Balance issues between 1/2 vw and pollini 303

[Glennlawson]

Does anyone have a idea on the weight and balance between the two, would you have to add weight aft to keep the cg in balance?

[Badland-F5 Pilot]

Does anyone have a idea on the weight and balance between the two, would you have to add weight aft to keep the cg in balance?

I don't know of any Badland with a 1/2 VW.

So, knowing that 1/2 VW's come in at 81 to 103Lbs (I'm sure this is basic bare engine to one fully ready to go with alternator, exhaust manifold, fuel pump... etc.)

The Polini Thor 303 comes in at a hare over 45Lbs.

So, undoubtedly the 1/2 VW would need to be placed as close to the firewall as possible, and I would think weight would need to be placed in the tail somewhere. There may be some give back if you use a wooden prop with the 1/2 VW since most UL's with the Polini use a carbon fiber prop. However, something to think about, if you must add any weight to the plane to shift the CG, you may push it out of the Part 103 weight maximum limit (under 254Lbs with no BRS and under 279Lbs (that may not be exactly right, but it's close) with a BRS)). The FAA grants 25Lbs for the BRS as a safety device. The lightest BRS we've found is 11Lbs. So The FAA doesn't care what your BRS weighs, so if you have the 11Lbs BRS, you gain and additional 14Lbs + the 11 Lbs BRS to add to your planes maximum weight to remain in Part 103.

For example, on my F5 because of the Titanium frame it (In theory) should come in 28Lbs lighter than an F2 (239Lbs - 28 = 211) if set up with the same engine, wheels....etc. Add the BRS of 11Lbs and we have a plane weight at 222Lbs. But, because of the BRS, I get an additional 14Kbs to maximum plane weight of 279Lbs. Max allowed 279 - approx weight 222 = leaves 57Lbs for me to add items (bigger engine, additional instruments, whatever) to the plane without having to make those items removable and carried as cargo. Cargo, referring to the Badland maximum gross is 550 Lbs.

Does this make sense or have I just muddied the water?

The regulations for Part 103 are very simple and few, but they are different than GA, but do have some similarities with LSA since LSA actually came about because of UL's.

Todd

[Mountain Cat]

My Polini 303 came in at 68 lbs flying weight. 45 lbs is the basic engine, add mount, fluids, and everything to be flyable and you are above 60 lbs. Still lighter than a 1/2 VW by a good bit and same HP. It was a little too light for my airframe, so Chris is making a new mount to move it forward 6" to bring the CG into range. Granted the SkyRaider is a little heavier than the Badland due to separate flaps, rigging and cables etc. I would have to think pretty hard before I gave up the Polini 303 for a 1/2 VW.

[Badland-F5 Pilot]

My Polini 303 came in at 68 lbs flying weight. 45 lbs is the basic engine, add mount, fluids, and everything to be flyable and you are above 60 lbs. Still lighter than a 1/2 VW by a good bit and same HP. It was a little too light for my airframe, so Chris is making a new mount to move it forward 6" to bring the CG into range. Granted the SkyRaider is a little heavier than the Badland due to separate flaps, rigging and cables etc. I would have to think pretty hard before I gave up the Polini 303 for a 1/2 VW.

Thanks for the update on the 303 weight. These are always so much fun to try to figure out. Sometimes they include the full engine ready to run and other times they don't. You did pull the starter and battery, didn't you? I think you had mentioned that or maybe that was Lane, hum, yep, could be Lane did that on his Badland. I'm thinking if I go with the Hirth F23 that I may have an issue with the CG. Since the F23 is 78Lbs (complete) and the titanium frame is going to affect CG, looking at Peer's F2 and his CG being slightly rear further than he'd like....it's going to get interesting with the F5. Of course, it could also balance out pretty good. Peer and I have discussed moving his engine slightly more forward as an option to get his CG more centered.

The good about this all is that the UL regulations really leave all this open for us to work on ourselves to resolve issues.

[Mountain Cat]

I think with the lightweight frame you won't have any issues with the 303. The F-23 is a great engine but with a higher fuel burn so with the 5 gal limit of Pt 103, you will be limited to approx 1-1 1/2 hrs. Of course, depending on what you want in flying time. The SkyRaider is almost the same basic airframe but several lbs heavier.

[Badland-F5 Pilot]

I think with the lightweight frame you won't have any issues with the 303. The F-23 is a great engine but with a higher fuel burn so with the 5 gal limit of Pt 103, you will be limited to approx 1-1 1/2 hrs. Of course, depending on what you want in flying time. The SkyRaider is almost the same basic airframe but several lbs heavier.

The fuel burn is one of my concerns about the F23. I am looking at the Smart Carb 2 as an alternative to the stock carbs that come with the F23. Smartcarb claims 25~30% increase in fuel economy and 8~10% more power. I've watched so many YT video's from those that installed the carb that I think I've gone blind in one eye However, not one, and I really mean not one has claimed that the estimates given by Smartcarb are inflated. It appears Smartcarb is not showing the typical over inflated numbers we see so often in the performance market. I also love the boxer style engine of the F23. However, looking at the three engine options I am considering, Scott's 4 stroke is looking really good.

F23 - 50hp, weight isn't bad at all for the power output and its 1000hr TBO is outstanding. Doesn't sound like a chain saw nearly as much as a regular two stroke. Drawback - it does drink fuel.

Scott Skalski's Thump-Air 4 stroke - 40hp, weight is amazing for a 4 stroke, TBO could be better but still in testing so maybe that'll change. Much lower fuel burn per hour. Drawback, still in testing and price is TBD.

Polini 303 - 38hp, lightest of the three, TBO is 400 hours (a little short of what I would like to see or expect from Polini). Polini does have a proven track record and once they fixed the 303 for US fuel, I've read nothing but good things about the engine. Drawback - it sounds like a chain saw, the typical 2 stroke.

There are more data points for benefits and drawbacks for all three. So far I'm still leaning towards the F23, but Scott's engine is close behind. My only issue with his engine is going to be since it's so new, the initial cost is going to be up there a ways.

[LA F2 Flyer]

"My Polini 303 came in at 68 lbs flying weight. 45 lbs is the basic engine, add mount, fluids, and everything to be flyable and you are above 60 lbs. "

I don't believe the UL weight needs to include engine fluids, or am I mistaken? (Just for my own edification.)

I am eager to see what Scott come up with in terms of number for the Thump-air, including price. I don't LOVE the sounds of a thumper, but I'd say it's a step up from the sound of a two stroke...

Todd, for your mission I imagine the fuel burn is at the top of the list (or close to it) of wants/needs from your power unit. On the bright side, you've got some time before having to make a decision. Who knows what else might become available in the next year or so?

[Mountain Cat]

Seems like you have done your homework on available engines. So you are informed as anyone. I tend to shy away from any new engine till I see one with a hundred hours or so on it. But, considering Scott's ability, that shouldn't take long to accomplish.

[Badland-F5 Pilot]

"My Polini 303 came in at 68 lbs flying weight. 45 lbs is the basic engine, add mount, fluids, and everything to be flyable and you are above 60 lbs. "

I don't believe the UL weight needs to include engine fluids, or am I mistaken? (Just for my own edification.)

I am eager to see what Scott come up with in terms of number for the Thump-air, including price. I don't LOVE the sounds of a thumper, but I'd say it's a step up from the sound of a two stroke...

Todd, for your mission I imagine the fuel burn is at the top of the list (or close to it) of wants/needs from your power unit. On the bright side, you've got some time before having to make a decision. Who knows what else might become available in the next year or so?

Yep, fluids don't count for weight. I don't like the sound much of the Thump engine either, but unlike 2 stroke, changing the exhaust system (for a different sound) doesn't affect engine performance nearly as much. You're absolutely correct, the Thump would provide the fuel burn that would be most advantageous for me. Plus with a SC2 the Thump could possibly produce 44hp, and get 30% better fuel burn. All around win win. Did anyone catch if the Thump is pull start? Being a 4 stroke I'd bet a pull start would be a very reliable way to start.

[LA F2 Flyer]

Pull start or hand prop would be nice options for sure. Its one thing I don't like about the Polini. I want to be able to hand prop if in a pinch (battery low or starter rope breaks) and the centrifugal clutch won't allow it.

On the other hand, with the Polini I am less likely to Cuisinart the neighbor's dog.

[Badland-F5 Pilot]

On the other hand, with the Polini I am less likely to Cuisinart the neighbor's dog.

I'm not saying I would ever do this to a dog, but some neighbors that don't keep their dogs quiet, well it would be fun to toss a stuffed toy dog through the prop while they are watching

[LA F2 Flyer]

Haha, that's a very "mafioso" way to roll!