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Jul 18, 2018, 06:38 AM
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My second EF Laser 74 v2 - Gas


My second EF Laser v2 74 is almost RTF! I just need to do the basic test and set up for the engine in my yard (I don't like surprises at the field), and make + install a custom push pull rod for the rudder. I will include more notes at the end of my build.

Key highlight is that gas is absolutely push pull for rudder, unless you are in the mood to add 4+ ounces to the tail. I am using a combination of bigger batteries on the turtle deck, and roughly 42 grams of weight at the tail to get the static CG roughly right based on my electric Laser.

To make a 200 mm custom push pull, my solution is to get a 4-40 all thread rod, a sturdy CF sleeve, and use the Loctite plastic bonder to lock the 3 mm ball link on to the 4-40 all thread rod for life. I tested this first with a spare piece of 4-40 thread to confirm it is exceptionally solid. I will include a pic when I am done with it. Right now waiting for the 4-40 all thread rod to arrive.

Equipment:

Falcon 20 x 9 CF prop
aluminum spinner
DA 35
stock DA muffler
MKS 1250 throttle servo
MKS 1220 surface servos
EF servo arms
EF tank
Plumbing from JerseyModeler
iBEC from TechAero

Radio and related:
10 channel Jeti receiver, DSM 10 switch, R/3 SW remote for DSM 10 switch, and a pair of 2S Lipos.

I have 2 x 2S 2200 Pulse (100 grams each) and 2 x 2S 5000 Glacier (200 grams each). I will likely start with 2 x 2S 5000 and adjust from there based on flying CG.
Latest blog entry: My second EF Laser 74 v2 - Gas
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Jul 19, 2018, 05:07 PM
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My second Laser 74 v2 In Gas is now RTF!

I set up the new gas engine in my yard, itís running great thru all 3D type changes.

Surfaces set up, hinge gaps sealed, decals applied.

I finished up the custom push rod for the push pull rudder, see pic. Turned out fantastic.

Now maiden will be when my schedule permits. Feels great to have an Electric Laser RWB and Gas Laser in classic Red. I think I am going to fly these two planes this season.
Latest blog entry: My second EF Laser 74 v2 - Gas
Jul 25, 2018, 10:10 PM
out to have fun
dbishw92's Avatar
looking good Noob was wondering if you could get me an all up weight without fuel and can you also weight the Electric with batteries and ready to fly? bathroom scale is close enough
Jul 26, 2018, 10:42 AM
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How do I do it? My weight and then carry major parts one by one? That’s what I am thinking. Will let you know by Saturday.
Latest blog entry: My second EF Laser 74 v2 - Gas
Jul 26, 2018, 10:57 AM
out to have fun
dbishw92's Avatar
just looking for a close estimate I am wanting to know how much weight was shed from v-1 (that I have)
Jul 26, 2018, 01:35 PM
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ok will do. Will have weights Saturday.

The weight savings thing is interesting. If I ended up having to add weight like I did (using 400 gram battery weight on the deck, 42 grams in tail)... how much did I save in the end, and to what end
Latest blog entry: My second EF Laser 74 v2 - Gas
Jul 27, 2018, 03:46 PM
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So I had a really fun maiden for the Gas Laser today. Quite gusty, but manageable. Only harrier landings today.

Just a couple clicks on aileron, a few on the elevator and I was in business in the first minute the plane was the air! Real pleasure to fly.

I did one easy flight to adjust trims, get a feel for the expos etc. The flying CG is a bit nose heavy compared with my electric Laser, I might do some adjustments after 10 or so flights of feeling this set up.

All predictable behavior through 3D / XA. In terms of thrust to weight, this feels closer to my MXS 76 than the Slick 70 (74). The plane weight and engine tuning are key considerations. The engine is brand new and needs to be broken in. I am sure I can tune it better also.. the high end might need a little more adjustment.

Flight two I was hovering just off the deck (the picture shows a few feet higher as I was descending), doing inverted harriers, KE and KE spins, snaps, etc. All good.

I will add a separate comment on the weight comparison between gas and electric.

There was one other pilot at the field and he took these pictures. He had brought along a cute little Turbo Duster so I took a picture with that.

Happy camper. When you are primarily flying electric, the flight time on gas feels ridiculous

The DA 35 is just sipping gas..

In terms of adjusting CG further...I am going to have to add even more weight to the tail, i am already using a heavy batt (pair is 400 grams in total) at the aft end of the rudder tray, and i am using push pull rudder plus 42 grams in the tail. This is one nose heavy set up if you go pull pull. I am glad I checked the rough CG before deciding on the rudder set up.

More later. This is one fun plane and I had a fantastic maiden day!
Latest blog entry: My second EF Laser 74 v2 - Gas
Jul 27, 2018, 03:57 PM
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Ok so here are the weights for the gas and electric set ups.

A. Wings weigh 2 pounds - say 904 grams

B. Electric fuse weighs 7.6 pounds - 3,435 grams without batts

C. Gas fuse weighs 9.6 pounds - 4,339 grams without fuel or receiver batts

D. Electric flight batts weigh 2 x 583 grams = 1,166 grams

E. Electric receive batts weigh 2 x 100 grams = 200 grams

F. Gas receiver batts I use (mostly CG reasons) = 400 grams

Total electric weight for me = 3,435 + 904 + 1,166 + 200 = 5,705 grams or 12.6 lb

Total gas weight for me = 4,339 + 904 + 400 = 5,463 grams or 12.5 lb

So gas and electric weights come out identical for me with dry weight for gas.

The main difference of course is in the distribution of this weight. I am still a little nose heavy with gas with the 400 gram receiver batt on aft end of rudder tray + push pull rudder + 42 grams in tail.

With electric, the flight batts are closer to the CG, which means balancing is a lot easier.

In terms of performance it stands to reason that the gas version with DA 35 will lack the punch that XPWR 35 has. My experience so far is that you need roughly 5cc more in gas capacity to get the punch you get from an electric of the same nominal cc rating. An XPWR 30 feels similar to a DA 35. I think this plane will really benefit from a 40 cc, but that of course will only exacerbate the CG issue.
Latest blog entry: My second EF Laser 74 v2 - Gas
Jul 28, 2018, 04:37 AM
It's safer at 400'
azflyinghigh's Avatar
Noob,

Thanks for this build thread on the gas version as well. You might want to consider the MKS 777a for the extra tail weight.
Jul 28, 2018, 07:06 AM
out to have fun
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thanks for the weights Noob
Jul 28, 2018, 08:22 AM
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Originally Posted by azflyinghigh
Noob,

Thanks for this build thread on the gas version as well. You might want to consider the MKS 777a for the extra tail weight.

Yes thats a great idea, thank you. I think I will get another 5 to 6 flights as is - yesterday was quite gusty, to see how I like it and how much weight I need in the tail. If it is in the order of 20 grams or so, then I think the 777A makes perfect sense.

Has anybody glued / attached weights inside a fuse at the formers toward the back? Or a strip of heavy ply? If I need to add more weight, i am thinking it might be better to do that inside the plane if I can.. also distribute it a bit so its not all within a couple of inches at the tail.

What I am pondering is this. If I can add something inside the plane - even a long strip of heavy ply or something like that, i can do two things...

1. I can add more weight behind the tube
2. I can possibly take down the overall weight of plane, since I can likely shave off 200 to 250 grams on the battery.

If I add a 100 gram (just speculating) heavy ply strip along the inside fuse, centered 24 inches behind the tube, it will immediately allow me to use a much smaller battery because of the CG benefit, and it will also push the CG back a bit at the lower overall plane weight.
Latest blog entry: My second EF Laser 74 v2 - Gas
Jul 28, 2018, 08:37 AM
It's safer at 400'
azflyinghigh's Avatar
I just worry about the strength of the MKS 1220. I have been more than pleased with the 777a+ on my 91 laser. Like you, I am doing 2 setups. One has and one electric. Gas is gonna be all mks777a and the electric is going to be Savox 1270. The MKS 777a is 75g vs 57g of the 1220.
Jul 29, 2018, 07:08 AM
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Originally Posted by azflyinghigh
I just worry about the strength of the MKS 1220. I have been more than pleased with the 777a+ on my 91 laser. Like you, I am doing 2 setups. One has and one electric. Gas is gonna be all mks777a and the electric is going to be Savox 1270. The MKS 777a is 75g vs 57g of the 1220.
thank you. I will try out a 777A, I am always interested in testing / learning.
Latest blog entry: My second EF Laser 74 v2 - Gas
Aug 03, 2018, 09:43 AM
ltc
ltc
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Is that Wrentham Lazy Looper field?
Aug 04, 2018, 08:32 AM
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Originally Posted by ltc
Is that Wrentham Lazy Looper field?
Yes ltc. Its a bit closer than SSRC for me and especially if i am flying intermediate size planes like this one, its more convenient. See you at one of the fields! Lazy Loopers has a Warbird Day Sunday August 5 '18, if you are able to attend.
Latest blog entry: My second EF Laser 74 v2 - Gas


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