Flair Fokker DVII downthrust

[David Germany]

Just started a Flair Fokker DVII and dry assembly of the front fuselage assembly shows about 4 degrees of side-thrust and about 6 degrees of down-thrust. The side-thrust looks right but the down-thrust "looks" a bit excessive. I'm sure it must be right but it is a lot more than my Puppeteer. Is this because of the low thrust line of the DVII ? I'm just looking for conformation before gluing up the assembly.

Dave

[Cuban8]

One of my old club mates (now passed on, sadly) built a beautifully detailed Flair DVII and I know for a fact that he was a stickler for building exactly as per plan. His D VII flew very nicely, so I'd go with what Flair recommend IIWY.

Good luck with it.

[Don Fry]

I have a Flair DVII, very nice flier, had it a couple of years. mine goes on a Laser 80, overpowered, but just nice on about 30 to 40% throttle. Will climb if power is increased with no extra down trim fed in. Centre of gravity is conservative on the plan, so be prepared to take weight off the nose as you get used to it. Mine is trimmed to require a mere touch of down when inverted.

Built as plan.

[David Germany]

Thanks for the info.

Don, did you have any issues fitting the Laser 80 as that is what I am hoping to fit also. How did you arrange the exhaust ?

Dave

[Don Fry]

Moter fits on mounts as plan. Photo one shows surgury required to fit the ABS standard cylinder head cover. Might be raised a mm of two as well. Can't remember the brutal fudges. The exhaust, photo two, is a piece of silicone from the standard 80 exhaust, to an entirely false "scale" exit from a bit of bendy pipe. Bit of a shoe horn job from memory.

The mess with the fuel pipes came when I swapped the original 75 to the 80, when the 75 would not run. The cause was a faulty remote glow as it turned out, but I have never tidied the installation. This machine has flown a lot. To claim I am not a philistine, the control runs are scale closed loop. Ailerons are pushrods underneath, with false elastic tensioned false closed loops on the top surface. Looks good. Little effort.

Before we note this oily aircraft is on the dining room table, SWMBO is bonding with her mother (AKA the witch of Pendle Hill, mother, not SWMBO, who I love dearly), in the UK. I am living in comfortable male squalor, with my dogs, and quest dog. But tomorrow, the house will be tidy, dogs brushed, and if necessary thrown in the river. I will be showered, shaved, in fresh clothes.

Any help, advice, shout. But this one is as kit instructions. The only gripe was the use of Solartex to hinge the ailerons. I did it as kit. A pain. If I did it again, I would use Robart hinges, as scale(ish)

 

Edited By Don Fry on 11/08/2017 19:18:22

[Jon H]

i used to have one of these powered by an asp 52. Is was fine for scale flying and I didn't alter the downthrust. The original was powered by a laser 62 and our current 70 is the same physical size. i would not recommend the 80 as its too big really and if you did use one of our engines the 70 would be the better choice

[Don Fry]

I agree a 70 is better, but you can nearly prop hang with an 80. Photos, promised above, attached.

[Don Fry]

[Don Fry]

[Geoff S]

I built a Flair SE5a sevaral years ago. It's powered by an OS52FS and flies well (as I recall - it's a bit of a hangar queen) with the recommended down and right thrust which looks to be quite a lot of both but I never measured it. I would stick to the plan settings. Flair seemed to know their kits very well.

Geoff

[David Germany]

Ok, Feel happier about the thrust angles now. In the light of Jon's comments I think I will probably go with the Laser 70, luckily I havn't glued in the engine bearers yet which I had trimmed to fit the 80. (Jon, can you tell me what the current lead time is on a new 70 ?)

[Jon H]

Hi David

I dont have 70's available at the moment I'm afraid. It could even be into September before I can get more built as I have shed loads to get done before I can do another batch Give me a call on Monday if you can and we can go through the whole thing.

I would also not recommend you use the wooden engine mounts in the kit. They should be cut short and a normal nylon mount used instead as wooden bearers really aren't suitable for modern high power engines and I wouldn't use them on anything over a 20 size engine if I'm honest.

[Frank Skilbeck]

Laser 70 should be fine, mine flies on an ancient Laser 61, and yes there is a significant amount of downthrust.

[Stevo]

Build as per the plan - you won't go wrong!

[Jon H]

I'm coming to get you Steve

[David Germany]

I've reached this stage with the fuselage, although the engine bearers are not glued in yet. I've cut them to fit the Laser 80 so I'll need to make up another pair to fit the 70, or use a nylon mount as recommended by Jon. I'm not sure how I could fit the nylon mount now to give the correct thrust angles, I'd definitely have to reinforce the firewall as this is only 3mm liteply. Would staying with the beech bearers and reinforcing them with glass fibre/resin be ok ?

[Denis Watkins]

David, beech bearers are very hard and strong, and correctly glued in, they will support a motor.

Your firewall does look to be birch ply from here, which is strong but too thin and could take another layer of 3mm birch ply.

Does it state in your notes that that is Liteply, as it is unsuitable in that position, though adequate further down the model

If you imagine those existing birch bearers glued in, and cut off flush

then another firewall added to the front, correctly drilled for a nylon mount would work

Edited By Denis Watkins on 14/08/2017 10:09:12

[Bob Cotsford]

I have several models with 60-90 two stokes bolted onto beech bearers, none of them have dropped off in this century. Beech bearers, captive nuts in the underside, job done!

[David Germany]

Dennis, the plan notes do state 3mm liteply for that part, I think I'll laminate that and the front former with another layer for extra strength and gluing area.

[Bob Cotsford]

sorry Jon

[Jon H]

The problem with hardwood bearers is not all hardwood is that hard and the engine eats through it, the bolts come loose, and then the engine is then falling about laughing which is not ideal. My Pica P40 suffered from this and the engine needed bolting back in every 5-10 flights. It was flippin hopeless!

In the fokker the formers are 3mm lite ply if i recall and are not man enough for the job. I do agree that getting the thrust line correct will be a challenge with the setup in the fokker so you might have to go for the wooden jobbies. If you do make sure you fuel proof them well and once the holes through them are drilled resin should be soaked into the innards of the hole. I thin my resin a bit for this job then hit it with a hair dryer for a moment to evaporate the thinner.

If there is any easy way to do it a nylon mount is still a better bet in the long term.

[Don Fry]

David, as I said mine is built as plan. With all the bits, formers as supplied. I did however glass the engine bay. , and soaked with finishing resin the bearers as Jon suggests. But overpowered, several hundred flights, and no signs of deterioration. And I really do try, on occasion, to prop hang it, and do all sorts of non scale hooliganisms. Don't worry about weight, they all require noseweight. Yours to too far along to mess with now.

Edited By Don Fry on 14/08/2017 13:16:33

[Jon H]

I dont think his bearers are glued in Don so he has some wiggle room.

If you do go for the 70, run it in on a 13x5 (first half dozen flights) and then grab something like a 14x5 or even a 15x4. You could also use this 15x5 from HK as the 70 turns it well. **LINK**

Edited By Jon Harper - Laser Engines on 14/08/2017 13:41:37

[David Germany]

Yes, the bearers are only dry-fitted at the moment, I need to get some more 1/2 x 5/8 beech to make some more, will try to get over to SLEC today to pick some up.I.m on the lookout for a used 70 but may have to save up for a new one.

Any thoughts on how to make the rigging easier at the field ? I built my Puppeteer with a split fuselage which makes assembly at the field a 2 minute job (2 servo plugs and 1 bolt) but that is electric and vibration free, not so sure about doing that on the DVII though.

[Jon H]

I had one of these fokkers and sold it because of the faff factor of putting it together. 14 screws was a bit excessive but its now matched by my 1/4 scale stampe so perhaps i was just lazy when i was younger.

In any case, you could use R clips from model car bodies to retain the interplane struts, or you could plug the struts into the wings on wires like mick reeves does with his 1/4 scale models. As the wings are strong enough for the model to fly even without th struts i cant see how this would be an issue, although personally i would feel better if they were secured in some way.

As for the cabanes, you could always get two long rods threaded at the ends and use them to hold the wings on. You could feed them through the struts, through the wing mount plates, and out of the strut the other side. Two nuts would have the whole wing fitted with only the interplane struts to go. It wouldnt be super scale but is that a big issue?