CMAD Too Sweet build thread

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KRProton
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Re: CMAD Too Sweet build thread

Postby KRProton » Mon Sep 25, 2017 2:45 pm

Once I wing alignment was confirmed, I removed the wing, added strips of double-sided tape to the saddle, repositioned the wing, aligned again and pressed it into place and added bags of lead shot to hold it down while I drill.

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The clearance holes are factory-drilled in the wing. Per Tom's instructions, using the holes in the wing as a guide, use a 1/4" drill to to trill into the saddle in the fuse JUST ENOUGH to dimple the fuse. What I then did was switch to my #7 drill and, leaving the wing in place, drill the pilot holes for the 1/4-20 tap. Remove the wing and tap the threads.

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Next, you initially pot the wing to the fuse with epoxy just around the wing bolt holes. This is to give a hard, consistent, stable mounting base. After the epoxy I’ll fill in the rest with RTV.


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Re: CMAD Too Sweet build thread

Postby KRProton » Mon Sep 25, 2017 2:51 pm

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After the epoxy hardened, I removed the wing, then cleaned up any residual epoxy. Now the wing will have a stable base for attaching to the fuselage.

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Once my wing was mounted, I installed the stabs to check their alignment with the wing. Mine was off a little as shown in the photo.

The options I’ve heard are to fly it as-is, or hog out the stab tube receptacles in the fuse and glue the stab on permanently. I came up with a 3rd option:

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First, I incrementally “hogged out” the fuse with a drill (I forget the size now – it’s a standard English size like 3/16” I think). I didn’t remove much and it took six or eight tries until I got the tubes to be able to rock up and down a little and the stab was aligned. But now the tubes have to be stabilized and the free play be removed – in other words, glue them in! So I installed the left stab half, rotated it down, then added a few drops of thin CA around the tubes where they enter the right side of the fuse. I then performed the opposite procedure for the other side.

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Now my stabs align with the wing and they’re still removable (thought the tubes are now permanent).

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Finally, I potted the wing the usual way with RTV silicone.

Another thing I learned from Tom’s instructions was to spray the wing with window cleaner before applying the food wrap barrier to the wing for potting. At first I didn’t know why, but now I see that it keeps the wrap from clinging to the wing so you can pull it tight. Any remaining air bubbles can be rolled out to the edges with a paper towel roll.

Think I’ll wait a good 48 hours before removing the wing.

Tim
Last edited by KRProton on Mon Sep 25, 2017 11:51 pm, edited 1 time in total.


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Re: CMAD Too Sweet build thread

Postby DHULEN » Mon Sep 25, 2017 5:07 pm

I love the Kevlar string idea so much easier than measuring


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Re: CMAD Too Sweet build thread

Postby KRProton » Mon Sep 25, 2017 11:19 pm

K&S makes Kevlar line. Hobbico used to carry it, but we don't anymore.

I'm sure you can get it elsewhere, or I believe they make Kevlar fishing line.

See you later Duane! :D

Tim


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Re: CMAD Too Sweet build thread

Postby iamtom » Tue Sep 26, 2017 9:42 am

Just a quick note about the Too Sweet tail. Since day one from Jerry small to Terrance to CMAD, all tail to wing alignment has been off the same. The only reason to try to fix this condition is to satisfy your own piece of mind. Most people do not do anything and there is no ill effect by leaving it alone. Thanks Tim for all your efforts on this.
Tom
123READY TURN


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Re: CMAD Too Sweet build thread

Postby KRProton » Tue Sep 26, 2017 10:09 am

Hey, thanks Tom.

I certainly didn't intend to disparage the plane. I heard some other guys saw the same thing and as you said, as far as I know they are flying them as-is just as you mentioned. It's just that with my R&D and instruction manual writing background we always illustrate in our manuals to level the horizontal stab with the wing, so it's just a force of habit. :oops:

When I get home this evening the RTV from potting the wing will have dried for two days, so I'll take off the wing and see how great it came out! :mrgreen:

By the way, while I have your attention, will you please tell me what these two balsa dowels are for?

Thank you!

Tim
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Re: CMAD Too Sweet build thread

Postby kane » Tue Sep 26, 2017 10:15 am

KRProton wrote:...By the way, while I have your attention, will you please tell me what these two balsa dowels are for?

Tim


Tim,

The balsa plugs are to be glued into the carbon joiner tube. The joiner tube is pultruded and prone to splitting. The plugs prevent this. I use 5 min epoxy to install them. Others have used CA.

DK


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Re: CMAD Too Sweet build thread

Postby KRProton » Tue Sep 26, 2017 10:17 am

Ahhh, brilliant - thank you Dan!

So just glue one dowel into each end even with the ends of the tube, right?

I realize some are critical of some of the "craziness" that goes on in internet forums in general, but in my opinion, this is what it's all about - sharing information and learning.

Thanks man!

Tim
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Re: CMAD Too Sweet build thread

Postby kane » Tue Sep 26, 2017 11:24 am

KRProton wrote:...So just glue one dowel into each end even with the ends of the tube, right?

Tim


You are correct. Glue one plug into each end of the carbon joiner tube.

DK


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Re: CMAD Too Sweet build thread

Postby KRProton » Wed Sep 27, 2017 1:17 am

Okay, just some random pics of this evening's progress, and a pic from earlier after I had the engine mount potted and the fuel cut tube installed.

First thing today, I untaped the Saran wrap from the wing, then the wing easily lifted and the Saran wrap easily pealed from the fresh RTV on the fuse. That was the easiest and best wing potting job I've done. First time I used Saran wrap and window cleaner like in Tom's wing mounting instructions. After removing the wing I trimmed away the excess RTV with a new #11 blade.

I then cut the holes in the fuselage for the elevator joiner bar.

After fitting the stabs with the joiner bar, time to cut the holes for the screws that fasten the joiner to the stabs. On my first Too Sweet I used the screw holes in the joiner to guide a 3/32" brass tube sharpened on the end at the correct angle for cutting the screw holes in the elevators. But now there seems to be more resin or other reinforcement in this area because the brass tube was getting nowhere. So I chucked up a 3/32" drill which did the trick - but use care not to cut the threads in the aluminum joiner bar!

I enlarged the holes in the elevators with a 1/8" drill, then countersunk the holes in the top of the elevators for the screws. Looks good to me.

Got the rudder and elevator pushrods connected at the tail end and the servo tray glued in. I'll install and hook up the servos tomorrow.

Tim
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Re: CMAD Too Sweet build thread

Postby KRProton » Fri Sep 29, 2017 12:22 am

Okay, got the CF nose ring in, the elevators and rudder hooked up, servo tray and servos in and ailerons hooked up. Now to do a mock-up and see where to position the battery...going straight for 4" on the C.G. With the battery hanging off the wing trailing edge she balances, but that's with no tape on the tail or no fuel line in the nose. I think it'll be close. Battery definitely not in the nose on this one.

She's getting close - might even have some time to throw a little paint at it before the east coast Champ race!

Tim
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Re: CMAD Too Sweet build thread

Postby Hanknsd » Fri Sep 29, 2017 9:54 am

Tim,
A few years ago, I had a few 2 Sweets and also noticed the stab was off slightly. I did a couple of the previously mentioned fixes and came up with another fix.
I concluded that the stab and vertical fin were at 90 degrees to each other as manufactured. Not sure if my fix compromised the structural integrity but this is what I did and did not see any ill effects. Heated the fuse between the tail and behind the wing with a heat gun and twisted the fuse.
Hank D


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Re: CMAD Too Sweet build thread

Postby KRProton » Sun Oct 01, 2017 9:45 pm

Hi Hank.

Thanks for the suggestion how to twist the fuse with heat to level the horizontal stab with the wing. I've messed with that procedure for other composite planes, but it scares me a little. As long as it works for you and I'm sure others have done the same. Cool! :D

Tim


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Re: CMAD Too Sweet build thread

Postby KRProton » Sun Oct 01, 2017 9:56 pm

As suggested by others, relocated the wheels higher and aft on the gear.

I used this drill bit countersink with optional collar to countersink the holes in my gear for the 10-24 nylon landing gear bolts. Most hardware store countersinks are just those short, stubby ones so you can't get the chuck of the drill past the landing gear leg. So this drill bit countersink did the job, but for future reference it would probably be better to get a long-reach countersink something like this:

https://www.mcmaster.com/#countersinks/=19moxhd

The drill bit one I used kept getting clogged and it took about three or four tries to get a clean hole because I had to unchuck the bit several times to clean it out.

Oh well, live and learn.

Tim
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Re: CMAD Too Sweet build thread

Postby KRProton » Sun Oct 01, 2017 9:58 pm

Here's pretty much the final radio installation.

I though I'd seen others mount the battery with Velcro, so I thought I'd give it try.

I also learned a good way to position your antennas is with one of them through a plastic tube with a 90-degree bend suspending the antenna across the middle of the fuse. the other antenna is taped directly to the inside of the fuse pointing upward...
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