PRE-FLIGHT AND LAUNCH TECHNIQUE
Location: San Diego USA
Online Status: Offline
Topic: PRE-FLIGHT AND LAUNCH TECHNIQUE
Posted: 14/Feb/2011 at 1:57pm
With the new release of the HK Bela Trike its time to post a quick how-to for foil readiness and pre-flight. The following will try to sum up many many pages of wonderful suggestions from forum members around the globe. The thread will be locked to keep it an easy one stop shop for newbies but if you feel something is missing or there is a question/answer missing please pm me and I will make adjustments as needed. Your feedback helps me improve this thread and will help others as well, so please don't hesitate to drop me a PM and let me know what you think.
First things first.
A list of terms you will hear allot in the next page.
AOA = Angle Of Attack
Brake lines = The two control lines loose from the rest, that attach to the trailing edge of the foil. Pulling these collapses the trailing edge of the foil and stalls or "brakes" the foil causing a turn in the direction of the line pulled. When both are pulled together the foil "flairs" and will either drop/descend or catch more lift depending on conditions and set up.
Bridles = These are the fabric carriers that all the foil's lines attach to. These will be what attach the foil to the pilot or "gondola". It is what we adjust the "AOA" with later.
Gondola= The universal name we here at the forum began calling the control pod or "trike" hung beneath the foil that acts as a ballast and holds the servos, batteries and accessories that make the complete unit a "para-motor".
The following will need to be performed to all hk 2.2m foils for proper flight BEFORE any flight is attempted. It is not optional. This step Needs to be done or your foil will not fly and you will cry. This video will guide you to the nominal adjustment of the AOA to get you flying. Minor adjustments can then be made to suit your personal flying taste.
It has come to my attention that a few HK foils have been received with the Proper AOA already set. If your foil already reacts as this thread describes it should AFTER the mod, than the mod is not required and you can skip this step.
The first set of lines you will see being adjusted in the video are the "D" lines (the ones attached to the Rear or trailing edge of the foil)...they are not changed.
Then the C lines are pulled to the bottom of the D lines ring.
Then the B lines are pulled to the bottom of the C lines ring.
Then the A lines are pulled to the bottom of the B lines ring, or a little bit more depending on preference. I like the A to be about twice distance of the rest. This will make the leading edge lines the shortest.
The "brake" or control lines are not adjusted here.
Ok, now to discuss proper test technique to make sure you did it right.
PRE-TESTING AND FOIL PREPARATION
The best way to test if your foil is ready for flight is to ground test it.
With your back to the wind if any (no wind is best), and the foil laid out in front of you on the ground... trailing edge at your toes. Grasp the bridle carriers between your fore fingers and thumbs. Wrap the Brake lines around your pinky fingers so they are contained and wont get tangled with the rest of the lines. You do NOT want to put any tension on these for this step.
Take a fast step backwards while pulling back on the lines in your hands. The foil should JUMP or POP up in the air and fly up to the sky in a straight and abrupt manner.If the foil twists to either side loosen that brake line on your corresponding pinky finger. Check all your lines and knots. Make sure they are straight and uniform side to side and fore to aft. If any knots are loose or have slipped they will need to be adjusted and re-glued with CA. If the foil "drags" and does not want to lift you will need to re-check the AOA and make sure the adjustments have not slipped. If they are correct and it still wants to drag then you will need to slacken the brake lines. You may also have to pull the A lines down a bit farther than the rest to achieve desired pop.
The idea here is to get the foil to "pop" up fast and straight. We are not trying to "Kite" or hover the foil, (you can get good at that later).
Once you have it where we want it we can attach the gondola and set the brakes.
SETTING THE BRAKE LINES
I'm going to assume for now that you have the gondola and know just how to attach the lines. In a few weeks I will address this in another post.
The procedure here is exactly as the above but we will now use the gondola's servos to hold the brake lines.
Do not tie the brake lines to the servos yet, but rather loop them through the holes a few times till they can be pulled and not slacken.
The adjustment here is the same as before but this time we are going to slowly start to tighten the brake lines till the foil stalls and will NOT pop up. This is boring and time consuming but hang in there, we are almost done!
Now, slacken the brake equally just a bit at a time till the foil just begins to pop up again and flies up straight and does not twist...just like before.
Tie them up! You are done! You can use the servo arms to make fine adjustments and loosen/tighten the lines as desired for control sensitivity.
*still getting a ton of requests for motor recommendations.
here are my top three picks. Of course many will fly the trike, but I have tried these personally and can say they for sure work.
Here at HK you can use this motor:
this is still the very best motor imo. Its the one I use-
Though the trike will fly with the recommended set up, the preferred performance package will consist of any motor capable of spinning a 12x6" standard prop and producing 800-1000Watts of power.
I have found that motors spinning 800 to 1000 rpm/volt and producing 800-1000W will fly amazing and with the added power of a 4s will tear holes in the sky.
I am hearing more and more people having great results with motors in the 450-500W range. This should provide plenty of power for little to no wind conditions and slow easy flights and limited weight shift aerobatics.
Of course there are many prop/motor/batt combos that will make this trike scream and I urge you all to experiment. I am but one man with limited resources for testing. I used what I had and wrote what I found to work the best. If you go with the above combo you will not be disappointed.
Don't mess around here. The foil is under extreme force when launching and the trailing edge of the foil is literally tied to the end of really long servo arms!!!
I say this and no more. GET HIGH TORQUE SERVOS WITH METAL GEARS.
I use these and love them. These are amp hungry and will need a large BEC or separate RX battery to run them. They are low profile so you can mount the servos from inside the trike (like I had originally intended them to be) and the bottoms wont hit each other.
Of course they will be out of stock so any servo with comparable torque and metal gear will be just fine.
these are good too!
Weight and balance
The trike will fly the HK 2.2m foil at an all up weight (AUW) of between 1.2-1.8kg.
Less than this and the trike will be at the mercy of the foil and will get bullied by the wind. More than this and the speed of the trike will over power the lift of the foil.
The difference between a proper weighted trike and one that is under/over weight is the difference between a trike that will fly beautifully with no drama, and a trike that you will constantly be fighting with and crying over.
Finding a good balance is essential and without it there will be many tears.
Your Belatrike will usually only come close to the proper flying weight even with the largest battery installed in the belly. You will NEED to add ballast for it to fly proper if it is under weight. Every trike will need a different amount of lead to ballast as each build will be unique.
Every flying style is also unique and some may prefer a lighter "floatier" trike while others may prefer a fast heavy "point-and-Go" ship. for this reason I did NOT recommend a specific weight, just a range with minimum and maximum suggestions.
If you find yourself struggling to keep your trike below the foil then it is most definately not heave enough. Though it sounds counter intuitive, ADD MORE WEIGHT.
LEAD (Pb) (Plumbum)
Lead makes the best ballast as its density allows the most weight in the least space.
Lead is POISONOUS! Do not touch it with your skin!
Lead can Explode when heated. Do not heat it!
You can DIE from lead. Stay away from lead!
That said, grab a hand-full of lead and melt it in a crucible with a torch
If you are not comfortable and absolutely certain how to do this please look it up on Google.
1)What I did was to drill a few flat bottom holes with a Forstner or Spade bit into some soft wood like pine. Make your hole only about 1/2" deep.
2)Press some modeling clay into the hole and smear it around with your index finger till all the rough edges and cracks,seams and drill point holes are smooth and covered with a thin layer of clay.
3)Remove all the excess clay. We are just using it to smooth the walls and bottom of the hole.
4)Allow it to dry overnight till there is no moisture left in the clay.
5)When clay "skin" is mostly dry, melt your lead as shown in the process you looked up on Google.
6) carefully and while WEARING GOGGLES pour your lead into the forms you have prepared. Fill to the lip of the hole but not over. Let cool for AT LEAST Ten Minutes.
7) When the lead is dry turn the wood over and smack it against the ground a few times till your lead rounds fall from the form.
Test temperature...(lead holds heat for a LONG time and will burn you).
8) Drill 1/4" holes through the center of lead "coins".
9)I mounted mine to my trike by drilling 1/4" holes in my rear land gear between the tires and frame. Also on the main "tray" in front of the Pod. You can stack the discs to save space and for a clean look and use 1/4" bolts and nuts to hold them secure.(this is also very scale as most full size will use weight plates the same way)
Mine used six of these discs and yours may need less or more depending on the gear used in your build and the final weight you desire.
I have made an important edit (see bold above).
In my fumbling I reversed the order of the description of bridle adjustment in the video.The video is correct but the description reversed the order of the bridles being adjusted. I apologize for the confusion and any pain this has caused. I will be more careful in the future.
Edited by Beladog - 30/Jun/2011 at 1:29pm
Thats the ugliest hat Ive ever seen...looks good on you though.
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