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PSS Dash-7 (DHC-7) build blog

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Ben-Erik Ness11/11/2018 18:04:11
26 forum posts
51 photos

I have had this idea on building a PSS Dash-7 for a while, and now I have started. I must say that John Hill's DHC-8 a good sourc of inspiration! **LINK**

The project in brief: It will be constructed from white foam that is going to be sheeted with balsa or abachii (yet to be decided) I have not calculated the scale of the plane but it's slightly under 1:10 with a wingspan of 238 cm.

The fuselage is made circular, so this is not to scale, but it makes it easier to make sections of the fuselage. the nose section is first cut by hot wire vertical and horizontal, then carved to shape with a sharp knife! The aft fuselage is made by hand, with a knife!

I'll upload a couple of pictures soon, so more to come!

Ben-Erik

Ben-Erik Ness11/11/2018 20:46:54
26 forum posts
51 photos

A few pictures...

This is my inspiration, having flown with Wideøe in the 80's and Petrolium Oil Services less than 10 years ago.

Hoping to acheive slow and floating flying capabilities in low to medium lift...

0475428.jpg12-1.jpg

Icut the circular sections by rotating the square into a circle, I have a needel in the center that the foam block is placed on to.

img_20181109_210925.jpg

img_20181030_222804.jpg

It's not a small plane!!

img_20181104_221939.jpg

Tony Bennett11/11/2018 21:14:39
avatar
5082 forum posts
129 photos

i like that sir.

not enough airliners moddeled.

Tony B

Former Member11/11/2018 21:22:20
1322 forum posts

[This posting has been removed]

Ben-Erik Ness18/11/2018 20:42:46
26 forum posts
51 photos

Working on the wing saddle. Getting the shapes right from the wing saddle to the forward foselage is kind of difficult... Not getting it right unfortunately.

I guess I have to make a new section just in friont of the wing sad

img_20181118_212742.jpg

img_20181118_212801.jpg

This is what it should have looked like...

wingsaddle.jpg

Note to self. Have a better look at pictures before carving foam next time...

Edited By Ben-Erik Ness on 18/11/2018 20:55:04

Ben-Erik Ness24/11/2018 10:35:20
26 forum posts
51 photos

I have now cut two new sections and reshaped the wing saddle. It's complex shapes, and it's far from scale, but it looks better than the last attemt. Isolated without any pictureas reference I think itlooks much better now. I have to remind myself that this is not a scale competition...

Last night I also god a huge chunk of balsa sheets on Black friday sale... wink

This is how it looks right now:

img_20181124_112427.jpg

img_20181124_112548.jpg

 

Edited By Ben-Erik Ness on 24/11/2018 11:02:59

Ben-Erik Ness30/12/2018 21:13:53
26 forum posts
51 photos

A little free time in the holidays to work on the Dash-7.

As I have stated earlier, I was happy with how the wing was blending into the body. But after some considerations I have done it over again. I have also glued the fuselage together permanently, apart from the nose section.

This plane will due to the layout come out tail heavy, so in order to utilize the fact that I will need nose weight I have started to improve strength in nose section. Due to the environment on the places I fly a strong nose will benefit to a longer life of the model.

Not rocket science, carbon and epoxy will do the job!

nese2.jpg

nese_1.jpg

Wings next!

Happy holidays smiley

Ben-Erik Ness03/01/2019 22:31:25
26 forum posts
51 photos

Got some time in my hangar the last two nights... Cutting wings. Haven't done this before, but I'm quite happy with the result blush

img_20190103_203013.jpg

img_20190103_204046.jpg

She's going to be big... Won't be a fast flyer either...

img_20190103_231625.jpg

Andy Meade04/01/2019 09:48:14
avatar
2789 forum posts
717 photos

Looking good Ben - I like the nose reinforcement, should go through walls now yes

Ben-Erik Ness04/01/2019 17:35:29
26 forum posts
51 photos
Posted by Andy Meade on 04/01/2019 09:48:14:

Looking good Ben - I like the nose reinforcement, should go through walls now yes

Thanks Andy!
The nose is rock solid, the rest of the foam nose section will be coverd with glass cloth and epoxy.

However, next step will be to cut the fin and the tailplane!

Ben-Erik Ness06/01/2019 13:40:43
26 forum posts
51 photos

Need some advise guys!


I'm trying to plan ahead of my progression. Now I'm planning the flaps on this monster. My plan is to have full offset flaps from the root to the second nacelle. Then a flap, bottom hinged half of the rest, and the outer rest will be normal ailerons. Then I can combine aileron and the center flaps in the turns and utilize lots of flaps upon landings.

I’m now on to the inner main flaps. They are 25% of the distance from Leaning edge to tailing edge.

Have a look at the video. Will this work?

Andy Meade07/01/2019 09:56:48
avatar
2789 forum posts
717 photos

I can't see why it wouldn't work. People have used the Robart pin hinges offset below the wing in hard balsa fairings in the past to achieve the same result. What's your worry - the mechanism, or the flap effectiveness?

Ben-Erik Ness07/01/2019 18:22:46
26 forum posts
51 photos
Posted by Andy Meade on 07/01/2019 09:56:48:

I can't see why it wouldn't work. People have used the Robart pin hinges offset below the wing in hard balsa fairings in the past to achieve the same result. What's your worry - the mechanism, or the flap effectiveness?

Technically it will work, it's the effect in flight I'm thinking of. I need the same stop effect as I have on my Xplorer...

Andy Meade08/01/2019 09:33:27
avatar
2789 forum posts
717 photos

I think it's quite a big slotted flap - generally slotted flaps produce lift more than a plain flap would, as the high pressure air from under the wing can bleed to the top surface and help offset the start of stall. As long as you can get a large angle on the flap, it should work as intended.

Ben-Erik Ness20/01/2019 16:58:54
26 forum posts
51 photos

After a busy week with 3 days travelling it's good to be back at the Dash-7. At least one part is getteing close to finished. The horizontal stabelizer is now sheeted with balsa:

img_20190120_173343.jpg

What concerns me is the weight. This one is 221 grams, maybe not bad for a 80cm wingspan. I realized that the 1,5mm balsa I got had a great variation in weight, and I think I could have built the wing lighter. But this is the first time I'm sheeting foam with balsa, so I might have to be happy with the result after all...

Any opinion will be appreciated!

Hope to have the wings ready for sheeting by the end of the coming week...

Andy Meade04/02/2019 09:17:34
avatar
2789 forum posts
717 photos

221g doesn't seem at all bad, I'd say go with it. If you need to make another in the future, at least it's a wing, right? I know that's not ideal, but that's what I always say to myself!

Ben-Erik Ness07/02/2019 21:48:52
26 forum posts
51 photos
Posted by Andy Meade on 04/02/2019 09:17:34:

221g doesn't seem at all bad, I'd say go with it. If you need to make another in the future, at least it's a wing, right? I know that's not ideal, but that's what I always say to myself!

I do agree... My main wings with 1mm balsa sheeting came out at 515 geams each (before glassing), so there is no doubt about it's possible to build the elevator lighter. I'll go on with the build and decide later. It only takes a few evenings...

Ben-Erik Ness19/02/2019 21:07:28
26 forum posts
51 photos

A litle update. Wings are now sheeted. I'm happy with the result, and I thought I'll show how I did it. The wings are really stiff, and as you will see, carbon does the job!

This is the underside. 6 strands of carbon rowing embedded in the foam with epoxy:

img_20190121_214402.jpg

Then I added the carbon mat along the length of the wing, all with epoxy:

img_20190121_215156.jpg

The same procedure on the top of the wing, apart from the embedded carbon in the wing:

img_20190127_205059.jpg

I let the carbon and epoxy cure with the wing under pressure..

The end result:

img_20190128_182838.jpg

All pieces together, It's going to be big...

img_20190218_214046.jpg

Ben-Erik Ness19/02/2019 21:11:36
26 forum posts
51 photos

Next task is how to design the tail. How should I attach the horisontal stab on the T-tail. This is my preliminary plan... Any ideas and suggestions out there??

img_20190219_213256.jpg

Ben-Erik Ness26/10/2020 14:23:54
26 forum posts
51 photos

My Dash-7 has been on the shelf for some time, but now I'm at her again.

I foud one of my own old photos taken after arriving from Oslo, way back in 1983, that got me going!

img_20201024_135755.jpg

I have done some stregthening of the wing box, in order to distribute load, and right now I'm in the midle of sheeting the fuselage with balsa.

img_20201026_135246.jpg

I also wanted to strengthen the area where the tail fin is mounted hence the carbon fiber!

img_20201026_135320.jpg

Hope to show more in the next few days!

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