Rafters/slinging

[otooley]

I'm interested to hear some of your techniques to having a load of wooden rafters from a house..fly so they don't spin or start swaying to the point that I thought it was going to be tit's up in the wabigoon. At the time we were short lining.We had tied a fair sized spruce tree on one end but that didn't work...it still spun....I was glad to get on the ground and let the pilot do the rest of the loads himself...Over to you.......

[mtnhopper]

Try making one lanyard shorter than the other Might work a bit better. I know it worked for me when I had to place some 24/12 bridge stringgers

[ray]

We generally use a swivel hook to keep it from spinning, and a tree or something to keep it steady.

[otooley]

We generally use a swivel hook to keep it from spinning, and a tree or something to keep it steady.

 

we tried making the endless straps uneven ....still spun and swayed side to side..we tried it with the apex of the rafters up......tried it with it down...no luck...when ever he got it up to about 30mph all **** wold break loose.each trip was about 10 miles.These were also rafters premade 30 footers,and it was a 204 we were using to haul .It was a long day and colder than **** ...gusty too....maybe that had something to do with the way they flew?

[splitpin]

I have seen this problem lots. Any load that even resembles an airfoil will try to fly. It's a matter of aerodynamics. Remember Bournoulis Therum (sp?) Increase in velocity, decrease in pressure. The load is trying to fly, but it is stalling, flying, on and on. Don't hang a tree 'from the load', wrap the load in trees, branches, spare engineers, etc. Good example, most loads fly well when in a net, right?

Fly SAFE Guys!

[rotrhd1]

At the time we were short lining.

 

All of the above are great suggestions. Especially the net... althought it might be tough to find one so large as to put the rafters in the net, using the net(s) as lift spoilers in some way is awesome.

 

The other comfort factor for me would be to get the thing as far away from the aircraft as possible by using a long longlline. Things don't seem to be so unstable when they're 130 feet away.

 

Happy New Year to all....

 

RH1

[JaJR]

I would have to go with the destroy lift method. I pulled a Beaver out of the bush a few years ago and strapped a same length tree along the top span of each wing then choked it from one end. Worked great, no swing and could go as fast as I wanted. Plus lots of long line and I did the speed increase slowly watching all the time. I think the tree weighed as much as the wing too but it was worth the effort.

[dammyneckhurts]

This is what I found worked the best for loads like this....

 

First, you need at least 130 feet of line, gets the load well away from the downwash

 

Second, rig the load with the heavy side down so to speak...in this case the rafters would be flown upside down.

 

Third, for a 30 foot long load, use two lanyards one that gives at least 30 feet of length, the other about 33 feet in this case. Hook the shorter lanyard to one end, and hook the longer to a point almost 1/4 distance in from the other end, so say 5 feet in this case.

 

On the very end of the load that has the longer lanyard attach a LARGE bushy tree with about 5 feet of rope between the tree and the load.

 

Using lanyards of different lengths allows the center of mass to be behind the suspension point (the point where the 2 lanyards meet and join to your 130' line). This allows more wind resistance to hit behind the suspension point. The five feet of load you have hanging out behind the rear attachment point kind of acts like a fulcrum for the wind resistance the tree offers to give it better leverage.

 

The reason to have lanyards of unequal length is also so that the load flies through the air in a nose high attitude.

 

If it's nose low the air hits the top side of the load and makes it swim from side to side like crazy. Using lanyards of EQUAL length with result in a nose low attitude in flight because the wind resistance drags the load behind the machine resulting in a "tilt" to the long line if you will...and results in dropping the nose of the load.

 

The amount of drag the load will experience in flight determines how much longer one lanyard needs to be over the other to keep it nose high. The more the drag, the further behind the machine it is in flight, the longer the rear lanyard needs to be to keep it nose high.

 

Regarding the tree that you are using as a drone....make it BIG. What about all the extra weight of the tree though.....well there are 2 issues. One is safety...keeping the load under control, don't want to get into a position where you need to punch it off because its swinging so bad...the other is total time to complete the task.

 

If the load is flying like crap and we are having to putt along at 20-30 knots it takes a long time if your going more than just a few miles. You total time on the job can be a lot less if you can fly at 60-80 knots even if you have to make more trips because of all the extra weight you are hauling with the huge tree as a drone. In the summer trees like birch or poplar are best....more leaves and not too bad for weight. I am thinking that for 2500 pounds of rafters, you are going to want a tree (or 2 trees tied side by side) about 15-20 feet long. Its all about enough leaves to get the wind resistance.

 

Using variations of this concept you can fly things like plywood and long lengths of pipe horizontally easily at vne (for a sling load.)

 

This all assumes that the load you are hauling is heavy enough to "outweigh" the "flying" tendency that very light bulky loads have. Then of course it all goes out the window...

 

DMNH