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#397539
I've been coveting a powered harness for a good while now. Haven't pulled the trigger yet because it's a lot of money, and I don't feel like I've got a solid idea what to expect from it. Specifically, what kind of conditions I should expect to be able to fly in and what will be beyond it's limitations.

Elevation where I live is about 2000'. Density altitude varies widely from near sea-level up into the 4000'+. I would expect to be able to launch and fly easily on the cold, denser days, but may not WANT to fly when it's freezing cold outside. I've also read that launching from 4k or 5k elevations is a dubious proposition at best, so I'd expect not to fly from my elevation on exceptionally hot and humid days.

What have your experiences been launching and flying relative to density altitude? At what point to you decide it's not flyable? And, what kind of glider and hook-in weight were you at?
User avatar
By DMarley
#397540
Hey Robert.
Have you been able to talk to Richard Cobb directly? I would hope that he could be the most help, but perhaps not if you still have questions.
I too have been contemplating a power harness. However, I question the Radne Racket's ability to get my 220 lbs hook-in weight up to a decent altitude on stable, warm days. Though, the only commercial alternative (if available around here) that has more oomph is the Wasp with the Vittorazi Fly 100 EVO mill. But then it does weigh a bit more than a Mozzi.

You've possibly read this already, but this thread has some interesting views...http://www.hanggliding.org/viewtopic.php?t=18074

Also, I'd give Steve Wendt a call (BlueSky) and perhaps a visit. I'm seriously considering visiting his place to try some scooter and truck towing.

Probably not much help. I hope other more experienced FLPGH pilots will post.[/quote]
User avatar
By RobertKesselring
#397545
Yes, I've talked to Richard and Steve, and they've both been a wealth of information. It's based on their input that I realized that some days may not be flyable for me due to density altitude. I'm trying to get a better sense of whether the unflyable days are going to be rare, when it is exceptionally hot and humid, or of the flyable days are going to be rare, when it's unusually cold and dry. Most likely, reality is going to be somewhere in between. I'm hoping to hear a variety of experiences from different places, flying the radne with different loads and different gliders, and from that broader library of experience, deduce what my experience is likely to be.
By Crunluath
#397565
You can fly powered any day that you can fly unpowered. You can also fly days when you wouldn't be able to stay up without a powered harness, ie light days or times with zero wind. Flying powered obviously does not expand your flying window into days where it would be dangerous to fly.

If your launching altitude is below 2000 feet, I don't think you should worry too much about density altitude. I have launched from near 2000ft on even very humid days. I just had to run farther before take off. Your climb rate may suffer a bit on humid days, but you will still climb.
User avatar
By Wagner24314
#397566
I fly power a lot and I'm at 1400' and max heat is 90F for me.

glider is a S2 155 and i clip in at 270lbs 5 mph head wind is a must.

Pm me and ill give you my phone #
User avatar
By DMarley
#397576
Wagner24314 wrote: i clip in at 270lbs
What is your harness brand and harness weight with your typical fuel load?
Thanks
User avatar
By combat.is.hell
#397591
I take off from sea level and weight 70 kg in t-shirt. The take off is easy in calm conditions and scary in rowdy days with thermals and sinking air. Despite my low weight and dense air conditions, I have experienced sinking air that made me fly parallel or even sink towards the ground. After a few dramatic take offs like that, I decided to stop flying in strong conditions altogether. If you can live with mosquito flying during calm thermal-free days, then you will take off safely, even if you weigh more and have to deal with high-altitude thin air.
User avatar
By Wagner24314
#397601
DMarley wrote:
Wagner24314 wrote: i clip in at 270lbs
What is your harness brand and harness weight with your typical fuel load?
Thanks
i fly a NRG hand grind my own props 54X23, cerkoted the piston face, combustion chamber and exhaust port. tuned pipe, WB-27-1 carb which has a tune able high needle. i get 8500 to 8600 RPM on the hot engine now where before the cerkote i only got 7600 to 7800 on the hot motor.



https://www.facebook.com/groups/FLPHG/?ref=bookmarks :mosh:
User avatar
By DMarley
#397609
Nice rpm results on the cerakote tests. Have you measured the exhaust temp differences?
Are these rpm results using your fab'ed wood 54x23 prop, or the original bolle 52x21 folder? I've heard that the folders can be somewhat of an engine hog to spin up to a decent rpm and thrust.
Have you measured the static thrust differences between your prop and the bolle?
It'd be interesting to measure the thrust differences at best climb speed. Say, mount the harness rig to the top of a pickup truck or van and get the vehicle up to the best climb speed on a flat stretch of lonely road with the harness pushing against a scale. Could turn out to be somewhat an involved procedure, but perhaps quite educational. Especially to one who crafts props. Though, if the new prop alone gives a measurable climb increase you could say it's good!
You should write up an article of your experiments and findings of the mozzy.
User avatar
By combat.is.hell
#397633
Wagner24314 wrote:i fly a NRG hand grind my own props 54X23, cerkoted the piston face, combustion chamber and exhaust port. tuned pipe, WB-27-1 carb which has a tune able high needle. i get 8500 to 8600 RPM on the hot engine now where before the cerkote i only got 7600 to 7800 on the hot motor.
That's quite a serious number-dropping post there :wink:

I am the guy who doesn't know much about engines and hates spending time in the garage. I bought my mosquito new back in 2012 and have flown it year-round ever since. I get an estimated 8900-9100 rpm with a wooden Born propeller and have never done anything to the motor. I have cleaned the spark plug twice and tightened the propeller brake once. That's pretty sweet for an estimated 100 hours in the air.

If you invest in a mosquito, make sure you get every bit of thrust out of the engine: I use Aspen fuel with a high-quality oil that is recommended by Rotax and a well balanced fixed propeller.
The foldable propellers are in my oponion totally useless. They tend to be out of balance and always deliver less thrust. They are supposed to offer less drag when folded during thermaling with mosquito. But unless you are gliding 10 miles between thermals you will not see any benefits from a foldable prop. Even if you were to glide 10 miles between thermals, you would still only gain a few meters. And they cost 3 times as much......

If you get the maximum thrust out of your motor, then you can start off by flying during "safe" days with good air density and a bit of headwind to help you during take off. Little by little you will experiment and see for yourself what conditions feel safe for you and which conditions make the take off feel risky. A modern wing in good condition helps, especially if your clip-in weight with mosquito is below the manufacturers max.
A good idea is to have a little engine tacho so that you can get a reading of the engine's revs when you are on the ground. I had such a device when I started flying FLPHG back in 2008 and it helped me develop a feel for engine thrust so that in the end I was able to realise if the engine was running OK or not without any instruments at all. The tacho is attach it to the spark plug wire with a crocodile clip and gives you a pretty precice reading of the revs. If the engine is running fine, you unclip it and you are good to go.
#397643
combat.is.hell wrote:A good idea is to have a little engine tacho so that you can get a reading of the engine's revs when you are on the ground. I had such a device when I started flying FLPHG back in 2008 and it helped me develop a feel for engine thrust so that in the end I was able to realise if the engine was running OK or not without any instruments at all.
Campers,

You can get an RPM app for most cell phones that will use the microphone to read the propeller RPM. Then tell the RPM app if you have a two or three bladed prop. Factor in the gear reduction ratio that you may have, if any, to get the correct engine RPM. You can make up a small "cheat sheet" to convert the propeller reading (and your reduction ratio) into engine RPM, if that would be more convenient in the field. Some RPM apps may read the exhaust pulses instead; in that case, the RPM app needs to know if you have a two-stroke or four-stroke engine.

:mrgreen:
User avatar
By DMarley
#397646
hey combat,
What are your prop dimensions? It could be that Wag's engine is a bit over-propped, or the older A-10 model?
User avatar
By Wagner24314
#397654
the born prop is a 54x21 last time i checked
User avatar
By Wagner24314
#397655
DMarley wrote:Nice rpm results on the cerakote tests. Have you measured the exhaust temp differences?
Are these rpm results using your fab'ed wood 54x23 prop, or the original bolle 52x21 folder? I've heard that the folders can be somewhat of an engine hog to spin up to a decent rpm and thrust.
Have you measured the static thrust differences between your prop and the bolle?

Well i havent check exhaust temp yet but I dont feel I need to.

Yes i only use my props anymore so a born or a bolly will get more RPM. my prop is on a third version but the V2 is proving to be the best.

at my weight 270# clip in on a S2 155 the bolly folding prop 150-200 fpm best climb. My props V1 prop 200 to 250fpm V2 prop 300 to 350 and V3 prop 250 to 300. the bolly spins just fine but there QC on setting the Pitch is not great i had 3 of them and all were diffrent one had just great performance and the others were ok. the one that was great hit 8800Rpm engine this one climbed well i remember 300Fpm. the others were at 9100 and 9500 rpm. the helix prop folder is a 52X19 and is the one that guys call useless well it is made for PPG.

Just checked them in climb to confirm thrust change. porp pitch isnt a one size fits all. slower wing can use less pitch and fly great more thrust at slower speed. but a faster wing needs a little more speed and more pitch

at 2400 rpm the Zero thrust point of a 19 pitch is 50mph

at 2400 rpm the Zero thrust point of a 23 pitch is 63mph

so with the higher pitch you have more usable thrust at a higher speed.
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#403647
My friend got one of the 1st Mosquitoes in the US and was a distributor/dealer for several years (he may still be). He learned a lot the hard way and broke a couple/few props in the beginning but has had many incident-free flights since. The carbon props were really expensive, so he sent the pieces of a broken one to Tennessee Propellers, who made him very nice replacements out of wood for a lot less $$. He's mastered the art of using his Mosquito to the point that he's back confidently to using a carbon prop. He loves to talk Mosquito--PM me if you want his #.

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