n3cal

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Just finsished building the Rich Uravich 52" OV-10 Bronco. I've installed Saito 40 engines and would like to know what a good 3-Bladed prop size would be? Both engines were brand new and have been run on a test stand for approx 100 min (1/2 gallon) each. I have a pair of 10 X 6 3-bladed props which give about 9000 RPM full throttle. Is this a good starting point? I'll be flying off a grass strip.

Cal

rryman

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Wow! Nice looking plane. I have one coming. Hope it turns out that nice. Sounds like the props you have would be a good starting point. I usually do the judging by how much accelerating ability they have. I'm running 10x6 3 blades on a TF DC-3 and they work fine. It's at about 11 1/2#. I tried 9 x 5 three blades on a Transall I have and it wouldn't even taxi in grass with them.
Do you have any tips for building the model? What did you think of the kit overall? I'm considering retracts, but only if I can fit in a set of Robarts I currently have. I've seen on here where some builders extended the wing by another rib to reduce the wing loading. Did you do that?
Good Luck,
Randy

n3cal

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Thanks for the reply. This kit was very difficult for me to build alone. It's only my second kit (first kit was a GP Profile-38 Twin). As much as I wanted to extend the wing (it would have been easy) I left it at 52". It just fits in the bed of my Ranger pickup that way. The plans and instructions were very vague and were not much help for me. Thank goodness I had a friend who had the ARF version. I used his ARF quite a bit to compare and get through the tough spots. I was going to put a pair of Spring Air Retracts on it but after seeing how little room I had in the booms and the fact I'm flying off a grass strip I opted to keep it simple with the fixed gear. I'm using two HS-81 micro servos for the throttles and using my helicopter radio with a 5 point throttle curve to sync the engines. I also opted to use two elevator servos (one each boom). I'm waiting for some warm weather to test fly. Will report back as soon as I can. Good luck with yours....

Cal

rryman

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Let me tell you Cal, if this plane is only your second kit, you did a helluva job on it. I just got mine this week and to say that the plans and written instructions are "very vague" is an understatement. If you got this one together, you will not have any problems with any other one that I can think of. I'm getting it together,but sure could have used a top view of some things. But, on the bright side, those laser cut parts are the real McCoy. Already made a couple screw ups, but nothing that can't be fixed. As I once had an architect tell me on a job we were remodelling, "beat to fit and paint to match."
I think I am going to extend the wing a few bays anyway. Certainly no one in our club will know the difference. I think it's going to be real tight trying to put robart 605 retracts in this one so may stay with fixed gear. Haven't really made that decision yet though. I hesitate to complain too much about plans and instructions, as that's usually a sign that you're in over your head!
Randy

rryman

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Well, got the wing framed up tonight. I extended it by two rib bays on each side. That may be a blessing, because I just noticed today that this kit does not show the sponsons on the fuselage, and I want to add those. A friend of mine who worked on the full size Broncos in 1970 send me some pictures with great detail on them. I plan on finishing mine as a FAC plane of the 23rd TASS, which operated out of NKP Thailand. Pretty much all grey. If I use my retracts, I can't see any way that the nose gear can retract forward like the real bird did.
Since they are calling for 25mph+ wind tomorrow here I guess I'll be spending the afternoon in the building shop.
Randy

Build-n-flyer-RCU

My Feedback: (4)

Beautiful plane!

Hope you have better luck with 3-bladed props than I did with my Twin-air. Tried 10x6 Zingers on my OS 46FX motors and the power loss was incredible.

Walt

rryman

My Feedback: (2)

Same thing here Walt on the 3 blade props. Only one I have with 3 blades is my TF DC-3/AC-47. I'm running 10 x 6 Zingalis on it and it flies fine. I think it's only because it is overpowered with 40's so the reduction on thrust on it made it come out about right. Tried 2 blades on my Transall and it wouldn't even taxi with them in grass. Probably would have been OK on pavement, but had to go to 2 blade 9 x 6.
Here's the status of my Bronco since receiving it Thursday. Most of the rough framing done-now for details and putting in the guts. All in all, nice kit-could have used a few more views and explanations, but overall I'm very satisfied so far. I added two rib bays to the wing on each side. Wingspan is now 63", but I don't think it looks bad. Probably till I get done I will have needed the extra wing area!
Randy

rryman

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Cal, I've got a question. When you detach the booms from the wing, how do you keep from breaking the stab. This think seems like it would become real fragile when detached. I'm thinkin you might have to build a brace to put between the pods to stabilize them for transit.
Randy

jmupilot

Geeze Randy why dont you stop and take a breath. Ya just got that kit last week it aint gotta fly this month.

Actually great job you build faster thanI do. Cant wait to see that at the club field. Let me know if you need some company if ya try the C-130 this weekend.

Pete

n3cal

My Feedback: (2)

Randy,

I haven't had any time to build a brace yet. My receiver is mounted to the wing so I keep the wing and booms together and just remove the nose pod. Its pretty easy to transport that way and I dont have to mess with all the servo connections in the booms. I did reinforce the elevator/boom with triangle stock above and below. I just hope thats enough reinforcement. I can't wait to test fly mine! The weather is just about right, I just wish the winds would die down a bit!

Cal

rryman

My Feedback: (2)

No kidding on the wind, Cal. I'm hoping to get a test flight on the C-130 tomorrow afternoon, weather permitting.
I added triangle to the sides of the vertical stabs on my Bronco also. Just didn't look strong enough to me. Plan on doing the same with the horiz. stab. I may just do the same thing and keep the booms on the wing and hang it on a wall in the trailer. I'm adding the sponsons to mine. Got some great pics of the real ones a friend sent me of the ones he worked on in Thailand. Shows good detail. May even put on the centerline tank later.
Read the article on the ARF version tonight in Fly RC magazine. That one came out aat 8.5#. I think the weight listed on the box was a little optomistic. I tend to build a little heavier anyway, that's why I increased the wing size to accomodate.
Randy

Walfam

My Feedback: (1)

Gentlemen,

I also have the 52" version, been working on it slowly for about 8 monts time permitting. First, i saw someone take a sq piece of wood with the monting hole to the booms matched up to use as a carrier. I looked like it
worked great. Second, I agree the instructions wee vague, in fact i sent email to the designer with questions on the boom tail set up. it looked very weak to me. So what I did was run a center 1/4 sq down the bottom of
the booms to use as a foundation for the boom with triangle stock along the sides. It is slightly fatter at the back but I know it will be strong enough. Third, just finishing the wing sanding and preping, so dont have to much farther to go.

Questions. 1. did u use two wing servos or go with the setup that was used by the designer?
2. What servos did you use on the rudders?
3. Did you do anything different on the elevator layout?

I have two 36 magnums for this plane as everyone I talked with said it they would be more than sufficient,

rryman

My Feedback: (2)

I'll try to answer your questions based on what I've done so far. I would also like to hear from someone who has finished theirs with retracts, as to what their finished weight is.

............So what I did was run a center 1/4 sq down the bottom of the booms to use as a foundation for the boom with triangle stock along the sides. It is slightly fatter at the back but I know it will be strong enough.
====I didn't find a problem with the booms so much as I thought the method of attaching the vert. stabs somewhat different than I like. I added triangel to both sides of it from the front of the dorsal back to the end of the booms and contoured them in.
1. did u use two wing servos or go with the setup that was used by the designer?
=========Since I can program in separate aileron servos to operate on ch. 1 & 6, I always use two aileron servos. Especially since I can also use them as flaperons for landing. Two aileron servos just are much easier to install than one for both ailerons. And, till you get done adding what it takes to use only one servo, you end up with about the same weight.

2. What servos did you use on the rudders?
=======Might hear from someone on this, but I'm using Hitech HS 81 servos on the rudders. One servo for each rudder. Also using HS-81MG on the ailerons. Using metal gears on those just for a little extra measure. Probably going to use a HS-225 on the elevator, or a futaba 3003. Also using HS-81's on each engine, as well as the nose wheel steering. I like the 81's because they are powerful little suckers for their size and weight, and very affordable. I am satisfied using those based on the relatively small size of the control surfaces on this plane, plus the fact that I don't plan on doing any violent manuevers with it. The only other thing I did that didn't show on the prints was to add some carbon fiber strands from boom to boom under the wing for some added strength.
I would also appreciate any tips anyone has that has completed and flown one of these. I read the article on the ARF version and it sounds good. As the previous posts state, I have increased the wing size to accomodate for the added weight of the retracts. (plus my tendency to build a little on the "heavy" side.

3. Did you do anything different on the elevator layout?
======I haven't got to the point of attaching the elevator permanently to the booms yet, but when I do I will probably add triangle to at least the bottom of each side to the vert. stab just to make it more rigid.

I'm really looking forward to getting this one finished. Looks like it will be a good flying plane. Should look good with retracts.

Randy

rryman

My Feedback: (2)

Cal, did you find that putting the servos in each boom got a little cramped? I've got three to put in the right boom, (throttle, rudder, elevator) and it sure looks like it will be just a tad cramped. Maybe I'm just used to working on bigger planes! The C-130 spoiled me, being able to get down in the fuse with both arms!
If I can get the rest of the servos in the booms, I'll be ready to start on finishing. The retracts went in pretty well. going to have to use quick couplers on each boom and the fuse pod.
Did you require any weight to balance? Looks to me that it's going to come out tail heavy.
Randy

MormonMike

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You guys are a wealth of information !! Stay at it please. This will be my sixth twiner kit.

n3cal

My Feedback: (2)

Randy,

Yes the booms are very cramped. I have a set of Spring Air Retracts and ended up not using them for that reason. It seemed like a impossible task for me so I took the easy way out and used the fixed gear. I've got two Futaba 9202 servos's for the elevator and standard 3003's for the rudder. I mounted micros servos just behind the fuel tanks for throttle.

As far as balance went. Mine was tail heavy but needed no weight with a 1800 mah nicad mounted all the way forward in the nose.

I'm hoping to maiden tomorrow (Friday) if winds are below 10 MPH....

Cal

rryman

My Feedback: (2)

Thanks for the reply Cal. Let us know if you get in a test flight tomorrow. I am just about ready to start laying the fiberglass to the fuselage pod and booms, except I need to glue in the elevator yet, and make a brace to hold the booms together. Might work on that tomorrow. I managed to get the Robart retracts in, but it was a time consuming process. I'm not familiar with Spring-Air retracts. Does the nose gear retract forward like the real one of does it go back. I looked at mine, but there is no way the Robarts would go forward, so it will be going back. I just need to be sure to balance this one with the gear "up" instead of down, since all three are retracting rearward. Read a horror story years ago about a guy that spent all this time building a giant scale Corsair, (back when giant scale was in it's infancy) and balanced it with the gear down. On the maiden flight, when he retracted the gear, the c/g also went rearward, and the plane was lost seconds after the gear retracted. Bummer!
I have the retract valve in the fuse pod. I ordered the cockpit kit for mine and made the whole thing removeable. guess I'll use small button head screws for attaching the canopy. Haven't got that far yet. But, it does give you a whole lots more space in the fuse to work with. I have a platform in the nose that ended up there from the nose gear retract, and I think I'll mount the battery there.
When I get all the pieces together again I'll post another pic.
Good luck tomorrow,
Randy

MormonMike

My Feedback: (2)

RRYMAN, Can you explain a little further please were your laying the fiberglass. Also, were abouts can i find a centerline tank ? . Have you guys considered modifying the gear to trail castor-like as on the real birds? Also , the triangle stock, I can't see much room in the verticals to really put any. My kit to arrive in a few days and Im staying close to this thread. Thanks for all the info. MJS[8D] [ some things are best to keep quiet about, even after 31 years]

rryman

My Feedback: (2)

I'l be doing the booms, stabs and fuselage pod in fiberglass just to avoid using iron on, which I am not good at.
I will be making my own centerline tank out of a balsa block. Going to wait until after flight trials for that though.
I did bend my own gear legs with the trailing arm, knee action or whatever you call it. Anyway, it looks pretty good.
I didn't put the triangle "in" the vertical stab, but rather sandwiched the stab and dorsal with triangle where they meet the fuselage. It looked a bit flimsy to me at that point. I'm not terribly concerned about weight at this point since I added more wing per the recommendation of someone else on RCU. I went out two extra rib bays on each side. Should keep the wing loading down. I've kept a picture diary going of mine in case you have anymore questions about something.
Randy

rryman

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Finally got the horizontal stab permanently glued into place tonight. I also added some triangle on the underside for reinforcement, as shown in the pic. Also shown is the boom support I made so I could handle them with the wing off and hopefully not break the horizontal stab apart. Going to be tricky to work with this, but the support also makes a conenient handle.Hopefully will get on with the glassing tomorrow.
Randy

n3cal

My Feedback: (2)

Randy,

The Spring Air Retracts also close rearward.


MJS,

I was able to use triangle stock (not quite a large as Randys) both on top and below the elevator.


ALL,

Didn't get the maiden flight in yesterday [] The winds are still being a pain in the butt here in Maryland.
I did go to the field and was going to do some taxi tests however I had a left engine problem where it would run for about a minute and then quit. I gave up and came home. Inspection of the engine and fuel tank revealed a crack along the seam of the fuel tank[] Looks like poor quality plastic. I'll try and get another tank from my LHS today.
I'm lucky I found it before flight. Hate to loose an engine on the maiden however I've done allot of one engine out practicing on Real Flight G2 with the P-38. I've got the procedures burned into memory if something does happen.

Cal

rryman

My Feedback: (2)

Cal,
I've got a couple questions for you.
1. What did you use for the elevator control cable?
2. Did you install it per the plans, which I interpretted as "pushing the elevator up"?

I figured the only way to get that installed was to use Sullivan flexible cable, like their throttle cable, which I use routinely on throttle servo hook ups. I guess I may be over-cautious, but after a lot of studying on it, I couldn't bring myself to use that cable to "Push" the elevator up, so I brought mine through the top of the horiz. stab and will attach to a small Robart control horn so that it will be "Pulling" the elevator up instead of "pushing". I know most airplanes push the elevator up, but also use a pretty solid hook up to do it. Something about this one kept nagging me. Anyway, too late now for me to change it.Besides, it will all be painted flat Gray, and won't be that noticeable.
Randy

n3cal

My Feedback: (2)

Randy,

I used the Sullivan Flex Pushrod w/Gold-N-Clevis 48" in both booms. They are per the plans and come out below the elevator. They push up and pull down. Because of the s bend through the vertical fin I opted for Futaba 9202 servos which give a little more torque than the standard ones. I also didn't feel using just one would be enough so I put one in each boom.

Cal

MormonMike

My Feedback: (2)

Randy, When you say "fiberglass", you mean your just "painting" the resin mix on to the bare balsa to harden the wood ? [ without the fiberglass cloth] Then you sand, prime and airbrush it with color. This plane does not look the easiest to ultracote with all the curves. Has anyone considered going electric for powerplants on this? I've already built an electic duellist and it promises to be quite a performer. Im at 4500 feet altitude here in Logan Ut. and cannot decide whether Saito 30s are too little or 40s are too much or go with 45-3 brushless [ or smaller]. Appreciate you taking the time to address my little problems. Thanks, Michael PS, Can you show me a photo of the elevator flex pushrod installation when its done. thanks!

rryman

My Feedback: (2)

Randy, When you say "fiberglass", you mean your just "painting" the resin mix on to the bare balsa to harden the wood ?
============
I use 3/4oz. glass cloth and lay it on the wood and then adhere it with Minwax "Polycrylic" water based polyurethane. then about two more coats on it will completely fill the weave. Then some light sanding and it's ready for the paint process. I used this method for the first time on my C-130 and liked the way it worked. The reason I used this on this plane is that I'm not the greatest at covering with iron ons, and two, you can completely assemble the plane, with control surfaces, etc. and the paint it. Different strokes for different folks, I guess.
This is the best stuff I've found to work with. No smell, dries quickly, sands easily. I fiberglassed a Sig Komet years ago, using fiberglass cloth and resin, and it was a real mess. I guess you could probably expect that on the first time. It did turn out beautiful, but the smell and resin was tough to deal with. I build in my basement and I get no complaints from the other half when using the Minwax stuff.
Randy