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Engine basics => Engine set up tips => Topic started by: Balsa Butcher on February 20, 2017, 08:02:25 PM
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Anyone running an LA-25 or FP-25 in SSR? Care to share your set up? Specifically wondering about venturi size and prop. I'm running an FP-25, older model w/.281 venturi, no muffler, APC 8x6, and stock NV but it's not competitive. I know the the BB LA-25 setup for stunt but racing is a different game. On the board is another plane planned for a Brodak 25 but in the meantime gotta run whut I brung.Thanks, 8)
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u didn't say what engines u are running against
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Pete, before you launch off in a different direction, first try to make what you have work better.
A .281" venturi is WAY too small! I suspect you will see quite an improvement by opening it up, perhaps as large as .315", always accepting the trade-off of needle sensitivity and take-off reliability.
Regards,
Bill Lee
PS: All comments above predicated on using a "standard" (.153") through needle assembly.
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Go to flyinglines.org and click on the Speed button at the top. There is a LOT of info on LA 25's for Northwest proto speed.
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Thanks all, will do. Flying against the usual SCAR suspects which is kind of like an Intermediate stunt flier flying against guys named Paul, Howard, Ted, Dave or Brett, but got to start somewhere. Fastest engines seems to be well worn Brodak .25's w/big venturis. Plane is a "Shy Fox Mk I" built from MA plans. With the right engine setup and an experienced pilot (currently lacking both :-\) it should be competitive. 8)
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The LA .25 is a plain bearing engine. They respond to breathing well so opening up the venturi will give you good results. If you are running pressure, open it up as much as possible,but remember you will still need millage, if suction then what Bill said. The head will give you some speed if you lower it. Maybe the best thing to do would be to lap the head so as to eliminate the shim. If that isn't your expertise, then send it to a machinist who can be found in speed times and have the stock head set at .015- .017 from the piston at TDC. A nelson style plug and head made to go with it would also get you a bit more RPM.
This should get you where you need to be. Have an experienced eye evaluate your engine before doing much.
Ken
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Walt is correct: SSR requires a stock motor as specified in the rules and must run on suction. See http://www.nclra.org/Rules/SSR.php
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Thanks Bill, I was going to mention that. One of the attractions of SSR and Sport Goodyear racing for me is the stock engine requirement. Fiddling w/engines I do, re-working is not in my skill set. 8)
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A good investment in one of these for racing is to get the liner chromed and fitted. Bob Oge did 3 for me and they were nicely fit. The nickle plating they come with is my least favorite but will last until you burn a lean run. The pistons are soft as an added benefit so get a few spares if you intend to do some racin.
K
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A good investment in one of these for racing is to get the liner chromed and fitted. Bob Oge did 3 for me and they were nicely fit. The nickle plating they come with is my least favorite but will last until you burn a lean run. The pistons are soft as an added benefit so get a few spares if you intend to do some racin.
K
Repeat: SSR has a stock engine rule. Re-plating an LA to get rid of the nickle plating is technically illegal. OTOH, Come on down, let's race! ;D
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Have decided to experiment w/ larger venturis and props on the FP. Break in the B-25 and run it on a test plane then build a new SSR for it. Might even run it in the current Shy Fox. Now, all that has to happen is our muddy flying field has to dry out. It might be a while. :-\
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Pete, I just flew up to Sacramento on the 10th. Is it still raining out there?? I went to Holt Cat to check out some stuff. It rained the entire time!
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Have decided to experiment w/ larger venturis and props on the FP. Break in the B-25 and run it on a test plane then build a new SSR for it. Might even run it in the current Shy Fox. Now, all that has to happen is our muddy flying field has to dry out. It might be a while. :-\
Pete, take a look at the "Mockingbird" SSR kit from PDK. It's B ill Bischoff's design, a NATs winner and quite a good model. Better, really, than any that have gone before. http://stunthanger.com/smf/pdk-llc-laser-cut-kits/mockingbird-ss-rat/ That model and a well-broken-in Brodak 25 will only leave you with a lot of practice to be more than competitive.
Edit to add: I see that you've already gone this route! You will not be disappointed!
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Thanks Bill, yup, I'm one model ahead of you. While I wait for the Mockingbird kit I will be finishing a Shy Fox Mk II. Same plane but with a lower aspect wing. Either one of these should work well with the B-25. Also have a Boo-Ray about half way built (and a Legacy stunter on the paint stand).I'm taking full advantage of this building season, since, as Dane mentioned, it hasn't stopped raining here for a month. Heck, If I wanted this type of weather I'd move to Seattle! FWIW: Clear, blue, and 22 today, time to do some painting. 8)