When is OpenPPG supposed to have new arms ready. I’d sure like to see if they will solve the problem before laying out $450 for Iris Arms, plus cost of spacers, fig 8 and whatever else is required. After my flight tonight I will be moving my hang point farther forward on stock arms. Static hang check looked good,but powered I was leaning forward almost.
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That makes sense and I think you are correct. I don’t think a bungee is a good way to move the fulcrum though. It is possible that the bungee could tweak things in such a way that the arms go up higher and the seat board tilts so that your knees are also higher. In other words, the arms can go up slightly if your knees also go up and the lifting force of the bungee could make it do that.
The SP140 tilts forward when throttle is applied. If the arms were higher the opposite would be true and thrust would add to the already bad motor angle instead of subtracting from it. Let’s not find out the hard way if this is true. Instead you should simply adjust the fulcrum to the right place. At your weight you shouldn’t need new arms. I haven’t seen pictures of your hang angle with the collars at the top of the straight section. The picture showing 24 degrees has the collars in the middle of the curved part of the arm.
Earlier in this thread I mentioned a backboard I made for comfort which also subtracts between 1 and 2 degrees from the motor angle. The harness has pretty thick padding but that is all that’s between your back and the lower bar of the frame. So I added a thin, light, plywood backboard. It flexes slightly to match the contour of my back and provides a nice surface for the harness pad to press against.
The hang angle could be improved even more by adding some type of spacer between the lower bar and the board. Perhaps something like the foam that is placed around pipes for insulation.
Here are some pictures before painting the board black:
And this shows how I attached the top with zip ties (after painting the board black):
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I don’t mean to bash the idea of buying new swing arms, or any other ideas presented in this thread. This is a great conversation and becoming one of the most detailed with fresh ideas.
The Iris arms are not a labor intensive mod at all, but they are expensive and they do take time to be purchased and shipped. As far as a modification that can be done with what you get with the SP140, the battery relocation is perhaps the easiest single mod to fix the issue. 6 18" diameter hose clamps, some inner tube rubber, and 8 gauge battery wire is all that is needed. At least this option is what I found while struggling through this issue the same way Grigsby is doing now.
Grigsby, to answer your question, handling on the ground feels cumbersome. The weight down low pulls back on your shoulder straps pretty hard and leans you backwards when standing or walking around. Think of an overloaded backpack with loose straps. Yet, I have been launching it and flying it that way for 30+ hours and I weigh 155lb, so it’s not like it’s so uncomfortable to make it impossible to launch. In fact an added tradeoff benefit is that the paramotor wants to lean you backwards, and as a result its easy to get really good lean back posture on your take off run, which in turn makes for an easier launch and shorter run. Landing you should prepared for the motor to lean you back as soon as you touch down and the wing stops lifting. I have turtled once but that wasn’t entirely the paramotor balances fault. It was a crap landing.
GP, you’re totally right about fulcrum point relationship to the mass of both the pilot and the battery. My comment was towards the fact that moving the fulcrum point is not possible with the current setup, and barely adequate with the last hole on the iris arms. Most will notice that even if they manage to move the hang point back far enough, they now won’t have enough room for their arms to be comfortable between the frame and the swingarm/risers. Perhaps the IRIS arms are more comfortable given their different shape. But without moving the fulcrum point much or at all, the issue can be solved by moving the respective masses around on the unit, like Gliderpilot explained. Yeah I chose to move the battery, which has downsides like the cumbersome handling on the ground, and that the battery is no longer easily removable from the paramotor for charging.
I’m now super interested in the foam. Adding the right amount of foam behind the harness to move the pilot forward sounds very promising. In a pervious post in July I actually mentioned I was going to try the foam behind the harness because I wanted to try and foot launch with two batteries, one relocated down and the other in the stock location, for a potential 1.5hr flight time. But I ran into the same issue here, hang point with both batteries was so ridiculous I never even tried launching it that way.
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You must be a pretty tough guy for your weight of 155 lbs if you want to attempt flying with 2 batteries!
Adding too much foam could give you the same landing problem. Like you said: add the right amount.
What size harness are you all using? I noticed with the large harness the foam from the harness can get stuck above the lower bar instead of in front of it. This issue would be more likely with the smaller harness so I wonder if that’s part of the problem.
The backboard idea insures that the harness foam stays in front of the lower bar and could improve the hang angle significantly if that scenario is prevented.
I am using the large harness even though I am a smaller size person. I did this because of availability of the harness at the time I ordered.
I have had the harness “slip” behind the lower bar instead of in front of it several times, but I have noticed that even if I launch that way, as soon as my weight is in the seat the harness will ride back to the correct position.
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Im wondering if I will need longer shackes if I add considerable foam between the harness and frame, say 1" of foam. This would push the harness out and raise the seat angle up? I think I could counter what you mentioned about too much foam causing an unbalanced unit upon landing by allowing the seat to drop lower and letting me get my footing down and get me lower in the leg straps by letting the seat drop lower by the same amount of foam added. I have head of longer shackles used as a contributing factor to getting a suitable hang angle for lighter pilots. Maybe 1/2" foam plus 1/2" longer shackes? or 1" foam + 1" longer shackles.
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Hi guys. With the collar placement @GliderPilot encouraged the hang angle is now 16 degrees. This is with the props installed and the reserve hung from the side (container still not here! errr!). I looked back through my pictures and found that I had tried this position previously, but the soft links were swung to the side. In my haste to find “a better way” I didn’t give this setup due consideration. Thanks GP!
I love the backboard idea and am gonna try it! What is the ideal hang angle I should be shooting for?
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I think 14 degrees is an acceptable angle for a static test with THIS motor. When my hang check measured 14 degrees I did several level flight passes at less then 10 ft high while my girlfriend took video. I took screenshots of the videos every time there was a perfect side view then measured my prop angle. I did this with 4 different pictures to show repeatability just in case the camera wasn’t held level. Each measurement was between 8 and 10 degrees which is just right.
I recommend 12 - 14 degrees with a static hang test then see how it feels in the air. With less then 14 degrees it may feel like it’s pushing you forward too much under power. If that’s the case back it off a little but it’s better to be reclined too little than too much.
I just did a quick hang check with some 1 inch spacers between my backboard and the lower bar. This changed my hang angle 2 degrees taking it from 14 down to 12 degrees. Remember, the board by itself subtracted 1 to 2 degrees as well so I think you will have good luck with using a backboard and it also adds comfort.
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I just went out and bought a 13" x 21" piece of black, textured ABS from TAP Plastics. I’m about to install it and see what effect it has on the hang angle.
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I tried one of the long pieces of the white closed cell foam that my battery was packed in. It’s 7/8” thick. This reduced the angle to 15 degrees. It was a bit too short but it had the right combination of being lightweight, firm enough to provide the desired offset spacing yet pliable to be comfortable. I plan to get a 1” piece with the right dimensions to attach to the frame, and then find another piece of something to add to the back of the harness, inside the zippered area where the factory padding is. There’s a bit of space. I think with those too additions I’ll be well hung (sorry guys, I couldn’t resist!).
Has anyone tried turning the collars 90 degrees to try and use the area with the larger profile (where the screw goes through) as a mechanical stop to keep the soft links from rolling to the outside?
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How thick is the ABS you bought?
How rigid is it?
How much does it weigh?
My plywood is 10 X 20 X 0.2" and weighs 10 oz
I chose not to place mine inside the zipper for a couple of reasons. The main reason is I didn’t want the fabric of my nice harness sandwiched between the wood inside and the bar on the outside. Specially since the harness would slide up and down on the cross bar as you transition from ground handling to flight.
The other reason is the bottom of the foam pad sometimes catches on the cross bar and with a piece of wood inside it would certainly get stuck. It shouldn’t be a problem if you keep the top buckles tight where the harness attaches to the frame but those tend to loosen with use. You would want to make sure wood is a perfect fit for the zipper pocket for that same reason.
Also, if you attach the wood like I did then you can use a simple solid spacer or collar on the bar to push the wood out to fine tune your hang angle. This picture shows what I used for the hang check. They wouldn’t stay in place during flight but it’s an example of the basic idea:
Thanks @GliderPilot. Yeah, I wasn’t planning to put any wood in the zippered area, just foam. I’m going to replicate what you did with the wood. Right now the foam I’m using is taking a degree off but I’m guessing the board will be more effective because it totally bridges the gap in the frame where most of the harness can push into. The foam doesn’t bridge that gap. I’m also going to try using webbing instead of the board to create the bridge and then use the dense foam for the offset.
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Adding the backboard to mine improved the hang angle. I used a piece of ABS cut to size: 13" x 21". I think it’s 1/8" or 5/32" thick, so it’s stiff but flexible. I attached the top to the upper motor mount crossbar with a couple of zip ties.
My hang angle now is about 10.5 - 13 degrees. (Previously I was at about 16-17 degrees.) I’m surprised at the dramatic difference – I have a feeling there’s some other variable that changed, too, but I’m not sure what it was. In any case, I do think it improved my hang angle by a couple of degrees at least.
I think I’m done making changes for now. I’m a beginner, so I don’t have enough additional knowledge to make further adjustments. I’m still not happy with how far back the collars and soft links have to sit, or that the soft links aren’t capturing the collars, so I’m looking forward to installing the Iris swingarms whenever they arrive. But for now, I think I’ve done everything I can with the hang angle.
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Thanks @GliderPilot and @grigsby for all the updates and detailed info. It’s nice to have a few options for tweaking the HA. I’m getting excited for my maiden solo launch! So, here’s a safety-related question:
Given this will be my first real solo flight, is it likely that I’ll get high enough that the reserve will be effective, in the event I need to throw it? The reason I ask is that I have yet to receive my reserve container. I plan to ask my instructor about this and see if he has a loaner container that will work with my harness. I’m tired of waiting but also want to be safe and smart about it all.
In my opinion if you fly in good weather and don’t plan to do acro then a reserve is not needed.
That’s like saying drive safe and a seatbelt is not needed, you never know, always a good idea to be prepared for the worst.
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There used to be a “rule” that tossing your reserve below 500 feet wasn’t going to do you any good since it wouldn’t have time to deploy completely.
But more recently, pilots seem to be rejecting that attitude and are coming to believe that tossing your reserve at any altitude is worth a try, since they can actually deploy pretty fast – within 50 feet even – and even at a low altitude it could slow your descent enough to make the landing a bit less, um, bad.