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Jun 27, 2002, 09:58 PM
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rays89's Avatar
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Dumas standard J-1


I just picked this kit up at the LHS. I put a few kits to the side. because I really like to try converting this kit to R/C. so far I have built 2 guillows kits and converted them to R/C one was the SE5a which was a success and the Neiuport 11 which was a total failure. so Im running at 50%.
Im just wondering if there is anybody here who has done this conversion. and some advice like motor choice. I was hopeing on using a gws ips drive for this. I should be starting this conversion hopefully by Sunday but Hopeing to get a little advice on this plane.
Thanx
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Jun 28, 2002, 02:50 AM
I sure can't help you with any mods necessary but would you please let me know the size of that kit and just how you end up handling the conversion. I've had a Sterling Jenny kit saved up for many,many years and while the wood is only suitable for making orange crates, the plans are fantastic,with lots of scale detail . I'm not home so I don't tremember the wingspan but seems to me its well over 32 inches. The beautiful decal set was shot but I spoke to someone at Sterling (Philadelphia?) about 7 years ago and he sent new ones, which I've refrigerated ever since so they're still good.
Seems to me I've read here about the need to enlarge the tail surfaces on this type of mod, do you usually do that?
Good luck with it, hope to hear from you.
Vince
Jun 28, 2002, 03:13 AM
Whoops, just did a search (I'm a little slow, but I'm new here) on Sterling Jenny and the news ain't good. Megowcoupe passed on the orage crates and made a coffin with the wood. But even with "the word" from an objective expert a little voice inside my brain says, "yeah, but you could do it with contest grade wood and a cheater tail".
Should just go turn up the volume on CNN but thats all bad news too.
Oh my, I still hear that voice.....................
Jun 28, 2002, 11:26 AM
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rays89's Avatar
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Vince
You hear the same voice? Well my voice says the wood will work trust me.......yikes. What I do is just improvised as I went on. I would lay the electric components on the plans seeing what would fit where. This dumas wood is light but very fragile. I figure a little bass wood at points that would need a little more Beefing up. I guess the Guillows kits are made from the same orange crate. Well it worked 50% of the time. Never enlarged the tail myself but I did cover it with 1/64" plywood
Jun 28, 2002, 04:18 PM
Balsa Flies Better!

Check Microflight


IIRC the Dumas J-1 was reviewed in Microflight. Apparently it worked well. Dumas stuff is much lighter than Sterling.

Vince- I did the Sterling Jenny before I had a good sense of what to use in terms of motors. I'd pick something different these days. Nevertheless, using the kit wood, it was way too heavy, and that's with a fair amount of hacking. I did get the airplane to fly, but it was something of a handful, although really pretty in the air. Landings were always arrivals. If you want to take a crack at the airplane, I actually think the stock tail surfaces are OK. Lighten the wings- that TE has enough wood in it for the LE spars, and the TE. Lots of wood can come out of the fuse as well. I'll bet at an ounce lighter in the wings, it might fly pretty well, although I really hated the high moment of inertia. Once the airplane was banked, it didn't necessarily want to come out. It's kind of like the full scale that way- only fly it when its calm.

Sam
Jun 29, 2002, 09:10 AM
Thats a better prognosis than I expected for the Jenny and the Standard sounds like it'll do the job. Well "Rays" optimism is well founded.
Haven,t looked at the Jenny in a while but I do remember that TE!
Humungous! Never was much of a fan of plastic films, what do you both think is a good covering for this size and type? And Sam do you think the bank recovery problem is dihedral (lack of) or just work on getting the weight out of it and go for ailerons?

Vince
Jul 01, 2002, 08:53 AM
Balsa Flies Better!
Vince

Re covering- I'm surprised by that one. Jap tissue with nitrate of course....

Weight is the enemy. Ailerons add weight, decrease lift, increase drag, and are often ineffective at these size ranges. A little more dihedral might help though.

In terms of power- I'd lean to an EMPS-1 running on a 5 cell 350 nicad pack. This airplane needed more power than I thought it would based on weight- it's clearly draggy and inefficient. I remember trying an HY-50B motor, a 2 cell Li-Mn pack, and a 6" Tern prop. It wouldn't climb on that combo. I eventually went to a 3 cell Li-Mn pack and a direct drive Speed 280. Occasionally it flew- needed lots of washout, tip stalls were a problem. But if I got everything right, and I was nimble on the sticks, it was pretty in the air.

You know that there is a Dare kit of this airplane, about a third larger that has a lower wing loading and supposedly flies superbly? I've got that kit- it's a much better starting point, but nowhere near as scale.

Sam
Jul 01, 2002, 09:12 AM
Hey Sam
My thoughts went to tissue also, have a great old collection of good tissue but I see even the tiny ones here are covered with some sort of synthetic, so......
I saw the Dare kit but noticed it wasn't very scale and of course the challenge of the Sterling is just that....
As I recall the Jenny had no dihedral or at least any easily discernable Hmmmmmm, no ailerons. Well, I'll put the Davis 049 CO-2 engine aside, make a note of the motors you list and start some engineering thoughts when I get home
Thanks
Jul 01, 2002, 09:53 AM
Balsa Flies Better!

Correction- HY-50D


Just caught an oops...I used an HY-50D motor, not the B motor. The B motor is even less power...Acutally, I think the Sterling model does have a fair amount of dihedral, as does the full scale airplane -seen at Rhinebeck.

Sam
Jul 01, 2002, 03:40 PM
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E-Challenged's Avatar

My Guillows PT17 Experience


Needed plenty of power, dihedral(both wings), downthrust, right thrust, positive wing incidence and downtrim or slight positive stabilizer incidence. Need to keep power on in duing landing, tends to tip stall and crash when bucking a head wind.

I built a Sterling Jenny for TD.020 power long ago, designed it so both wings could be removed with wing struts and brace thread permanently glued in place. ( Tops of cabanes not glued to upper wing) Remove lower wing mount rubber bands, rotate fuselage and pull out to separate from wings( I think).

Avoid tail heaviness, let it ROG off smooth surface for first flights, may take 30-40 feet , let it lift off when ready. After sucessfull ROG trim flights, it may hand launch ok , must have flying speed and keep nose level to horizon.

Good Luck
Jul 02, 2002, 11:25 AM
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Gerald's Avatar
Rays, if you can build the J-1 to an all-up weight of about 8oz then a GWS 'DXA' motor should fly it fine. I just finally got my Guillow's Thomas Morse Scout flying well with this motor. I replaced the POT-02 motor with the GWS unit and changed to a 9x4.7 APC SF prop and 8 370mAH NIMH cells. All-up weight has gone up to 8.5oz but it flys very nicely now.

As far as Guillow's kits go I'm four-for-four now (all 4 flown), with others in the works. I've always used all the kitwood and with careful construction they do fly. I would have to expect that the Dumas kits will do at least as well. The main challenge with these rubber conversions is figuring out what works and what doesn't and still having a model in one piece by the time you discover what works.

As far as covering goes, I'm still searching for the 'perfect' material and technique. Each plane I build gets something different. Sometimes the same model will have different coverings on various components. My Scout has litespan wings and silkspan fuselage, both doped with Aerogloss. My SE5A is doped tissue, and the PT-17 is doped silkspan. The Cessna 172 was Monokote and Econocote. I hear that litespan is not really that light by the time you get it painted. I may try Ultracote light 'clear' on my next 24" Herr Pitts special project, and then paint that.
Jul 02, 2002, 05:23 PM
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rays89's Avatar
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A post from Gerald the "guru of Guillows" Reading your webpage is what motivated me on building the SE5a and successfully flying it. Right now Im having motor or the esc problems with that plane it keeps cutting out. I had to make an emergency landing in tall grass. working on that is going to involve some serious surgery. everything is buried.
But back to the Dumas kit. been holding off a little while, its flying weather right now. I was planning on using a GWS s-1 or s-2 motor. the reason is from the layout I dont think there would be enough clearance for a 10 inch prop. Covering would possibly be Nelson litefilm. Its a little on the shiny side but so far Ive had good luck using it. Im just a little concerned because the balsa is a little more fragile compared to a guillows kit. litespan isnt an option because it does add a bit more weight
Oct 07, 2002, 03:22 AM
Leave me alone!
Martin Hunter's Avatar
Any update to this thread? Did the J-1 get built?

Martin
Oct 07, 2002, 05:40 AM
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rays89's Avatar
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Martin
Unfortunetly, the J-1 project has been temporarly pushed aside, The farthest Ive gotten was tacking down the plans. From what Ive seen from the plans, the fuselage is going to have a few weak spots, I was thinking carbon fiber cloth in strips for reinforcement, any other ideas?
I picked up the motor for the plane (GWS ips s-2) a 7 inch prop is the only size for proper clearence.
I picked up the MM Cesna 180 which I think Ill build first. (Need a little more building experience). Starting that on Tuesday (gotta clean the shotguns today) I heard a lot of positive feedback on that plane. Then hopefully start on the J-1. Building season is coming up now. Ive been pretty occupied flying the switchback. To do any actual building. Ill keep you posted when construction of the J-1 is under way.
Thanx for asking
Ray
Oct 08, 2002, 12:04 AM
Happy happy, joy joy!
Goge's Avatar
I was eyeing the Dumas kit also- but probably won't end up building it any time soon.

I thought I'd put in a little success story for the Dumas kits though- I built the Mr. Mulligan (see avatar), I'm running it on one of the GWS s-motors (can't remember if it's -1 or -2). Came out about 8 oz. with two Li-Poly cells, HS-50s, and an R4P rcvr.

I was worried about high wing loading, but it flies just great!

I mostly stuck to the kit wood, with a few bits of basswood here and there in stress areas. I think the GWS motors are perfect for kits of this size and weight- the J-1 would be great with one.

Just my $.02, FWIW.

-TH


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