stretching the tubing and line, actually holding the plane from climbing. I want to gain an additional 100’. Any feeling on whether it would be better to add 25 more feet of rubber or an additional 100’ of line?

kwmtrubrit

Most hi-starts are 100' tubing and 400' of nylon line/mono, so I would say that you are a bit short on the line end. Depending on the strength of your tubing, I bet you could add 50', if not 100'.

mocgp

Unless you have 1) a field with no obstructions for 500 or 600 ft. in every direction and 2) a lot of extra time to retrieve your line, I would recommend sticking with what you have. I used to use a 100/300 setup and switched to a 50/150 setup simply because the extra launch altitude you get with all that extra rubber and line are typically not worth the effort it takes to set it up and retrieve it. I'll freely admit that thermals are typically more well-developed at 400 ft. than they are at 200 ft., but I have grown to love the challenge of finding and coring the ones at lower altitude (Discus Launch flyers, feel free to chime in here). Last time out, I ran across a weak bubble at about 75-80 ft. and worked it for 2 or 3 minutes - plane (all 5 lbs. worth) didn't go up but it wasn't coming down either. Anyone can speck out by launching into a hat sucker at 400 ft.

BMatthews

If you're able to lift the rubber off the ground completley and still can ping it off the line a little then you could easily go with a lot more line as suggested and no worries about the rubber. It's also a good observation about the room needed. It's all about balancing and compromise, ain't it....

Propwash in Pa

Thanks folks. I actually changed out my line tonight with the hot pink mason's twine and measured. 100' rubber and 200' line. I cut a length of 100' that can be swiveled onto the end of the 200'. As far as room, generally not a problem. I could easily go another 200'. Let you know how she does.

glidagida

Hi Propwash

Go for as much rubber and line, the old 100' rubber, 400' mono is a good comnpromise. As for the builders line, if its the same pink plaited stuff we have in AUS then it will be OK but it has drawbacks compared to 50lb mono.

1. The 'weave' is heavier than mono and your plane has to drag that weight up.
2. The 'weave' is greater in diameter and has more line drag, ask any F3B guy about line diameters vs wind strength, there is a reason why the experts usually have 2 winches with different diameter line.
3. The open 'weave' absorbs moisture on dewy/wet days and again adds to your line weight.

You do not say what plane you are using, but the smaller the span the more critical the weight/drag issue is with the line and launch height suffers dramatically on still days. A 2m will be affected much more than a 3m, and if you fly strictly 2m I would even consider the 'cheap' versions of 'Spiderwire' mono fishing line to keep the line weight/drag down, usually these are only a couple of dollars dearer than nylon these days.

Cheers
GG
www.rc-sailplane.com.au

Propwash in Pa

I am flying a 100" (2.6 meter) Antares. All-up weight is slightly under 3 1/2 lbs. I will keep your comments in mind. If the twine actually hurts the performance, I will change back to mono.

vintagesailplnr

My Feedback: (40)

Hi: If you really wish to get the best launch with a highstart. Get a cheap used turn-around, like winches use. Or make one from a bicycle wheel hub. Most bike repair shops will give you several, ball bearing, etc, some cost over a 100 bucks new!!!

Have the rubber staked at your feet, run the line out to the turn-around and back to you. Stretch the rubber and ......... This way the plane does not have to lift the rubber. Much better and higher launches!!!!!!!!! depending on the set up, you will get launches better than a winch!!!!
regards,
Jim

Propwash in Pa

This sounds like a great idea. Do you have any pictures?

aeajr

My Feedback: (2)

Depending on the strength of your rubber, you may still short on line. Keep adding line till the plane can't lift at least 3/4 of the rubber off the ground or until the plane runs out of climb before it hits the top of the launch.

Get a fish scale and see how much pull you are getting. Typically you want a minimum of 3X the weight of the plane and preferably 4-5X the weight of the plane. So you want at least 12 pounds of pull for your and would do better with about 16+ pounds of pull. You have to judge the strength of the wing.

Most tubing can pull back 3X the rested length. So you should be able to pull back up to 300 feet or when you hit these pull strengths. Build up to that pull if you are not doing that much now. Watch to see if the covering wrinkles a lot.

I have a 38 ounce Spirit, aobut 2.4 pounds. I launch it at 12-14 pounds of pull, or about 6X the weight of the plane, with no problems. The Spirit can take up 500 feet of line with a 5 mph breeze. I get a little monokote wrinkle on launch but I have to really look for it to see it.

When I launch my 80 ounce legend, I pull it back further to about 20-25 pounds and only use 400 feet of line.

Tow hook placement also greatly influences the height of the launch.

Propwash in Pa

Thanks Ed. This past weekend, I launched the plane about 10 times. Stepped off roughly 3X rubber (300') and had a total of 225' of line. Although my field is very large, roughly 100 acers, I ran out of room due to the farmer's fences. The pull was not measured but was pretty tight. At least 3/4 of the rubber came off of the ground during the better launches. I did notice that not all of the energy was released from the rubber because of high grass in the field. I am planning on a couple of changes. I like the idea of using the turn-a-round. With a 3X pull-back I should be able to launch to 400' while needing roughly 700' of total launch area. The area that the rubber will be stretched will be along our 500' R/C runway. The rubber should release all energy. I did pick up a rear ball bearing axle from a local bike shop at no charge. (maybe because I just spent $1,600 on a new mountain bike). I will post pics and performance info once complete and I get a chance to use.

daveosoar

Make sure the turnaround system is strong enough and VERY well staked. If it comes apart its lethal, as is a winch. A good system but just take care, particularly if there other people about.
Daveosoar.

aeajr

My Feedback: (2)

I have never used a turnaround hi-start but I have heard both good and bad. I just let the plane carry the rubber.

Good is that you don't have to lift the weight of the rubber.

Bad is that the rubber drags on the ground giving up a lot to friction on the ground or dragging in brush.

If you mount the pully high, like on the top of a fence, that would probably be best.

Happy flying!

da Rock

Turnarounds are also more trouble if the wind changes direction. Just like a winch is. Of course, we live with that. But with a normal hi-start setup we don't have to live with it.

vintagesailplnr

My Feedback: (40)

Hi:
You do not move the turnaround, you move the plane! The turnaround stays in the same place, you just move yourself! Of course the turnaround is able to shift directions up to 90 degrees
This is a no brainer for the hight start.
Jim

FlyMeCourageous

I was using a "flat" style dacron string on my heavy-duty highstart, but noticed a wipping noise during launches (DRAG . . .lots of drag).
Changed over to 30lb test braided monofilament. Not only did it weigh less, the drag was reduced and gave a very noticeable gain in launch speed. At $11 for 300 yard roll, I plan to stick with this.
100 ft rubber 400 ft line (could probably add 150 to 200ft with 5mph+ wind)
Great Planes Fling 2M at 21.7 oz and 10-12 lbs pull (Too chicken to try more)

scootertrash340

Another type of line that you can use to good effect is Spyder Fishing line. I replaced my twine on my hi-start with 80lb test Spyder Wire fishing line and the launch difference is amazing! One spool of Spyder Wire is 450ft, so that should be enough. You will notice quite a bit of weight difference compared to the construction twine that you can get at the hardware store. You will be getting the maximum out of the rubber by using this!

I am launching a Soprano with this setup (100 ft of tubing and 450 of Spyder Wire) and I am getting a good 500ft launch! And this is with a hi-start that is 25 years old! I have not broken the Syder Wire yet and that is stretching it to the maximum!

The only drawback with the Syder Wire is it is green! It can be very hard to see it in the grass but if you have a good colorful chute should not be a problem.

You will probably have to go too Bass Pro or Cabela's to find this weight.

Good luck!

Mark

Aientonni

Does anyone have any pictures or other examples of the hi-start turnaround mentioned by vintagesailplnr. I have a field close by that is about 1400 ft long by about 650 ft. wide. The wind, as you'd guess is rarely in the proper direction. This turnaround system sounds like a great way to get high launches in a limited space. Any advice would be great. (grin)

Propwash in Pa

If you do the math, the turn-a-round does not cut the launch dimension in half but does reduce it. For example, if I want to launch to 400' and have a 100' of rubber that is stretched to 400'., the total launch dimension is 700'. It is the same whether you put the turn-a-round at 200, 300, or 400' from the anchor point. As far as pictures, once mine is finished, I will post.

Aientonni

Thanks Propwash in Pa. I'm interested in the bicycle wheel axel that you purchased? Is it from the front rim or the rear? (with the sprocket removed I'd assume). And how did you plan to secure it to the ground?

slopemeno

My Feedback: (2)

A front hub from a BMX bike store will do it. You probably would want something with the tall flange where the spokes are inserted.

And while we're on the subject, you should be experimenting with moving your CG and towhook gradually back in small incriments. I found big differences in launch height with that technique. Youre there when the plane *just* starts to wander slightly in yaw on the high start.

glider_pilot

I have used the fishing line scootertrash340 was talkin about and yes i find it reduces the drag sooooo much. it also stretches a bit aswell and this will give even more pull on the line.

Gider pilot

Regina Tech

Propwash, are you using 1/4 or 3/8 inch tubing?

Stay away from the mason's line. I got maybe 10 launches before it frayed and broke. I bought the pink unbraided kind. I'm now using braided 75LB fishing line and although it has broke once, I must have used it 40+ times. I'm going to try some mono soon. Mind you I am launching from fields that have some brush and I haven't been too gentle unsnagging the line.

I would like to see some pictures of a turn-around too.

I have also heard of people using items to keep the tubing off the ground reducing drag at launch. If anyone has info about this please post.

Right now I have 75' of 3/8 tubing and about 250 feet of line. This setup will lift a lot of the tubing off the ground (maybe 50 feet) so I'm going to add some more line. Starting to run out of room to launch room so interested in the turn-around.

Also, I'm only stretching the tubing about double, but the pull is around 8 pounds and with this set-up my gentle lady (1.5 LBs) takes off really fast. Much faster and I fear the wing will fold.

marc 540

My Feedback: (6)

Hi all,
I'm very interested in this turn around hi-start system due to my limited space. 600 foot runway's surounded by corn or bean field's. I can walk into the field's to strech but only certain times of the year. Do I need to add line to make up for the turn around? what would be the best distance between the stake and the turn around? I have a 100' rubber with 350' line system.

Thanks' Marc 540[8D]

Propwash in Pa

The turn-a-round did not work well. For one thing, the rubber stays on the ground and looses much energy through drag / friction. It was also a big hassle to set up. For now, I am just talking a long walk useing normal high start process. I go about 3X rubber and try for a 12 lbs pull. Launches are pretty good, perhaps the problem is the pilot.