Author Topic: Legacy (Read 2715 times)

andreas johansson · « **on:** July 22, 2009, 03:02:34 AM »

Hi all!

When I have finished my E-banshee I have a legacy kit in my shop that waits to be built. I first tought of using an ST51 I/C engine, but now I would like to use an electric motor.
To find a motor to this aircraft isnt easy, probably due to my low level of knowlege in electric motors.

What do you think of this motor:
Model: SK35-48 900
Kv: 900rpm/v
Weight: 171g
Rated Power: 770w (some sites say 840w)
Cell count: 3~5 Lipoly (I would like to use a 4s)
Suggested Prop: 11*8, 13*6
Power equivalent : .40+ glow engine

Andreas

Matt Colan · « **Reply #1 on:** July 22, 2009, 06:15:35 PM »

Quote from: Andreas on July 22, 2009, 03:02:34 AM

What do you think of this motor:
Model: SK35-48 900
Kv: 900rpm/v
Weight: 171g
Rated Power: 770w (some sites say 840w)
Cell count: 3~5 Lipoly (I would like to use a 4s)
Suggested Prop: 11*8, 13*6
Power equivalent : .40+ glow engine

Hi Andreas, I'm no electric guru, but the info says that that motor is the power equivalent to a .40+. I would go for something that puts out more power because a Legacy is a pretty big airplane if you use a 40ish displacement engine.

I know absolutely nothing about electrics but that is my two-cents.

bob branch · « **Reply #2 on:** July 22, 2009, 08:53:08 PM »

I think I would opt for lower kv so I could turn a bigger prop on less amps.

bob branch

Alan Hahn · « **Reply #3 on:** July 23, 2009, 01:59:41 AM »

Quote from: bob branch on July 22, 2009, 08:53:08 PM

I think I would opt for lower kv so I could turn a bigger prop on less amps.

bob branch

I agree with Bob.

I don't know that particular motor, but I would guess that something equivalent to the AXI 2826 should be able to easily handle the 13-6 type prop. So if that motor has similar internal "guts" to the AXI (stator diameter and length), it should be fine.

It is hard to compare electric to glow, although we all do it. Most 40 glow engines don't handle 13x6" props, so you gain a lot in efficiency by turning the large prop slower to provide the thrust you need.

Other people with large plane experience should chime in at this point!

andreas johansson · « **Reply #4 on:** July 23, 2009, 02:26:54 AM »

This isnt easy, with smaller aircrafts in the .30-.40 range its much easier because people have more experience to share. I honestly dont know what I'm looking for in this case.

Please, large plane pilots, chime in.

Andreas

Will Moore · « **Reply #5 on:** July 23, 2009, 07:59:10 AM »

Hi Andreas;

The AXI 28-26-10 might be at the limit for this model. ~^The Legacy has an area of about 688 sq. in. I do not know whether that figure is including
flap area, and if it isn't, that brings the area up higher. It is a fairly large airplane, with large surfaces.
It is designed for IC 40 -60 size power. Most guys would tend toward 60 size in wet power. (unless piped) If I were flying this bird in 4-stroke, I would
not hesitate to mount a Saito 62. (which weighs about 15 ounces)

That being said, the AXI 28-26-10 is on the lower power spectrum in electric for this bird. I am unfamiliar with the motor you referenced.
It might work. I would like to see a motor that would comfortably put out 700 to 800 watts for this airframe. I would want a reasonable amount of reserve power. You don't have to use it, but it's nice to have in case you need it, for the small weight penalty incurred in going to a slightly larger motor. If you go too small, the motor will be at it's max or beyond, and not too happy.

Although AXI advertises you can use 5 cell LiPo's , not many in electric have used that motor in that configuration. It is usually used in 4 cell configuration, which means to get the wattage up there you need to use some serious amperage.

Might work, then again, for an additional 3 ounces, with much more power range, why not consider something like:

Hacker A40-10S (750 kv , 900 watts, 9 ounces weight) or its brother the

Hacker A4012S ( 610 kv, 900 watts, same weight)

You can see them on line @ Espritmodel.com

You can go 4 or 5 cell without penalty, ( if 5 cell, lower kv, 4 cell larger kv )they will swing whatever prop you throw at them, for this airplane, and they have ball bearings on both sides of the shaft for longevity, have internal cooling fans, and are very efficient without being too expensive. I tend toward higher
voltage,( 5 cell) , lower amperage to get the same wattage. Higher amperage can generate more heat.

I've used Hacker's in my twin electric fantasy bomber (A30's) and they performed very well.

Any questions, fire back.

Will Moore

Dennis Adamisin · « **Reply #6 on:** July 23, 2009, 10:02:02 AM »

Andreas:
I think the SK35-48-900 will work great in the Legacy with a 12x6 prop (try a pusher) and a 4Sx3600 or so battery. I think the Legacy is comparable to Will DeMauro's excellent electric SV-11 that he flies with a similar size power system - see his listed in the "List your Set-ups" thread

BTW the SK35-48 has a 28mm comutator and uses 26mm magnets - making it similar to the AXI-2826 series. The SK also is built on a 5mm shaft and uses larger bearings versus the normal 35-48 so those things help. My Nephew did some back-to-back tests and determined that the SK motor was clearly strongler than the normal 35-48 motor; I think Mike Andereson reported similar results here in SH - but I do not remember which thread that was in.

A larger motor might come in handy if you have any trouble balancing and need the weight, and of course a larger motor will work less hard, but the power is coming from the battery and is delivered by the prop. The motor can hurt you if it is too small, but does not do anything for you if it is too large.

I think you are on the right path...

Mike Anderson · « **Reply #7 on:** July 23, 2009, 10:51:52 AM »

Quote from: Dennis Adamisin on July 23, 2009, 10:02:02 AM

Andreas:
I think the SK35-48-900 will work great in the Legacy with a 12x6 prop (try a pusher) and a 4Sx3600 or so battery. I think the Legacy is comparable to Will DeMauro's excellent electric SV-11 that he flies with a similar size power system - see his listed in the "List your Set-ups" thread

BTW the SK35-48 has a 28mm comutator and uses 26mm magnets - making it similar to the AXI-2826 series. The SK also is built on a 5mm shaft and uses larger bearings versus the normal 35-48 so those things help. My Nephew did some back-to-back tests and determined that the SK motor was clearly strongler than the normal 35-48 motor; I think Mike Andereson reported similar results here in SH - but I do not remember which thread that was in.

.....

One of our SK users reported that by switching from a C3548-1100 to an SK 3548-1100 (same prop and battery) the RPM gain was right at 300 (with the timer power level maxed) on a 12-6 prop/3 cell setup.

We have one user with an SK 3548-900 flying on 4 cells in a Brodak Tanager/4 cells -- excellent power system and excellent flying model. He is currently building a full-fuse for an identical motor system.

My own SK3548-1100 replaced a C3548-1100 and the gain was almost TOO dramatic. The 'C model' was not performing like everyone else's 3548-1100's. In fact it almost duplicated the -900's, but when I did a spin test, I computed the Kv at 1085, so I don't really know why it acted like it did. I'm saving it for an E-Banshee and will probably fly it on 4 cells. The SK3548-1100 on my E-ssisted Twister has been slowed down to 5.2 sec. laps, most often using a 12-6 APC on 3 cells. The plane has issues, but not power related ones.

All that to say that I would think that the Legacy will probably fly on the 3548-900 w/ 4 cells. You may have to crank the power up a little over what we are using but our experience indicates that the headroom is available. Definitely go with the SK model - they are much improved over the C model and the difference in price is negligible.

andreas johansson · « **Reply #8 on:** July 23, 2009, 10:55:42 AM »

Will: Thanks for your answer, it certainly give some food for thoughts... However, I think the Hacker motors are a bit expensive.

Dennis: Thanks for your answer. If I have read and understand it correctly the 3026 in DeMauro's SV-11 is a bit more powerful than the SK35-48, 1000W vs. 770W.

hmmmm, this thing with e-motors isnt easy

Andreas

Mike Anderson · « **Reply #9 on:** July 23, 2009, 11:11:48 AM »

Quote from: Andreas on July 23, 2009, 10:55:42 AM

Will: Thanks for your answer, it certainly give some food for thoughts... However, I think the Hacker motors are a bit expensive.

Dennis: Thanks for your answer. If I have read and understand it correctly the 3026 in DeMauro's SV-11 is a bit more powerful than the SK35-48, 1000W vs. 770W.

hmmmm, this thing with e-motors isnt easy

Andreas

To compare a 3026 in one setup with a 3548 in a different setup requires much more information than a manufacturers rated max power.

A motor is as 'powerful' as you make it (right up until the time the magic smoke escapes) - those ratings are maximums, and you won't be anywhere near 770 watts continuous. With a 4 cell and a 12-6 inch prop, you will probably be pulling in the 30 amp range or ~450 watts.

Frankly, I am confident that the 770 watt rating for the SK is quite a bit understated. We have flown it at over 45 amps and it hardly warms up.

andreas johansson · « **Reply #10 on:** July 23, 2009, 11:53:55 AM »

Hmmm, its tempting to order the SK35-48, but I wait for some more opinions...

Andreas

Mike Anderson · « **Reply #11 on:** July 23, 2009, 12:25:49 PM »

Here is another that I've been tempted to try:

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8489&Product_Name=Turnigy_4250_Brushless_Motor_1000kv

Kv is a little higher than normally used but for a 13 inch or less prop, this should be a pretty good match. This is one of the 'Red&Blue" Turnigy motors that have many of the same features as the SK series.

One of our members has a 4250-850 (Not a Turnigy, but similar enough) flying in a Top Flite Score, which is a big plane. It flies OK, but we haven't had a chance to try to tweak the power system yet. I'm thinking that it needs a 13-5 or so on 4 cells.

Will Moore · « **Reply #12 on:** July 23, 2009, 04:08:02 PM »

Quote from: Mike Anderson on July 23, 2009, 11:11:48 AM

To compare a 3026 in one setup with a 3548 in a different setup requires much more information than a manufacturers rated max power.

A motor is as 'powerful' as you make it (right up until the time the magic smoke escapes) - those ratings are maximums, and you won't be anywhere near 770 watts continuous. With a 4 cell and a 12-6 inch prop, you will probably be pulling in the 30 amp range or ~450 watts.

Frankly, I am confident that the 770 watt rating for the SK is quite a bit understated. We have flown it at over 45 amps and it hardly warms up.

Mike:

Where is the web site of these motors you are referring to. I'd like to check them out.

Will Moore

Mike Anderson · « **Reply #13 on:** July 23, 2009, 05:21:48 PM »

http://www.hobbycity.com/

Hobby City, Hobby King or (used to be ) United Hobby --

It is a Chinese distributor - the "Turnigy" brand name is their house brand - they apply it to motors, batteries and ESC's. They also stock some brand names and some other Chinese derivative brands. Everything gets shipped from Hong Kong.

The prices on-line are quite good, the shipping is a little expensive and things can take awhile to get to you. Also, you have to keep an eye on the "Quantities on hand" numbers or the whole order can get back-ordered for something that may take a long time to get in.

In short, there is an art to buying from them - and there are extra price breaks for becoming a "Platinum" member which appears to be after your 10th order from them (or some dollar benchmark).

Our local hobby shop has become a dealer for them and has a pretty good inventory of their often used items (according to my flying partners - I haven't been there yet since he got it in). His prices are also in line with ordering on-line and paying the shipping, so I may have him do all my ordering from now on.

They also have a "US Warehouse" if you order certain items - the prices are higher, the shipping is lower and I assume that it is a little faster, but I've never bought anything that was in stock in the US warehouse.

Alan Hahn · « **Reply #14 on:** July 24, 2009, 05:15:46 AM »

Andreas,

If I look at Paul Walker's setup in the Sticky at the top of this forum, I notice his Impact is 750 sq in, weighs 69 oz, and flies 5.3-5.4s laps on 70 foot lines with a 13.6"x~7" carbon prop at an rpm of 8650.

So I think this would represent the top power needs that a Legacy would use.

I include a file of how a Scorpion 3026 (kV=840), nominally equivalent to the AXI 2826 of similar kV I think) behaves with several props and supply voltages (nominally 3s, 4s lipo packs).

If you look at the APC 13"x6.5", I note that this motor will statically turn that prop at 8650 rpm pulling about 800 watts. This would certainly be the maximum that you would need (I think) to fly a Legacy, which is a little smaller than the Impact. Scorpion claims these size motors can run 1000 watts continuous (I don't know that I would go there tho'). 8650 rpm represents ~73% of the no-load rpm at full throttle from the 4s pack. Again I think actual power needed in the air (during the boring level flight period) would be significantly less, so the motor would only be stressed during the maneuvering part, and I think it is fine to handle those power bursts.

I would think the AXI 2826 would be about equivalent, as would any outrunner with similar inner guts. If you are trying to keep costs down, then I think an outrunner is your only choice---but I could be wrong. In any case, the main cost isn't the motor but will be the batteries.

One comment, Scorpion has replaced that particular model with the new V2 models, which they say are more efficient that the old one (new kV is 890 rpm/volt, a little higher than the original one). The cost is $80 for the new version. This is just to provide a cost point. Here is a link to the new model. Unfortunately they don't have the prop chart for the new version.
http://www.innov8tivedesigns.com/product_info.php?cPath=21_25_80&products_id=525

andreas johansson · « **Reply #15 on:** July 24, 2009, 06:27:46 AM »

Hi all!

Rightly or wrongly I came to the conclusion that the SK35-48 *should* be enough to power my Legacy. The SK35-48 is more than equivalent to the AXI2826 in terms of power. The 2826 can handle up to 600W = 600W/14v = 43A, the SK3546 770W = 770W/14v = 55A. I know that this is theoretical and that the reality sometimes prove different. Many seems to use the CC45 ESC in larger aircrafts (and so will I), and that should mean that their setups wont use above 666W (is the devil involved?) more then in short bursts. Again, this is theoretical and I know that that the CC escs can take a bit more power is properly cooled.
The weight of the Legacy will be critical (isn't it always?). Many Legacy's seems to be in the range 59oz-62oz (wet power). I think I will need to keep it under 60oz = 3.75lbs. I think I have read that Mike Palko have said that you need 160W per pound, 3.75lbs x 160W = 600W and that should mean that I have almost 200W to spare, again theoretical.

What to do to keep the Legacy as light as possible?:
Exchange some of the wood in the kit for more lightweight wood.
No fuselage doublers.
No engine bearers

No paint, monokote or Oracover over the complete airframe.
Moulded turtle deck instead of carved blocks.
Very minimal use of epoxy glue.
Fuse mounted CF landing gear.

/Andreas

bob branch · « **Reply #16 on:** July 24, 2009, 07:02:34 AM »

Look at the numbers with the axi 2826/12 rather than the /10. You will get much lower current draw, never in the 40 amp range. And it will turn a bigger prop. I have been flying a 62 oz airplane with an axi 2826/12 on an apc 12X6E and 63 ft lines. 8600 rpm yields 5.2 second laps, and 29 amp draw. I fly with a phoenix 45 in governor mode with a Wil Hubin timer. The 2826/10 will go very close to or over max rated amps on a legacy and you will be limited to an 11 inch prop to keep it under max. I stopped using the 2826/10 2 years ago because of the current draw issues. The 2826/12 is a much more flexible motor for or uses, can turn a wider variety of props, uses less amps, and allows smaller batteries. I fly on 4 cell 3000 mah packs and on a 5 min 32 sec full pattern flight (plus about 5 laps) flight consume about 2000 mah. Rick Sawicki is also flying similar setup on multiple aircraft and we get similar numbers and results on all our planes. Much thanks to Rick on his help in my setups. He has really made this power system plug and play.

Also a note, there appears to be a change coming from axi. The radial mount for the 2826 series has been discontinued. I talked Todd's models and they had checked with their distributors and found it had been discontinued. Apparently the 2826/10 is discontinued according to the Tower site. Tower no longer has the mounts either. Tower does still have the 2826/12 available and the mounts are still available from Lobby HObby as of this week as are the motors. I have ordered a few more because of the success we had and its flexibility.

bob branch

Dennis Adamisin · « **Reply #17 on:** July 24, 2009, 08:48:45 AM »

Andreas:
I think you are on the right path. The only item on your "Lightening" list you might want to reconsdier is ELIMINATING the fuselage doublers. After building with and with out I think the best answer is to keep the doublers BUT make then out of 1/64 plywood instead of the normal 1/32 or 1/16 ply. The reason I say this is that I find it handy to attach things inside the fuselage when the surface is more substantial than plain balsa. This could just be a silly preference of mine too.

You might also consider "ventilating" some of the wood. FOr example on the rear fuselage cut openings in the fuselage sides (like your Nobler!) and on the stab, make it an open framework structure (if it isn't already).

I think you will have adequate power for a "normal" Legacy, however, losing weight is ALWAYS a good idea!

andreas johansson · « **Reply #18 on:** July 24, 2009, 10:55:35 AM »

Bob: I have some strange suspicion that you are right, if the SK35-48 had been available in 800kv (as the "normal" 35-48 is) i would have ordered it. However, I have noticed that there is more than one way of powering a E-Stunter and I really hope that the "SK" is gonna work out. If it doesn't, it was only $25.

Dennis: Naaah, fuse doublers are for wimps

Seriously, you got a point there. I have thought of making doublers like a "frame" and not covering all the wood. If you have seen the tank/battery compartment of an ARF Nobler you know what I mean. However, I don't think the E-Legacy needs any doublers at all.

OT: I have 5 weeks of vacation now :-) = Hopefully a lot of C/L (and finally relearn how to fly inverted)

/Andreas

William DeMauro · « **Reply #19 on:** July 24, 2009, 05:53:23 PM »

Andreas,
I know I'm late jumping in here, but I just haven't had time for posting and barely any for flying. Like Dennis says your Legacy numbers are very similar to my SV11 and if you use my numbers and shoot to improve on them(that should be easy), you should have no trouble ending up with a good flyer. I would think you have a good chance of the SK35-48 working out but make sure you give it plenty of cooling and if you run a pusher prop on it make sure it can cool in "reverse". I smoked my original Scorpion(expensive lesson) cause I didn't know that the V1 motors don't cool in reverse. I have a 3026-890 now on it that has more power than I could ever use and lets me run the pusher prop. I've also opened up additional cooling holes in the top of my plane. I've also come to the conclusion that no matter which motor you choose,all these "so called" max rating are under the most optimal of test conditions with plenty of cooling. In a full fuse stunter, we know optimal conditions do not exist. I too think you should do some sort of doubler thing on your plane. Even though E-motors don't really vibrate much,we still put alot of stress on our planes in hard maneuvers and I know you don't want to tear the front off your plane. Good luck with it and keep us posted.
William

bob branch · « **Reply #20 on:** July 24, 2009, 06:25:57 PM »

Another reason for some doubler, even light is that it makes changing motors easier if you glue in mounts. You can seperate the glue line off the ply with almost no damage while off balsa you will have damage and weakening. If you use a removable mount you will need the ply to prevent pull thru.

Bob Branch

andreas johansson · « **Reply #21 on:** July 25, 2009, 01:24:46 AM »

Guys!

It seems like the general opinion is to use doublers and so I will. It will be something like 1/32 - 1/64.

As for the cooling I have been toying with the idea of making a P47 like front on my Legacy. However, I dont really know, I'm more fond of a P51 style nose but it equals less cooling.

Andreas

Kim Doherty · « **Reply #22 on:** July 25, 2009, 09:28:49 AM »

Quote from: Andreas on July 25, 2009, 01:24:46 AM

Guys!

It seems like the general opinion is to use doublers and so I will. It will be something like 1/32 - 1/64.

As for the cooling I have been toying with the idea of making a P47 like front on my Legacy. However, I dont really know, I'm more fond of a P51 style nose but it equals less cooling.

Andreas

There is no need for plywood doublers in the nose. The easiest way to add some stiffness in a box type fuselage is to use 1/32 or 1/16 hard "C" grain balsa or just "A" grain applied across the existing structure. If you want a light but very strong firewall use 1/4" balsa sandwiched between two layers of 1/64" ply with pine crush blocks let into the former where the bolts will go. The thicker former will give you the surface area you need.

Cooling is not optional. It is everything!

Kim.

Dennis Adamisin · « **Reply #23 on:** July 25, 2009, 09:52:47 AM »

Quote from: Kim Doherty on July 25, 2009, 09:28:49 AM

There is no need for plywood doublers in the nose. The easiest way to add some stiffness in a box type fuselage is to use 1/32 or 1/16 hard "C" grain balsa or just "A" grain applied across the existing structure. If you want a light but very strong firewall use 1/4" balsa sandwiched between two layers of 1/64" ply with pine crush blocks let into the former where the bolts will go. The thicker former will give you the surface area you need.

I found that I liked the idea of having the HARD surface (as I think Bob metnioned. I do not think the doublers are really needed for the strngth. mor like for the maintenacne and handling of the bird in sevice (that make sense?) I could probably get what I want with a layer of 1/2oz cloth vac-bagged onto the inside surfaces.

I also completely concur with your firewall sandwich. I used 1/4" dowels as the anti-crush posts.

quote author=Kim Doherty link=topic=13349.msg119913#msg119913 date=1248535729]
Cooling is not optional. It is everything!

[/quote]

AMEN Brother Kim!

I like how the radial cowl on my Mythbuster cools, but remain on search for good generic cooling guidelines and installation. Have not ruled out the fan-equipped heli-motors either.

On the P-51 there is a little chin opening just under the spinner; that with a little creative ductwork ought to do the deed. Will DeMauro did a really neat inlet on his SV-11 that rotutes air directly into the Scorpion.

Kim Doherty · « **Reply #24 on:** July 25, 2009, 10:09:59 AM »

Quote from: Dennis Adamisin on July 25, 2009, 09:52:47 AM

I found that I liked the idea of having the HARD surface (as I think Bob metnioned. I do not think the doublers are really needed for the strngth. mor like for the maintenacne and handling of the bird in sevice (that make sense?) I could probably get what I want with a layer of 1/2oz cloth vac-bagged onto the inside surfaces.

Hi Dennis,

I don't disagree with the idea of a harder point to mount the firewall too. If I was going to do this I would only put the ply doubler 1/4" ahead and behind the firewall mounting point. On the other hand, IMHO you should not build airplanes to "survive" maintenance and handling. We should be building them to "fly" in the air. Handle With Care!!

Kim

William DeMauro · « **Reply #25 on:** July 25, 2009, 05:50:11 PM »

I have 1/8 balsa doublers on my SV11 with a layer of carbon fiber matt in between. Looking back now I would probably do it Kim's way,
The easiest way to add some stiffness in a box type fuselage is to use 1/32 or 1/16 hard "C" grain balsa or just "A" grain applied across the existing structure. If you want a light but very strong firewall use 1/4" balsa sandwiched between two layers of 1/64" ply with pine crush blocks let into the former where the bolts will go. The thicker former will give you the surface area you need.
The vacuum bag thing is very tempting too.
What I have is overkill !!! But as more people build E-Planes, we pool our knowledge and improve on them. I think by now you have the message that it MUST HAVE COOLING!!!!
William

andreas johansson · « **Reply #26 on:** July 26, 2009, 01:32:56 AM »

Hi guys!

This thread turned into a real good E-CL discussion.

The main problem with cooling is to get circulation of the air. To get the air in isnt that hard but to get it out is difficult as you dont want cooling exits all over the aircraft. To get effective cooling the cooling exit(s) should be about 2-3 times larger than the intake(s). That way you get a venturi effect.

Andreas

john e. holliday · « **Reply #27 on:** July 26, 2009, 01:04:03 PM »

Wouldn't it be logical to design a cowl/nose in that there is an airvent around the outside of the spinner? In other words use a spinner that is smaller than the nose of the plane. DOC Holliday

Alan Hahn · « **Reply #28 on:** July 26, 2009, 01:58:16 PM »

Quote from: john e. holliday on July 26, 2009, 01:04:03 PM

Wouldn't it be logical to design a cowl/nose in that there is an airvent around the outside of the spinner? In other words use a spinner that is smaller than the nose of the plane. DOC Holliday

That's what I do, sort of like a Folke-Wulf 109. Works well with an outrunner--which shares some features of the radial and rotary engines (large diameter).

Alan

andreas johansson · « **Reply #29 on:** July 26, 2009, 02:46:21 PM »

and thats why I thinking of making a P47 style nose for my Legacy.

Andreas

John Witt · « **Reply #30 on:** July 26, 2009, 06:16:30 PM »

Here's are some pictures of the nose structure of my Panther which has worked out pretty well. The fuselage sides are two layers of 1/8 in medium weight balsa. There are four 5/16 sq oak stringers glued to the balsa. These wooden pieces are tapped 1/2 inch deep x 6-32 machine screw threads. In my original set up, these screws mounted the ends of the X-form aluminum motor mount for the E-Flite 46.

When I changed over to the smaller Rimfire motor, I needed a spacer which mounted to the original E-Flite rails and provided a mount point for the smaller X-form piece. This spacer is cut out to follow the X-form mount and allow air flow around all four sides. These cut-outs also make the spacer fairly light in spite of its 5/8 in thickness.

The horizontal lite-ply rectangle on top is glued across the top oak rails and to a slanted lite-ply bulkhead that forms the exit air duct out the bottom cowl. Part of the inlet air is split off by this piece and flows over the battery and ESC, down the fuselage and out the hole where the elevator pushrod comes out through the fuselage side.

The motor is just nominally warm to the touch after a flight as is the battery and ESC. Nothing is what you would call hot, and this in roughly 80-85 deg ambient air temperatures. I intend to get a small spinner and pretty it up a little more. Someday.

This nose has survived one cartwheel so far that only popped out the cross piece on top and cracked the slanted bulkhead. The top and bottom cowl blocks come off for easy access to the motor mount screws.

The oak rails would have been better from maple. They need to be hard wood to accept the tapped screw threads. One could probably make these lighter by using hard balsa for the rails and embedding dowels for the threads. I drill the 6-32 tap holes at the minimum size for the tap, tap them, and then soak the threads in thin CA. After the CA sets up, I chase the threads again with the tap. This gives a reasonable good grip on the screws, seeing how nothing has pulled out yet. I use a minimum of 3/8 inch of thread engagement for the 6-32 screws.

Hope this is of some help.

John

Author Topic: Legacy (Read 2715 times)

Alan Hahn

Alan Hahn

Kim Doherty

Kim Doherty

Alan Hahn