somegeek

My Feedback: (2)

CA that pin in place. I had this drift on me during a flight and was lucky to land it in once piece after one of the wings began to rotate.

somegeek

buzzingb

My Feedback: (2)

The antirotation dowel is what put my last SSE into the ground. Glue it well with exopy! It is plenty strong enough as is but must be glued well. I was trying to save weight and never tought about vibration over time.

iron eagel

I used ca to secure the dowel in place when I set the wing alignment before I installed the lower fuselage piece. I wanted to make sure it was glued both to the sides and to the bottom of the servo tray where it seemed that that was a design consideration as it dowel in combination would absorb most of the inward force of the wing root. The servo tray adds most of the rigidity to the wing center structure, and I did not think it would be all that easy to secure afterwards. And it is a going to be a bit of a pain when I finish the fuselage sides, but I wanted to make sure about it bing fastened well. I will also need it for a reference for the fairings that I am going to use to blend the wing into the fuselage with, as well as the wing tube. The wing is going to slide into a 3/4 inch pocket on the side of the fuselage.

iron eagel

I had thought about using carbon fiber for the dowel just for the weight savings....

But I need the carbon fiber more in the tail and the difference in weight was only marginal.

iron eagel

Some small progress made…

I managed to reduce the weight of the plywood base for the canopy hatch from .6 oz to .4 oz so that is another .2 oz to add to the total weight reduction. That now puts the total amount of weight reduction at 3.7 oz thus far. After that I installed the two formers three stringers to the hatch assembly and am now ready to start adding sheathing to the hatch.

Now a bit more about this build regarding weight…
I have estimated the weight of the balsa sheathing for the cowl, cooling duct, fuselage and tail along with the carbon fiber veil for the entire fuselage and control surfaces at 3.4 oz (not including adhesives or finish).
Normally it would take roughly 1.5 yards of monocoat to cover the plane, the weight of that monocoat would be around 2.7 oz (not including adhesives or finish). So worst case I am adding .7 oz to the extra weight of the airplane at this point (estimated) to add a full cowl, cooling duct, sheathing to do the stressed skin finish of the plane (not including adhesives or finish). That stressed skin, along with some added composites will allow for some further weight reduction when I do the tail feathers, by eliminating the weight of the screws, dowels, fittings wire and solder used to make up the flying wires used to strengthening the tail feathers. So with that being said the stressed skin finish will have a three fold benefits of strength, reduced drag, and reduced weight (hopefully) of the finished plane to allow for all of the modifications I am adding to blend the fuselage and wing into each another.

iron eagel

Got the canopy hatch sheathed, and built and sheathed the tank hatch. Got the skin to sheath the turtle deck glued up other than that not much progress other than taking a hard look at the tail feathers and how they are going to be modified.
I have not finished the sanding on either hatch as of yet, I will do the finish sanding after the cowl is shaped and the rest of the fuselage sheathed.

pt40crasher

Hey, how goes the build?

Nice job on the hatch. I did mine incorrectly but it works. Not sure why I had such a hard time with it.

iron eagel

Thanks for the compliment but the canopy hatch has some filler on it, thank goodness for microballoons … The wood was a bit stiff and I cracked on that side as I bent it, and it was soaked down fairly well. The forward hatch was planked on the sides and then skinned, lots of sanding on that but not much filler. Basically sand away anything that doesn’t look like an airplane…

As far as progress..
I have been working on the plans for the horizontal stabilizer and vertical fin modifications I intend to do and plan to start putting them together in the near future.

I have the turtle deck sheathed and one side of the fuselage sheathed just sanded out the skins for the other side tonight after our club meeting. I hope to have it done tomorrow night and will try to post some photos as an update then.

iron eagel

Just a quick note and some pictures to update my progress thus far.

The first picture shows the turtle deck sheathed and the second shows the sheathing applied to the sides of the fuselage. You may make note the sides are sheathed with the grain vertical as you would do a shear web for the same reason. This along with the carbon fiber veil should add a lot of strength to the airframe. And allow me to add a radius to the bottom of the fuselage to clean up the airflow a bit.

Alex7403

Nice!
is the white nyrod for the antenna?

iron eagel

Yes that is the antenna tube that comes with the kit. Normally I just leave a string in the fuse to fish the wire out when I install the radio.

Alex7403

when you insert the antenna please show how you do it, i'de like to learn better method then fishing wire i'm using.

iron eagel

Actually your method of using stainless fishing wire leaders, sounded like something I was going to try...

Alex7403

not stainless! nylon.
i glue the tips with thick CA, then pull and cut 1/2 mm of the antenna.

iron eagel

Even that should work I was just thinking the stainless leader would slide through the tube better because it has a tad less flex and would bind less, a dab of ca to fasten it to the antenna then pull it back out.

I started to work on the my version of the horizontal stabilizer and elevators tonight but it is getting late I did not get much more done than the basic outlines done at this point. Hopefully I will be able to get the ribs and spars done tomorrow night so I can start on final assembly this weekend. I will post some photos on this whole process as it comes together over the next couple of days.

Alex7403

i guess you right about the binding.
i just didnt know how CA penetrate stainless steel surface, worth trying.
let us know how it goes and good luck.

iron eagel

Ca does not, nor will it penetrate the stainless steel, it is just a surface bond. I don't need a structural bond all I want is to tack it to the antenna, the only force put on the joint is to draw the antenna through the tube.

iron eagel

At this point because I felt that the construction of the tail group, couples with the change I intend to make in the shape and size of the components I decided it was time to sit back for a moment and consider it carefully. (A “measure twice-cut once�, type of approach to this part of the modifications for this airplane build.)
Where the tail group contains two of the major control systems and I plan to modify these from stock, I was concerned as to the impact of the changes as far as their effects vs. aerodynamic considerations. So, once more as I have done often before, I went to the well (the Aerodynamics Forum) and pestered them with yet another series of questions, to make sure that any of the theories I wanted to try out were anywhere near right at what impact if any they may have.
You can find that discussion at:
http://www.rcuniverse.com/forum/m_7067047/tm.htm

What I found out was that using airfoil shapes in the construction of the built up tail group I intended to use, would only have a minimal impact if any as far as drag reduction. Oh well, at least it will look good if nothing else. Next it was confirmed, that a strong rigid structure to take the force during aerobatic maneuvers was a must. And as in every step of the build thus far keeping the weight down would be the one thing that would give me the “biggest amount of bang for the buck�. With that having been said, as always in dealing with an airframe, a strong rigid structure is a must, but that has to be balanced around keeping the weight down.

So now I am back to my build, the sheathing of the fuselage did a lot to stiffen up the tail of the fuselage and when finished it will transfer a lot of the force of the horizontal stabilizer and fin into the bottom of the fuselage and tie all of the individual components into a rigid structure. The stock stabilizer set up has a lot of flex and the original fuselage did not have a lot of stiffness to transfer that into the entire tail, the sheathed version make the wing saddle where the stabilizer sits much more rigid and more than strong enough to transfer the twisting and up done forces into the fuselage. The stock setup has a lot of flex and uses external braces to make up for rigidity of the horizontal stabilizer and tail. Page 21 step 84 of the manual has the following caution: “We would urge you to include this support system in your model.� Given that the plane is designed with aerobatics in mind, I can understand their concern here; it would be real easy to rip the stock tail feathers apart during aerobatic maneuvers if you left the braces off. I can not however look at an airplane with external braces without thinking there is a better way of building it, and lose those unsightly drag producing assemblies.

Time to take a look at the stock setup the combined weight of the components of the tail surfaces (stabilizer/elevators, fin/rudder, braces/hardware and elevator joiner wire) is 4.6 oz. that is a total of over a quarter of a pound hanging off the tail. The hardware for the tail braces and the braces themselves add up to 1.8 ounces. The elevator joining wire is another .2 ounces so we have a total of two ounces there so the weight of the wood alone is 2.6 ounces. Wow, that is a lot of wood for something that is not strong enough to work without the added weight and drag of the external braces.

I will add some photos and information in a bit.

iron eagel

The stock horizontal stab weighed .8 oz my replacement weighed in at 1 ounce without sheathing, but with carbon fiber spars joined into the balsa root and rib arrangement. The holes you see in the photo attached, were to drip ca into the wood/carbon fiber joint to bond them and harden the balsa contact surfaces. The horizontal stab like this was much more rigid and resisted twisting much better than the stock assembly. My built up assembly was than sanded to a taper at the wingtip and will then be sheathed with 1/32 inch balsa.

N1EDM

My Feedback: (2)

Paul,

Are you planning on putting some Tee nuts into the tip ribs so that you could bolt on tip plates on and off? Was that part of your plan???

Just being curious (and nosey).

Bob

iron eagel

Bob,
The main reason I built the horizontal stabilizer like that, was to distribute the strength of the stressed skin across the span of the tip to balance the load forces of the elevators back into the fuselage from the tips. Those wingtips of the horizontal stabilizer are only 1/8 of an inch thick so no way to embed t nuts in there. The structure I built was to be able to lose the external tail braces while adding airfoil structure to the tail feathers. I have the glue drying on one part of the skin that was applied to the stab tonight and am headed back to the workbench after this came out to get a cup of coffee.

edit to add:
I had hoped to be a lot further than this but i had about four versions of the tail group drawn up before committed to build this version. Rather than use counterbalances and increased span to increase the elevator area i have decided to go with a longer root cord, which should increase control response, because of the increased area and the fact that this will move moment arm back just a bit also. While keeping the major portion of the span of stab and elevator closer in to the roll axis.

N1EDM

My Feedback: (2)

Hmmmm, it looks like I goofed... I meant to ask if you were intending to put tip plates on the wingtips of the main wing...

mea culpa...

Bob

iron eagel

Bob,
I hope I won't need the tip plates for the main wing unless I want to do some experimentation with compressive lift. Hopefully the added side area of the cowl and cooling duct will improve knife edge flight to a point that tip plates or side force generators will not be needed.
I can understand how by a quick look you may have take that picture as a main wing...

N1EDM

My Feedback: (2)

Hi Paul,

I know that you didnt need the side plates, just curious if you had wanted to experiment with them where you're building all these other neat features into the plane as well. It was just a curiosity-type question. The build is looking really good. I liked the idea of using the carbon veil on the stab. Neat idea...

Bob

iron eagel

Bob,
I had planed to set up the wingtips so that they are interchangeable so I can experiment with several setups. this plane is going to set up so there are several options, perhaps even another set of wings as well. Last night I got the stab sheathing on and plan to start on the elevator halves and fin tonight, if I don't get side tracked.

So did you decide to bash the remains of your twist?

Paul