Thread Tools
Jan 15, 2015, 08:27 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
Quote:
Originally Posted by ksqm
Lockey,

You are one of those rare builder/designers, who see's what they want to build and just do it. One of the "Masters". And you have the TIME!!! You can sign me up. I have EDFs from 20mm up to 50mm. Decisions, Decisions, Decisions!!!

Ksqm
What size you want to build this one ksqm ? full size is for a 64 - 70 mm fan

By the way mate, how is the Gripen going ?

Lockey
Sign up now
to remove ads between posts
Jan 15, 2015, 02:38 PM
Registered User
Lockey,

I'd like to go with a 50mm EDF, but I need to measure the FSA of the unit. I'll do that when I get off work later. I'd would size the build based on inlet size needed. The Gripen is slow at the moment. Hoping to be able to get air under the wings by Sunday though. 🙏 I'll post pics of deviations I did. More to come!

Ksqm
Jan 15, 2015, 07:33 PM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
Quote:
Originally Posted by ksqm
Lockey,

I'd like to go with a 50mm EDF, but I need to measure the FSA of the unit. I'll do that when I get off work later. I'd would size the build based on inlet size needed. The Gripen is slow at the moment. Hoping to be able to get air under the wings by Sunday though. �� I'll post pics of deviations I did. More to come!

Ksqm
50 mm sounds good ksqm, I just had a look and this would give you about 535 mm wing span as against the full size of 760 mm

By reducing the whole thing in Sketchup and doing a simple area test on the inlet v's the fan size (no allowance for motor etc) ... the 50 mm fan area is 1941 mm˛ and the inlets are 1055 mm˛ each, making 2110 mm˛ in total

We might have another beta builder joining us too mate, he wants to build the full size only as a pusher .... this should be fun

Lockey
Last edited by Lockey; Jan 15, 2015 at 07:41 PM.
Jan 15, 2015, 09:05 PM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
I posted on the EDF forum about the CF tube running through the duct and was advised to go this way (see pic) so will take their advice

Say I was to use 4 mm CF spar, I would use 2 x 2 mm lite ply for the centre formers and either 2 mm lite ply for the outer ones or I could use .8 mm ply

Lockey
Last edited by Lockey; Jan 15, 2015 at 09:40 PM.
Jan 16, 2015, 02:02 AM
michigan jet guy
mrshea's Avatar
i think the .8 mm ply for the outside would be fine. Most of the spar load would be up and down and not side to side. I think it would be enough and would save a little weight in the process. just one persons opinion. Phil
Jan 16, 2015, 06:43 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
Quote:
Originally Posted by mrshea
i think the .8 mm ply for the outside would be fine. Most of the spar load would be up and down and not side to side. I think it would be enough and would save a little weight in the process. just one persons opinion. Phil
Think you are probably right Phil

Lockey
Jan 18, 2015, 07:26 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
I have started the build and found the front section was a bit of a cock-up but not difficult to fix, just need to re-design it a little, apart from that its all going together well

I will change the thread now to a "build log"

Lockey
Last edited by Lockey; Jan 18, 2015 at 07:55 AM.
Jan 18, 2015, 06:59 PM
Registered User
Lockey,

Seems like you're in a bit of a pickle here. Well, all is not lost. You can go with open ducting, closed area ruled, or a combination in between depending on how much work you want to put into it.

Now, you can go with what you have and just continue the build. I would at least continue the inlets back to within two times the length of the EDF. Create a chamber in front of the EDF and call it a day. My T-50 Golden Eagle build is a good example. If your EDF unit has a ring or bell mouth, use it. If you don't have one, you can make one. Or if you look closely, I sanded a cone in a piece of foam, that funneled air to the EDF.

An in between solution would be to angle the inner walls of both inlets to meet at the face of the EDF. You could gracefully curve them and not just have sharp angles. The outer walls of the inlets would be parallel to the inner walls and just cover. Now, you can transition to half circles that meet at or before the EDF face. Or have two rectangles that form a square around the EDF. You can add a bottom to the duct at any time to elevate it to just fit over the EDF.

Finally, you can hotwire or sand a set of ducts. This can been done in any number of ways. If you go this route, you can "Area Rule" the ducts. This will give you the most efficient ducts. My F-20 Tiger Shark build shows a very down and dirty way of doing the ducts. Believe it or not, I used packing tape and hair spray over the plugs.

Now, one last thing. With the sized EDF your using, I would test any enclosed ducts before installing. Depending on the power levels, they will collapse if not reinforced. Good Luck!

By the way, I have the plans printed. Send the update front fuse when you can.

Ksqm
Jan 18, 2015, 08:10 PM
Registered User
Lockey,

What I said above is to resolve the issue with your current design, as is. To really address the issue, you need to redesign the front fuse connection to the main fuse and apply the above. If you look at Jetset44's designs, they all have the same key design feature, that lends itself to EDF conversion. The forward fuse/main fuse transition design. After the forward fuse joins the main fuse/wing/inlet area, the forward fuse walls (generally inner walls of the ducts) angle towards the planes center line. Or there is a lot of room to continue to the center line. Very, very important. It provides room to deal with the inlet to EDF face transition.

The builds above are decent enough examples of open and closed ducting. The key is getting airflow from the inlets to the EDF as smoothly as possible.

Ksqm
Jan 18, 2015, 08:40 PM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
Aaron, this is the only bit you need to discard really (see second pic) I am re-doing the front end and playing with the ducts right now

I didn't want to go down the fiberglass road for the ducts, but make it as easy as possible for other guys to build

The forward part of the duct is (sort of) already there (see 1st pic) between the inner and outer fuselage, so its really only the back part to worry about

I had a look at Jetset44's models and most seem to be pushers (maybe I should stick with pushers eh)

Lockey
Last edited by Lockey; Jan 18, 2015 at 08:57 PM.
Jan 18, 2015, 11:49 PM
Registered User
Lockey,

Then easy it is. Try this in sketchup first. About 3.5" from where the inner fuse wall meets the bottom edge of the inlet, angle the inner fuse wall towards the planes center line. Intersect the planes center line at a point, twice the diameter of your EDF, in front of the EDF. So, if your using a 60mm EDF, the fuse inner walls will meet 120mm (4.7") in front of the EDF. Run a parallel outer wall, the width of the inlet opening. Cover the air channels. This will channel airflow towards the center line. Place a former to consolidate the two air channels, at the point the two inner fuse walls, meets the center line. The opening in the former should match the inlet area. That's it, down and dirty ducting. Your just channeling the incoming airflow to the center, for the EDF to suck it in. You can also do the same thing with your current design, just enclose the inlet to the first former. Open ducting to the fan from there. Hope it helps.

Ksqm
Jan 19, 2015, 12:41 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
Ksqm, thats sort of what I have been working on

Just thought maybe from 3 mm Depron

EDIT ... modified the front piece slightly (see last pic)

Lockey
Last edited by Lockey; Jan 19, 2015 at 01:53 AM.
Jan 19, 2015, 02:49 AM
Registered User
You could try that, but you're going thru three big changes in area. Gotta go to bed. Getting up in the morning to take my nephew and friends to an indoor fly in. Will take my cutting board and cut plans out. See what I can come up with. Keep at it.

Ksqm
Jan 19, 2015, 05:34 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
Got to thinking about launching this one and there will be no where to get hold of this beast

Maybe one answer will be to have a hand grip inside an elongated hatch (similar to the way RC powers does his models)

Lockey
Jan 20, 2015, 05:27 AM
Tony Audsley Retired Locksmith
Lockey's Avatar
Thread OP
This one is proving to be a lot of work with the EDF

I have gone for a proper duct system, I only hope its worth the extra effort ... made the ducts out of 3 mm Depron, this is a lot lighter than 200 gsm card (and that is VERY thin card) ... had a bit of black 3 mm stuff left over from another project so I used it for the front duct and used 3 mm white for the rear duct

Now I know the ducts work, I will refine them somewhat to be made from 3 mm Depron

Pics later, I will be doing a bit more this evening, had about 4 hours or so this afternoon

Lockey


Quick Reply
Message:

Thread Tools