So I was wrong about the noise! Good to know a gas engine can be made silent enough too.

I'm still a beginner in F3A but I agree that lighter weight has many benefits. I probably won't notice small differences but I bet even I can feel something after I get the motor changed. I have seen a Sensation bipe fly at 4600 g and it was like on rails even in windy conditions. Of course it matters a lot who's behind the sticks...

Finn, I would not say wrong, just uninformed. Being new to pattern, welcome btw, you have more options than ever. That could be good and bad because some options are very expensive and some are very inexpensive. For now I suggest you use proven setups that experienced guys use. One thing certain, no matter how expensive, there is no guarantee the plane will fly the way you would like or want. Connect with the most experienced guys you can and hopefully they will steer you well.

I have a couple YouTube videos somewhere on their servers where you may hear a couple different setups, an OS 33 on pipe and DLE 35 on canister. The piped OS is quieter and stronger.

MTK,

Have You noiticed any vibration related problems on the plane itself or the equipment (servo wear for example) with Gas engine in your pattern plane(s)?

There is a new OS Gas Engine, GF40 (40 cc) - what do You think about such engine in a 2M pattern plane?
GF40 almost twice ($800) as expensive then GT33 ($420) and is little heavier also (1170+113+95=1378 grams compared to GT33 984+160+105=1249 grams) so the price gap is a big disadvatage. But if we disregard the price, is it suitable for F3A flying do You think?

What pipe are You using on Your OS GT33?

/Bo

Bo,

I have discussed the whole setup on the thread sticky in the regular pattern forum. I am using the ESComposites 40G pipe and Hatori 2501 header plus a 4" extension to the header. There's a lot of info in that thread and frankly I forget some details and I have to look up myself from time to time.

Interesting question regarding damaged equipment from vibration of the gas engine. I have not yet had any damaged equipment. 10 years ago when I was flying Webra glow, I had a servo fail on aileron. Come to think of it, it's the only failure of that kind I recall in about 7000 flights over the past 30 years or so. Even when I flew non-iso mounted 60s in the 70s/80s, don't recall failures caused by vibes. On second thought, I remember control clevises wallowing out servo arm and control arm holes in the days before ball bearing and ball links. Every year or two, these were replaced.

I have the GF40 four stroke. I got mine at around 650$ if I recall. I have not run it but have heard it and it sounds great. It should work fine with the ESC canister Ed Skorepa sent me. The weight delta is a concern and its performance is probably not as good as the 33. Suitable for F3A? Possibly....it will turn 20x8 props according to the instructions. In practice, if it turns the 20x10 at 7k, any F3A model could be flown well except maybe a two meter bipe. The 33 will spool up to7800 and rip the 20x10 on premium gasoline. It's way more than needed.

a better option for the really beefy 2 meter Bipes is a 40cc twin on twin pipes. I have the engine and pipes but unless I designed it myself, no bipe ARF. This engine should turn 22x8 pretty well and will be plenty for a 12# bipe. It's only 25 grams heavier than the 33.

I talked to Micheal Ramel about this topic at the last AOC in Thailand .. The governing body for F3a were worried that if the weight limit is increased it will make for very big biplanes that fit within the FAI rules, he said the biplanes would have an unfair advantage being much larger .. This would intern make the cost a lot higher and also harder for the monoplanes to compete..

Hi,
Maybe a wing area rule could prevent that big 2 meter wingspan biplanes get any advantage?
Like 100 dm2 (square decimeter) wing area limit. Most 2M F3A biplanes today has less then 100 dm2 wing area, usually between 90-100 dm2 (9.688 - 10.76 square foot, 1 395 - 1 550 square inch).
A 100 dm2 wing area rule would not give any negative effect for 2M monoplanes since they have usually wing area (including any top/lower small canard wing) in intervall 60-90 dm2, mostly between 60-70 dm2.

Examples:

Biplanes:
Citrin ST EP 93.9 dm2
Acuracy Bi-Plane 96.9 dm2
Finals Touch Bi-Plane 91.3 dm2
Ascent Bi-Plane 92.6 dm2
BJ Craft Passion 84.8 dm2

Monoplanes:
Galactika EP/GP 59.1 dm2
Allure 67.74 dm2
PrometheuS 89.3 dm2 (including top and lower small wing)
MythoS Pro 63.3+6.7(top wing) =70 dm2
BJ Craft G2 Invitation 57.5 dm2 (probably without top wing area)
BJ Craft Essence and Agenda CD 58.6 dm2 (probably without top wing area)

Another possible solution would be to allow higher weights but then with a system for point reduction as weight increase over 5000 grams. That way one can encourage F3A flyers to keep weight under 5000 grams if that is desired. The point penalty should then be so that it hurts a little to be at 5500 grams (if we assume that would be a new weight limit). This would for sure have the top flyers weight pros (maybe higher flight points) and cons (weight point penalty). Probably the weight point penalty must be so it is rather clear that one get an disadavantage that is rather hard to compensate by flying very good.
Just a thought, might be unrealistic.

/Bo

One down side of raising the limit, is electric models will need bigger batteries to pull the weight, which in turn raises the weight more. currently a set of 5000mAh 5 cell lipos can be used in an F3A model, and at 92W/hr they can be taken on board when travelling overseas to competitions. If larger batteries were required, taking batteries would not be an option.

It is easier and cheaper to get a F3A model to be at the limit (5050gr) or lower than increasing the weight limit.

If the weight limit would get to be increased, then all the manufacturers of F3A airframes/engines will develop new stuff, and this will come with a price, then competitive pilots will see a dissadvantage, so the race to have the best will start all over again, meaning everybody will end up where we are today, and the complaint will be why not to increase the weight limit to 6Kg as the 5.5Kg airplanes are to expensive and the cheaper options can not deliver the same performance, and so on.

The F3A is and has been 5Kg for a reason, but that does not mean that the lower clases should not have a higher weight limit, this, in order to get more people into pattern, which has less interest nowadays, those are the clases that need to be changed, F3A has a worldwide standard, the lower classes are different on each country, and there is enogh room for change there, something that could also help to change F3A in the future if a trend is established.

My opinion of course.

Alejandro