abufletcher

OK. With some careful cutting and filing, I've got most of the problems with installing the RCV91cd licked. First step was to move all the square holes in F1 and F2 "down" (i.e. towards the left side) 3.6mm (or thereabouts) to compensate for the RCV's shaft position. I did this with a small chisel and file. I also removed 3.6mm of material from the top edge of the ply brackets so that the top of the beams would be flush with the brackets again.

Next step was to epoxy the beams to the ply brackets, making sure everything was straight and square. After those were ready I epoxied in the lower beam/bracket making sure it was square in both directions with the help of two metal triangles. Then I did the same with the top beam/bracket.

When everything had cured, I put the engine on the beams, measured the distance to the front of the thrust washer, and the marked the mounting holes with my trusty special tool (from GreatPlanes?) Then I driilled the holes for the 4m bolts.

Once the engine was bolted in place I checked F1 for fit from the front. A slot needed to be cut to allow for the crankcase breather nipple and the curve on the bottom had to be opened up a bit to avoid hitting the crankcase edge. As I was test fitting F1, I was concerned with whether I would be able to pull the engine out once F1 was glued in place. But I'm happy to report that after a little Chinese puzzle thinking, it is possible to remove it without breaking the plane of the top of F2. So, I took the engine off, and epoxied in F1 again checking that all the angles were square as the epoxy was curing.

Then the only thing left to do was slip the engine back in to check the fit once more. No problems. There are still a couple details Chris and I need to work out on the side panel that will go around the engine head. Namely, we need to make that removeable so that it's possible to get at and removed the engine from the finsihed model in the event that repair or replacement is needed. I'd feel uncomfortable building it permanently inside of the nose structure. We'll also have to think about exhaust options and the placement of the needle valve and throttle arm.

But things are looking good. And this represents the first official pieces glued together.

On the other hand, I may have to send the RCV back to the manufacturer.

udet1918

Abu,
I will enjoy watching this one come together! A 1/4 scale CIII is in my future. It will be interesting to see how you overcome any hurdles that may arise!
Best of luck, Ron

abufletcher

Mein Duff

Noticed you haven't built any side or down thrust on your engine compartment? Is this something you don't do as a rule with biplanes, I have always built in at least 1.5 degress of side as a precaution and never regretted it but may not be necessary. Or do you compensate somehow after test flying?

abufletcher

Chris' designs follow Dave Platt's practice of not using engine thrust (either down or right) on scale models. There seem to be two schools of thought on this. One camp always includes at least a degree or two of right thrust. Down thrust seems a bit less common. The other school claims that engine thrust is mostly a hold-over from freeflight days and that it's not really needed with RC flight. Additionally some would argue that side or right thrust only have an effect when the model is accelerating. Builders like Dave Platt are concerned with the impact on the scale accuracy of the model. I'm no physicist or aerodynamics engineer so I'm just following Chris' design. I guess we'll see.

That having been said, it would be very easy on the CI to add either down or right thrust (or both) simply by angling F2 (the firewall) when gluing it to the other fuse parts. And in the CI's case including thrust wouldn't mess up the engine positon relative to the cowl which can be more of a problem with round cowl aircraft.

I'd be happy to hear other people's idea on the thrust/no thrust debate.

Mein Duff

Since I have always built both side and, sometimes down thrust , in all my modells (not always biplanes) I have nothing to compare it to.
Even with side thrust the pull to left on takeoffs is still noticable especially with 4 strokes it seems...it is a problem on scale round cowls and would be nice to dispense with. A friend recently finished his 1/4 scale Hanriot without any side or down and is basically pleased without it.

abufletcher

Just got off the phone with the extremely helpful RCV tech guy in the UK and he says the engine should be fine, that the sound is ok. He added that if there are further problems just ship it directly to them and they'll repair it and have it back to me in a week or so. So that's very good news.

So I guess I'll get it back on the test stand and then maybe put it in a test-bed model of some sort to get some flying time on it. So anyone know of a cheap 90-size ARF?

Mode One

Hanger 9 .60 sized Ultra Stick.

TFF

If using a computer radio,  all the re-trimming a full scale pilot would do can be popped into the radio, leaving the incidences scale for proper looks.  If you want to skip the radio part, it would be smart to add the down right thrust. for ease of flight.

Prop Nut

My Feedback: (3)

Hey Don, you are much to busy these days to waste your time with such trivial matters as engine run-in time. Sooo...I am willing to help you out, send that motor on over to me and I will put it on one of my planes and fly it this summer for you! What a deal! I know, I am too nice of a guy, what can I say? :P

Mein Duff

Found this comment on the giant scale photo threads:

Nieuport 17
Description:	First flight nothing out of wack, typical bipe pulls to left and needs down trim.

abufletcher

A couple of hours to identify and label, cut out, and lay out the parts for the lower wings. This helps a lot in figuring out how it all goes together. A small chisel was just the thing for cutting the tabs to release the ply parts. A few taps and they're free! I'd like to add that Chris and I spent a lot of time making sure the spars were in the scale locations. The Cross and Cockade special issue on the Albatros aircraft was very helpful in this.

In the photos you can see the tabs on the ends of the ribs. This is part of a, for me, new construction method that Chris is using, where the wing is built "up in the air" so to speak. Chris builds on a plate of glass and I think I might give that a shot if I can find someplace that sells a large sheet of safety glass at a reasonable price. But Chris says it can be built this way on a traditional building board as well. I've been sticking pins since I was 10, but maybe it's time to try something neew. Not shown are the balsa "jacks" that are placed under the spars during the construction. They are included as CNC cut parts.

abufletcher

I'm sort of amazed at myself that with my minimal Japanese skills I was able to find a local supplier for glass sheet. A sheet of 5mm by 1m x 2m glass (the size of my building table) would cost about $120 and the 6mm glass would go up to $150. That's more than I was hoping to spend and I'm wondering if I could get away with a smaller panel just a bit bigger than a single wing panel. I don't think I'll be converting completely to "glass building" anyway, so a smaller piece would be more convenient to remove and store.

udet1918

Abu,
Ask that supplier if they have scraps leftover from jobs that may have small blemishes or incorrect cuts. They may not be the exact size you're looking for but they are usually more than willing to get rid of them for a "song".
Ron

abufletcher

Ron, that's a good suggestion. Now if I can only think of how to communicate that in Japanese!

abufletcher

Slowly I'm making progress towards actually starting to build! Here are the parts laid out for the top wing.

The wing LE's are made from 3mm carbon rod and the TE is a lamination of thin ply and 2mm balsa. As on the Snipe the balsa gets mostly sanded away (in a wedge shape) so the result is a strong and very sharp (and therefore scale) TE. One challenge modeling these early aircraft, however, is that the wings were almost transparent and any non-scale structure shows through, particularly in flight. The original aircraft used a wire TE and I've thought seriously about trying to do this. But I think at this scale and on this kit, that's maybe pushing too hard. At present the kit's TE's are a typical width for flying models and probably a prudent choice for a kit. But as my first mod, I'm thinking of cutting them down between the rib positions (and leaving it full width at the ribs). This will give a more scale effect in the air but still allow me to build the wing as per the kit.

Trev

Hi Abu, just dropped by for a quick hello. That looks like an absolutely stunning kit! a very desirable project you've got your hands on there! I'll be keeping a keen eye out for this thread, the CI seems like such an elegant subject and with all that wing area it should be a floater even fully 'scaled out'. I know this can probably change with a prototype, but what's the assumed weight of the finished airframe?
Out of curiosity, what are the TE tabs for on some of the ribs? My guess is to allow for better alignment or building accuracy but I can't see how.

Can't wait to see the build really taking off!

abufletcher

Great to see you around again! Hope you get that nasty Ph.D. business wrapped up soon and can get back to what's really important!


This style of wing construction will be new for me. The idea is that the spars are "jacked up" and this allows the easy building of an undercambered wing with washout.

Trev

Looking back a few posts I see that you'd already addressed my question, apologies! Seems like a clever solution alright, do the spar jacks also align the ribs or does their position have to be marked out on the spar first?
How is the CI wing geometry, does the washout occur at the aileron or is it more complex ? Without having seen how it works yet, I'd expect this system could probably be adapted to the halberstadt D-series wing with its odd TE droop.

abufletcher

Here are the spar jacks in place over the top wing plan. The kit provides the parts for all 24 jacks required (2 sets of 6 for both top and bottom wings). These will be tack glued to the glass building surface.

I picked up all these blocks for $3 at the local 100-yen shop. I figure I can used them for making sure the ribs are square and they can also be tack glued to the glass so they are sort of like "pins for glass."

abufletcher

The next step in the wing "pre-construction" is to do all the ply/balsa laminated parts, including the TE's and some of the ribs. This method of pinning the parts then slipping the top part up on the pin is the best way to ensure that parts stay properly aligned. I paint the Titebond glue on with a brush and then slide the part back down.

After a few minutes for the glue to set a bit, I remove the pins and put weight on the parts until they dry to prevent warping. I didn't do this on the Snipe parts and was unpleasantly suprised when I came back a few hours later.

Note: It would be very easy to goof up and glue the ply to the wrong side so it's wise to lay the parts out on the plan first.

Mode One

Abu, when you get a prototype to build from CD ScaleDesigns, are there any instructions provided; or, do you need to determine the building procedure yourself?

abufletcher

No instructions. Just lots and LOTS of emails with Chris! But I have to admit that that's somehow part of the fun. One goal of all the construction photos is that this will eventually result in an online manual.

On the topic of construction manuals, as a writer and communication researcher I find them often problematic. The descriptive text often only communicates if the builder already knows what to do but may mean nothing to someone who doesn't. The 5 pages of typed text that came with my Flair Legionnaire are a prime example of that. Then there's the fact that we live in a world of many many languages.

The solution lies in photos and diagrams (e.g. isometrics). The recent incarnation of the Flair Puppeteer plans take this approach with very little text.

CTDavies

abufletcher

It's taken a while to get all the wing parts laminated and cleaned up ready for construction. But then I fear the day when kits are just elaborate (foam plastic) puzzles with pieces that just snap together straight out of the box. The parts all fit perfectly, but I had to clean up the glued edges and sand off the "nubs" where the parts connected to the sheets.

I've also got my glass building surface now and it looks like it will be interesting. Though Imust admit from a photography point of view this is definitely going to complicate things. There are obvious reflections but it also throws off my camera's meter and auto-focus and the "auto color" and "auto levels" functions in Photoshop don't deal with the reflections well.