rossmick

alanc

No problem, and by the way I am looking at all the builders of B-25s so thanks for the address. Building techniques are very interesting to me and sometimes you see one that makes you go " why didn't I think of that". One of the reasons I like Sam's work is that his and my shop are almost exactly the same, I guess it is from our woodworking background but it sure is handy and helpful to have the equipment. One of the more fascinating things about this RC hobby is that there is something new to learn everyday, I really enjoy that.

alanc

rossmock, only just seen your PM, here is the link
http://www.largemodelassociation.com...php?f=9&t=1149

rossmick

alanc

Thanks, just read through the entire build and got some great ideas.

acdii

I just ordered a set of Z 101 plans. ANy thoughts one what power plants to use? It says 38cc Gas, so wondering if I should go with a pair of DLE35 RA @ 4.1HP or a pair of DLE 40 Twins @ 4.8HP. . How much power would be safe for it without an obtrusive cylinder head sticking out?

samparfitt

My Feedback: (43)

Acdii,
I'm guessing there's not that much difference in head size between the two engines. I like to go big on engines to get more scale props (3 blade) but you gotta' go with your tastes: more prop or less engine sticking out the cowl. Also, for me, if the plane ends up heavier, I've got the power to fly it. The G-38's to DLE-40's should fly the 101" with no problems.
For overkill, for the 118" I've got two DA-50's turning 3-blade 20X(variable pitch props).

acdii

I haven't been able to find the power output ratings on the G-38. Knowing that can help me decide. If I have to have a big head sticking out, then a single cylinder sticking out the bottom would be the way to go. Not much in the way between 35 and 50CC out there that I can see.

samparfitt

My Feedback: (43)

g-38 specs:
http://www.chiefaircraft.com/radio-c.../zen-ep38.html

• Type: 2-stroke Airplane
• Displacement: 2.32 cu. in. (38.00 cc)
• Bore: 1.50 in (38.0mm)
• Stroke: 1.30 in (33.0mm)
• Cylinders: Single
• Total Weight: 57 oz (1.6kg)
• Engine (Only) Weight: 49.3oz (1.4 kg)
• Muffler Weight: 4.0oz (117g)
• Crankshaft Threads: M8 x 1.25
• Benchmark Prop: 18 x 10 APC @ 7,300
• Prop Range: 16 x 8 - 18 x 10
• RPM Range: 2,100 - 9,500
• Fuel: 32:1 Gas/Oil Mix
• HP: 2.6 at 7200
• Cylinder Type: Ringed Nikasil Plated

acdii

Hmmm, only 2.6 HP. The DLE 35RA is 4.1 HP @ 8500 RPM. Swings a bigger prop too. Looks like a pair of those would fly it nicely!

When I did a search for the Zenoah, that site didn't come up. Thanks for the link, this helps a ;lot for this one and the P-61.

acdii

I am just now reviewing your thread on the Ziroli P-61, which I have a full kit on order and ordered the plans for today as well. Thinking of either the DLE 61 or the new Evolution EFI 61. Fitting power plants 61's for the 61.

rossmick

Here are some images of the glue up stage of the center wing. I am using Aeropoxy as I spent some time collecting data on the strength of various glues and decided on its use for this center section. As per Sam's suggestion I am gluing up the center wing components with epoxy (Aeropoxy) but will use Titebond III to attach the skin when I get to it. I see little use for the epoxy on the skin as the Titebond absorbs deeper in balsa and, is the case with most wood glues, the glue joint is stronger than the wood. However, I would use epoxy if I had a plywood to plywood connection.

I have found that I can reuse the Aeropoxy nozzles by blowing the epoxy out on to wax paper with my air compressor and then cleaning them with Acetone and then blowing them dry with the compressor. I try and leave a small area to glue with the left over material on the wax paper. Although more expensive, I find Aeropoxy to be easier to use such as by using your finger to create a nice corner fillet and it does not gum up your hand like regular epoxy does. Additionally, it is best to wait until the end of the day and then do all your gluing at once as the setup time is recommended to be 24 hours. I find the glue is hard to the touch in about three hours but I leave it over night to be sure I have a good bond.

I used a square to position the ribs, but also measured from the center line of W1 out each side to make sure I was an equal distance for each rib. Yes there was a difference and sometime more than I would have thought. I believe that the wing is square and true. My supplies from PCM came up missing the triangle pieces so it was a 50 mile round trip to get them from the hobby shop. However, it was a good excuse to pickup many of the additional hardware items I needed for the wing. I also used a spruce spare for the bottom slot just in front of the triangle, this wing should be very strong.

I also used Sam's recommendation on extending the cardboard tube through W4, I had the tube length so I just drilled and sanded out an additional hole. Also the plywood leading edge looked like a great idea so I replaced the balsa ones with plywood. The PCM kit came with a 1/4" W1 but I had some 1/2" stock so I used it and recut W1, again something I noticed on Sam's build.

When I first saw the plan I wonder about the thickness of the N1 and N1s stock so when Sam said he was going with 1/2" I thought it sounded much better. On N1 and N1s I intend to drill through, and besides gluing them to the box, I will have two bolts and nylock nuts per piece. You might be able to make out the lines on the pieces where the bolts will go through to the box, small cutouts will be cut in the outside curve to allow the bolt and washer to set flat. I believe that this will kill any chance of vibration shaking these parts loose.

I bought 24 ounce fuel tanks, but if someone suggests a larger tank I will use that suggestion, never have used DA 50s I just guessed on the size based on the fuel used by my smaller gas engines. I also picked up the mid size Hi Tech 81 servos for the throttles and the chokes and will get them mounted before I skin.

I finally found the small cardboard tubes and they are rocket body tubes, I checked prices and the hobby shop was less expensive than ordering them due to shipping. The 1/2" size is D5 and the only small problem is that they are only 18" long so for long runs they will have to be spliced together.

samparfitt

My Feedback: (43)

Looking good Ross.
I agree with you on the PVA polyvinyl acetate (carpenters glue), I don't think most people realize how strong this glue is when properly used ie, using two porous materials.

acdii

I've been using Titebond on several of my builds and it seems to make a really strong joint. The Aeropoxy you refer to, is that the stuff that uses a gun and nozzles? I think its from BJM. I have a few of those laying around and since it takes so long to setup I have not really used it for anything. Since I have two long term builds over the next few years, looks like I have a use for the stuff finally.

Edit. I have a question on downsizing. I ordered the 1/7th scale plans, and wonder how much would I need to reduce them to fit .91 Fourstrokes? I will still build the 1/7th, but would also like a somewhat smaller one too.

alanc

sadly, there is just no way to not have a head sticking out, but if it helps, you dont notice them, the 38zenoahs, from my observations of our test flights, are more than enough, but i do like the look of the new dle 35, sim to the 38, rear muffler, and a slanted plug, made for cowl use, the zenoah 38s where swinging 18x10 carbon probs, with gusto, i also made 2 stainless steel, prop nuts, looking like rotol centres, to help the balance, the small one, 1/7th, i have seen fly very well with 2x zenoah 23cc, they just do NOT need the power of 2 50cc motors, i really cant see the point,

rossmick

acdii

Yes Aeropoxy is from BVM but is really just a repackage of Loctite Hysol 9462. I am sure you can find it somewhere else rather that the hobby shop but there only seems to be a few dollars difference and it is not a glue that you use everyday. The other nice thing is that Aeropoxy stays where you put it, this comes in really handy on all vertical joints. Additionally, when slots have to be widened the Aeropoxy will fill in the gap and not run out (gap within reason of course). I really like the long mixing nozzles as you can reach right in and put the glue where you want it, and by reusing them it keeps the costs more reasonable. I understand every ones desire to have short setup times but I find it very handy to have a longer time to adjust things if required. The gun is really pricey, but I believe Sam has made his own from dowels and a block of wood, I wish I would have thought of that. I also keep my glue cartages in the freezer and then take them out and warm them up before use. I have had them stored for months and months and all seems fine, however, I am sure there is some shelf life expiration. I know Hysol is used in full size aircraft construction which I think it keeps the price right up there. Great product, and I notice that many of the larger ARF planes and turbines are now using it on all their internal plywood structures.

Sam

Thanks for the comment. I am sure learning that the plans are sort of a recommendation and not a true depiction of where things should actually go which makes cutting parts in advance problematic as they have to be recut or the slots constantly modified to fit. Once you understand this and do all the required measurements first all goes pretty well. Example, I found if you used the main spare precut pieces as a guide one nacelle would have be farther out from the center line that the other, not good. Now to figure out the main gear and gear door arrangement, at this point I think I will use the same idea that I did on the nose gear and connect the solid mounts to the box sides, we shall see. I will layout the scale location for the doors and see if all will clear the gear when it moves in and out and cut the formers to fit. It appears the nacelles on the plans are not really scale so I am looking in to that as well. Thanks for all the leadership on this project.

rossmick

Alanc

Just for some additional information, DA is about to release a 35cc engine. I have seen it in the shop and have watched Jeff from DA fly a Extra 300 with the engine installed, it runs great and is priced reasonably. I was on the waiting list of over 200 for the engine as I intended to use it on the 120" B-25 but decided it was not enough power, possibly a mistake, but really there is no such thing at too much power (just joking). I had a rather long discussion with Jeff on horse power ratings and he convinced me that it is not a reliable indicator of engine performance from manufacture to manufacture. When I told him I was looking at a 50 pound airplane he was hesitant as well that the 35 might not be enough power.

I also considered using my Brison 40cc as this engine is a very strong performer, but I could not find a second engine to match the one I had as it had electronic ignition and not the old mechanical system the engine use to have. I even tried to buy a new one, but the sole source for the engine really is not interested in producing any more. One reason I really wanted the Brison is that it fit inside the cowl, now it is just setting on the shelf looking for a plane. I had a transmitter fail and the Extra 300 that the Brison was in was destroyed. I had the engine rebuilt and effectively it is a brand new engine, someday I will find the plane for it.

samparfitt

My Feedback: (43)

Ross,
Jeff's right about horsepower ratings. They are not the way to measure power for any motor (gas or electric): take my wood planer in the picture. That motor is 7" in diameter and a foot long yet rated at only 2 horsepower. If you relied strictly on horsepower, then you should be able to take that 5 hp hand drill and connect it up to the planer (and that 4 cylinder engine has more horsepower than my vette's V-8!). The old saying is still true: there's no replacement for displacement.
Most manufacturer's list in fine print that's 'peak' performance: which is for about a split second. And that's about as long as the engine will handle that power output before it's 'toast'.
Probably the easiest check is to take the average prop being used.

acdii

This is how I have been comparing engines lately. The bigger the prop it swings the more power it can put out. Any engine can have HP, but unless it has torque to go with it, it can't do very much. When comparing the Zenoah to the DLE I see the DLE swings a a much larger prop. I have been flying a DLE 20 for the past 2 years, and it has been a good runner. I also have a DA 100CC win, but have only about 20 minutes on it and no flights yet, but once it gets fuel to it, it runs like a champ and fires off on a couple flips.

OK this is what I thought you were using. I have several tubes and the gun packed away in a drawer, along with a few packs of mixing tubes. Good to know I can reuse them once the epoxy has been cleared out. I do pretty much this with my mixing cups, wash them out with Acetone once I am done with them.

rossmick

Sam
Nice planer, and even nicer board. What did you use the lumber for, it looks beautiful.

FireBee

My Feedback: (34)

Power choice 101 Ziroli,

I too have opted for the zenoah g-38 magneto's and will live with the heads exposed. I fit 16 oz tanks and the throttle servo inside the nacelle behind the firewall. Although my g-38 have never failed me, my concern was being able to make a single engine circuit should one fail. I have set it aside for 6 months as I finish a triplane.

my orig B-25 plan was to fully enclosed gas engines. I decided reliable, know engines was much lower risk!
I now have two r/c showcase RCS 140 (22cc) Gasoline Engines sitting in my shop. Key was they spun a 3 blade prop at very high Rpms to counter the smaller 22cc size but potential overall aircraft weight led me to swap. Fuel: 32:1 gas/oil mix. Ignition:Microprocessor auto advance 4.5 - 6.7 (MAX) volts. Rpm Range1200-9500 rpm ( 16x8-10, 17x8 props )
Said made by Moki, but also found ZDZ mentioned. See. TBM model s link for instruction sheets.

P.S. Sam,
I have many ideas saved and marked from your build thread as I pick up the assembly again later. Awesome info and ideas. Thanks for sharing!

rossmick

Here are a few shots of the outer wing panels being built with the connection to the center section and initial alignment. I extended the wing tube through W12 and added a ply doubler to give additional strength. In the fighter squadron we had a saying that went 'its better to be lucky than good' and when I put the outboard wings on the center section I was astonished as to how well they came together - better lucky than good. I had visions of wide gaps, however that is not how it came out. The connections fit pretty well, but wait - I have to align the wing.

I decided that the concrete floor here in Arizona was not a suitable level device no matter how you spun things around, and besides I get to use my self leveling rotating laser. The laser is calibrated to less than 1/16" at 50', so it should provide the accuracy I am looking for. As the work bench is movable, on casters, it was far easier to level the wing than the work surface. With that accomplished, I turned on the laser and had a perfect level datum plane to work from. As the plan shows a 1/4" negative dihedral, I can see that I will have some adjusting to do on the tube connections to bring the left wing up 3/4" and the right wing up 1". Also the right wing must be adjusted back 1/4" to align the main spar, left wing is right on the money. I could rotate the laser for that alignment as well but I think my 8' straight alum. channel will get the job done.

So I will do the adjustments and then cut and join all the required items to get a perfect fit of W8 to W9 at the center section, anyway that is the plan for tomorrow. This is a big wing and with the laser I can check all leading and trailing points from side to side at each rib to make sure I have no twist, warping or difference. This might seem like over kill but a straight and true wing sure makes for a much better flying machine on that first flight. My goal is to have little or no trim adjusting required on that first flight - yaw right, I know. I will recheck the wing once more after I get the top sheeting put on per Sam's suggestion, hopefully, I will have little adjusting to do.

alanc

All I can tell you is what I was told, in a twin, fit simple engines that are reliable, This sums the zenoah 38 up well, And, I have the benefit of seeing them fly the b25' it does NOT need full throttle, I do like the look of the new doe 35 motors, but if I was doing a twin, simple all day long wins for me

acdii

I got my pair of plans yesterday. Holy Sheeitie is that P-61 big! The B-25 is just a tad smaller at 101". Looks like I will need some new work benches. The laser is a great idea, now I have another use for mine other than collecting dust.

As far as the DLE engines go, mine has been very reliable. Not once has it ever cut out on me in a flight. It took a bit to adjust the carb, and once I have another gallon or two in it I should be able to fine tune it just a touch more, so I have no issues running a pair of DLE on one of these planes. Giving some real consideration for a pair of the 40CC twins for the P-61 and 35RA for the B-25. Or just go hog wild with a pair of 55RA for the P-61. The 20 is a gas sipper, 14 ounce tank gives me 30 minutes or more(fly 25 minutes and still had 3/8 tank left) in my 4*120.

The B-25 didn't have a material list that I can see, but I haven't looked at all the plans, so don't know if it is on one of the sheets or not. What amount of stock would I need for this one? I see 1/8th aircraft plywood on the first sheet, is that used a lot on the build? For those who cut their own, what was the most economical size you found for this?

samparfitt

My Feedback: (43)

Looking good, Ross.

========
Priming:
While I was priming the 110" P-47, I had significant leftover primer so I got the B-25 ready. The primer is a 2-part so, once mixed, there is no shelf life and it has to be used. The primer comes from the local auto paint store. All painting is done outdoors. Parts got two coats, the second coat perpendicular to the first. I'm partial to the 4 oz size paint gun purchased from harbor freight for about 14 bucks.
The bottoms are done first and by the time I come around for the tops, the primer is sufficiently dry for doing the tops.
Using lots of water, the primer will be wet sanded using 220 grit paper.

acdii

Metal cup with the plastic lid? Mine has a plastic cup with screw on lid, which leaks like crazy unless you screw it down really tight, then have a heck of a time getting it off is any paint dries. I will revisit HF and see if they have the metal cup one, all they had was plastic, which is what I have now that I got from them.

samparfitt

My Feedback: (43)

acdii,
The 4 oz cup is metal with a push on metal lid. The larger ones are usually plastic to save on weight (also cheaper to make) and the screw on to keep the large volume of paint contained in the cup.