News:


Advertise Here

  • June 21, 2021, 01:35:20 AM

Login with username, password and session length

Author Topic: Lightening holes in profile fuse - worth it?  (Read 2236 times)

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2965
Lightening holes in profile fuse - worth it?
« on: March 01, 2021, 02:55:49 PM »
Rebuilding a profile fuse and looking to save some weight. This will be full electric so no full length hardwood motor mounts  but it will still have plywood doubler on the nose. I am thinking about using a 3/8" core and laminating 1/16" cross grain on each side to get to 1/2" and have some stiffness. I am considering cutting lightening holes in the core and wonder if this really saves a significant amount of weight? The core is medium balsa and weights around 1oz. What has been the experience of the group?

Update: I just weighted the piece that I cut out for the wing, it weights 3.3gm (just under 1/8 oz.), the whole core weights 25gm (0.88 oz.). Not sure it is worth it but it might save the weight of the laminating glue?

Best,     DennisT
« Last Edit: March 01, 2021, 03:30:18 PM by Dennis Toth »

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 6443
  • Millville NJ PDQ Flying Clown Country
Re: Lightening holes in profile fuse - worth it?
« Reply #1 on: March 01, 2021, 04:33:01 PM »
Cut it all out except for 1/2 x 3/8 top and bottom then put in warren truss ribs. When you box it use hard 1/16 balsa with the grain running long ways.


Motorman 8)
Remove victim to fresh air

Offline Avaiojet

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7628
Re: Lightening holes in profile fuse - worth it?
« Reply #2 on: March 01, 2021, 04:46:44 PM »
Dennis,

If you think you have a heavy model have at it. A hole weighs nothing. What was in the hole has weight.

The more holes you make the more weight is removed and the model gets lighter. "Science."

Best kept secrete in the Forum is this Build. And boy, did I ever make some holes! ;D

You've seen the finished model, comes in around 54 oz, tank, engine and finish included.

Here's the build,   

https://stunthanger.com/smf/cfc-graphics/'mig-3-reconnaissance-aircraft-and-warbird!'/

Holes start around page 3 or 4.

Trump Derangement Syndrome. TDS. 
Avaiojet Derangement Syndrome. ADS
 Please visit my updated Website! www.cfcgraphics.com  If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot.  Owner of CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder."  "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten.  I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.  "Ya gotta love it when a plane comes together."  Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Online Trostle

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2964
Re: Lightening holes in profile fuse - worth it?
« Reply #3 on: March 01, 2021, 05:05:46 PM »
Not really related to weight savings for holes in the nose of a profile fuselage, but I sometimes wonder if lightening holes are worth the trouble.

Next time you assemble built up wing with cut out made in the ribs.  Weigh the rib before and after the holes are made.  The material removed from the holes does not weigh very much.  Yes, a gram saved here and a gram saved there adds up, but those cutouts do not make much difference.  More weight can be saved by simply using lighter wood.

Keith

Offline Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4727
Re: Lightening holes in profile fuse - worth it?
« Reply #4 on: March 01, 2021, 05:34:12 PM »
   Making holes in balsa wood after the fact doesn't really safe a whole lot and you might be surprised at how little it saves. If a hollow structure is designed to be that way and has proper structure it can still be light and quite strong and resist twisting. Like Keith points out, better wood selection is a better option if possible, but if you are using a kit supplied piece of wood and have no other option, keep the wing/engine section more solid and sand the aft section a little thinner. Drilling and cutting holes interrupts the grain and that is most of the strength. If you cut a bunch of holes then you have to cover them with something else and you are just putting weight back on with that wood and the required glue.  You build in lightness right from the start. It's almost impossible to take away significant weight as an after thought. You are better off trying to save some weight with the finish by keeping it simple and not so busy.
  Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Online Dave Hull

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1254
Re: Lightening holes in profile fuse - worth it?
« Reply #5 on: March 01, 2021, 07:03:54 PM »
If you cut large holes in the tail area, consider:

--You will need ribs or truss structure to support any external skins. They need to be sized to handle buckling loads (compression induced bowing) Gluing to the overlying skins prevents buckling until the glue line fails or the wood crushes. Thinner and harder internal struts might be considered better if well glued to the skins

--If you choose to leave out the wood skins, then be aware that the covering is now supplying much of the stiffness. Or, the stiffness removed is not actually replaced if the modulus of the finished covering is poor. However, I've seen some pretty "holy airplanes" that performed way better than I expected them too. Around here, Tim Meeks was a proponent of this kind on construction, I believe.

--If you leave out the wood skins, also be aware that people handling your plane will have to be advised, repeatedly, where they can hold it. Or you will get holes. An after the fact, unintended holy airplane. Trust me on this one....

--Orienting balsa skins with the grain pure fore/aft direction may improve the lateral stiffness and help avoid tail whip, but it is not as good in torsion. If your plane handles corners funny, ask someone to watch from behind as you pull out of a square corner. Does it have pronounced stab tilt? How much is it interfering with your trim? If memory serves, when you twist the fuse you will get some max stress aligned at 45 degrees to the longitudinal axis. (Balsa is a non-isotropic material. Stronger and stiffer along the grain. In composites, they layer uni materials to take advantage of that. You can also do it with wood. That's why plywood is so versatile.)

--The best way to figure out a building style is to keep weighing everything and keep records. Build it one way, but compare what you likely would have gotten the other way. I've done some studies like this and as Keith pointed out, you can get pretty fancy and not save much. Worse, you can get fooled into using more zoot, like carbon fiber pushrods and such when they are not needed and simply get heavier. Weight is a touchy subject, especially during the design of full scale aircraft where careers are at stake. Just ask any Mass Props guy....

The Divot


Offline Ken Culbertson

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3394
Re: Lightening holes in profile fuse - worth it?
« Reply #6 on: March 01, 2021, 10:57:43 PM »
Before you start saving weight consider where you are saving it and how you build.  If you build nose heavy then saving weight in the tail only means adding it back in the form of lead later.  Opposite is just as true.  Only place saving weight is neutral is in the center.  I once thought that the lightest plane possible was going to be the best plane possible until I built two pigs that outperformed all of the feather lights I had built in the past.  We are no longer limited by the vertical lifting weight of a Fox 35.  Twist in a profile fuselage will do more pattern damage than the extra ounce or two you saved by cutting holes.  If you want it light you are going to have to use a built up profile.   Some of you out there will remember giving me that exact advice, well you were right.   I am not against cutting holes, it is where you cut them.  I still grind away everything that doesn't add to strength so that I can beef up areas that commonly fail.

I am probably in the minority - Ken
     
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC

Offline Gerald Arana

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1318
Re: Lightening holes in profile fuse - worth it?
« Reply #7 on: March 02, 2021, 07:56:36 AM »
Dennis, Short answer.....................No!

See Ted's post about his ultra light (Can't think of the name) plane that he added weight to before it would do a decent corner.

If I can think of the name, I'll post it. Jerry (Got old timers!)

Ah got it! "Tucker Special"
« Last Edit: March 02, 2021, 07:14:22 PM by Gerald Arana »

Offline Serge_Krauss

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1288
Re: Lightening holes in profile fuse - worth it?
« Reply #8 on: March 02, 2021, 12:52:54 PM »
First off, you can compute your weight savings, if you know the density of your chosen fuselage blank, but weight savings is not the whole story.  I have cut out sections from behind the wing's trailing edge of 1/2" balsa and used 1/16" balsa laminations to complete the 5/8" thick box, without going quite to the accepted extreme of just using balsa strips for the fuselage outline. The 1/16" sheet butted against 1/16" ply nose doublers for a smooth surface. I did not bias the 1/16" balsa grain, but used biased-weave, .56-oz fiberglass over it in finishing. Then with diagonal truss pieces in the cutouts, the structure was amazingly stiff in torsional loads, while saving some weight. I did keep track of the weights of all parts, as construction proceeded, but I don't have those notes anymore. My purpose was more to achieve the structural stiffness, than save weight, but with this structure and a slimmed down profile, I saved over four ounces in overall weight over my original P-Force fuselage. The opening was only a small part of that. The stiffness is what counted for me.

Offline Howard Rush

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7329
Re: Lightening holes in profile fuse - worth it?
« Reply #9 on: March 02, 2021, 01:37:43 PM »
Dennis,

If you think you have a heavy model have at it. A hole weighs nothing. What was in the hole has weight.

The more holes you make the more weight is removed and the model gets lighter. "Science."

Best kept secrete in the Forum is this Build. And boy, did I ever make some holes! ;D

You've seen the finished model, comes in around 54 oz, tank, engine and finish included.

Here's the build,   

https://stunthanger.com/smf/cfc-graphics/'mig-3-reconnaissance-aircraft-and-warbird!'/

Holes start around page 3 or 4.

Wow.  That airplane has enough holes to fill the Albert Hall.
The Jive Combat Team
Making combat and stunt great again

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2965
Re: Lightening holes in profile fuse - worth it?
« Reply #10 on: March 02, 2021, 01:37:53 PM »
OK, I tried it. The fuse core with only the wing section cut out weights 25g. After adding holes through the back and bottom I saved a whopping 3g. It took about 20 mins to do as I had to clean out the hole saw after every 2 holes were cut. I hope this save at least half the weight of the glue for the 1/16" overlays to bring me up to 1/2" total (didn't have 1/2" in stock). The ship is using a fairly light power package that on the original fuse was bordering on tail heavy so a little lighter back there won't hurt.

For the overlay what glue have you used? I was thinking of doing the card-scraped expoy method like putting on wing skins.

Best,   DennisT

Offline Avaiojet

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7628
Re: Lightening holes in profile fuse - worth it?
« Reply #11 on: March 02, 2021, 05:12:10 PM »
OK, I tried it. The fuse core with only the wing section cut out weights 25g. After adding holes through the back and bottom I saved a whopping 3g. It took about 20 mins to do as I had to clean out the hole saw after every 2 holes were cut. I hope this save at least half the weight of the glue for the 1/16" overlays to bring me up to 1/2" total (didn't have 1/2" in stock). The ship is using a fairly light power package that on the original fuse was bordering on tail heavy so a little lighter back there won't hurt.

For the overlay what glue have you used? I was thinking of doing the card-scraped expoy method like putting on wing skins.

Best,   DennisT

Dennis,

You could dope some glass cloth on the fuselage eliminating the 1/16.

.75 or something a bit thicker.

Remember, you'll have to put something over the 1/16 anyway.

Finish it without the 1/16.

I'd leave out the 1/16 but that's me.

Charles
Trump Derangement Syndrome. TDS. 
Avaiojet Derangement Syndrome. ADS
 Please visit my updated Website! www.cfcgraphics.com  If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot.  Owner of CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder."  "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten.  I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.  "Ya gotta love it when a plane comes together."  Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 11925
Re: Lightening holes in profile fuse - worth it?
« Reply #12 on: March 02, 2021, 06:07:37 PM »
Dennis, I've done this a couple of times, and had good results using the card-scraping epoxy method, only with Sig-Bond.  Things that folks will tell you will happen are, (1) the glue will never dry, (2) your fuselage will warp up because of the water in the glue, and (3) it'll be heavier because of all the glue.

As to (1) -- I build slow.  If you're going to glue it today and cover it tomorrow, use epoxy!  I'd give it at least a week for the water to wend its way out of the 1/16" sheet.  As to (2), put it on something flat and weigh it down.  I've taken to building on glass (1/2" thick), but this works on a regular ol' building board.  I did have one fuselage come out warped -- and it un-warped by counter-warping it with 1" thick blocks at each end and a weight in the middle for a day or two, whereupon it released to flat.  As to (3), don't use much glue.

I've got a plane with well over 500 flights on it, including some not-too-bad-for-a-profile flights in Expert (and it's the one that got warped and was corrected), so I think the method's OK.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Dave Hull

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1254
Re: Lightening holes in profile fuse - worth it?
« Reply #13 on: March 02, 2021, 08:54:18 PM »
I'm with the Timmer on this.

An appropriate amount of TiteBond (original), which I like to thin with water, applied with a brush gives good penetration. It will dry out just fine if let sit for a few days. Thinning the glue does a couple of things: it increases the open time of the joint, and allows you to more easily control the amount of glue which is the weight left behind after drying.

Just lay it out flat (in my case I was using a forming jig) and let it thoroughly dry. No warps. And much more stable than a single piece of wood that goes thru humidity cycles (or rain), or heat cycles. Just like air-drying lumber cut from standing trees, you should allow air to pass all around the wood to let it come to equilibrium with your shop humidity. A layer of fabric does a pretty good job here. You need something if you are working over a glass tabletop. And don't do this over a cast iron table saw top. You won't like the rust damage as the moisture comes out.

In my experiments with laminated elliptical leading edges, I was very pleasantly surprised how little weight was added by this gluing method. No strength appeared to be lost. (Refer back to the old "the wood will fail before the glue" logic.)

The Divot


Offline Mike Griffin

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2127
Re: Lightening holes in profile fuse - worth it?
« Reply #14 on: March 02, 2021, 10:19:11 PM »
For what it is worth, I never bored holes in a profile fuselage, flaps, stab etc etc.  I built several of Pat Johnson's designs which have framework and the core is 1/2 Styrofoam and sheeted with 1/16 balsa. 

They were incredibly light and straight.  I think we get a little OCD about weight sometimes.

Sorta like chasing the 16 ounce Ringmaster.  I built many in the 24-26 ounce range and they flew good for a Ringmaster and i never bored a hole in any of them. 
But i defer to the Ringmaster GOD Joe Gilbert.
Mike

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2965
Re: Lightening holes in profile fuse - worth it?
« Reply #15 on: March 03, 2021, 08:16:02 PM »
If one uses the epoxy scrape method to laminate the wood do you apply a coat of dope to both surfaces? Does this reduce the strength of the joint? I read the Hunt article on laminating the molded leading edge caps he didn't indicate that they are using any dope or scraping off of the Z-poxy finishing resin.

Best,   DennisT

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2965
Re: Lightening holes in profile fuse - worth it?
« Reply #16 on: April 05, 2021, 02:11:49 PM »
I finished laminating the 1/16" cross grain balsa to the 3/8" fuse core (with holes) using the finishing resin. The first side I did the brush and scrap but really didn't get much off. On the second side I just brushed it on smooth but thin and add the cross grain wood. Both sides seemed to be on very solid but I had one piece on the first side that didn't adhere well so I needed to apply a bit of resin to get it down solid. Now that is has cured the fuse is 1.6 oz. It is very very stiff.

Has anyone tried using gel CA for laminating? Just interested?

Best,   DennisT

Offline Paul Smith

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 5193
Re: Lightening holes in profile fuse - worth it?
« Reply #17 on: April 05, 2021, 03:51:50 PM »
Drilling holes is a waste of expensive balsa and it makes a mess and the grain ends up wrong.

It's better to build a truss and cover it with sheet wood.
Paul Smith

Offline Dave_Trible

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 5319
Re: Lightening holes in profile fuse - worth it?
« Reply #18 on: April 06, 2021, 03:14:58 PM »
I wouldn't make any lightening holes, especially on larger-.40 + size profiles.  Fuselage twisting aft and vibration issues forward can be hard enough to deal with as is.  In a couple of cases I've had to strip off the finish and fiberglass the fuselage to eliminate vibration issues causing bad engine runs.  It's pretty difficult to build a profile over weight.  You aren't starting with much balsa anyway.  I'd prefer to use balsa that is pretty stiff, then covering it with a layer of carbon to minimize stab twist in the wind.

Dave
AMA 20934
FAA Certificate FA3ATY4T94

Offline FLOYD CARTER

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4234
    • owner
Re: Lightening holes in profile fuse - worth it?
« Reply #19 on: April 06, 2021, 05:35:33 PM »
I vote YES.  Strength comes from the outside surface., If you drill holes, you remove weight which doesn't add to stiffness.  Covering the core (holy core) with 1/16" sheet provides greater stiffness than a single plank would offer.  You end up with slightly more weight, but that is easily offset by using lighter wood all around.
"Growing old is easy.
 Staying old is hard"
AMA #796  SAM #188  LSF #020

Offline Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4727
Re: Lightening holes in profile fuse - worth it?
« Reply #20 on: April 06, 2021, 06:00:48 PM »
  If you were able to add up the weight of the material you drill out I think you would be disappointed. Everywhere you drill a hole, you interrupt and sever the wood grain and remove a lot of strength doing that. When you g to spread epoxy over the structure, you wipe epoxy into those holes and unless you go to great measures to some how remove it, you just replaced what miniscule bit of weight you drilled out. I think better wood selection in both weight and wood size and proper construction techniques is a better way to go.
  Type at you later,
   Dan McEntee

  PS to add: If you think strength comes from the outside surface, which some call a monocoque (my spell checker doesn't know how to spell it correctly either!!) type of construction, but a square or rectangle shape doesn't lend itself to that very well. I think you are better off have each piece in the construction doing it's fair share of carrying the load. That way the strength in the fuselage is the sum of it's parts.
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline mccoy40

  • 21 supporter
  • Trade Count: (0)
  • Lieutenant
  • *
  • Posts: 113
Re: Lightening holes in profile fuse - worth it?
« Reply #21 on: April 13, 2021, 10:42:48 AM »
I use the built up truss method. Not because of strength or lightness but because of cost. Oh  and availability.    It is very hard ti find 1/2 inch sheets around here  - I use 1/4 and cover with !/8 inch sheet. I am also going to try 1/4 with 1/16 by 1/4 cap strips with 1/16 inch sheet soon.  y1


I'll crash compare the relative strength of each and get back to you with the results.   <= %^@

Offline L0U CRANE

  • AMA Member
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1035
Re: Lightening holes in profile fuse - worth it?
« Reply #22 on: April 16, 2021, 03:00:51 PM »
Might glance at my reply #4 to the Wing Sheeting thread...

The method of laminating sheeting to structure  puts glue only at glue-joints. That can be a weight savings.

Cure of white or yellow glues is quick and certain.

Balsa is expensive. Much less is wasted in cutting useless holes.
\BEST\LOU

Offline Howard Rush

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7329
Re: Lightening holes in profile fuse - worth it?
« Reply #23 on: April 19, 2021, 03:05:34 PM »
I have nothing to offer, but it's good to see "lightening" spelled correctly.  Onward to "lose" and "loose".

Dan spelled "monocoque" correctly.  I should know this because I have only one myself.
The Jive Combat Team
Making combat and stunt great again

Offline John Carrodus

  • Trade Count: (0)
  • Ensign
  • **
  • Posts: 34
Re: Lightening holes in profile fuse - worth it?
« Reply #24 on: May 22, 2021, 03:34:25 PM »
Dave Hull put his finger on it....er...um - through it maybe! I have used copious holes of various sizes and shapes wherever I see wood that is redundant. This can make a significant difference at the end of the day, especially if you have to mess around adjusting CG with weights on a finished model. I always point out to anyone handling the model to "No touch" areas.- usually on the rear fuz. I don't cover holes with thin balsa, I use silkspan or shrink wrap. I have also lightened tail surfaces, elevators and flaps, but only where there results no loss of rigidity. 

Offline Avaiojet

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7628
Re: Lightening holes in profile fuse - worth it?
« Reply #25 on: May 22, 2021, 07:09:08 PM »
Dave Hull put his finger on it....er...um - through it maybe! I have used copious holes of various sizes and shapes wherever I see wood that is redundant. This can make a significant difference at the end of the day, especially if you have to mess around adjusting CG with weights on a finished model. I always point out to anyone handling the model to "No touch" areas.- usually on the rear fuz. I don't cover holes with thin balsa, I use silkspan or shrink wrap. I have also lightened tail surfaces, elevators and flaps, but only where there results no loss of rigidity.

John,

I enjoyed reading this.

You should read my Threads or Builds where I use the removal, "removal," an important word, of wood material, using various size holes.

As you well know, it works wonders.

CB
Trump Derangement Syndrome. TDS. 
Avaiojet Derangement Syndrome. ADS
 Please visit my updated Website! www.cfcgraphics.com  If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot.  Owner of CFC Graphics. "Model Airplane Graphics from a Model Airplane Builder."  "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten.  I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.  "Ya gotta love it when a plane comes together."  Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline Gerald Arana

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1318
Re: Lightening holes in profile fuse - worth it?
« Reply #26 on: May 22, 2021, 07:31:03 PM »
I have nothing to offer, but it's good to see "lightening" spelled correctly.  Onward to "lose" and "loose".

Dan spelled "monocoque" correctly.  I should know this because I have only one myself.


 LL~ LL~ LL~ LL~ LL~ LL~ LL~ LL~ LL~ LL~ LL~ LL~ LL~

Good one Howard!

Jerry

Offline Ken Culbertson

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3394
Re: Lightening holes in profile fuse - worth it?
« Reply #27 on: May 22, 2021, 08:09:25 PM »
I have mixed feelings about removing wood in the aft fuselage.  For years I have carved out the sides, Nobler style.  On my last ship I had all of the holes cut and the stab mounted when I was admonished by my flying group that it was a mistake.  The plane felt strong and the stab didn't want to move any more than normal but I caved to the group pressure.  But before I glued the cutouts back I clamped the fuselage in a vise and measured how much the stab moved (twist).  Glued them back in and measured.  At least half of the twist was gone.
Another benefit was that I almost always end up nose heavy and have to add lead in the tail.  Why cut out balsa only to replace it with lead?

The rest of the plane is fair game.  If it is internal and not load bearing, it still goes but I am beginning to question this whole fetish we have with light planes.  Isn't the real goal wing loading vs power?  A Fox 35 on the 2 of a 4-2 setting would lift a 42 oz Nobler if held pointed straight up.  A Cobra 3520 will literally pull a 65oz plane from your hands if you let it.  Wing loading on the Fox was probably around 11-12.  The Cobra was lifting about 13 and could probably handle 15-16.  I for one have stopped worrying so much about weight and more about design.

Just me and I could be wrong - Ken
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC

Offline kevin king

  • 21 supporter
  • Trade Count: (0)
  • Captain
  • *
  • Posts: 758
Re: Lightening holes in profile fuse - worth it?
« Reply #28 on: May 30, 2021, 10:52:14 PM »
The short answer? NO no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no no. And....no.

Offline Warren Wagner

  • 21 supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 261
  • Bradenton, FL (winter), Clay, NY (summer)
Re: Lightening holes in profile fuse - worth it?
« Reply #29 on: May 31, 2021, 10:43:26 AM »
Hi gang,

I'm in the process of building a Fancher "Imitation" kit that was produced by Mike Griffin.  My main consideration
was to make the rear of the fuselage as 'twist resistant' as possible....any weight reduction would be a bonus.

The plans called for 1/8" x 38" geodetic stringers in the open bay.  I used firm wood here, and used CA glue get
a rigid joint.   Also use 30 minute epoxy for adding the 1/16" skin applied at a small bias.

When I get to the finishing stage, I will cover the entire fuse with carbon veil.

My conclusion:  It does appear that this structure provides for a more "twist free" rear section of a profile fuselage
(purely subjective).

When the model is complete, I have a Prowler that I can compare it to.   The Prowler twists so much that you can
see it during flight, so my money is going to be on the Imitation.  <g>

Cheers.

Warren Wagner

Warren Wagner
AMA 1385

Offline Ken Culbertson

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3394
Re: Lightening holes in profile fuse - worth it?
« Reply #30 on: May 31, 2021, 01:11:17 PM »
Sandpiper Trifecta just prior to adding the side sheet.  There is virtually no twist once the glue dried (titebond).  Unless it is a kit and you have no choice, it is good to remember that the profile rules allow for a 3/4" width.  When using an internal "geodetic" structure that extra 1/8 - 1/4" width really makes a difference for little in weight gain.

Ken
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC

Offline Dan McEntee

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4727
Re: Lightening holes in profile fuse - worth it?
« Reply #31 on: May 31, 2021, 02:13:19 PM »
Sandpiper Trifecta just prior to adding the side sheet.  There is virtually no twist once the glue dried (titebond).  Unless it is a kit and you have no choice, it is good to remember that the profile rules allow for a 3/4" width.  When using an internal "geodetic" structure that extra 1/8 - 1/4" width really makes a difference for little in weight gain.

Ken

   Now remember, you are injecting a rule that doesn't exist except for AMA C/L Profile Scale. There are no official C/L stunt profile rules unless you are trying to meet some local contest rules.
   Type at you later,
   Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2965
Re: Lightening holes in profile fuse - worth it?
« Reply #32 on: June 01, 2021, 08:55:46 AM »
If you sheet it with 1/64" plywood it can be even 1/2" thick and be extremely stiff. Tom Morris built profile fuse's this way and they are very stiff strong and light.

Best,   DennisT

Offline Ken Culbertson

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3394
Re: Lightening holes in profile fuse - worth it?
« Reply #33 on: June 01, 2021, 12:33:43 PM »
   Now remember, you are injecting a rule that doesn't exist except for AMA C/L Profile Scale. There are no official C/L stunt profile rules unless you are trying to meet some local contest rules.
   Type at you later,
   Dan McEntee
The only "rules" we go by here center around the Thumb.  I have never seen anything DQ'd locally and I have never seen anybody trying to stretch the rules here either.  If it has a thin flat fuselage, exterior controls and an exposed engine it is a profile.  My use of the 3/4 was only to illustrate that the wider you can make the internal bracing the less it will twist.

Ken
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC

Offline Ted Fancher

  • 2018 Supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2132
Re: Lightening holes in profile fuse - worth it?
« Reply #34 on: June 07, 2021, 02:42:38 PM »
Strangely missing in this thread is a discussion of the "goal" of reducing weight by tiny fractional amounts...other than winning the lightest airplane trophy.

How light is light enough?  Can a stunt ship be too light?  What would the line tension be on a zero ounce Ringmaster at five second laps on Dad's good old 60' eyelet to eyelet set of lines?.  At five second laps how much line tension would be necessary to displace the zero oz Ringmaster's big elevator against the airloads at 50 or so MPH?  Where would that line tension come from? What angle of attack would be necessary to fly a loop on a zero ounce Ringmaster?  How well, at that angle of attack would the angular relationship of the zero ounce Ringmasters fuselage match the flight path of the rule book loop...especially at the intersection of round eights...of which we have bountiful numbers?

etc!

The "answers" to these (yeah, I know) "silly" questions were pretty much the bottom line results of our experiment with "adding" weight to the "very" light when naked Tucker Special that Brett and I have addressed numerous times on Stunt Hangar.

Truth be told, in my experience as power train development has accelerated and "control" of that power source's "form" as it is delivered to the airborne air-frame the ratio of porkers to feather weights in the winners' circles has pretty much tilted in favor of the more "developed" approach...something like the ultimate merits of "Marilyn (in my day) versus Twiggy" in the sales of Playboy mags      y1 y1 Z@@ZZZ Z@@ZZZ.

On the other hand.........

Just being a Smart A$$ guys.  But it doesn't do any arm to consider some of that stuff and, as a result, balance where we utilize our available time at the work bench.

Offline Ken Culbertson

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3394
Re: Lightening holes in profile fuse - worth it?
« Reply #35 on: June 07, 2021, 03:01:53 PM »
"Marilyn (in my day) versus Twiggy"
To even make that comparison you have identified yourself as "multiphobic"  That ringing sound you here is your neighborhood WOKE representative at your door.  ~^   It will probably not know who either of them were. LL~

Ken

ps.  To your point, IMHO it is the power to weight ratio along with wing loading/lift that matters.  If those are right and the plane weighs 10 lbs it will fly a decent pattern.  We needed planes to be light when the Fox 35 was king of the hill because it had to practically lift the dead weight of the plane through the last "loop" of the square 8 on a calm day.  Not so today.

Ken
AMA 15382
If it is not broke, don't fix it.
USAF 1968-1974 TAC

Online Trostle

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2964
Re: Lightening holes in profile fuse - worth it?
« Reply #36 on: June 07, 2021, 03:52:09 PM »

How light is light enough?  Can a stunt ship be too light?


Maybe one of those feather weight stunt ships would be suitable for the zero stroke engine that I once saw a picture of.  (Really, there was a picture of it in one of the magazines years ago.)

I am not sure of the technical problems here, but maybe almost limitless RPM.  Probably need a very low pitch prop, like 0.1" pitch.  Fuel usage is unknown but should be very very low, so would only need a very very small tank.

Keith
« Last Edit: June 08, 2021, 11:19:35 AM by Trostle »

Offline Chris Wilson

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1639
Re: Lightening holes in profile fuse - worth it?
« Reply #37 on: June 08, 2021, 09:09:23 PM »
Drilling holes in an existing structure is simply correcting mistakes at best and ruining it at worst.
If you want it lighter then build it that way from the start.
Chris.
MAAA AUS 73427

You have enemies? Good. That means you've stood up for something, sometime in your life.
 Nothing in life is so exhilarating as to be shot at without result.  It's not enough that we do our best; sometimes we have to do what's required


Advertise Here
Tags:
 


Advertise Here