jet22b

Hi farfar;
Welcome to the thread!!! Look back into the thread and you will find that we talk about the tanks and how they was move to be in-line with the crab. Adam is also going with 2 four stroke engine in his bird!! So when you start your build, you will find a lot of help here!!
Again, welcome to the thread!!
Sonny
aka
jet22b

mike early

I have found that tank height is normally not that critical in my Saitos..

Herc Pilot

My Feedback: (15)

farfar,

Like Sonny said, check out some of our earlier posts. We've discussed the tank issue quite a bit and that seems to be the biggest concern, tank placement and also rear engine cooling. We posted some pics of a few different ways we mounted ours in previous posts. If you mount your tank sideways, I'd be concerned that if you bank one direction that fuel will ran away from the clunk at lower fuel settings, and it could starve and lean the engine. I think your ASP's will be a fine choice for this bird. Welcome to the thread and good luck with your build.



Larry and Shawn have made a lot of progress on the Skymaster. Shawn has taken a huge amount of the pressure off me and covered a lot of the plane since the last time I was there. Today we nearly finished covering, got the cowl vents cut, and started trial mock ups. I'm in love with this airplane! I will say, if anyone decides to re-cover this plane, you will need a TON of patience with that center section! It's a pain!

Here is a pic of how we ended up placing the rear cooling vents and exhaust exit. Not totally scale, but close enough for us.

jet22b

Hey Adam;
Now you done it!!!! I like what you did to the rear cowling!!! I was thinking about that last night and now looking at your cowling. I must do this!!! And yes it do look scale too!! The way you have your back end, I don't think you will have a cooling problem. The next big thing for us is not the weight of the plane, but will the CG fall at the point of 80 MM that the manual call for without adding weight!!
Sonny
aka
jet22b

Herc Pilot

My Feedback: (15)

Thanks, Sonny. The cowl was Larry's handiwork. Be careful if you try this, the cowl was very brittle. He first cut the slots, then filled the cracks, then gave several coats of primer to get it to that point.

The covering is now all done on our Skymaster. We started mounting servo's today. Next major task is going to be painting. We have to paint both cowls, the strut mounts, servo covers, the windshield frame, and the top leading edge of the wing which has a fade going back into the silver. After paint is done, we will finish the scheme off with the fuselage stripes but luckily those will be done in vinyl. This is probably the most complicated scheme I have worked on in a long time so it's nice to have that part of things wrapped up.

Shawn took some good pics tonight. He doesn't normally get in RC much and basically taught himself how to cover on this project. His help has been invaluable.

jet22b

Adam;
Please past on to Shawn that he did a great job on the cover!!! When you take you SkyMaster to the field, you will turn heads!!! I hope someone from Red Bull would see this thread and take note of the job you and your friends have done to show off their Cessna 337. The two planes would make a great photo shoot!!! The main receiver battery should be in today so I can do the CG and see if I have to add weight to get it at 80 MM like the manual call for!! Will post the outcome and the final weight with no fuel!!!
Sonny
aka
jet22b

rcflunky

Adam that plane looks AWSOME! You guys do great work. Thanks for the pic of the rear cowl I did mine just like it and was shaking the hole time I was carving out those slots. Mine is pretty much complete so I decided to weigh it and came up with 10.6 lbs. I also checked the CG from what the book said 80mm and mine was tail heavy so Iadded 4.5 ounces to the nose and it almost came in to being level. Now this was just a rough look at it so I could see kinda where it is. If I can finish up the rest tomorrow I be able to maiden it by Thursday the weather here is supposed to be in the 50s and calm winds this week. I'll let you know if it happens. Thanks again to you and Sonny for all your input.

Joe
aka
rcflunky

Herc Pilot

My Feedback: (15)

Thanks for the comments, guys! It's much appreciated!

Sonny, let me know if you have to add weight up front like Joe did once you get your battery installed. We are going to try to put everything up front, but are adding weight quickly as we add more stuff like lights, and the 4 strokes are heavier than the engines you guys are running.

Joe, doing some quick math, that puts you around 30oz per sq ft. Not great, but should be manageable. Keep your ladings long and shallow and keep some speed up and I think you will be fine. I wish you the best on your maiden and make sure you take some pics if you can. I'm anxious to hear how it goes.

For us, it's back to the hobby shop tomorrow so we have more parts for the weekend.

jet22b

Adam & Joe;
My CG was spot on with no added weight. As you see in the pictures, I had to remove the wings struts to balance her with my Great Planes CG machine, because the 80 mm fall right at the struts. The string test was sweet. Both wings was level!!!
Final stats:
CG As per manual No Added weight.
Weight 11 lbs Max weight
Controls Set per manual
String Test Both wings was level!!!
Tomorrow I will start the front engine to see if I need to move the tank!!

Joe,
Good luck on your maiden flight and please post a flight report.
I hope the weather will break for me, so I can do the same. I think this will be a keeper!!
Joe, did you put your main battery up front next to the tank?? That's where I put mines and the CG was right on the money!!
Now if this plane fly good, I will pick up one more!! Stay tune for my flight report
Sonny
aka
jet22b

rcflunky

Hey Sonny your plane looks great.I have one of those GP cg machines like yours but I didnt use it when I checked mine I used my fingers so I know it wasnt that accurate but I'll use the cg machine when Im all done. Ihave a 1700 mah battery 5cell that I was using when I checked cg. I still need to get a bigger batt tomorrow. So I hope mine comes in as good as yours. I ran a tank through both engines today and those AX 46 ran awesome. I did what the book said and they ran so smooth, never sputtered or anything and I only had to start them once. I also did what Adam said and ran the rear one with the puller prop. Tomorrow I should be able to finish things up and be ready for thursday and hopefully be able to maiden if the weather holds out. I'll take some pics of the finished product before It goes airborn.

And Sonny I'm thinkin your right about gluing the wings on mine have a little bit of play and I don't trust just that wing tube. Im gonna tape that seem I think for now with some electric tape and see what happens but I will probably glue them on like you did.

Joe
aka
rcflunky

mike early

where we at on the wheel pants search?

jet22b

Thanks Joe!!

Yes go ahead and use the CG machine. You may find the CG as per manual. Just remember to remove the wings struts before you use the machine. I went with the Hobbico HydriMax Ultra 6.0V 2000mAh flat pack Rx battery. Use them for the last 2 years with no problem. Look in one of the packs that had the servos cover and you will find cover strip for the wings joint. In away I am glad I went with the gluing of the wings. That way I know the wings will not come apart in flight!!!
When you use the CG machine, let me know if you balance as per the manual!!
Sonny
aka
jet22b

jet22b

Mike,
I wish that Seagull would sell a pair of pants for this bird!!! I found wheel pants for the full scale Cessna 336, but not a set for this one. Maybe a set for the Top Flite Cessna 182 will fit this bird!
Sonny
aka
jet22b

Herc Pilot

My Feedback: (15)

Larry has a Top Flite 182 with an extra set of wheel pants (he buys extra colws and pants for all his planes in case they are discontinued). The TF 182 wheel pants are just about perfect for this plane. They may be a touch on the large size, but had we decided to use them, those are what we would have went with. I'll try to hold them up to the plane and take some pics for reference next time I am there.

farfar

Hi Guys,
Still not started the build of my cessna but have been following the thread, all you guys are doing a great job with your planes, will look forward to the flight reports, I think I will definately mount the rear tank accross the fuz I have done this before with no problems, I don't have the clunk right to the end of the tank so unless you run it right low on fuel there should be no problems it also keeps the fuel pipes shorter anyway I will have a better look when I start the build,
good luck with your maidens,
farfar

jet22b

Hey Guys,
I got to test the engine today and found that the front engine ran real good with the tank as per the manual, but, I did find at low throttle the engine will die because of low muffler pressure!! Over all I was happy with the front engine run. Now for the back engine run test. Today temp was 39 degs and no sun. I ran the engine with the cowling in place and must say that I am glad I did move the tank to where I have it. I do said this, I think it will fly on one engine. The prop I have on the 2 Evo .46 11/7 and 11/7P. Did not take a RPM reading. Will do that next. I ran the back engine for 4 min in the outside temp as I said before, but when I shut down the engine and took a temp check and I was at 198 degs F. The front engine temp was around 105 to 110 degs F, so that tell me that the front engine is running cool. So the bottom line is this, start the front engine first and than the back and get it in the air as fast as you can!! Plus run the back engine a little on the rich side. The extra fuel will have for cooling!! When I do fly this bird, I will maiden her with the APC 11/7 props and than move to the APC 10/7 and see how the plane fly!!

Adam;
Can not wait to hear your flight report on how the plane fly with two four stroke!! I know the sound will be sweet!!!
For what we have post here on this build thread, I think we have put out a fair review on this ARF. We all know this is a model 336 not the 337 and I think this will be a sweet plane to have in the hangar. For sure this will be a head turner at the field.
Flight review are coming when the weather let us fly!!!
Sonny
aka
jet22b

optech

My Feedback: (9)

Regarding cooling for the rear engine, why are you guys keeping the flat plate area where the spinner is. Not only does it look "model airplane-ish" but its not helping getting air out through the cowl. I would cut that hole open to within 3/32" - 1/8" of the edge or so. Or better yet, line the edge of the cowling inside with some narrow strips of 1/8" balsa. Then cut out the spinner hole to til it meets the balsa and use some sand paper to round the edge and provide a smooth air exit. Look at the full scale pic. The cowl is wide open in that area. There is supposed to be a difference in diameter of the cowling exit and the spinner.

Mike

Herc Pilot

My Feedback: (15)

Hey Mike,

Good points. We had originally thought of cutting that area out as well, but ruled it out when we cut our cowl in half and put it back together because we didn't want to loose any rigidity. We went up slightly on rear spinner size also because, IMO, the difference between the side of the cowl and spinner backplate was much more than it should have been. The difference between front and rear spinner is not noticeable and the rear now looks much more in proportion to the real one. Still... we may revisit this as now you have my brain gears turning again. I'm anxious to see what the telemetry numbers end up being on the engine temps. I really don't want to cut those big ungodly holes in the bottom of the cowl for air exit. I may play with your ideas when I go back over to work on it again tomorrow.


Sonny,

Glad to hear your ran your engines. Do you think you will be able to get the idle on the front engine consistent? I'd hate to see you have a flame out and then have to go around on one engine due to a missed approach, etc.


Joe,

Any news on your maiden? Did you get a break in the weather and a chance to try it out? My fingers are crossed for ya!


Adam
aka Herc Pilot

jet22b

Adam;
Just came in from running the both engine and got to check both RPM. On the 11/7 APC props, on full throttle, both ran at 10,900 and on the low in, they came in at 2100 rpm. Any thing lower than that, the front engine will stop. I think that is from the tank is below the high speed needle and the muffler has not enough pressure to keep the fuel moving. As far as the back engine cooling, for you with the cooling vents you have as per the full scale plane. Also I found out today that if you could have a way to take some of the front prop wash, that would be a big help in cooling the back engine. I also look at the area that Mike is talking about and will wait and see if the engine need it. One thing I did do today was to run a full tank in the front tank and watch the engine pull every drop of fuel out of the tank.
I can not wait till Joe maiden his plane and give us a flight report. For me the weather person is calling for snow this weekend!![>:] Oh well, count down to spring!!!
Sonny
aka
jet22b

rcflunky

Sorry guys I didn't get to maiden her, It rained and now its windy and cold so I may have to wait another week. I had my club expert look at the plane and cg and he thinks it's pretty close so he said we should be able to fly it and see. If it needs weight on the nose he suggested a brass prop nut and the spinner is big enough to cover it. It wouldn't hurt my feelings if one of you guys maiden first ha ha. Well the weather might be good next weekend so I will give it another go if that happens.

Joe
aka
rcflunky

jet22b

Joe,
Just take your time!! Today would be a very good day for. The sun is out, the sky is blue, But, the temp is only 5 degs F!!! My hands would not get by the engine start stage. One thing when you get old, you can not take the cold like you could when you was young!!!
Like I said, please take your time on the maiden flight report!!
Sonny
aka
jet22b

Thomas B

My Feedback: (4)

I don't know...without wheel pants, it looks exactly like like a 337 flying around gear down with slightly funny looking gear legs, more so than it does a 336 with no wheel pants.... There are better ways to make the distinction.

If you look past the superfical difference in the landing gear, there are some airframe differences between the 336 and the 337. The most noticable is the fact that the 336 vertical tails have a much different shape below the tail boom (also noticably larger in that particular area) when compared to the 337. Also, the 337 has noticably different shapes to the front engine cowl and rear engine airscoop above and behind the wing. As I recall, the 337 has different versions of the O360 with more horsepower than the 336. That might explain some of the cowling difference.

The Seagull model is definitely a Cessna 337 based on the cowls and the vertical tails....just without retracts.

I would love to get one of these and build up a nice detailed O-2 version, with lots of interesting ordinance under the wings...

optech

My Feedback: (9)

Herc,

I didn't think of it til you mentioned the need for reinforcement but if that is a concern in that area you could layer several narrow strips of heavy weight fiberglass inside the cowl to build up a "lip". That would definitely stiffen up the area and with a little sanding and paint would look perfect.

Anybody,
I did a little searching but could not find anything definitive, but did the Marine Corps have/fly O-2s?

Mike

Thomas B

My Feedback: (4)

I don't think so..the Marines operated O-1s and OV-10s, but I think they missed out on the O-2.

jet22b

Thomas B;
Thank you for your input and welcome to the thread!! I think you will love this bird. We have talk about the problem we found with this ARF and the way we went about to fix them. I would love to see your O-2 version and what you put under the wings!!!
Sonny
aka
jet22b