Mustang Fever

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Thought I'd start another thread on this, as the original is way long.

I've got all the ribs cut, and the right wing panel begun. I decided to build the wing as an evenly tapered structure, root to tip. If the wing is built as per the instructions (ribs flat on the board) one ends up with a left and a right wing, both flat on the bottom and tapered on the top. I don't think Laddie intended that to happen, as the front view of the airplane on the plans shows an evenly tapered wing section. So....

I determined that the centerline of the W1 rib is exactly 15/16" from the widest part of the rib at the bottom. Thus all the alignment tabs you see are 15/16" down from the centerline of each rib. (I learned this trick from Sig and Lanier. Many of their kits use alignment tabs. You just cut em off after the upper part of the wing is finished.)

Strykaas

Subscribed. Maybe Laddie could chime in and comment on that [sm=49_49.gif] ?

Mustang Fever

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I've built a couple of swept wings that had swept spars, and learned that it's better not to cut the spar notches in the ribs until they are pinned in place and ready for the spar to be installed. I lay the spar on top of the ribs over its location on the plans, and use a felt tip to mark both sides of it on top of the ribs. It's then fairly easy to use a razor saw and a hobby knife to cut out the notches. This results in a very tightly fitting spar with good glue joints.

Strykaas

Not a bad trick

Strykaas

I've thought about it twice : what you will achieve through this is having a no washout wing... I am now wondering what the original way to build the wing (I've re-read RCM's article about it, and indeed ribs have to lay flat on the trailing edge and front sheeting). I'm having a hard time figuring out what kind of washout that would yield (if any).[sm=confused.gif]

Mustang Fever

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Strykaas:

No washout either way, near as I can figure. Based on my limited experience with an F-4, deltas don't seem to need washout.

Mustang Fever

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OK. Returned from visiting and flying in NJ, and made a bit more progress.

The leading and trailing edge pieces are glued on and shaped, as is the trailing edge sheeting, and the spruce main spar.

After experimenting for a bit, I discovered that ordinary round, cedar pencils fit the ID of the carbon tubing perfectly. Cut up eight pieces and epoxied them in as plugs, as per instructions, to keep water from getting into the wings.

The tubing I got is from dragonplate.com It's .375 OD and .290 ID, a bit thicker in the wall than Laddie specifies, which is OK by me. (I think about 0.08" vs 0.06")
Very consistent OD/ID, very smooth, very rigid. $18.20 for a 48" piece, including shipping. They have a wide range of CF products.

pmisuinas

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Bob, go for it. I now have some motivation to get back to mine, I would be ashamed to have you get yours done and in the air given how long ago I started mine However, in my defense I will say I have done a kit bash of a Rascal, a Seawind, half a pylon seaplane to use the wing from the crashed Seawind, and a second Seawind (as I say, I do get sidetracked). Also did a Splash 3D, but now really need to get back onto the Arrow...Pete

Mustang Fever

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I dunno, Pete. My build rate is going to depend on when I can scrape the $$ for the various components. I'll be lucky to get her done before the snow flies this fall.

Got the carbon spars all epoxied in today. The 3/8 holes in each of the three ribs did not quite line up correctly, it was necessary to "hog" out the #2 and #3 holes a little so as to get the CF spars 90 degrees to the #1 rib. (I'm leaving the #1 holes on both panels alone, so the alignment will be the same for both.) To insure good strength, I made some plywood versions of the little "paper rectums" that are used to strengthen pages in a binder. They're epoxied on the outboard side of the ribs where you can't see em, but there's one laying in the foreground.

Tomorrow I'll do the leading edge and center section sheeting, then she'll be ready to come off the board for the other side.

Mustang Fever

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Was goofing off down at the field, flying my Wonder, so didn't make a lot of progress.

Here's the first piece of leading edge sheeting. Every time I sheet a wing it seems I'm trying something different. This time, because the wing is up off the board like it would be with a jig, I TiteBonded the first piece to the LE only, using clamps in four places and mucho pins elswhere. Looking in from the back side, I can see no gap, and squeezing the sheeting against the LE causes no glue to run out. Should work ok. Tomorrow AM, I'll soak the top of the sheeting with water and then thick CA it to the ribs in front of the spar, Poly it (Gorilla) to the spar, and thick CA it to the ribs aft of the spar.

Mustang Fever

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I know now why Laddie hasn't chimed in on the "tapered wing, alignment tabs" issue. He can't stop laughing. The wing comes out the same regardless. After I got it sheeted on one side and took it up off the board, and removed the tabs, it laid perfectly flat on either side. I guess it's because of the constant trailing edge thickness, and the fact that all the rib bottoms are flat up to where the LE sheeting ends at the spars.

Live and learn, eh? Anyway, here's one panel complete with CF spars.

Strykaas

Hi Bob !

Actually this wouldn't be the case with a different wing section along the wing (dfifferent ribs). This looks like a particular case. I haven't checked the ribs myself.
Your panel looks good

Mustang Fever

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This is probably something that is a lot simpler than it appears to me, but I've been sweating this step:

Making the two 1/8 ply boxes that go in the fuse to accept the wing tubes. I made the pieces and did a dry run, trying to get them all aligned properly around a piece of the carbon fiber tube. Kinda like wrestling snakes. Gluing them all at once would be really tough.

Maybe this will get it started. I clamped one of the pieces to a square, while both items were sitting flat on the building board, and pinned the other piece up against it. When the Gorilla glue sets, I'll try the next step.

Mustang Fever

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I'll try to explain this without confusing everyone.

I found it easiest to make the two halves of the spar box first, by clamping the vertical piece to a square as shown previously (Pic 1)

Next step was to put the CF tube into the corner of each box half, and use a pencil to mark a trim line. Then sand the edges until perfectly lined up with the OD of the tube. (Pic 2)

Last step is to stick the tube in there, and glue them both together with Gorilla, well clamped to maintain alignment. (Pic 3)

I'm pleased with the results- the CF tubes fit very snugly in the boxes, and everything appears to line up OK. (Pic 4)

Mustang Fever

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Strykaas:

Both our posts got lost yesterday during the RCU difficulties.

I''ve had good luck with poly glues (Elmer''s and Gorilla) since I started following the instructions and wetting the surfaces prior to gluing. The consensus on the Verse seems to be that they are superior to epoxy long term because they don''t keep curing and get brittle. Not too sure about that, I''m not going to quit using epoxy, but poly does seem to bond balsa to plywood much better than epoxy, and plywood to plywood.

As far as the boxes go, I''m not trusting to just the glue and the wood. 1/8 ply is kind of thin for the stresses generated by the wing tubes, so after I stick them to the bulkheads I''m going to put a layer of fairly heavy glass on the exposed sides and the bulkhead.

knifeedgeyak

Question to you guys,

I am looking to build something different. I fly in central California and most of the people in my club fly seamasters or some form of a cub on floats. I finally had a great weekend with my new cub and I am looking to get a different looking plane in the air. I had planned on buying the Northstar kit, but while looking for some reviews I ran across the Arrow. I have lots of flying experience but I have only built a couple of planes. I read the entire other thread and it scared me about haveing to fight to get the arrow to fly right. In your opion which plane will be easier for me to build and get flying without to much trouble?

Thank you

Mustang Fever

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I''m not super knowledgeable on this, but my impression is that the Northstar is probably easier to deal with. It is much harder to balance, though, so go with the smallest engine recommendation.

Mustang Fever

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Wing all framed up, complete with hinged elevons.

Turning 3/8 sheet balsa into tapered control surfaces used to seem like a lot of work, before I got halfway skilled with a Master Airscrew razor plane. Now it''s easy. I just draw the triangle shape on the end of each blank, and the centerline on the trailing edge, and plane away until it''s pretty close to the final shape, then sand it a bit.

For hinging, I centerline the LE of each elevon, then locate and cut the hinge slots with the power tool. Last step is to plane the LE to a tapered shape for easy movement.

I really like the way this airplane builds. I have not put that much time into it each day, maybe an hour or two, but it is going together very quickly and is a lot of fun to build. I've been working on it since 25 March, and here's the wing all ready for finishing and covering and it's only 15 April.

Mustang Fever

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A pic so you all don't get the idea I've stopped. Got all the fuse/fin/pod parts cut except the sides- had to order some 48" long sheets for that. Overlooked it somehow and wound up with all 36".

I studied a lot on putting some downthrust in this critter, and concluded that it's not worth the hassle. Any change to the pod angle means 1) prop clearance issues and 2) making a shim to go between the spruce uprights and the firewall. Risky.

In flying my Mariner, with it's high mounted engine, I've noticed that even with all that upthrust (almost 4 degrees) at lower airspeeds one must compensate with a lot of up elevator that is not needed once the airspeed gets up there. This is very noticeable on takeoff- I don't dare back off on the up elevator once she's airborne, or she'll go right back into the water. After the speed is up, though, the trim is perfect.

Maybe the Arrow won't be too awfully different.

I ordered the engine (OS 55AX) and an OS aluminum mount for it a couple days back, so that I'll be able to completely frame everything.

Strykaas

Cool. I guess this 55AX will make up for a nice trouble-free engine combo. Will you run the std muffler or use a UT / Jett / Bisson style one ?

Mustang Fever

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The one on the Mariner runs very consistently with the standard, so I think I'll stick with it.

I used Gorilla to glue the 1/4x1/4 spruce sticks together, for the motor mount upright inside the lower fin.

Framed up the left half of the fin this afternoon, using my favorite rib props: a piece of 1/4" triangle stock CA'd against the inside of each rib so there's something to stick a pin through. It keeps them vertical, and gives more gluing surface later on when the fin halves are joined.

Mustang Fever

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Got one half of the fuse framed up, with formers F3 thru F9. These plans are very well drawn, as the various pieces fit together with very little alteration from the original. I had to sand a few of the formers where they fit onto the 1/4 square balsa at the fuse bottom, that's all.

I trial fitted one of the wing panels to one of the fuse sides before I cut the holes for the wing tube boxes. The distance between the carbon tubes on the wing and the holes for the boxes on the fuse sides (as drawn) were just slightly different - probably my "Isolated 13000" quality control. By moving F7 a bit, it all lined up real nice.

Mustang Fever

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There comes a point in every projects life when it starts to resemble the finished item. Then I start to get excited. [>:] Especially when it all fits together and turns out as nice as this one is.

After bonding the 1/2" triangle and 1/4" square sticks to the left fuse side, there was just a bit of fitting required to make it sit correctly against the formers. About 5 minutes worth, mostly around the 1/4" notches on the bottom, like the right side.

The wings/wing tubes/wing tube boxes all came out as near to perfect as my old eyes will ever get them. In these pix, the left side is not yet glued on, just fitted in place, as are the wing tube boxes.

I am very pleased. Laddie M is to be commended for a great set of plans.

Mustang Fever

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It's been blowing 25-30mph all day today, so no flying, but lots of time at the building board.

Glued the left side of the fuse on, epoxied the wing tube boxes in place, tapered the nose and installed the two forward formers. I'm still breathing hard.

It took a lot of kerf cutting on both the 1/2" triangle and the 1/4" longerons before the nose was flexible enough to draw together without cracking. I wet the outside of the balsa heavily, as well.

Strykaas

Nice progress