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Seagull DH-98 Mosquito engine choice

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Ray Charnock16/11/2017 08:43:24
5 forum posts

Hi Richard

Sorry to hear about your maiden crash mine is not quite ready yet i have to get the cg set and the control throws set weather not so good a quick question did you have to add any weight to get recommended cg.

Regards Ray.

Richard Wills 216/11/2017 08:52:40
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103 forum posts
7 photos
Posted by Ray Charnock on 16/11/2017 08:43:24:

Hi Richard

Sorry to hear about your maiden crash mine is not quite ready yet i have to get the cg set and the control throws set weather not so good a quick question did you have to add any weight to get recommended cg.

Regards Ray.

yes, 13 oz on the nose bulkhead. ended up at 15.2 lbs dry.

Ray Charnock16/11/2017 09:29:03
5 forum posts

Hi Richard. thanks for the information what engines are you using 2 stroke or 4 stroke.

Ray.

Richard Wills 216/11/2017 09:44:27
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103 forum posts
7 photos

4 stroke, Saito 82's

Jon Harper - Laser Engines16/11/2017 10:29:53
3178 forum posts
130 photos
Posted by Richard Wills 2 on 16/11/2017 09:44:27:

4 stroke, Saito 82's

boooo

Chris Walby16/11/2017 10:47:44
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269 forum posts
31 photos

Jon,

What's the difference in weight between a Saito 82's and a Laser offering to save on the 13 oz of lead and to buy British + increased reliability? smiley

 

PS - I am a member of the anti lead freedom fighters! our motto "down with lead"

 

PPS sorry to go metric, but Seagull say AUW 6.2 to 6.4kg Richard's was 6.895 dry so that's somewhere (best case) between 7 and 10% overweight (no fault of Richard as you need CofG in the right place) and I have had this with the BH Mossie (adding lead to get correct CofG)

Would the + 10% weight have an effect on low speed flight characteristics, more abrupt tip stall?  

Edited By Chris Walby on 16/11/2017 11:01:13

Jon Harper - Laser Engines16/11/2017 12:05:51
3178 forum posts
130 photos

At the size of model we are looking at the weight is not an issue i wouldnt think. My 80'' fighters are 19-23lbs so 15 or so is plenty light enough.

In terms of engines our 80 is 190g heavier than the saito effort and our 70 only 80g heavier. I am sure twin 70's would be plenty but the 80's would turn a larger prop which might be quite nice.

As for the ALFF i will pass on membership as adding lead has never worried me. Its got to balance at the end of the day. I do agree though that lead can be minimised by careful placement of parts. No need to add 2 lbs when 1 will do.

The spin was likely due to a number of factors all related to it being a new model. Very low experience with said model, imperfect rates/balance, imperfect approach and perhaps slightly mismatched engines.

I dont know if you tested the stall at high altitude Richard? for me this is a key point of any test flight as it gives me a clue what will happen at the stall. some say its pointless and give numerous reasons for it, but for me knowing that a model will flip on its back is important information and will encourage me to be gentle on approach.

Richard Wills 216/11/2017 13:24:46
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103 forum posts
7 photos

Don't think the weight of the model is an issue, in fact comparing it to my 60 sized Mustang at 11 lbs, it is quite light. Had a quick check over the model last night, and the rudder linkage does have a bounce in it under load so maybe that explains the soft rudder. I'll sort that and increase the throw.

The engines are almost as far forward as the position of the lead, so 2 80's would balance better. The model was more than adequately powered, so the 70's would be great. In fact it took off at about 2/3 throttle without elevator on a nice long run so lots more than necessary. I have 14x6 2 blades on it they look just right.

I spent quite a while matching the engines with a curve on one channel through the rev range by ear, didn't resort to a tach but I have spent a lot of time balancing twin 2 barrel webers so I know they sounded close.

Jon I did do a stall test, which was vicious, but didn't seem to be at a speed/AOA that seemed dangerous, and also noticed it's tendency to want to fall into a spin if you bulied it in a bank so did keep up the approach speed.This was my first proper twin, not counting the foamy 110 have, so John is right on the low experience thing. I spent some time last night working out what I was doing, and I think I made a big mistake in coming in about 30 deg to the wind because there was a longer run of clear sand on the beach in that direction, not thinking about the trouble I was having with the rudder. At the moment of doom I was just starting to think about a flare, doing my final heading correction with you guessed it, a bit of left aileron just as I started to feed in elevator and also without thinking reducing power. Lesson learned, and I can't wait to get it back in the air and have another go.

Jon Harper - Laser Engines16/11/2017 14:58:34
3178 forum posts
130 photos

It sounds like you covered the bases as well as is reasonable to expect so it would seem that the model itself is just very flicky. Tweaking the ailerons will help a bit but you may also need to change your landing technique and use throttle instead of elevator to control your decent. I have to use this method with my Sea Fury as it will slow up and stall easily if a 'normal' approach is used. I run in with a fair bit of power and only use the elevator to tease to nose up to horizontal before wheeling in. 3 point landings are a nono and i suspect the mossie will be the same.

Ray Charnock16/11/2017 16:10:20
5 forum posts

Hi all

Last year i was flying the Freewing Mosquito and when i was flying it i always thought about the opening scenes in the movie 633 squadron were the aircraft are coming in to land as you can see they always approach at speed and put the aircraft down on two wheels same on take off its slow opening of the throttle then raise the tail to get rudder authority this is how i flew my mosquito and that is the way i will fly this one.

Ray.

PS i am not trying to tell people how to fly their mosquito thats just my way of doing it.

Martin_H19/11/2017 11:23:27
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120 forum posts
54 photos

Fitted my Saito FG11's to the ply nacelle mount - perfect fit! Was worried I'd have to redo the mount holes to suit the Saito engine mount but no problem!

Ian Moody19/11/2017 15:38:55
36 forum posts
10 photos
Posted by Martin_H on 19/11/2017 11:23:27:

Fitted my Saito FG11's to the ply nacelle mount - perfect fit! Was worried I'd have to redo the mount holes to suit the Saito engine mount but no problem!

Do you have any photos of the installation and of the inside of the nacelles also of the inside of the fuselage please Martin. There is very little to be found on the web about this model yet except for someone flying it like a pylon racer in Vietnam and I would love to see some more detailed pictures of the parts. I quite fancy one of these.

Thanks Ian

Martin_H20/11/2017 22:58:48
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120 forum posts
54 photos
Posted by Ian Moody on 19/11/2017 15:38:55:
Posted by Martin_H on 19/11/2017 11:23:27:

Fitted my Saito FG11's to the ply nacelle mount - perfect fit! Was worried I'd have to redo the mount holes to suit the Saito engine mount but no problem!

Do you have any photos of the installation and of the inside of the nacelles also of the inside of the fuselage please Martin. There is very little to be found on the web about this model yet except for someone flying it like a pylon racer in Vietnam and I would love to see some more detailed pictures of the parts. I quite fancy one of these.

Thanks Ian

Hello Ian,

Check your inbox, I can send a copy of the Seagull Manual in glorious technicolour!

Martin_H20/11/2017 23:12:07
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120 forum posts
54 photos
Posted by Jon Harper - Laser Engines on 16/11/2017 14:58:34:

It sounds like you covered the bases as well as is reasonable to expect so it would seem that the model itself is just very flicky. Tweaking the ailerons will help a bit but you may also need to change your landing technique and use throttle instead of elevator to control your decent. I have to use this method with my Sea Fury as it will slow up and stall easily if a 'normal' approach is used. I run in with a fair bit of power and only use the elevator to tease to nose up to horizontal before wheeling in. 3 point landings are a nono and i suspect the mossie will be the same.

Interesting...I thought it was common practice to use throttle to control rate of descent and elevator to control approach speed - just as full size... I suggest all modellers read 'Stick and Rudder: An explanation of the Art of Flying' by Wolfgang Langewiesche. If you cannot get a copy of this book then it is available on digital download from Amazon, and at a quite reasonable price, considering what I paid for my hardback copy! I learnt to do flapless sideslip landings with my 1/4 scale Cub using the techniques in this book.

Gavin Mack05/12/2017 21:29:42
71 forum posts
12 photos

Link to manual

http://www.skysharkrc.com/Downloads/Mosquito_Instructions.pdf

 

 

Edited By Gavin Mack on 05/12/2017 21:31:25

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