Dealspeed

My Feedback: (17)

Im actully surprised this plane didnt get more feedback, its a good size plane and id say 12 lbs for a 78" span is just about right.
Its definetly the next plane on my list to get, if it flies anything like the ST4D its a winner in my book.

mikeboyd

Okay, the price has come way down and I have several possible engines for this plane. I have seen it fly okay with an OS 1.6FX, I have one with both the stock muffler and a Bisson muffler, I also have a ST 3250 with Bisson Muffler and a Moki/Mark 2.10 with a slimline muffler. My friends are all telling me to go with the Moki/Mark engine and use throttle control.

Has anyone else tried a ST 3250 or Moki/Mark 2.10 on one of these. With one of these engines, I would most likely use upgraded, big bird hardware, aluminum arms and heavy duty servos, such as 8611 or 5955's or 5945's.

It appears the FX 1.6 would mount well with the stock muffler, inverted, with the muffler sticking out the side. If anyone has that setup, could you please let us know how it worked out and if you used the GP 1.20-1.80 adjustable mount without any problems.

Thanks in advance for your insights and advice.

Happy Landings,
Mike Boyd

mikeboyd

Mine's in the mail, I guess I will make the engine decision when it arrives and I get a chance to start weighing everything that will go in it. Still leaning towards a Moki/Mark 2.10, broke it in this weekend on a stand. Running rich it is spinning a 20X8W APC almost 7,500. Will most likely mount the engine sideways, with a Bisson muffler, with engine head sticking out the side of the cowling, just to keep things simple and cool. Don't plan on using a pump at this point, since the engine idles great and transitions fine on just muffler pressure. Still have the OS 1.6 FX, just in case it won't balance without adding weight to the tail.

If I don't hear from anyone about using the big Moki, then I guess I'm gonna be the Guennie Pig on this set up.

I'll keep posted progress, problems and information once the big brown truck comes.

Cheers,
Mike Boyd

3DFix

My Feedback: (29)

Hopefully I can save you alot of time and money. I have the Obsession with an OS 1.60 (w/perry pump) and it is a perfect match. When I first put the plane together I used a YS 1.40, way under powered! So I did alot of research. I really wanted to put a gas engine in it but the main problem with that was weight. All the gas engines weighed significantly more than what the palne was designed for. The extra weight would have required at least 8-12oz to be added to the tail to get it to balance. As it is with the OS 1.60 I had to add 6oz. All this extra weight would have thrown the wing loading off the chart and he flight characteristics would have ruined the way it was designed to fly.

The second problem is that the cowl is very narrow. This makes it very difficult to use any engine without hacking the cowl. The third problem is the clearance from the ground. I am running an APC 18x6 with the OS 1.60 and I have only 2" of ground clearance. If you go with the larger engine (Moki 2.10) and run a 20" prop that would only give 1" of clearance. Unless you plan on having a perfect landing on an asphalt strip every time you will be breaking or chipping your props contantly.

I hope this helps and good luck!

mikeboyd

Mine is finished.

Key gripes:
[&o]Covering very loose and wrinkled worse than any other ARF I have done. Got so fed up trying to get the covering sealed and tight, took out a good old clothing iron and went to work for a couple of hours, so not to pull, warp, or ruin the covering. I don't know what kind of Ultracote they are using, but it isn't very sticky or it was applied in a dusy or moist environment.

[:-]The next day had to do it all over again. No wonder they put a disclaimer in front of the instruction about covering.

[X(]Missing Hardware; missing the tail wheel, small collars, cowl screws and velcro strips. Luckily had it all in stock at the house. There wasn't a hardpoint installed for the tail wheel tiller post to go through. Had to harden the bulsa with thin CA. Hope is will hold.

[X(] There were allot of joints and areas that were barely even glued. I guess it's better than some ARFs with about a ton of hot glue on everything. A couple of hours with some medium CA had most of the fueslage done. Kind of wonder about the wings.

[&o]Many of the lightening cut outs on the fuselage horizontal mid formers are not well thought out for simplifying good installation of battery and receiver. Tank mounting seems okay by design.

[&o]CA hinges that are provided are very light for a plane of this size. Quality of the hinges doesn't appear too good, also were dirty, like they had been swept up from a dirty floor, before being placed in the sealed bag. I would have thought they would have gone with hinge points, like they have on their 30% Ultimate.

[:-] Motor mount is very small. Upgraded to a GP 1.20-1.80 and had to drive out blind nuts, to install 10-32's in their place. The doubler plate was not glued in sufficiently and came out with the removal of the original blind nut. Throttle control rod, supplied is not long enough for two stroke engine, would only work on a four stroke with a rear carb.

[:'(] Landing gear blind nuts were all full of glue and had to be drilled and re-tapped out.

Good Things:
Seems to be very light, so the OS 1.60 FX with a stock muffler should work fine, inverted.

good contrasting color scheme from top and bottom to help visual orientation.

Directions and illustrations were adequate for an experienced builder. There were some obvious mistakes in the instructions, such as instructing the builder to be sure to install thread lock on the two 4-40 screws to hold the top canopy/hatch cover in place while gluing the conopy on. Since these screws have to be removed and reinstalled constantly for airplane assembly, threadlock isn't a good idea. Instructions do not show or discuss any details about cowl cutouts, cooling flow or intallation. This would be fine for most of us old time builders, but newer people to the hobby may not understand things like air-dams, ducting, three times the area for air to exit, than entry and so forth. A picture with the two side vents closed off and a section of the lower cowl opened up, for inverted engine installation would have been helpful to beginner builders.

UPDATE, finished this weekend, final weight with OS 1.6FX with Std muffler is 13lbs, 6 ounces, so the wing loading comes out at 24 ounces per square foot. Ran the engine and tweaked it in the front yard, between storm clouds this weekend. It doesn't seem to mind running inverted at all with standard muffler pressure and a Fox idle bar glow plug. Had to lean the bottom end a little bit, but idles and transitions great. Hope to get a test flight on it next weekend. Had to cut a hatch in the rear of the fuselage behind the elevator servos to install a 4000 5/4 A 6 V NiMH battery (9.5 ounces) to get it to balance at the recommended 9 3/8" behind the leading edge. At 13.5 pounds, the 1.6 should pull it just fine. If not, I've got the Moki 2.10 sitting in the box in hot standby.

Good luck to all, great thread, thanks for all the helpful hints and suggestions. This one went together very quickly and appears to be of good quality.

Mike Boyd
AMA 7197

thedak

My Feedback: (21)

I have an extra one in the classifieds if anyone is interested.

mikeboyd

Flies great, if I can keep the engine running. Time to go to a pump. I have replumbed with large fuel tubing and clunk. Even with the stock muffler, if doesn't want to transition good and deadsticks at some inopportune moments. With the tank so far back, I should have put the Perry pump/regulator in, in the first place. This plane flies as good as my 30% Yak, only straighter. Once I get the engine running reliably, I should be able to finish trimming it out. It is so neutral now, with just a little aileron differential dialed in, I may not need any/much mixing.

Hope everyone has a terrific Easter!![8D]

RobertC

My Feedback: (157)

Good to hear Mike (that it flys great-- not that the engine doesn't want to run!). I have one of these still sitting in the box... only because the 1.60FX that I plan to use is in a Giant UCanDo at the moment. Absolutely gorgeous plane! I can't believe that everybody hasn't purchased one at the price Tower is selling them for now.

Speaking of the 1.60 inverted, this is the exact setup I am currently using in my Giant UCanDo, and it has worked extremely well (since I upgraded the fuel tubing to the larger diameter-- both the carb feed as well as the muffler-pressure line). With the tank in the "stock" position-- right at the firewall-- it idles all day and transitions very well. I was actually considering using a 1.40DZ for the Obsession but based on my experience with the 1.60 in the UCanDo I may just sell the DZ.

Just curious, did you mount the wing and stab per the directions (with a bolt through the top and into the aluminum tube)? I guess that this seems ok for the stabilizer but wouldn't it be fairly simple to add some plywood to the wing root and lock it to the fuse in a more "standard" way (bolt and blind-nut)?

mikeboyd

I mounted the tube in one wing side, then put the bolt in with some red locktite and cover off the hole with some ultracote. I leave the wing tube in one half. When I get to the field I use a fairly long grade 8 socket head bolt with some silicone tubing as a washer. Once the wings are in and the bolt is snugly in place, I cover it with a piece of magic tape. I have flown 35% planes with the same set up. When you think about it, the wing doesn't really get much force or pressure on it in that direction. I thought about drilling a hole in the antirotation pins and installing a circlip in one of the pins on each wing as a back up, but everything fits so tight, that it doesn't seem necessary. You may want to look at some large plane on-line instructions and how they mount the main wings. There are so many ways of skinning that cat. The way the wing mounts and the servo tray and tank tray are mounted, doesn't leave much room to install blind mounting nuts. The fuse is very narrow, so once you get everything set up inside, the circlips on the rear anti-rotation pin seems to be the simplest backup method. The front pins are not easy to get to, you may be able to go at them from 180 degrees, if you have enough room to get the circlips in place. Anyway, I think what they have works fine, with tape over the top of the bolts.

When I got home yesterday, I drilled a hole in the side of the engine, just below the (160), tapped it and install a pressure tap with red locktite and re-installed the engine back on the plane. I'll let the locktite dry a couple of days, then start setting up the perry pump about mid week. I believe the real problem is that the tank is back almost a foot from the engine. Even with large tubing, drilling out the tank fittings and installing larger aluminum tubing and a large clunk, the tank pressure from the muffler just isn't enough to provide good consistent fuel flow on uplines. The engine has to be run very rich, in order to keep it running. I don't like running a large engine lean at all. They don't last too long. I'll post the results, once I get the engine and pump set up and test flown again.

BTW, the reason I went through the side of the engine, is that the backplate is very thin and has all that webbing and other interferences in the way. I didn't want an off set hole to the side, as there is the potential for interference where the crank pin and rod rub against the back plate. The side of the engine is very thick and there isn't any possible mechanical interference in that area. It also made it very easy to hook up the pressure lines to the pump.

Also, the plane lands like a glider on deadsticks, even at 13+pounds.
Good luck to all!!
Mike Boyd

RobertC

My Feedback: (157)

Thanks Mike! Good information on wing-mounting. I was just curious if anybody else was using the "recommended" method-- and what the results were. Sounds like what you have works well.

Good luck with getting the pump working. Keep us posted on how it goes!

Tailgunner-RCU

Have to say, maybe an Obsession is not in the cards for me. I ordered one from Tower, one of their "100 Best Deals", and looked forward to receiving it...

The box showed up in good shape (for a change...) yet when I opened the box I was surprised to see that the kit box was pretty beat up, a couple of large holes were in the box (the cardboard was ripped open) and the box looked like it had been dropped (several times, hard...) on each end...

Called Tower and as usual their customer service was great...They shipped me another one and sent me a UPS label to return the first one...

The second one arrived today...Outer box looked good...Inner (Goldberg) box...looked not so good. It wasn't as bad as the first one so I decided to open it and see how it was. Well the contents were a bit jostled. The ailerons were no longer taped the wings...and one of the wings had the aileron servo hole precut (the other didn't...). Probably a good thing because I could see the broken wing ribs through the hole. Don't know if there is other damage, but I'm not off to a good start...

I contacted Tower and they told me to send this one back too...

Should I try for a third, or just quit while I'm behind????

ILIKE3D

Heres a question for you guys with the Obsession 3D with an OS 1.60 FX can you run the Slimline Inverted Pits ?? I really dont want to run the stock muffler out the side it kills the looks of the airplane IMO i like the idea of have it sleek and smooth..

Also what prop are you guys running with the 1.60 fx ??

Thanks Again Guys

3DFix

My Feedback: (29)

I have the Obsession with an OS 1.60. I run an APC 18 x 6. It is a good prop for 3D. I also have the Slimline inverted pitts muffler. It looks and sounds way better than the stock muffler. You will have to slightly trim the left flang on the firewall where the cowl mounts. Also cut a pretty large area from the left side of the cowl. Don't worry it still looks good. Let me know if you would like some photos.

Good Luck

P.S. I am going all gas and my Obsession is for sale if you know anyone that is interested.

Tailgunner-RCU

All right....I went for Obsession #3...

The box showed up in good shape...No apparent damage to plane (except for two broken top formers in the rear fuslage, I can get to these and fix them).

I had to spend some time (carefully) opening the anti-rotation dowel pin holes to get the wing to even mount onto the fuselage. I guess they don't even check this at the factory....

One question for all you Obsession owners. How well do the wings mate with the fuselage? My right wing has a gap of 1/8" in the back, the left a 1/8" gap in the front. I checked the wing alignment (measured to the tail) and it's about a 1/2" off...I just don't see any (easy) way to correct this.

Funny thing is, the wings fit better if I mount them upside down.

ILIKE3D

YEah some photos would be great man. Thanks AGian how does that thing fly ??

3DFix

My Feedback: (29)

I hope these pic's help. It is an awesome flying airplane. The rudder and elevator control services are huge and let the plane do anything. It is very stable and by far the easiest plane to land.


Good Luck.

Big Oakden

My Feedback: (3)

Hey all,

Am Building one for a friend, and we are converting it to Electric.

Power provided from Visionhobbies.com :
PJS6000
CC110HV ESC
(2)Poly RC 4350 5s1P (18.5v) 20-30c batteries
Prop should be an APC 18x6E

We expect to draw about 15lbs thrust at 70-80amps.

am using Hitec 625MG at all locations.
and seperate battery for powering servos

SHould have completed and maidened by June 10th.

Radio will be JR 9303

mikeboyd

IRT Tailgunner,s last message;

My anti rotation pins were also too tight and required some work with some fine files and sanpaper to get them in. I have a slight gap between the fuselage and wings, similar to yours, but not as much. This should not cause you any problems as long as the rotation pins are snug and the tubes are tight as possible.

I had a question (PM) about the 440 wing retainer screws, being strong enough. I left the left one in with blue locktite and white monocote over the recessed hole. I don't remove the tube from that wing at all. I put the right wing on and install the retaining screw and put celephane tape over it. I still use a piece of silicone tubing on the screw to provide friction to keep the screw from backing out against the tape.

I had a much large plane with a much larger gap between the fuse and wings than you have and there was never a proble with flight characteristics. As long as your wings are on snug, the rotation pins in and snug, you should be good to go, It just looks a little off, but shouldn't hurt anything.

Let us know how your ST 2300 works with the perry carb and pump regulator. I have had great success with the new 2300's, but haven't had to use a pump with them yet. There is a great manufacturer's thread here on RCU that talks about setting midrange on the ST's. You may want to visit that site, since the instructions there are much better than the one's that came with your engine.

Have a great memorial weekend!!
Mike Boyd
AMA 7197

Tailgunner-RCU

Mike,

I'm not running the Perry pump carb on the 2300. I'm going to try the stock card with the Perry pump that I have. I have removed the "dog leg" slot from the throttle valve on the ST carb, so that should help it run better. I really don't want invest more money in to this engine, so I'm going with what I have. If it doesn't work out I'd rather put the money towards another OS 1.60...

I haven't started building yet. I'm waiting for some replacement parts from Goldberg. From the looks of it, building shouldn't take too long.

mikeboyd

TG, I ran a Perry pump/reg in my 3250 with the stock carb and it ran great. Just had to spend about an hour tweaking and tuning the set up. It should work great on the 2300 stock carb too, I would believe. My 2300's turn about 250 RPM's less than my FX 1.6. For no more than the ST's cost these days, they are really a good buy. You just have to learn the three ways of adjusting the carbs, with the pump, you now have four adjustements to make.

Good luck, let us know how it turns out.

Mike Boyd

rustypep

My Feedback: (6)

This thread has been open a while and I thought I would check and see if anyone has had any luck in getting the weight down further or has any new ideas. Does anyone know if Goldberg has changed some things in the more recent runs? If Craig is watching, I am curious what he did to get his down to 11.5 pounds. The obvious thoughts to reducing weight are carbon tubes, landing gear, and prop but I haven't looked to see if anyone is making any gear. Careful selection of hardware, servos, wheels, and battery might help too. The plane is on sale for $250 and I have a $150 gift certificate to Tower so I might be willing invest in replacing a few parts to cut weight. Any thoughts? Engine choice is important and I was leading towards the OS 1.6 but am keeping an open mind [8D] and will also check out the Moki. I do not plan to use it in competition but this seems like a great value even if I don't use it right away. Thanks!

mikeboyd

Rusty, I just installed a GP Nylon Spinner with the Aluminum backplate and a lighter battery in mine. My dry weight is almost 12 pounds exactly. I am running the 1.6FX with Perry pump/regulator on Power Master 5% fuel. Vertical is unlimited. The engine is finally tuned and running very reliably and strong using the stock muffler. I am using an APC 18X6W prop. This is definitely a pattern airplane. I have quite a bit of ailreron differential dialed in and it rolls almost perfectly straight with no elevator or rudder corrections. It is a very easy plane to live with. I finally had some decent weather today, to work on trims. It really doesn't have any adverse coupling issues, so anyone can practice pattern flying with it. This thing has allot of wing area, so even over 12 pounds, the wing loading is very low.

Hope you enjoy yours.

Mike Boyd

thedak

My Feedback: (21)

Mine is still for sale

Snowmass

My Feedback: (12)

Mine also had most of the problems mentioned: tight antirotation pins, poor quality hinges, white covering that doesn't stick well, etc. But once you get past that stuff you end up with a plane that impresses everyone at the field with amazingly smooth 3D as well as pattern capabilities. The YS 140 DZ will rocket the thing straight up, and hover at less than half throttle. It spins, flat spins, and snaps way better than the UCanDo, and lands at a walk. All up weight is exactly 11.5 lbs, and it is 100% stock, even the hardware, and I use a fairly heavy 18x8W APC prop. But I did get flutter in the tail on the first flight. JR 811 digitals were not enough for the elevator halves; I had to upgrade to some very strong metal gear coreless servos to prevent more flutter back there. I also added some counterweights. No more flutter after that.
Overall this is one of the best planes I've owned over the last 17 years. It is an amazing value for the current price.

AirPatrol

My Feedback: (1)

VIDEO!!! WE NEED A VIDEO [X(][:@]