Help! De Havilland Sea Vernom - Tip stall
 

One of my friends have a De Havilland Sea Vernom from Grumania, which tend to tip stall at low speeds, it makes it difficult to land without losing a wing and landing goes wrong. I've attached a picture of the plane. He tried to fly it with crow and make it nose heavy, but nothing works. Do you have a bid on a solution that can get this plane more stable at low speed?

Thanks for any help that can get the plane to fly well it is otherwise a very nice flying jet and good looking to.
Data:
Scale 1/6
Wingspan of 218 cm
Length 186 cm
Weight 12 kg
Engine P80SE

RE: Help! De Havilland Sea Vernom - Tip stall
 

Hans,
Has the model got slats on the wing tips? The full size did. There may have even been stall strips inboard but I'm not sure about this. If there are no slats, try adding them.
John

RE: Help! De Havilland Sea Vernom - Tip stall
 

Picture #1 is a takeoff or a landing?

RE: Help! De Havilland Sea Vernom - Tip stall
 

Hans

I suspect your plane is difficult because it is heavy. the Grumania web site says it should weigh 10 Kg and yours is 2 Kg heavier. The p80 is very capable engine but is heavy. Swapping the motor for one of the new smaller engines like the new Jets Munt Vt80 would make significant savings. I have found that adding a ACT fuzzy pro gyro to the ailerons can delay the tip stall point on difficult models. You could try one and see if it helps.

John

RE: Help! De Havilland Sea Vernom - Tip stall
 

Hi all,

This plane seems to have very small rudders aera. I suspect this plane to lose the rudder effectivity at high angle of attack due to fuselage and wing slipstream, thus having some yaw movement and great variation of speed at tip end of the wing, thus improving tip stall tendencies. It's not rare with those "low profile" style rudders.

Have you noticed some yaw movements or snacking problems ?

Maybe a gyro on rudders, not ailerons, should help to keep the plane "straight in line" and thus not tip stalling. That's the first thing you learn when you fly reals ones : keep that ball centered !
Other help should be a slight negative aileron to put some negative washout at landing, but you said you've tried the crow function with no effects. (Please not too much negative, you need some lift...)

RE: Help! De Havilland Sea Vernom - Tip stall
 

Have you checked the wings to make sure you dont have any "wash-in"? This is a very docile aircraft, I would check your wing incidence from root to tip on both wings....
As mentioned, you are a little on the heavy side but I dont believe this is the issue....

RE: Help! De Havilland Sea Vernom - Tip stall
 

The Sea Venom has a very distinctive wash out of 3 ° ! This is not the problem.
If the model is heavier than 10 kilos, you have to take care about landing speed and angle of attack.The full size Sea Venom has tail bumpers under the fin that restrict the possible AOA.When you have the model on the ground and press down the tail until it touches the ground - you see the maximum AOA that was possible for a deck landing. That is not much. The Sea venom was not designed for high AOA landings. Slowing down the plane was not made by lifting the nose, they used the air brakes at that time.
With 12 kilos of weight you have to land faster and avoid high AOS`s.
Another point to look after is checking if there is a trim change at high and low throttle settings.If yes, the angle of the jet pipe needs to be adjusted.The Sea Venom is really nasty if this angle is not correct and if a wrong thrust vector misleads the modeller to correct with trims or ballast.

Ilja

RE: Help! De Havilland Sea Vernom - Tip stall
 

Hans,
John is spot on. I have the Mick Reeves Venom and to my knowledge the Sea Venom and the land based Venom both had leading edge slats at the tip. Because of the severe leading edge taper they need to be installed. Take a look at the picture below. IF you look closely just inboard of the tanks, they are there.

Cary

RE: Help! De Havilland Sea Vernom - Tip stall
 

Hi Hans, Very nice aircraft. The previous threads offer good possible solutions. I wish to add another possiblity for you to investigate assuming that the Venom is being flown in a proper manner considering its weight etc.

I believe the Sea Venom has split main flaps similar to the Vampire, therefore I wish to share an experience I had with a customer who had a very similar situation as yours with one of my Vampires. His airframe was with-in the design limits all around so we had trouble figuring out what caused the wing to drop on the flair to landing as this is not typical to the Vampire. We looked at everything to no avail. Becuase the Vampire has 4 sizable split flaps, I asked the customer to do a pull test on each flap with the radio on and flaps fully extended to make sure that each independent flap servo was holding its load compared to each other.

This test revealed that one of the 4 flap servos was NOT holding to the same load as the others and was attempting to close under the simulated air load while the other 3 held equal. The effect of this condition was to induce a roll to the side with the bad servo when flaps were fully deployed. Once this was discovered, the faulty servo was replaced and and the wing drop vanished. This condition will be exagerated if not using digital servos on your flaps which have much greater holding power.

Also, while I'm confident that you have looked at the flap alignement to each other, if they are not properly aligned, they have the potential to yield the roll tendency as well. What may appear as an Aileron stall may be a condition generated by the flaps especially if the wing tends to to roll to the same side everytime. (assuming the wing is true)

Best of luck in your future flights and I hope this info may be of help to you.

RE: Help! De Havilland Sea Vernom - Tip stall
 

Hello Hans,

What you can do is to put the ailerons a little bit (about 3 mm up) in the landingmode and flaps down
this will help

best regards,

marijn

RE: Help! De Havilland Sea Vernom - Tip stall
 

The problem is solved. Now my friend’s Sea Vernom flies like a dream!

Tailplane/Stab was placed too high in front, after having lowered the tailplane at front approx. 1.2 cm the plane flies like a dream with no bad tendencies to tipstall or similar, it flies like a boomer :D

Took some pictures along the way, the pictures tell it all. Thank you all for your help and excuse the late update on the thread.

RE: Help! De Havilland Sea Vernom - Tip stall
 

Cool !
Thanks for the news !

Did you change the CoG by the way ?

RE: Help! De Havilland Sea Vernom - Tip stall
 

Always good to hear that the problem has been found and fixed.

Thanks for taking the time to report back.

RE: Help! De Havilland Sea Vernom - Tip stall
 

I wonder if something has been reported incorrectly here, or got mangled in translation. I do not see how the tailplane incidence is related to tip stalling.

RE: Help! De Havilland Sea Vernom - Tip stall
 

You mentioned moving the CG forward making it nose heavy. Usually, a nose heavy aircraft will tip stall sooner at low speed becasue it takes more elevator to hold the nose up, thus adding more wingloading.