Screamin cross the sky -

I've used balsa spars extensively over the years. Very few people would ever say that my models were slow or docile. When using balsa spars, fiberglassing the center section is a necessity on high performance aircraft. I've never had a spar failure once I began using fiberglass. I've used hard wood spars. To me, they are unnecessary extra weight.

Besides wrapping the center section with fiberglass, choosing the proper balsa for a spar is important.

Over the last ten years or so, I glue carbon fiber matt to the top of my balsa spars. Little weight and no failures.

Ed Cregger

Reply to
Ed Cregger
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The amount of weight added on this particular plane is minor. What's the weight of all that glass versus replacing a spar or two?

Wrapping the center section with fiberglass? Have you ever built a Shrike? The "center section" is the fuselage. How much of the unsheeted wing would you wrap with glass? Wonder what how much weight that adds versus changing the spars.

This is certainly an alternative to using hardwood. I don't happen to have any carbon fiber mat lying around. However, I've got plenty of hardwood stock and a tablesaw. When I needed a stronger spar for my Shrike I just ripped one to size. Much easier than going out for some carbon fiber. These planes are typically so overpowered that a tiny weight saving is just not going to matter.

The point was that the supplied balsa spars don't cut it. Your post both disagrees and agrees with me. First you say balsa spars are ok, but then you go on to list the different ways you reinforce them.

Reply to
C G

I'd hate to get in the middle of an arguement between Ed & Chuck :-) But I have the Shrike-40 directions courtesy of Lanier sales dept and this is from page 8:

"**IMPORTANT - glue a piece of 2-1/2? nylon glass tape (GOLDBERG #451) along the upper and lower joints between the wing and the fuse with CA as shown on the plans."

If anybody wants a copy, email me off list & I'll send it to you.

Cheers - LeeH

Reply to
LeeH

Interesting, it seems they know some reinforcement is needed. What is are the spars made of? Anyway, this is different from the directions of the Shrike 10, which is the one I have. The 10 size says nothing about reinforcing the spars, and as many have discovered, not doing so can be fatal to the plane.

Reply to
C G

That's because for some stange reason the 10 sized shrike is designed to be powered with a .10 motor. Crazy, I know, but there you go.

The stock spar is fine with stock power. The 10 size shrike really doesn't come up to potential, though, until you get 15 or better power on it. And then you MUST change to hardwood or cap the spars with Carbon.

Reply to
John Alt

Thanks, that's just about what I said before someone decided to second guess those who have experience with overpowering this plane. It's a load of fun with the K&B 3.5. :-)

Reply to
C G

Spruce spars and ribs have cap strips 3/32 (apparently balsa).

"The wing spars are installed in the fuselage, the ribs slid in place and then the sheeting and cap strips applied."

"Always launch with up elevator for reflex action."

"THIS IS NOT A BEGINNERS AIRPLANE"

Cheers - LeeH

Reply to
LeeH

A good point, indeed. Well, I haven't had good luck in finding good spar material in either balsa or hardwood (spruce?). My wings generally fair better when fiberglassed. They seem to last through more assembly/disassembly cycles than just balsa sheeting and covering. I'm not claiming that my ideas are the best for any particular application. It's just what I like to do.

I have had more trouble finding good spruce spars than balsa spars. That could just be something that is a fluke. The way I apply fiberglass (toilet paper roll absorbing extra binder) is very light. Also, I don't use really heavy fiberglass cloth (2.5 oz. versus 4 to 6 ounce as in the old days).

I usually glass to about three inches beyond the fuselage on either side. Remember, I am an oldster that flew pattern in the seventies and early eighties. Technology has passed me by, no doubt.

I didn't see the original post and I am very sleep deprived. Anything is possible. I'm not arguing with you, just conversing with you. Please remove the chip from your shoulder. It isn't necessary when talking with me. In any pissing contest, I would surely lose. Furthermore, I wouldn't even care.

On the models I build with carbon fiber (not matts, don't know what I was thinking) I can use much lighter balsa spars and omit the fiberglassing. Although, I have found that the model holds up longer with at least some very thin fiberglass around the center section.

Ed Cregger

Reply to
Ed Cregger

I must have been half asleep when I responded to this post originally. Sorry for the hub-bub. No argument intended. I'm sleep typing again.

Ed Cregger

Reply to
Ed Cregger

No problem with that, it's a fairly traditional construction technique.

Only for those who keep up with technology :-) There are still many who build with the more traditional techniques. The issue with the Shrike is that it does not have a center section to which glass can be applied. You build the fuse, insert the spars through it, and then build the wing. On the .10 size there's not even any sheeting between the fuse and the second rib (the first is glued to the fuse), so there's nowhere to glass. This is why those who overpower them beef up the spars.

No chip, I was just pointing out the inconsistancy.

No doubt that they do.

Reply to
C G

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