My Akromaster is Fat ! How do you guys get them so lite?

I have built a "by plans" Akromaster. After reading this forum I shortened the nose 1/2" and added 1 1/2" to the fuselage to get rid of some of the added lead tail weight. I replaced some old rubber wheels with foam, and still have a plane that weighs 23 OZ!
I'am running a Magumn 15 that weighs 5.8 OZ., but just ordered a OS 15 LA-s C/L that weighs 4.56 OZ. That should let me get rid of some more tail weight but won't bring the total weight down to the "heavy" 16 OZ. range.
What are you guys doing to to get the weight down on this plane?
Rob Johnson
Orange,CA.

Rob: Please describe your wood selection, and finishing techniques. What sort of glue? Tip wt? Other details.

Remember that engine weight from the manufacturer probably doesn't include the muffler.

The wood in the SIG kit is heavy, at least mine was. The silkspan I put on I used minimal paint on. Wanted to fly it, not look at it. I'll probably use monokote next time.

Light wood, sparse on the glue and even sparser on the covering will bring the weight down. But 23 ounces? They must have used Pine in your kit.

A lot of it can be in the wood. But a lot of weight problems are in the finish as well. A good silkspan job should be no worse in weight than Monokote, so if done properly you aren't going to save weight there. I have a SIG chipmunk that I built in my "earlier days" and it was (is) heavy. I at first blamed it on the finish, so one day peeled it all off. Guess what? It wasn't the covering or the finish. I went back to silkspan and dope.

But some SIG kits got heavy wood. I have another Chipmunk that is extremely light. Both were stock kits. Best thing to do is to weigh each piece of wood, and if anything is overly heavy, replace it. Hollow all blocks (not a problem with the profile kit, but I had hard balsa blocks on the Chipmunk and did not hollow as thin as I could have.) Weigh the plane before and after finish and you will know exactly what you gained there. Then ask yourself if you could have made it lighter for the next time?

Looked more like Oak!
I used epoxie where I should have used CA and covered it with Monocoat. It does have some paint, but not much.
Think I'll build another and be a bit more carefull as to weight.
Sure am learning on this forum. It takes a lot of planning to get a well flying plane!
Rob Johnson
Orange,CA.

>Looked more like Oak!
>I used epoxie where I should have used CA and covered it
>with Monocoat. It does have some paint, but not much.
>Think I'll build another and be a bit more carefull as to
>weight.

Unless you dipped it in epoxy, I doubt the adhesive is the problem.

>Sure am learning on this forum. It takes a lot of planning
>to get a well flying plane!

Well, larger models are a lot easier to deal with, and more tolerant, than little ones. Even my kit Skyray (plywood ribs and spruce spars) flew OK with a 15FP, and gangbusters with a 20. But when I rebuilt it with balsa and saved 6 oz (36 down to 30), it really flew pretty much the same! Maybe a little better and certainly with more margin for error, but still not drastically better in areas like overhead tension or precision.

My recommendation to guys trying to start: Get a Skyray 35 kit. Copy rib shapes, save plans. Build from kit, use 25LA Remote Needle/APC 9-4/Bru-Line air filter, Sullivan clunk tank, 2-wheel gear, Monokote on wings and tail, Rustoleum or epoxy paint on fuse.

As soon as the first one gets finished, make two more using full ribs made from 3/32 light balsa at every station, and everything else the same. Should take no more than a weekend or week of evenings for each one. Take care, but don't spend a lot of time looking at them, just build them straight. Finish them and take them to the field. When the first one gets dorked, clean the engine off with brake cleaner, put on a new prop, bolt it on to the next airplane, and just keep flying.

Treat the airplane like a baseball. When the ball gets hit into the stands, or gets scuffed up, you don't have a wake for it - you just go get another one and the game goes on!

Must be wood.

But if one wants to emulate the Big Boys in lightweight building, notice how much attention gets paid at every stage of construction. Weigh the material, select different if needed. Weigh the ship at various stages, keep a log, and you'll see where the weight appeared.

I've been convinced a couple times now that I was heading for a 44 ounce airplane (early in construction). The finished ship unexplainedly ended up about 10 ounces heavier.

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"I was under medication when I made the decision to burn the tapes." -Richard Nixon

I am to the point that I don't care how much the stupid airplane weighs. I figure if I am still alive (such as it is) and lucky enough to be able to get out to the flying field and get the puppy in the air at all then that is a good thing and I should appreciate and enjoy it accordingly no matter what.

Jake

Ron,
When I built my Acromaster, the preformed solid leading edges where pretty "scruffy", so I wrote Sig and they sent me two new ones. However the new ones were pretty heavy, so in the end I sanded the original "scruffy" ones. Then I setup my router on my crummy Sear's router table, and hollowed out the leading edge. At least this way I reduced the weight.

I also covered the wings with MicaFilm, a nice light but amazingly tough covering material. Itg lacks adhesive, so you need to use the original (Fabric) Balsarite to attach it.

I also use an FP10, again to save weight. I can't tell you the weight, because, alas, it was a sacrifice to the CL gods in my (semi-successful) attempt to learn the full pattern. I am not exactly sure why, but I felt much more comfortable putting this small plane into harm's way than a larger 35 size plane. Ultimately a Ukey 35 with LA25 got me the rest of the way through the pattern, giving me the confidence to fly my own "hand-made" 35 size planes though the pattern. Along the way a well-worn Skyray 35 was also sacrificed!

Rob,
I forgot to answer your question---we lie a lot!

It's probably a lot of things, starting with the parent material...the balsa. The epoxy added a little. How many coats of paint? Oh yes, what kind of wheels? Modern ultralites (like David Brown) can knock a lot of wt off, even on an intermediate sized model.

>I have built a "by plans" Akromaster. After reading this
>forum I shortened the nose 1/2" and added 1 1/2" to the
>fuselage to get rid of some of the added lead tail weight. I
>replaced some old rubber wheels with foam, and still have a
>plane that weighs 23 OZ!
>I'am running a Magumn 15 that weighs 5.8 OZ., but just
>ordered a OS 15 LA-s C/L that weighs 4.56 OZ. That should
>let me get rid of some more tail weight but won't bring the
>total weight down to the "heavy" 16 OZ. range.
>What are you guys doing to to get the weight down on this
>plane?
>Rob Johnson
>Orange,CA.

Hi Rob, I have two Akromasters, one weighs 10.5oz's..the other
weighs 17.5oz's let's forget about the lighter one and talk about
17.5oz one: I built it using the kit wood and the supplied lexan(?)
canopy. I covered it with aluminum Micafilm and finished in nitrate
dope and Pactra Aluminun Polyurethane. I had to add about 3/4oz of
lead at the tail to bring the CG to the appropriate spot. I have a
five ounce engine installed(Silver Swallow .15 diesel), and a 1.33oz
fuel tank. It flies the pattern in big smooth form but gets into
trouble if I try Combat tight direction changes...Why?...Because
the wing loading is way too high...If it had a three ounce engine, it
probably wouldn't need the tail ballast. It would likely weigh a bit
closer to 14.5 -15 oz's. This would be a much better flying model.
So I suggest you mount a 3-3.5oz engine instead of those heavier
choices You (and I) initially made. I have seen lots of suggestions
from other Forum listers to use TD.09s, Fox .15s; That Norvel .074
shoud be a great choice too. I wish You the Best;
Tony (Corona, Calif.)

Thanks Tony,
A lighter engine would be the way to go. I'd be able to dump somemore tail weight using one. Then the weight should be more in line.
My wifes going to kill me! Another Engine!
Rob Johnson
Orange,CA.

Rob,

Tis a noble thing to die for the cause.

>Thanks Tony,
>A lighter engine would be the way to go. I'd be able to dump
>somemore tail weight using one. Then the weight should be
>more in line.
>My wifes going to kill me! Another Engine!
>Rob Johnson
>Orange,CA.

Rob, surely you've learned how to deal with that by now. I used to come back from the hobby shop with about $50 worth of balsa, walk in, shake my head, and complain loudly to my wife: "It's sickening how little $15 buys in balsa nowadays!"

Buy the new engine, complain loudly: "It's pathetic how little $30 buys in a model engine nowadays!"

You're NOT LYING!

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"If I have not seen as far as others, it is because giants were standing on my shoulders." -Hal Abelson

by any act, error, or omission, I have, intentionally or
unintentionally, displayed any breedist, disciplinist, sexist, racist,
culturalist, nationalist, regionalist, localist, ageist, lookist, ableist,
sizeist, speciesist, intellectualist, socioeconomicist, ethnocentrist,
phallocentrist, heteropatriarchalist, or other violation of the rules of
political correctness, known or unknown, I am not sorry and I encourage you
to get over it.

Go to EBay bid on a nib Fox 15X and say Wow I got this great motor and it only cost $30.00. Isn't that what your wife would say to you. Dennis

Yes, shes always telling me what great "sales" she has found! I should learn from her.
I have a OS 15 coming that in that I'm not going to even use now.
Now, off to E-bay!
Rob Johnson
Orange,Ca.