DamonTX

I've been thinking about this one for a long time and finally went for it. The changes I've made to the kit are sheeted wings & turtle deck, twin (.25 FXs), shortened canopy, modified fin & rudder and monokote hinges.

Can someone give me a little advice on thrust angles. The engine mounts are even and parallel to the fuse thrust line. I've read that a little bit of outward thrust would help in stability and engine out situations. Is this correct? Also, does anyone think there needs to be any downthrust as well? I've got to get this figured out before I start building the nacelles.

Thanks for your help.

Damon

William Robison

My Feedback: (3)

Damon:

Your SE is supposed to be an aerobatic plane, if you want to maintain this the engine thrust line should be on zero vertically.

Down thrust is used to keep the plane from climbing with an increase in power, opening the throttles. It works, but with an aerobatic plane what works upright is against you when inverted.

Out thrust is the subject of much debate. To be really effective it needs to be at least five degrees, eight degrees is considered minimum by some. Ed Moorman has a twin bash he calls the "Outsider," if you do a search on the name you'll be able to read his arguments in favor of out thrust. I've only used it on one twin, the Tiggerkitty, and that was 1 1/2 degrees on the right engine only. I just don't like the looks of the plane with out thrust.

In favor of out thrust: Easier to handle with an engine out. If you run a vector analysis you'll find almost no power loss to pay for the ease of single engined flight.

Build it with or without, you can shim the mounts later to change it.

Bill.

DamonTX

Excellent explanation.... thank you, now I'm off to build the nacelles.

JohnBuckner

My Feedback: (1)

Out thrust certainly will contribute to the longevity of your Airplane. I use five degrees out on a forty size bashed trainer, four out on a dualist, four degrees out on the outboards and two degrees out on the inboards of a bashed Quad and am just finishing up a Wing P-38 for Warbird racing with four degrees out.

Every degree you go with will decidely contribute to buying you time on an engine out at critical times (after T/O) to identify and get the proper rudder in, it will reduce your single engine VMC and inprove your throttle up takeoffs to prevent that runway dance due to uneven spoolups. Excessive outthrust is not neccessary to make a noticeable differance. I will never agine do any wing mounted multi's without some.

John

DamonTX

hehehe, I can't wait to fly this thing. It should probably be called "Somethin' Different" As it is in the pics, (without battery, receiver and aileron servos) it balances per the plans. As soon as I figure out a color scheme I'll get started.

I took Bills advice and kept all indicences at 0 degrees. The original idea was for more streamlined nacelles with the engines inverted and with tuned pipes. I decided to mount the engines upright just to keep things simple this time around and wanted it to resemble a true twin version of the original. I didn't use the tuned pipes because there isn't enough clearance over the wing.

Damon

DamonTX

Ok, it's covered, and everthing is installed. I need some advice on balancing it. As it is, it balances just right at 3.5" from the leading edge with 2oz of lead in the nose. However......this planes has two 6oz tanks just behind the main spar which is the CG. Shouldn't this be taken into consideration when balancing? Should I fill the tanks and rebalance? Or maybe fill them half full?

I'm asking this because on takeoff with both tanks full it seems like it would surely be tail heavy. Then again, on landing with the tanks near empty and with too much weight in the nose it would be a fast touchdown.

Damon

William Robison

My Feedback: (3)

Damon:

Remember the cg has an acceptable range, and uis normally adjusted with the tank empty. With "Normal" fuel tank placement the cg shifts forward with a full tank.

With this in mind, and noting your plane will have an aft shift with full tanks, I'd start with the cg on the aft limit with full tanks. Then with the tanks again empty see how far forward the cg has moved. If not too far forward of the recommended range I'd just fly the plane, and do later cg adjustment tio get the plane to fly how I liked it.

If the cg has really gone further forward than I liked I'd redo the cg with half fuel and fly it, again adjusting if needed.

Bill.

DamonTX

Bill,
Thanks. Once again its sounds like you've provided solid advice. I'll do just that then start breaking in those engines. Hopefully the maiden will be next weekend. I'd better get some pics just in case. [X(]

Damon

DamonTX

All finished! If anyone has or know anyone who has tried this please let me know, it would be nice to hear from them. Thanks.

Connery

Wow! turned out great! Looking forward to hearing how it flys.

Meesh

My Feedback: (135)

That looks great. Nice job!

Bob

roncoleman

My Feedback: (14)

Damon, Being that no one has put the question to you after all this time.

How does it fly?

Ron

DamonTX

Ron... She's a keeper! So far I've taken it out twice and have made a total of four flights. Each flight has been really smooth and it never needed any major trim adjustments. It ended up weighing 8.5lbs which is pretty heavy considering my single engine SE's are around 5.5.lbs. However, the twin is has a sheeted turtledeck and wings, two tanks & engines with mufflers, two throttle servos, a large nose block, about 3 or 4 oz. of lead for bablance, now has heavy duty Dubro gear and the weight of the extra material making up the nacelles. Whew! After putting it that way, I'm a little more understanding of the weight difference.

Since it's a twin, I always make long, controlled takeoffs and it always tracks straight down the runway with a nice gradual ascent. Landings are a little different..It wants to come in slow (or maybe it's me from flying the singles). I have to remember to keep the throttles up a little. I bent up the originals from a rough landing caused by too low of an airspeed.

In the air, it's just like any other airplane. Loops and rolls aren't quite as tight as the singles but that was expected. I just have to say the best part of this plane is how smooth it feels in the air, I really like that. I haven't gotten too crazy with aerobatics yet because I want a few more flights to test the reliability of the engine setup.

I never would have guessed it, but I could have gotten away with putting .32SXs on it rather than .25FXs. As it is now, it's a little faster than the singles with .46FXs but I thought it would have been a lot faster.

This was pretty much just a test plane. I'd like to build a larger one with .46AXs this winter. I learned a lot from this one and plan to do some things quite a bit different on the next one. Some of these changes are a single gas tank, larger engines, more flexible gear and some internal changes to the nacelles.

Damon

roncoleman

My Feedback: (14)

Damon, Thanks for the update. It's good to know that you ended
up with a keeper. Now let's see if Sig puts out one too.

rrudytoo

My Feedback: (27)

DamonTX,

Congratulations on a fine job! Your "SD" came out looking like it was meant to be that way from the factory. I'll bet it's a hoot to fly!

I'm glad that you're going to continue to refine your efforts with another build and I have a suggestion. Move your engines inboard as much as you can. The further out, away from the fuselage centerline, they are the more adverse yaw will be induced should you lose an engine. This should be a relatively easy modification for one of your talents and it should improve your roll rate and roll recovery, too.

Good luck and keep those posts coming!

Al

DamonTX

Thanks guys! I got three more flights on it Sunday. Two weeks ago I was having trouble getting the engines synched but all is fine now. The flights the other day were great. I'm moving past the test flight stages and am now really starting to ring it out.

Al... I totally agree with you on moving the engines inboard a little more. Found this out on a dead stick a while back, whew! that was a close one! When I do the bigger one this winter, I'll probably make it so there's only about 1.5" of clearance between the tip of the prop and the fuse. For balance reasons, the tank will likely be in the fuse and the nacelles will be a little longer to help out with balance as well.

Now would someone else give this a try? I promise you'll have a blast.

Damon

DamonTX

I figured I'd give those interested an update. After 21 flights, she lost an engine and went in. The only damage was a large dent in the left leading edge and the fuse is ripped where the tube goes through. Also, the right wingtube was torn loose inside the wing. I've taken all the hardware out and retired it.

The engines should have been closer to the fuse and it really needed more power.

I'm going to do another twin SE but it's going to have twin fuselages like a twin Mustang.

Damon

Ed_Moorman

My Feedback: (1)

Sorry you lost a great looking plane. You needed the out thrust.

I am using 8 degrees and I can lose an engine on take off, take off on 1 engine, do acro on 1 engine, turn either direction.

DamonTX

Ed...I definitely learned my lesson. I had no out thrust at all and felt it when the engine cut out. For a second (in level flight) I had it under control but lost it when turning around to get to the runway. What do you think about the twin fuse idea?

Damon

Ed_Moorman

My Feedback: (1)

I built, actually, my flying buddy, Flaps Laffert who is 83 built it, a twin fuselage World Models Sky Raider Mach II. Excellent flying plane. I just had about 4 degrees in it-I ran out of thrust plates-but it holds pretty well on 1 engine. Bill "Straight Ahead" Robison, who is in my club, and whom I'm picking on, has seen me take it off on 1 engine. Even though the Twin Stick flies great, I do think the twin fuselage configuration is safer with an engine out than twin nacelles.

If you are interested in a twin fuselage plane, I can send you some more photos on how we did ours.

DamonTX

Ed...Yes I'd appreciate it if you could send some add'l pics showing construction. I've pretty much decided that I am going to do it. I'm thinking the two fuselages would be permanently mounted together by the stab and center wing section. The outbooard wings would be traditional removeable Somethin' Extra wings and I'd use a pair of .40 FXs. If I'm feeling crazy then I'll do retracts, one on each fuse.

One question I've got is would you built it with dihedral?

Thanks,
Damon

SIMCO

My Feedback: (33)

Yor airplane looked great. I did a tiger twin P-82 style. flew real nice.

Ed_Moorman

My Feedback: (1)

Simco,

Looks great. How about e-mailing me a couple of photos of your plane that I can use in my column. Send to [email protected].

I modified a Tiger 2 ARF with twin necalles, but it turned out heavy. Flew OK, but landed fast and every time you point it down, you can tell it's heavy.

DamonTX

All done...and it flies GREAT! It's probably the fastest plane I've ever flown with 2 .46 FXs but it slows down and lands almost as well as a single SSE. So far, we've got 4 flights and after a full checkup will take it out again this weekend. Thanks Ed for all the advice.

Ed_Moorman

My Feedback: (1)

I think the twin fuselage configuration is about the best. The extra center section keeps the wing loading down and the plane is streamlined and usually fast. I have a clunky, twin-fuselage Sky Raider and it's fast so I would think your sleeker SE would be really speedy. I'll also bet you have tons of vertical. I am using APC 11-5 props, by the way. They seem to perform better than the usual 11-6.